Tuning Up DC Motors and Tuning Up DC Motors and Generators for Commutation Generators for Commutation
and Performanceand Performance
Rich HallRich Hall-- National Electrical CarbonNational Electrical CarbonWestern Mining Electrical Western Mining Electrical
AssociationAssociationJune 8, 2007, Billings MontanaJune 8, 2007, Billings Montana
Sometimes your machine may not Sometimes your machine may not run just like it shouldrun just like it should
That is an indication That is an indication that it might be time for that it might be time for
a a ““tunetune--upup””
Spark PlugsSpark Plugs Breaker PointsBreaker Points
CondenserCondenser RotorRotor
Distributor CapDistributor Cap
Spark Plug WiresSpark Plug Wires
But even with all new But even with all new parts, the machine may parts, the machine may
not run right!not run right!
UnlessUnless you make the you make the ““tunetune--upup”” adjustments!!adjustments!!
That That includes includes setting setting
the the spark spark plug plug
gap, the gap, the ignition ignition
point point gap or gap or dwell, dwell,
and the and the ignition ignition timingtiming
DC machines need tuneDC machines need tune--up adjustments to run up adjustments to run
properly, too!properly, too!
DC machines tuneDC machines tune--up up adjustments to run adjustments to run
properly, too!properly, too!
These adjustments include These adjustments include setting neutral and adjusting setting neutral and adjusting
the commutating field the commutating field ((interpoleinterpole) strength.) strength.
Electrical Neutral MethodsElectrical Neutral Methods
•• Black BandBlack Band•• Kick Inductive NeutralKick Inductive Neutral•• AC NeutralAC Neutral•• Speed ReversibilitySpeed Reversibility•• DC Current In ArmatureDC Current In Armature•• Pencil Volt NeutralPencil Volt Neutral•• Tram Markings/Mechanical MethodTram Markings/Mechanical Method
Electrical Neutral MethodsElectrical Neutral Methods
•• Also see Also see ““Setting Neutral by AC Setting Neutral by AC Curve Method for DC MachinesCurve Method for DC Machines”” by by Rick Scherer, Flanders, WMEA, Rick Scherer, Flanders, WMEA, November 2005 (WMEA Web Site, November 2005 (WMEA Web Site, www.wmea.netwww.wmea.net))
Electrical NeutralElectrical NeutralSetting Neutral on an electric motor or Setting Neutral on an electric motor or generator is similar to setting timing generator is similar to setting timing on an engine.on an engine.
The brