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Table of Contents
The DC Power System 1
1.1 DC Power Overview 11.2 Rectifier 71.3 Battery 161.4 Distribution 271.5 Battery Return Bus 311.6 Supervisory and System Control 331.7 Low Voltage Disconnect Contactor 401.8 CEMF Cell 431.9 Battery Temperature Compensation 45
1.10DC - DC Converter System 511.11DC Power System Integration 541.12Inverters/UPS 58
Power System Sizing and Ordering 622.1 Calculations 622.2 Formulas 652.3 Power System Design Example 662.4 Ordering Information for Power Systems
and Loose Items 67
Site Engineering for DC Power 693.1 Site Layout and Loading 693.2 Grounding Network 713.3 Surge Protection Devices (SPDs) 743.4 Wiring 763.5 Engineering Drawings 80
Initial Installation 814.1 Safety Precautions 814.2 Tools List 83
4.3 Inspection 844.4 Power System Assembly/Mounting 85
4.5
Battery Installation 86
4.6 Cabling 894.7 Power Up Procedure 924.8 Battery Initial Charge and Discharge
Test. 944.9 Documentation 95
Power System Commissioning 97
Retrofit Installation 996.1 Precautions 99
6.2 Tools List 1006.3 Distribution Circuit Addition 1006.4 Common Ground Bus Addition 1006.5 Distribution Panel Addition 1016.6 Rectifier Addition 1036.7 Shunt Replacement 103
Maintenance and Field Repair 1057.1 Power System and System Controller 1057.2 RST Rectifiers 1077.3
RSM Rectifiers 109
7.4 Pathfinder 24-3kW, 48-3kW, and 48-
10kW Rectifiers 1127.5 CS and CSM Converters 1147.6 Vented Batteries 1167.7 Valve Regulated Lead Acid (VRLA)
Batteries 1187.8 Battery Failure; Detection, Prevention
and Corrective Action 119
Troubleshooting 1218.1 Power System and System Controller 121
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D C P O W E R S Y S T E M S H A N D B O O K
ARGUS TECHNOLOGIES 075-053-10 Rev D
CHAPTER
The DC Power System
The DC power system is a vital part of the communications network.
Most communication equipment, including PBXs, telephone switches,microwave transmission, fiber optic transmission, mobile radio, cellular,
etc. are designed to operate from a DC input voltage. A DC source has the
inherent benefit of higher reliability as compared to an AC source. This is
because the battery, which is often used for backup, is directly connected to
the load with no intermediate stage such as an inverter that may fail and
disrupt power to the load. The basic power system consists of a rectifier and
usually a battery, but may include various other components. The various
components are discussed in detail later in this section.
1.1 DC Power Overview
1.1.1 Typical DC voltage and current requirements
The two most common input voltage requirements for
communication equipment are +24V and -48V. The use of -48V is
rapidly becoming the most predominate as this is the maximum
safe working voltage according to both the National Electrical
Code (NEC) and the Canadian Electrical Code (CEC) that has no
current limiting requirements. The high voltage reduces the
current requirements making fuses/circuit breakers/cables smaller.
+24V evolved from the mobile radio industry, where equipment
was designed to operate from either an automotive (+12V)
charging system or a truck (+24V) charging system.
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-48V evolved from the telephony world where 48 volts was
chosen because it was the maximum voltage that was considered
safe as technicians had to make live connections. The negative
polarity (positive ground, similar to the old British -6 VDC
automotive charging system) was chosen as it reduced the galvanic
corrosion that occurred when the lead sheathed telephone twisted
pair cables were originally deployed and buried in the earth.
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Load
LoadLoad
ACPowerOn
DC
DC
DC
ACPowerOff
Battery
Battery
AC
AC
DCPSB01A
Rectifier
Rectifier- -+ +
Load Load
Figure 1 Basic DC Power System Operation
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Table A Typical Telecom Equipment Voltage and Current Requirements
Application Voltage Current NotesMobile Radio BaseStation
+12 VDC
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Typical AC voltage sources
There are many different voltage sources around the world.
Identify the source that you are using and watch the rectifiers to
the source. See Table B.
Service Configuration LL Volts L-N Volts Where used? Notes
120/240V 1 PH3W
Single Phase 240 VAC 120 VAC USA, Canada
120/208V 3PH4W
Three PhaseWye
208 VAC 120 VAC USA, Canada
277/480V 3PH4W
Three PhaseWye
480 VAC 277 VAC USA
347/600V 3PH4W
Three PhaseWye
600 VAC 347 VAC Canada
208 V 3PH 3W Three PhaseDelta
208 VAC N/A USA, Canada
480 V 3 PH 3W Three PhaseDelta
480 VAC N/A USA
220/380 V3PH 4W Three PhaseWye 380 VAC 220 VAC EuropeAs iaSouth America
Table B Typical AC Commercial Voltage Sources
Figure 2 Single or Split Phase
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Figure 3 Three Phase Delta
Figure 4 Three Phase Wye or Star
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1.2 Rectifier
1.2.1 Description
The rectifier is a device that changes an AC (alternating current)
input to a regulated and filtered DC (direct current) output. The
DC output supplies power to the load (communication equipment)
and charges a backup battery if required.
1.2.2 Connection
The rectifier is connected in parallel with both the load and the
battery (if applicable). Multiple rectifiers may be connected
together in parallel, with their corresponding (+) and (-) leads
connected together.
1.2.3 Operation (Float charge mode)
The rectifiers are adjusted to the voltage requirement (float
voltage) of the battery and to share the load or supply the same
output current in systems with more than one rectifier.
AC-ON - The rectifier supplies current to the load and provides a
trickle charge current to the battery.
AC-OFF - The rectifier turns off and the battery will supply
current to the load until the battery is completely discharged.
AC-ON- The rectifier supplies current to the load, any extra
current available from the rectifier will be used to recharge the
battery.
1.2.4 Sizing details
The rectifier size is chosen by determining the most cost-effective
means of satisfying the total capacity requirements.
N+1 redundancy should always be considered. N isthe number of rectifiers required to satisfy the total
capacity requirements of the load and the 1 is an
extra rectifier added so that a failure of a rectifier in
the system will not jeopardize system integrity.
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Correct choice of either positive ground (-48VDC) or negative
ground (+24 VDC) is critical. The grounded potential is connected
to a common point and the live cable is connected through either
fuses or circuit breakers. Refer to power system design calculation
section.
1.2.5 Features and selection criteria
Low output noise/ripple ensures that the load is unaffected by
the rectifier in both battery and more importantly battery-less
operation. Note: the battery acts as a filter, but VRLA batteries
will fail prematurely when connected to rectifiers with high output
ripple voltage.
Tight voltage regulation (line and load) to ensure that the
battery is properly charged and the load does not receive
fluctuating voltages.
Modularvs. monolithic configuration; modular rectifiers allow
for easy replacement and expansion.
Unity power factor(P.F.>.95) is becoming more important as
the utilities move toward increased monitoring of power factor. A
poor power factor at your Telecom facility may result in the
electrical utility adding a surcharge to your electrical bill. InEurope, unity power factor is a CE requirement for Residential
and light commercial applications. North America may soon
follow this trend. There are two types of power factor
measurements displacement and true. The displacement component
of power factor is the ratio of the active power of the fundamental
wave (60 Hz), in watts, to the apparent power of the fundamental
wave in volt-amperes. This is the value used by utilities to
determine billing. True power factor is the ratio of the total power
input, in watts, to the total volt ampere input, this includes the
fundamental wave (60 Hz) and all the harmonics (120, 180, 240,
360, 480 Hz, etc. This value is used for efficiency calculations.
Early Argus rectifiers utilize passive power factor correction to
achieve reasonable power factor at low cost. The Pathfinder
rectifiers offered by Argus have a true power factor of >.99.
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Figure 5 Power in an Inductive Circuit
Figure 6 Power Factor Triangle
Low THD (total harmonic distortion) and damaging
harmonic currents to meet CE requirements and to eliminate
AC generator and transformeroverheating and interaction
problems. THD refers to the distortion of the incoming AC voltage
or current waveform when the rectifier is connected and is
expressed as a percentage.
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Three phase AC input - For higher power applications this
becomes more important to ensure even balancing of load on a
three-phase AC source.
High efficiency as well as having the obvious power savingsbenefit, reduces the size of the input feeder circuit breaker and
input cabling.
Wide AC operating window for both frequency and voltage to
tolerate fluctuations without the rectifier shutting down. Argus
rectifiers have a wide input tolerance range for both frequency and
voltage. This allows uninterrupted operation and also allows
universal operation for 208/240V 60Hz operation and 220V 50 Hz
operation with no modification or reconfiguration required.
Pathfinder 48-3kW & 24-3kW rectifiers (208/240 VAC I/P) will continue to
operate down to 90 VAC (with reduced output)!
Compact and lightweight helps reduce installation,
maintenance and shipping costs.
Balanced load sharing should be achieved between units of
the same design and with other types of rectifiers. Argus rectifiers
accomplish this with a combination of forced sharing
(master/slave) and/or adjustable slope regulation. Adjustable slopeallows you to tailor the voltage regulation characteristics of
different brands of rectifiers.
Forced sharing works by the rectifiers electing a
master unit (the rectifier with the highest output
voltage). The other rectifiers are forced to adjust their
output voltage to track the master and therefore share
the load.
Slope Regulation (Output Voltage) allows the user
to drop the output voltage of the rectifier a small
amount from no load to full load. This is done at a
fixed rate. The slope in the voltage regulation of the
rectifiers helps to allow the user to set the rectifiers to
load share easily and also allows you to tailor the
voltage regulation characteristics of different brands
of rectifiers.
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Figure 7 Output Slope Voltage Regulation and Current Limit
Adjustable current limit restricting output current of the
rectifier, in either a discharged battery or overload condition. The
rectifier can operate in this condition without damage.
Power limit allows the rectifier to supply greater output current
when the output voltage of the system is low. This reduces battery
recharge time and also provides greater overload capabilities
reducing the need for redundant rectifiers.
Figure 8 Current Output P 48/10 kW e/w Power Limit
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Figure 9 Power Limit (P 48-3kW) - Current Limit (RSM 48/50)
Comparison
A float/equalize mode selectorswitch allowing selection of
two operating modes:
1. Float mode for normal charging of the battery.
2. Equalize mode for boost charging (at a higher
charging voltage) of batteries when required. This
boost charging eliminates any sulfation on the
battery plates resulting in cell voltage imbalances
and poor performance. This is an important feature
for vented lead calcium batteries floated at
reduced voltage levels. Typically not required
with VRLA batteries under normal operating
conditions.
Automatic high voltage shutdown (HVSD) or over-
voltage protection (OVP)to switch the rectifier off in case of
a high output voltage condition, preventing damage to the batteries
and load. An automatic restart feature should be included in the
event that a site temporary abnormality surge as a ground surge
resulted in the HVSD.
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Soft-start gradually steps each rectifier on-line at power up. This
eliminates start-up current surges associated with many rectifiers.
The feeder breaker and feeder size requirements are decreased,
reducing the installation costs of the rectifier.
Adjustable delay start allows staggered start-up of rectifiers
reducing stress on the AC generator and also allows the rectifiers
to be started after the site air conditioner compressor (drawing
high surge current) has started.
Alarms provide indication of rectifier failure and should be of
fail safe design. Local indication plus remote relay contacts are
required.
Remote sensing leads are connected directly from the battery
to the rectifiers via a sense fuse distribution panel located in the
supervisory panel. This allows the charger output voltage to be
regulated at the battery improving voltage regulation at the
battery. This is important with power systems that incorporate
separate charge and discharge circuits or power systems where
there may be a significant voltage drop in the battery cables. If
this feature is not connected, the rectifiers automatically revert to
internal sensing, regulating the rectifier output voltage to the
rectifier output terminals.
Remote Control and Monitoring allows the rectifiers to be
remotely controlled and monitored from a central supervisory and
control panel.
Model Voltage Current Features
Pathfinder 24 VDC 18, 50,100 A Convection or fan cooled
RSM 48/10 48 VDC 10, 30, 50, 180 A Modular design
200 kHz resonant converter design
RSM 24 VDC 7.5, 50,100 A Convection or fan cooled
48 VDC 15, 30, 50, 100 A Modular design
100 kHz forward converter design
Passive power factor correction
RST 12 VDC 50, 100 A Convection cooled24 VDC 30, 50, 100 A Monolithic Design
48 VDC 15, 30, 50, 100 A 48 kHz forward converter design
Passive power factor correction
Table C Argus Technologies Solutions
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1.2.6 Theory of Operation RSM 24/50, 24/100,48/30 and 48/50
Please refer to the power circuit block diagram. The 184-264 VAC
50/60 Hz input is fed through a circuit breaker into a full wave
rectifier, which provides a 120 Hz 340 V peak pulse train to aninput filter circuit. The input filter provides a nominal 290 volts
DC "raw supply" with approximately 30 VP-P 120 Hz ripple to the
transistor switching circuit.
The transistor switching circuit chops the raw supply into
nominally 525VP- P, 100 kHz rectangular waveform with a nominal
66% duty cycle. This waveform is fed into a ferrite power
transformer, which steps down and isolates the high frequency
switching waveform. A rectifier circuit converts the power
transformer output to a DC pulse train of nominally 136 V peak. A
two-stage output filter averages and smoothes this pulse traindown to provide the nominal 52 VDC output with low noise.
A voltage error amplifier circuit senses the output voltage and
compares it with the voltage reference to provide a voltage error
signal. Similarly, a current error amplifier senses the output
current using a shunt resistor and scaling amplifier to compare the
output current to the desired maximum output current to provide a
current error signal.
These signals are fed into the pulse width modulator (PWM) via
OR-ing circuitry so that either voltage or current regulation is
achieved. The pulse width modulator controls the "ON" time of the
switching transistors to vary the output as commanded by the error
amplifiers. It also senses the switching transistor current on an
instantaneous basis to provide cycle-by-cycle protection of the
switching transistors. An auxiliary supply, powered via a small
50/60 Hz transformer, and a DC/DC converter power the control
circuit and front panel circuitry. The PWM receives the ON/OFF
command and clock signal from the front panel circuit and control
circuitry.
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FrontPanelCircuit
MicroProcessor
InputRectifier
Input185-26
5VAC
50/60Hz
60Hz
120Hz
525V
250V
136V
0V
52V(48VUnits)
290VDC
100kHz
+3
40V -3
40V
O
V
Auxiliary
Supply
Local
Current
Sense
O
utput
V
oltage
S
ense
Output
Current
Sense
PulseWidthModulator
(PWM)
Input
Filter&
Storage
Capacitors
Transistor
Switching
Circuit
Outpu
tRectifier
Isolation
Boundary
Transistor
Drive
DC/DC
Current
Error
Amplifier
Voltage
Error
Amplifier
Output
Filter
Shunt
OrGate
V INAU
X
IOut
Voltage
Reference
Current
Reference
-Adjustments
-Display
-Monitoring
VO
ut
Communication
On/Off
C
ommand
Output
RemoteSense
DCPSH07A
-
-
+
+
Figure 10 RSM Block Diagram
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1.3 Battery
1.3.1 Description
The battery is an electro-chemical means of energy storage. When
AC power is interrupted to the rectifiers or when there is
insufficient current available from the rectifiers to support the
load requirements, the battery will automatically supply current to
the load. The battery may be used in combination with a generator
to provide back-up power for extended time periods to the load. A
battery consists of a series connection of multiple cells. The
number of cells in series is determined by the operating voltage of
the system and the operating voltage of each cell.
1.3.2 Connection
The battery is connected in parallel with the rectifier and the load.
1.3.3 Operation
As detailed in the rectifier operation section.
Some batteries may require periodic equalization. Equalization is
where a higher boost voltage is applied to the battery to ensure the
proper cell voltage balance and correct conditioning of the battery
cells.
Parameter Valve Regulated Lead Acid Battery (VRLA) Flooded or Vented Battery
One Cell 24 V System 48 V System One Cell 24 V System 48 V System
Nom. V 2 24 48 2 24 48
Float V 2.25 27 54 2.20 26.4 52.8
Equalize V 2.30 27.6 55.2 2.30 27.6 55.2
End V 1.75 21 42 1.75 21 42
Op. Win. V 1.75-2.30 21-27.6 42-55.2 1.75-2.30 21-27.6 42-55.2
# cells 1 12 24 1 12 24
Table D Typical battery operating parameters
1.3.4 Sizing details
Determine your load profile (i.e. amps per hrs) and select the
battery using the manufacturers sizing table (See: Table E).
Batteries are rated using the following criteria:
Temperature (25 deg C in North America, 20 deg C
in Europe).
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Endvoltage (the lowest voltage that the cell is
discharged down to). The end voltage used in
calculations is usually the minimum voltage that the
battery can be discharged down to without damage. A
more conservative end voltage will increase the life
expectancy of the battery but reduce back up time.
Refer to IEEE battery sizing guidelines for calculating battery size for complex
load profiles Evaluate battery charge rate for sizing intercell and inter-tier
connectors
Apply temperature performance correction factor for average
temperatures below 25 deg. C, (77 deg. F), if applicable (See:
Table F).
Ensure that the battery operating voltage coincides with the
acceptable operating voltage window for the equipment connected.
Apply the beginning and end of life de-rating factor. This factor is
20% and allows for:
The battery shipped at less than 100% capacity,
typically 90% (Full capacity is achieved after a short
period of float service).
Cells that are tank formed ship at 100 % capacity.
Battery end of life considered as 80% of capacity
(See: Figure 11).
Battery capacity is determined by the number & size of the plates,
therefore the larger the battery the greater the capacity.
Battery strings may be connected in parallel to obtain additional
capacity. Strings should be equal in capacity and interconnecting
cables should be of approx. the same size and length to obtain
optimum charge and discharge characteristics. The maximum
recommended number of parallel strings is three.
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Smaller applications commonly use mono-block batteries. Mono
blocks are batteries that have more than one cell contained in the
assembly (i.e. an automotive battery is a 6 cell 12 VDC mono-
bloc).
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Average Cell Performance Data*
Discharge rates in amperes.
1.215 SP. GR. ELECTROLYTE AT 77 (25C), INCLUDING CELL CONNECTORS
TYPENOM.A.H.CAP.
72HR.
24HR.
12HR.
8HR.
5HR.
4HR.
3HR.
2HR.
1.5HR.
1HR.
30MIN.
15MIN.
1MIN.
TO1.50VPC1 MIN
To 1.75 VPC Final
EA-5 230 4.6 11.1 18.8 26.6 44.0 49.9 59 75 87 102 152 197 290 530
EA-7 270 4.8 12.9 23.7 33.3 49.0 58.5 73 98 120 154 226 291 426 790
EA-9 350 6.4 17.2 31.6 44.4 65.3 78.0 97 131 160 205 298 380 548 1010
EA-11 440 8.0 21.5 39.5 55.5 81.7 97.5 122 164 199 257 367 465 685 1270
EA-13 530 9.6 25.8 47.4 66.6 98.0 117 146 197 239 308 435 558 792 1460
EA-15 620 11.2 30.1 55.3 77.7 114 137 171 229 279 359 507 651 924 1700
EA-17 710 12.8 34.4 63.2 88.8 131 156 195 262 319 411 571 728 1010 1870
EA-19 800 14.4 38.7 71.1 99.9 147 176 219 295 359 462 634 801 1100 2030
EA-21 890 16.0 43.0 79.0 111 163 195 244 328 399 513 694 870 1190 2200
*Rates shown depict average values and are subject to IEEE-485
CONSTANT CURRENT DISCHARGE RATINGS AMPERES @ 77FOperating Time To End Point Voltage
EndPointVolts/Cell
5min.
15min.
30min.
60min.
2hr.
3hr.
4hr.
5hr.
6hr.
7hr.
8hr.
10hr.
12hr.
20hr.
24hr.
48hr.
72hr.
10hr
1.75 274 162 105 61.5 34.8 25.0 19.6 16.2 14.0 12.3 11.0 9.08 7.79 5.00 4.19 2.13 1.43 1.0
1.80 240 151 99.0 60.1 34.0 24.2 19.0 15.8 13.6 11.9 10.7 8.80 7.58 4.89 4.10 2.10 1.42 1.0
1.85 203 136 92.0 55.0 31.4 22.8 18.0 15.0 12.9 11.3 10.1 8.44 7.23 4.67 3.92 2.02 1.37 0.9
1.90 156 110 75.0 47.0 28.9 21.0 16.8 14.0 12.0 10.6 9.50 7.90 6.73 4.34 3.65 1.88 1.26 0.9
Table E Typical Battery Performance Table
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Electrolyte C Temperature F Cell sizecorrection factor
-3.9 25 1.520
-1.1 30 1.430
1.7 35 1.3504.4 40 1.300
7.2 45 1.250
10.0 50 1.190
12.8 55 1.150
15.6 60 1.110
18.3 65 1.080
18.9 66 1.072
19.4 67 1.064
20.0 68 1.056
20.6 69 1.048
21.1 70 1.04021.7 71 1.034
22.2 72 1.029
22.8 73 1.023
23.4 74 1.017
23.9 75 1.011
24.5 76 1.006
25.0 77 1.000
25.6 78 0.994
26.1 79 0.987
26.7 80 0.980
27.2 81 0.976
27.8 82 0.972
28.3 83 0.968
28.9 84 0.964
29.4 85 0.960
30.0 86 0.956
30.6 87 0.952
31.1 88 0.948
31.6 89 0.944
32.2 90 0.940
35.0 95 0.930
37.8 100 0.910
40.6 105 0.890
43.3 110 0.880
46.1 115 0.870
48.9 120 0.860
Table F Temperature Performance Correction Factor TableThis table is based on flooded le ad-acid cells only.
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For further information, please refer to:
IEEE-485-199 - IEEE recommended practice for
sizing large lead-acid batteries for stationary
applications.
IEEE-1184 - IEEE guide for the selection and sizing
of batteries for uninterruptible power systems.
IEEE-1689 - IEEE guide for the selection of valve-
regulated lead-acid (VRLA) batteries for stationary
applications.
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Figure 11 Battery Performance vs. Time
1.3.5 Features and selection criteria
There are three main types of lead acid batteries that are used in
telecommunication applications. The three types, based on acid
classification, are listed below.
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Acid Classification
Description Advantages Disadvantages
Flooded Technology free liquid electrolyte, similar to an
automotive battery
-proven technology
-flat, tubular, plant options -bestlife expectancy of lead acidbatteries at higher operatingtemperatures
-high maintenance
-transportation restrictions
VRLA-AGM(Absorbed GlassMat) Technology
a small quantity of liquidelectrolyte is held in suspension inthe fiberglass mat
-low maintenance-minimal vented gasses-easy installation in any position-easier shipping classification-will not freeze
-difficult to evaluate battery stateof health-rapid reduction of life expectancwhen operated at hightemperatures (above 25 deg C)
VRLA-GelTechnology fumed silica is added to gel theliquid electrolyte -lasts longer than AGM at highoperating temperatures -performance (AH per kg) is lessthan AGM battery
Table G Battery Type Comparison
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Figure 12 Battery Construction
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Cycling requirement - different cell plate alloys and plate
configuration affect the cycling (charge and discharge)
performance of the battery. Determine the cycling requirement of
your application (i.e. float with light cycling, float with heavy
cycling and full cycle service) and choose the correct battery for
the application.
Rate of discharge:
High < 15 minutes
Medium 15 min. - 2 hr.
Low 2 hr +
Maintenance requirements.
Physical design parameters, ventilation, floor loading,available space.
Costincluding life expectancy.
VRLA batteries of both AGM and gel type are usually the first
choice for backup. Some of the important features to look for in
a VRLA battery are:
Jar material with low water vapor diffusion rate i.e.
polypropylene or PVC to prevent dry out.
Flame retardant jar materials. Even compression of plates through a fixed method of
jar compression to maintain, plate to microporous
separator integrity (AGM).
Designed to prevent strap corrosion and lug corrosion
(AGM).
The Battery may be packaged on a traditional battery stand or be
of bolt together self supporting construction. For smaller battery
strings the use of relay rack shelves or cabinets is a consideration.
There are also AGM batteries available from the manufacturesprepackaged for easy installation into a relay rack.
1.3.6 Argus Technologies Solutions
Argus does not manufacture batteries, but will provide batteries as
part of the integrated power system.
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DCPSB02A
Rectifier#2
Rectifier#1
Charge(-)
Circuit
Breaker
Distribution
Battery
- -+ +
Charge(+)
ShuntBar
Termination
Panel
Load
GroundBar
Load
Figure 13 Basic System e/w Distribution
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1.4 Distribution
1.4.1 Description
Fuses and circuit breakers are used to safely distribute the DCpower from the rectifier and battery to the loads. These devices
protect the loads and load cables from short circuits, overload
conditions and allow easy manual shutoff . This helps to isolate
faults between circuits. Circuit breakers and fuses are also used
for protecting the battery and battery cables and to allow an easy
means of disconnecting the battery from the system for safety, fire
prevention and maintenance.
1.4.2 Connection
Primary DistributionLoad fuses or circuit breakers located at the power system are
connected in series between the power system and the loads and/or
between the power system and the battery.
Secondary Distribution
Large main fuses are installed in the power system to distribute dc
power to remote BDFBs (Battery Distribution Fuse Boards) or
BDCBBs (Battery Distribution Circuit Breaker Boards). From the
BDFB power is distributed to the loads with smaller individual
circuit breakers.
1.4.3 Operation
Fuse
Excessive current flowing through the fuse melts the internal link,
disconnecting the load from the power system. A guard fuse is
connected in parallel with the main fuse and will blow when the
main fuse blows. The guard fuse provides a local indication and
also will send an external alarm signal via a built-in contact.
Circuit breaker
Excessive current flowing through the circuit breaker causes
excessive heat (thermal) or an excessive magnetic field (magnetic)
to trip the circuit breaker to the off position. Alarm sending is via
breaker auxiliary contacts or electronic trip detection circuitry.
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Electronic trip detection circuitry
A 10 000 ohm bypass resistor is connected across the circuit
breaker (to limit current) and the output voltage of the circuit
breaker is monitored. The benefit of the circuit is that an alarm is
indicated only when a breaker is off with a load connected and no
connection to the auxiliary contacts is needed.
Breaker ON with no load voltage on breaker
output is high no alarm.
Breaker ON with load voltage on breaker output is
high no alarm.
Breaker OFF with no load voltage on breaker
output is high (due to bypass resistor) no alarm.
Breaker OFF with load voltage on breaker output
is low (due to load forcing voltage down to zero V)
alarm is indicated.
Voltage will be measured on the output of a circuit breaker even when the
breaker is off, however current flow is limited to a few mA due to the 10,000
ohm resistor.
Sizing
Most communication equipment requires fuses or circuit breakers
with short delay curves fast blow to provide proper protection
Fuses with different curves may be utilized to match specific load
requirements.
Load fuses and circuit breakers should be sized 1.25 to 1.5 times
the maximum continuous anticipated load on the circuit for
reliable operation.
Battery fuse/circuit breaker should be sized at 1.25 times themaximum current rating of all the rectifiers in the system
(minimum).
Ensure that the current capacity of the circuit breaker panels is not
exceeded by the current draw of the connected loads.
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The interrupting capacity (highest fault current that the device is
rated to safely interrupt) of the protection device should match the
application. Battery protection devices require higher interrupting
capacity due to the high short circuit current capability of a
battery and the large cables (low impedance).
Features and selection criteria
Remote alarm sending via guard fuse or remote
contacts on circuit breaker.
Alarm indicating lamp and an isolating relay.
Traditional bolt-in, plug-in or snap-in circuit
breakers.
Guard bars to prevent accidental tripping of circuit
breakers.
Electronic breaker trip detection circuitry.
Various types of fuses and circuit breakers can be
combined in different panels to meet load requirements.
Current monitoringvia series shunts to ensure circuits
are not overloaded or power consumption monitoring for
billing purposes.
Battery protection features:
EPO - Emergency Power Off control capability
using contactor or shunt trip breaker for locations
that require a mandatory emergency power
shutdown to meet local fire codes.
LVBD - Low Voltage Battery Disconnect control
capability to automatically disconnect and
reconnect the battery during an extended ac power
outage.
Manual battery disconnection - Single string
disconnection for maintenance and fault isolation.
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Fuses or circuit breakers?
Fuse advantages - high interrupting capacity,
cost, flexibility, fast speed.
Circuit breaker advantages - can be reset,
accuracy, low speed.
1.4.4 Argus solutions
Fuse blocks:
Type Rating-Range (block size)
GMT 0-15A
70 Type 1/2A used for indicating purposes
BAF 0-30A
Cartridge 0-30A, 31-60A, 61-100A, 101-200A
TPL 61-800A
Breakers:
Manufacturer Type Rating Interrupting Capacity Usage
Heinemann AM 5 - 100 A 5 or 10kA Load or battery
Heinemann CD 5 - 100 A 10,000A Load or battery
Heinemann GJ 100-700 A 25,000A Load or battery
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1.5 Battery Return Bus
1.5.1 Description
The battery return bus (BRB), also referred to as the
common ground bus, provides a common return/reference
point for the connected loads and the power system. This common
reference point is connected to the site ground to provide a low
impedance path to ground for transients and noise.
1.5.2 Connection
The ground lead of all DC load inputs, batteries and rectifiers
should be connected to this point. This bus must also be connected
to the site ground grid (see grounding network section).
1.5.3 Sizing
Ground bars are sized according to load requirements.
1.5.4 Features
Allowances for termination oftwo-hole lugs of
various sizes should be provided.
Ground bars must be isolated from the relay rack
through glastic insulators so that the power system can
be integrated correctly into the site single point
ground network.
Provisions for small cable termination shall also
be provided.
Tin-plated copper construction for corrosion
resistance.
1.5.5 Argus solutions
Various types are available from Argus including flat bars and U
shaped bars for additional cable termination.
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DCPSH03A
APower
Superviso
ryPanel
GroundBar
Charge(-)
Battery
- -+ +
Charge(+)
ShuntBar
T
ermination
Panel
Rectifier#2
Rectifier#1
V
Load
Shunt
Circuit
Breaker
Distribution
Figure 14 Basic System e/w Supervisory Panel
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1.6 Supervisory and System Control
1.6.1 Description
In most power systems it is desirable to have a central control andmonitoring panel to provide local and remote indication of system
operating parameters and alarms and also to provide system
control.
1.6.2 Connection
Various connections are made to the supervisory panel from
different components so that different parameters and levels may
be monitored and controlled.
Shunts can be installed in the grounded or live load, battery or
system conductor.
1.6.3 Operation
The battery (charge) and load (discharge) voltage is monitored
with a direct connection of the sense leads to the source; battery or
load.
The battery (charge) and load (discharge) current is monitored
with an external shunt. Shunts are calibrated low resistance
resistors designed to provide a specific voltage drop at a specific
current (linear relationship). This voltage drop is measured by the
ammeter. A typical shunt rating would be 200A, 50mV. Therefore
200 amps of current flowing through this shunt will cause a
voltage drop of 50mV.
Calculated values may also be displayed such as total rectifier
output current (numerical addition of individual rectifier output
currents). In systems where there is no battery shunt an estimation
of battery current can be calculated by subtracting the discharge
current from the rectifier total output current.
Room and battery temperature can be monitored with temperature
probes.
Additional analog parameters can be monitored using available
inputs.
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Events such as distribution fuse alarm, battery fuse alarm, rectifier
failure, converter failure, etc. are monitored by the supervisory
panels.
Alarms are based on an analog or digital event. Each alarm has atwo to five second delay before extending an alarm. The delay
eliminates false triggering due to line transients or false alarms.
Analog alarms usually incorporate a hysteresis into the trigger
level to prevent oscillation of an alarm condition caused by a level
fluctuating around the set point. Alarm functions provide both
local (visual and audible (optional)) and remote (relay contact)
indicators.
Relay contacts may be configured as form A (NO), form B
(NC), or form C (NO & NC).
Control functions are extended from the supervisory panel to
control various other power system components.
Microprocessor based supervisory panels have direct
communications with rectifiers for monitoring and single point
control. Communications is via RS-485 connection.
1.6.4 Sizing
Shunts are sized according to load requirements and limit the
initial capacity of the power system. Current flowing through ashunt must not exceed 80% of its nominal rating on a continuous
basis.
1.6.5 Features (panel dependent)
Typical Alarms
high/low voltage (1 & 2)
AC mains high/low/failure
distribution fuse/breaker
battery fuse/breaker
control fuse trip
rectifier failure alarm minor (one rectifier)
rectifier failure alarm major (>one rectifier)
converter failure alarm minor (one converter)
converter failure alarm major (>one converter)
auto-equalize
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high voltage shutdown
low voltage disconnect
CEMF (out)
CEMF (fail)
rectifier communication lost Power system minor alarm (logical or-ing of various
non critical alarms)
Power system major alarm (logical or-ing of various
critical alarms)
etc.
Controls
Control features are used to control power system devices such as
rectifiers and contactors.
Manual equalize - Allows the user to initiate all the rectifiersinto the equalize mode with one common switch. Used for
maintenance purposes with VRLA batteries, i.e. equalizing cell
voltages in a battery string.
Auto-equalize - Common in applications where flooded batteries
are deployed. This function initiates the rectifiers into the equalize
mode (boost charge) for a preprogrammed amount of time
(duration). It is used with vented batteries floated at low voltages
to prevent lead plate sulfation or where a quicker recharge of the
battery is required after a power failure. Auto-equalize is initiated
in one of three ways:
1. after power failure based on the voltage of the
battery;
arm voltage (indicating that a long outage has
occurred, rectifiers are off and the batteries have been
discharged) and
activate voltage (indicating the battery is nearing
full charge and the equalize mode is triggered,
rectifiers are on) The rectifiers will remain in the
equalize mode for the duration.
2. periodic equalize; where the batteries are
equalized at the interval programmed in days.
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3. manual initiation using the duration setting to
return the rectifiers to float after the duration has
expired.
HVSD/OVP - automatically shuts down all the rectifiers when anoutput DC over-voltage condition is detected.
LVD - controls 1 or more contactors that automatically open when
a low battery voltage condition is detected and close when the
battery voltage returns to normal. See LVD section.
LVD override control - switch for maintenance.
Battery temperature compensation is used to adjust the
rectifier output voltage to ensure that the battery float voltage is
correct for the operating temperature of the battery. See batterytemperature compensation section.
Charge current control is used to limit the flow of current into
the battery when recharging commences after a power failure. It is
programmed typically at C/5 (capacity of the battery/5). This
ensures that the battery is not charged too quickly, resulting in
excess heat generation and possible reduction in battery life. This
can be very important for VRLA type batteries.
Battery diagnostics
Battery capacity estimation - the capacity of the
battery at the current point in time expressed as a
percentage of the battery manufacturer's specification.
Battery state of health estimation - a continual
measurement of the batteries performance and state of
health. It is expressed as a percentage of the
manufacturer's specification. Alarm triggers can be set
to alarm when the battery state of health falls below
80%.
Battery run time prediction - the algorithm
predicts the number of hours that the battery will last,
before the battery will be fully discharged or a LVD
will occur, at the present discharge rate.
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Rectifier group single point adjustment - allows the
operator to setup and adjust all the rectifiers at one central
location.
CEMF (counter-electro-motive-force) controls 1 or morecontactors that automatically close when a high load voltage
condition is detected and open when the load voltage returns to
normal or is in a low voltage condition. See CEMF section.
1.6.6 Other Features
VAR (Visual alarm reset) - Is used to clear visual alarms.
Lamp test - Illuminates all lamps to verify operation.
Test - Combined with an external power supply, allows the userto test and calibrate the power system while in service (SD series
only).
ALCO (Alarm Cutoff) - Is provided to clear the relay contacts
and audible alarm associated with each alarm condition this allows
extended alarms to be canceled while alarm condition is being
resolved by local personnel.
1.6.7 Advanced features (SM series)
Remote access for control and monitoring,LocalRS232
Remotedial-in
Remotedialback
SNMP (Simple Network Management Protocol) alarm
reporting over network LAN or WAN
History and statistics
Programmable alarm relays
LCD display of alarms, parameters, etc.
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1.6.8 Argus Solutions
SM02
This microprocessor based supervisory panel combines a large
LCD display and keypad with optional modem card to provide
advanced power system monitoring and control features.
SM03
This microprocessor based supervisory panels provides many of
the features of the SM02 (without the remote access) in a smaller,
reduced cost package.
SD02 & 04
These discrete component supervisory panels provide
comprehensive metering, control and alarm functionality.
SD03 & 05
These discrete component supervisory panels provide basic
metering, control and alarm functionality.
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DCPSH04A
APower
Superviso
ryPanel
Charge(-)
Battery
- -+ +
Charge(+)
ShuntBar
V
Load
Circuit
Breaker
Distribution
LowVoltage
Load
Disconnect
GroundBar
T
ermination
Panel
Rectifier#2
Rectifier#1
Shunt
Figure 15 Basic System e/w Load Disconnect
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1.7 Low Voltage Disconnect Contactor
1.7.1 Description
The low voltage disconnect (LVD) contactor is used to disconnecteither the load from the system (load disconnect) or the battery
from the system (battery disconnect) when the battery has been
completely discharged in a long duration power outage. There are
three reasons for using a LVD:
1. Prevention of load damage due to an under voltage
condition. Some communications equipment may
be damaged when operated with an excessively
low input voltage or draw excessive current that
could trip a feeder circuit breaker.
2. Prevention of damage to the battery due to over-
discharge. Discharging a battery below the lowest
recommended end voltage (see battery section)
might permanently damage the battery.
3. Load shedding - to disconnect specific loads in a
prioritized sequence to maximize backup time for
more critical loads (ex. up to three individually
controlled contactors can be used with the SM02).
1.7.2 Connection
The low voltage disconnect can be connected in series with the
load (load disconnect) or in series with the battery (battery
disconnect).
The LVD is controlled by the supervisory panel.
1.7.3 Operation
The supervisory panel continuously monitors system voltage.
After an extended AC outage the batteries will discharge down to
the disconnect point. The disconnect point is typically set to the
lowest acceptable battery discharge voltage (end voltage). In a
Telecom application the end voltage typically used is 1.75 volts
per cell (21 VDC in a 24 VDC system and 42 VDC in a 48 VDC
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system). When the disconnect point is reached the load or battery
will be disconnected from the system.
The load or battery will remain disconnected until AC outage is
over. On return of AC a load disconnect and a battery disconnectsystem function differently (see below).
Load disconnect The rectifiers will pre-charge the
batteries for a few minutes until the battery voltage
reaches the reconnect point (typically 25 VDC or 50
VDC). When the reconnect point is reached, the load
is connected on line at this voltage level.
Battery disconnect Immediately after the
reapplication of AC, the load will see a slowly
increasing DC voltage (0-50 VDC over an 8-10 secondperiod, due to the soft start feature in the rectifier). At
the 50 VDC point the battery will be connected on
line.
A wide voltage differential between the in and out settings (i.e.
out 42V, in 50 V in a 48V system) prevents the contactor from
oscillation because the battery voltage will naturally rise after the
load has been removed from it and reconnection without the
rectifiers on-line would not be desirable.
Load vs. battery disconnect - In some cases battery, insteadof load, disconnection is desirable. The advantage of this system is
that an accidental operation of the LVD will not disrupt power to
the load unless the AC is also off. The disadvantage of the battery
disconnect that the load will see a slowly increasing input voltage
0-50V as the rectifiers perform the soft start this may cause
damage to the load or inadvertent fuse or circuit breaker tripping.
Careful evaluation of the load specifications is required to verify
that this method of disconnection will not affect the load.
1.7.4 Sizing
Low voltage disconnect contactors are available in various sizes.
The rating of the LVD indicates its maximum current
carrying/switching ability.
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1.7.5 Features and selection criteria
Able to switch high current loads reliably.
1.7.6 Argus solutions
200A, 800A and 1200A available.
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1.8 CEMF Cell
1.8.1 Description
The CEMF cell is a diode array that is connected in series between
the power system and the loads. A contactor is installed in parallel
with the diodes. The diodes are used to reduce the voltage applied
to the loads by a fixed value during normal operation or when the
batteries are equalize charged. The contactor automatically
bypasses the CEMF when the system is on battery to maintain
maximum backup time for the loads.
CEMF cells are rarely used in modern telecommunications systems
as they introduce step voltage changes to the load voltage when
switched in or out that may affect load operation. It alsointroduces another single point of failure.
It was historically used with both step by step and crossbar
telephone switching offices.
A common alternative to the CEMF cell is to remove one battery
cell from the string and lower the rectifier output voltage to reduce
the operating voltage of the system; for example: 23 cell system
with VRLA batteries 23 x 2.25 V per cell = 51.75V.
1.8.2 Connection
The CEMF cell is connected in series with the load.
The supervisory panel controls the CEMF cell.
1.8.3 Operation
The supervisory panel continuously monitors system voltage.
There are two scenarios for CEMF use:
1. CEMF cell normally IN to reduce load voltagein the float and equalize mode. The normal system
float voltage is above the IN setting of the CEMF
cell the CEMF contactor is opened so that current
flow is through the CEMF diodes and the load
voltage is reduced. When a power failure occurs
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and the voltage drops the contactor is closed to
increase the voltage at the load to ensure
maximum back up time. When power is restored
the contactor will open when the voltage returns to
normal diverting current through the diodes andreducing the load voltage.
2. CEMF cell normally OUT to reduce load
voltage in the equalize mode only. In this system
the IN setting of the CEMF is set higher than the
float voltage and the contactor normally bypasses
the diodes. When equalize mode is selected the
voltage rises above the IN setting and the
contactor is opened, current flows through the
diodes and the voltage at the load is reduced.
When the rectifiers are returned to float mode the
voltage drops below the out setting and the diodes
are again bypassed by the contactor and the load
voltage returned to normal.
1.8.4 Sizing
Voltage drop required.
Current required by load.
1.8.5 Features
Monitoring of cell status.
Alarm on failure of cell.
1.8.6 Argus solutions
Cells and contactors in various sizes are available.
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1.9 Battery Temperature Compensation
1.9.1 Background
Battery performance and life expectancy is directly related to the
battery ambient temperature. The optimum temperature fo r battery
operation is 25 deg. C (77 deg. F). Above this temperature, battery
life is compromised and below this temperature battery
performance is reduced.
VRLA batteries have a negative characteristic called thermal
runaway. This occurs when the internal temperature of the battery
rises due to overcharge, high ambient temperature or internal fault.
The rise in internal ambient temperature causes the battery to draw
more float current which in turn elevates the internal batterytemperature. This cycle continues until the battery fails. The
failure of the battery may be quite dramatic.
1.9.2 Description
Temperature compensation is the process of automatically
reducing the charge voltage applied to the battery at high
temperature (to increase life and prevent thermal runaway) and
increasing the voltage applied to the battery at low temperatures
(to increase the battery capacity and to ensure correct charging of
the battery).
1.9.3 Connection
Connection is as follows:
1. Traditional rectifiers with non-SM supervisory
panels use a temperature compensator module
(TCM) connected in series with the rectifier
remote sense line input and the battery that
requires temperature compensation.
2. Smaller rectifier systems (i.e. RSM 48/7.5 and
48/10) have this feature built in; there are no
additional sense/battery connections required.
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3. RSM/Pathfinder rectifiers with SM supervisory
panels, require no additional sense/battery
connections.
Temperature probes (1-4) are mounted directly to either the samebattery negative termination post or to multiple negative posts to
monitor multiple battery strings.
1.9.4 Operation
Operation is as follows:
1. Non-SM based systems, the TCM adjusts the
output sense voltage to the rectifiers based on
ambient temperature detected at the battery. The
rectifiers will adjust their output voltage accordingto the sense voltage level detected at their remote
sense input. (See Table H & I)
2. Small systems adjust the rectifier output voltage
based on ambient temperature detected at the
battery. (See Table H & I).
3. SM based systems, the SM will automatically
adjust the rectifier float voltage based on the
battery temperature detected. It will repeat this
process at the interval programmed. The rectifierRS 485 communications link is used for this
purpose.
At 25 deg. C (77 deg. F) no voltage compensation will occur.
At temperatures below 25 deg. C, the rectifier will increase its
output at a fixed rate(ex. -2.5 mV per cell per deg. C change from
25 deg C reference).
At temperatures above 25 deg. C, the rectifier will decrease its
output at a fixed rate(ex. -2.5 mV per cell per deg. C change from
25 deg C reference).
To prevent excessive voltage from damaging the load, the battery
or causing a high voltage alarm condition; the battery voltage
maximum compensation may be limited (lower break point) at a
fixed temperature (ex. 0 deg C).
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To prevent excessively low voltage from undercharging the battery
or discharging the battery; the battery voltage maximum
compensation may be limited (upper break point) at a fixed
temperature (ex. 50 deg C).
1.9.5 Sizing
Temperature compensation slope
Match the compensation slope to the recommendations of the
battery manufacturer. Default to conservative 2.5 or 3.5 mV if this
information is unavailable.
Breakpoint
The selection of the breakpoint is critical. This determines the
maximum and minimum voltage that will be applied to the batteryand the load. Match the breakpoints to the recommendations of the
battery manufacture. Carefully select the lower breakpoint as this
determines the maximum voltage applied to the load.
Check load acceptable input voltage operating window; for example: a 4.5 mV
slope with a -40 deg C breakpoint in a 48V system will result in 61 volts applied
to the load in a low temperature condition.
1.9.6 Features and selection criteria Fail detection circuitry.
Redundant temperature probes for increased safety.
Automatic turn off if a fault is detected and an alarm
extended.
1.9.7 Argus solutions
TCM
This external temperature compensation module can be either
relay rack or surface mounted. It will operate with RST (6 max.)and the larger remote sense input equipped RSM rectifiers (6
shelves max.). It will also operate with non-Argus remote sense
input equipped rectifiers.
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TCM Internal
This feature is available built into Argus non-sense line equipped
rectifiers, including RSM 48/7.5, RSM 24/15 and RSM 48/10.
SM System Controllers
Control larger RSM rectifiers and pathfinder rectifiers through the
communications link.
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Table H 24 Volt Temperature Compensated Battery Float Voltage
These tables are provided as a guideline only. If battery
temperature falls between values on the above scale,
estimate the voltage setting based on the closest numerical
values.
* Refers to ambient temperature at the battery terminal
posts.
** BFV refers to Battery Float Voltage Check battery
manufacturer's recommended settings.
*** Refers to Nominal Battery Temperature. This is theoptimum temperature for battery operation. No compensation
occurs at this temperature (use as a reference point).
TEMPERATURE* BFV**=27.00V BFV**=27.25V BFV**=27.50V
C F @25C(77F) @25C(77F) @25C(77F)2.5mV(volts)
3.5mV(volts)
4.5mV(volts)
2.5mV(volts)
3.5mV(volts)
4.5mV(volts)
2.5mV(volts)
3.5mV(volts)
4.5mV(volts)
-40 -40 28.95 29.73 30.51 29.20 29.98 30.76 29.45 30.23 31.01
-35 -31 28.80 29.52 30.24 29.05 29.77 30.49 29.30 30.02 30.74
-30 -22 28.65 29.31 29.97 28.90 29.56 30.22 29.15 29.81 30.47
-25 -13 28.50 29.10 29.70 28.75 29.35 29.95 29.00 29.60 30.20
-20 -4 28.35 28.89 29.43 28.60 29.14 29.68 28.85 29.39 29.93
-15 5 28.20 28.68 29.16 28.45 28.93 29.41 28.70 29.18 29.66
-10 14 28.05 28.47 28.89 28.30 28.72 29.14 28.55 28.97 29.39
-5 23 27.90 28.26 28.62 28.15 28.51 28.87 28.40 28.76 29.12
0 32 27.75 28.05 28.35 28.00 28.30 28.60 28.25 28.55 28.85
5 41 27.60 27.84 28.08 28.60 28.09 28.33 28.10 28.34 28.58
10 50 27.45 27.63 27.81 27.70 27.88 28.06 27.95 28.13 28.31
15 59 27.30 27.42 27.54 27.55 27.67 27.79 27.80 27.92 28.04
20 68 27.15 27.21 27.27 27.40 27.46 27.52 27.65 27.71 27.7725*** 77 27 27 27 27.25 27.25 27.25 27.5 27.5 27.5
30 86 26.85 26.79 26.73 27.10 27.04 26.98 27.35 27.29 27.23
35 95 26.70 26.58 26.46 26.95 26.83 26.71 27.20 27.08 26.96
40 104 26.55 26.37 26.19 26.80 26.62 26.44 27.05 26.87 26.69
45 113 26.40 26.16 25.92 26.65 26.41 26.17 26.90 26.66 26.42
50 122 26.25 25.95 25.65 26.50 26.20 25.90 26.75 26.45 26.15
55 131 26.10 25.74 25.38 26.35 25.99 25.63 26.60 26.24 25.88
60 140 25.95 25.53 25.11 26.20 25.78 25.36 26.45 26.03 25.61
65 149 25.80 25.32 24.84 26.05 25.57 25.09 26.30 25.82 25.34
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TEMPERATURE* BFV**=54.00V BFV**=54.50V BFV**=55.00V
C F @25C(77F) @25C(77F) @25C(77F)
2.5mV
(volts)
3.5mV
(volts)
4.5mV
(volts)
2.5mV
(volts)
3.5mV
(volts)
4.5mV
(volts)
2.5mV
(volts)
3.5mV
(volts)
4.5mV
(volts)-40 -40 57.90 59.46 61.02 58.40 59.96 61.52 58.90 60.46 62.02
-35 -31 57.60 59.04 60.48 58.10 59.54 60.98 58.60 60.04 61.48
-30 -22 57.30 58.62 59.94 57.80 59.12 60.44 58.30 59.62 60.94
-25 -13 57.00 58.20 59.40 57.50 58.70 59.90 58.00 59.20 60.40
-20 -4 56.70 57.78 58.86 57.20 58.28 59.36 57.70 58.78 59.86
-15 5 56.40 57.36 58.32 56.90 57.86 58.82 57.40 58.36 59.32
-10 14 56.10 56.94 57.78 56.60 57.44 58.28 57.10 57.94 58.78
-5 23 55.80 56.52 57.24 56.30 57.02 57.74 56.80 57.52 58.24
0 32 55.50 56.10 56.70 56.00 56.60 57.20 56.50 57.10 57.70
5 41 55.20 55.68 56.16 55.70 56.18 56.66 56.20 56.68 57.16
10 50 54.90 55.26 55.62 55.40 55.76 56.12 55.90 56.26 56.62
15 59 54.60 54.84 55.08 55.10 55.34 55.58 55.60 55.84 56.08
20 68 54.30 54.42 54.54 54.80 54.92 55.04 55.30 55.42 55.54
25*** 77 54 54 54 54.5 54.5 54.5 55 55 55
30 86 53.70 53.58 53.46 54.20 54.08 53.96 54.70 54.58 54.4635 95 53.40 53.16 52.92 53.90 53.66 53.42 54.40 54.16 53.92
40 104 53.10 52.74 52.38 53.60 53.24 52.88 54.10 53.74 53.38
45 113 52.80 52.32 51.84 53.30 52.82 52.34 53.80 53.32 52.84
50 122 52.50 51.90 51.30 53.00 52.40 51.80 53.50 52.90 52.30
55 131 52.20 51.48 50.76 52.70 51.98 51.26 53.20 52.48 51.76
60 140 51.90 51.06 50.22 52.40 51.56 50.72 52.90 52.06 51.22
65 149 51.60 50.64 49.68 52.10 51.14 50.18 52.60 51.64 50.68
Table I 48 Volt Temperature Compensated Battery Float Voltage
These tables are provided as a guideline only. If battery
temperature falls between values on the above scale,
estimate the voltage setting based on the closest numericalvalues.
* Refers to ambient temperature at the battery terminal
posts.
** BFV refers to Battery Float Voltage Check battery
manufacturer's recommended settings.
*** Refers to Nominal Battery Temperature. This is the
optimum temperature for battery operation. No compensation
occurs at this temperature (use as a reference point).
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1.10 DC - DC Converter System
1.10.1 Description
ADC-DC converter system takes a DC input voltage and converts
it to the same or a different output voltage. The converter system
is utilized for any of the following reasons:
Provide different voltage levels; i.e. -48V to +24V
conversion.
Ground swapping; i.e. +24V to -24V.
Galvanic or ground isolation; i.e. +24V to +24V,
floating ground.
Voltage regulation for equipment, with a tight input
voltage operating window, operated from a batterysystem.
1.10.2 Connection
The DC-DC converter system is connected in series between the
main DC power system and the load.
A converter system consists of single or multiple parallel DC-DC
converters and may incorporate many of the features found in the
main DC power system including distribution, common ground bus
and supervisory.
DC-DC Converters should have dedicated fuse/circuit breaker
positions on the main DC power system for protection and
isolation.
If converters are located in the same relay rack as the main DC power system,
direct connection to the busswork on the input is permissible.
1.10.3 Operation
Since the converter system does not have a battery connected to its
output adjustment of the output voltage is less critical and LVDs,
temp comp, etc. are not required. The output voltage of the
converters is adjusted to match the requirements of the load and to
ensure correct load sharing between parallel converters.
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1.10.4 Sizing
The converter system should be sized to adequately supply the
load under all conditions.
There should be substantial converter redundancy built in to the
converter system to account for fuse clearing and circuit breaker
tripping. If this redundancy is not built in, the converters may not
be able to clear a fault and current limiting will take effect and the
output of the converter system may be affected.
Always use fast acting fuses in converter system distribution
circuits and do not use excessively high fuse ratings.
DC - DC converter systems can add substantial load to the main
power system, allowances should be made for this when sizing themain system.
1.10.5 Features and selection criteria
Standardization of unit for ease of maintenance.
Modularvs. monolithic configuration. Modular converters allow
for easy replacement and expansion. Supervisory and distribution
may be incorporated into a modular converter system.
High efficiency
Physical constraints in most new facilities demand compact
designs. Lightweight converters combined with space saving
designs help reduce installation and shipping costs.
Balanced load sharing should be achieved between converters.
Argus converters accomplish this with output slope regulation it is
adjustable on CS units to allow load sharing with other types of
converters. CSM units utilize a fixed slope set at 1%.
Current limiting should be provided, Argus units are factory set
at 105% of rated output, to provide protection in a overload
condition.
High voltage shutdown to switch converter off in case of high
output voltage condition, preventing damage to the load.
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Soft-start to gradually bring the converter on line from zero load
to the load requirement, eliminating high inrush currents surges.
The feeder breaker and feeder size requirements are decreased,
reducing the installation costs of the converter.
Alarms provide indication of converter failure and should be of
fail safe design. Local indication plus remote contacts are
required.
1.10.6 Argus solutions
The converters are available in various input and output
configurations including 24V and 48V input; 12V, 24V and 48V
output. With current ratings from 5 Amps to 40 Amps. Specialized
converters with 130 V /100VA output are available for powering
FITL (fiber in the loop) applications.
CS series monolithic
Traditional converter packaging - each individual converter is a
stand-alone unit.
CSM series modular
Modular construction - three or four individual modules are
housed in a hardwired cabinet. Each converter is easily removed
for maintenance purposes.
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1.11 DC Power System Integration
1.11.1 Description
The DC power system integrates and connects all the components
mentioned in previous sections.
1.11.2 Connection
Intersystem
In a typical power system there should be provisions for easy
termination of intersystem cables.
Buswork should be copper; cables should meet electrical code
requirements and utilize quality compression lugs.
Lock washers or Belleville washers should be used on
electrical/mechanical connections to ensure integrity under
different temperature conditions, (high/low load). All
terminations should have provisions for connection of standard 2
hole lugs (typically 3/8 hole, 1 spacing).
Argus power systems include all these features and utilize tin-
plated copper buswork to eliminate oxidization.
The intersystem wiring and buswork determines the ultimate
capacity of the power system.
The vertical discharge riser busis used to connect the distribution
panels to the charge/discharge termination in a traditional power
system.
Battery
Separate charge/discharge configuration - This method of
connecting the battery was utilized in the past to reduce therectifier ripple voltage at the load. The vented battery was used as
a filter. With the advent of low ripple rectifiers this method of
battery termination is generally not required.
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Two busses are provided for both negative and
positive termination. Rectifier negative output cables
are terminated to one bus (- charge bus) and a cable is
run to the neg. battery terminal from this bus. A
second cable is connected from the negative batteryterminal back to the second bus (- discharge bus) and
the neg. load feed is also connected to this bus. This is
repeated for the positive side also. This method has
the added benefit of better load regulation and a
slightly reduced voltage level seen at the load.
Common charge/discharge configuration - This is the
current standard method of terminating the battery cables. One bus
is provided for the negative connections and one for the positive
connections. Rectifier output cables, battery cables and the load
feed are connected directly to these bus.
1.11.3 Sizing
Power systems should be oversized by a factor of 20-25 %. To
calculate the power system size multiple the maximum anticipated
load by a factor of 1.2 - 1.25. This over-sizing factor will ensure
that the shunt is not overloaded and that adequate capacity is
available in the buswork and cables to accommodate both the load
and battery recharge current.
1.11.4 Features and selection criteria
Access requirements front only or front and rear.
Open relay rack or box bay.
Size restrictions.
1.11.5 Argus solutions
Traditional power systems
Traditional power system packaging is in either open
relay rack or box frame. Choices of 19 and 23 rack widths.
Access is required from both the front and the rear.
Up to 10 000 amps.
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Front access power system
With less space available in many of the new
communications facilities front access power systems
have become popular. Argus front access power
systems require some rear access upon initial
installation. After initial installation the power system
may be relocated closer to the wall, with allowances
for ventilation of course.
All maintenance and circuit termination may be
performed from the front.
Up to 1200 amps.
Miscellaneous power systems
Variations on the traditional packaging techniques
include mounting the equipment in portable cabinets
on castors or utilizing wall mount brackets.
There would be obvious limitations for either of these
methods, but they do provide solutions for specific
applications and ensure flexibility of Argus
equipment.
Ultra compact power systems
RSM 48/10 and 24/18
These fully self contained power systems (except forbattery), may be configured in various packages
combining up to five rectifiers modules, distribution,
supervisory, temperature compensation and low
voltage disconnect. Packages are 17 wide, 12 deep
and 5.25 high.
RSM 48/7.5 and 24/15
These fully self contained power systems (except for
battery), may be configured in various packages
combining two or three rectifiers modules,
distribution, supervisory, temperature compensation
and low voltage disconnect. Packages are 17 wide, 12
deep and of various heights from 3.5 to 7.
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US Series
Combine battery, rectifier and supervisory in a single
package to provide either 5 Amps at 48V or 8 Amps at
24V backup time is approx. 2 hr. with internal battery.
Extra extended backup battery cabinets may be added.
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1.12 Inverters/UPS
1.12.1 Description
The inverter or Uninterruptable Power System (UPS) is utilized to
supply AC voltage to loads such as computers in the Telecom
environment. These systems are often connected to the DC power
system.
There are a various options for providing uninterruptable AC for
your loads including:
1. On-line Inverter- DC input, AC output.
Connected directly to DC main power system.
Has a standby AC line available (optional).
2. Off-line Inverter- AC input, AC output. Has a
standby DC line connection available. The DC
standby line is connected to the DC power system.
3. Double conversion UPS - Dedicated rectifier,
battery and inverter, Traditional concept.
4. Line Interactive UPS - Ferroresonant
transformer with small battery charger, battery,
inverter and intelligent control. Normal operation
is through a Ferro circuit. Ferro provides filtering
and some energy storage. Inverter is switched on-
line when required by the control. Battery charger
charges the batteries only
Type Advantages Disadvantages1 -simple -inefficient
-reliable -heavy DC system loading and inrush
-utilize main DC battery
-may be paralleled for redundancy
2 -compact
-reliable
-efficient
-utilize main DC power system
battery
3 -rugged -inefficient
-good energy storage -large, heavy
4 -compact -internal battery
-easy to install
-efficient
Table J Inverter & UPS comparison
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Both inverter system designs (type1 &2) will be discussed in this
section since they connect to and affect the operation and design
of a DC power system.
1.12.2 Connection
On-line inverter- The inverter is connected in series with the
DC power system and the connected loads. A connection is made
to a standby AC source for redundancy.
Off-line inverter- The inverter is connected in series with the
AC source and the connected loads. A connection is made to the
DC power system for redundancy.
1.12.3 Operation
On-line inverter- In normal operation the inverter draws
current from the DC power system and coverts this to AC to power
the connected load. If the inverter fails or the DC supply is
interrupted there inverter automatically transfers to a connected
AC stand-by source.
Off-line inverter- In normal operation the connected load is
powered from the AC source through the inverter. Upon loss of the
AC source the load is transferred to the inverter. There may be a
ferroresonant circuit to provide energy storage while the load is
transferred to the inverter.
1.12.4 Sizing
Inverters/UPS should be sized such that the continuous load (VA)
does not exceed 75% of the inverter rating (VA).
Inverters often supply computers that incorporate switch mode
power supplies and other non-linear loads. If loads with high crest
factors (i.e. > 2.5) are connected, the UPS rating may have to be
de-rated. See the manufacturer for further information.
Neutral current should also be monitored after UPS installation to
ensure it is within the limits of the conductor. Unbalanced loads
and low power factor often generate substantial neutral currents. It
is possible for these currents to overload the neutral conductor
since there is no protection for the neutral conductor.
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If the on-line inverter is utilized both the DC power system battery
and the rectifiers will have to be oversized to supply the additional
load imposed by the inverter.
If the off-line inverter is utilized only the DC power systembattery need be oversized since the inverter is normally operating
from the AC source and will only draw current from the DC power
system when there is a failure of the AC source.
Inverters may also draw substantial inrush current on start-up;
breaker/ fuse curve coordination may be required.
1.12.5 Features and selection criteria
Many UPS systems combine the battery in the UPS. These
batteries rarely see proper maintenance and tend to be forgotten.These batteries never achieve proper ventilation due to the often-
cramped compartments that they occupy. Many UPS systems
utilize high DC voltage battery systems. Each of these many small
cells is the potential weak link in the chain. Powering your AC
loads from an inverter connected to the high quality, well-
maintained DC main system battery, reduces many of these
problems.
1.12.6 Argus solutions
We will provide assistance in helping you chooses the right ACsolution and integrating it into the DC power system.
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CHAPTER
Power System Sizing and Ordering
2.1 Calculations2.1.1 Step 1 System load analysis
To determine your DC power system requirements evaluate your
loads and the backup period required.
Review all system components and determine:
(A) Loads that require voltage conversion.
(B) Loads that require battery backup. Dont forget AC loads i.e.
computers that require backup. Determine the individual loadcurrents for the different load voltages required. The voltage with
the highest load is generally chosen as the main system voltage.
(C) Battery details:
Main system Voltage______ current_______________
Secondary system 1 Voltage______ current_______________
Secondary system 2 Voltage______ current_______________
AC Secondary system Voltage______ Watts______ P.F.______
Redundancy N+______
Batterydischarge time hrs.______
Battery
recharge time hrs.______
Battery end Voltage______
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Warning:Check and record the polarity requirement of your connected loads.
Which polarity is connected to the common ground? This is vital information
to ensure functionality of the DC system and load.
2.1.2 Step 2 Converters
Determine the quantity and type of converters to meet each of the
secondary DC voltage requirements (if applicable).
Add redundant converters as required.
Determine the total load that the converters will have
on the main DC system. Use formula (i).
Refer to converter sizing section for extra details.
2.1.3 Step 3 Inverters
Determine the size and type of inverter to meet the secondary AC
voltage requirements (if applicable).
Determine the load that the inverter will have on the
main DC system. Use formula (ii).
Refer to inverter sizing section for extra details.
2.1.4 Step 4 Total system load
Determine the total system load using formula (iii).
2.1.5 Step 5 Total rectifier capacity
Determine total rectifier capacity. Total rectifier capacity includes
capacity to supply the load and recharge the discharged battery in
the spe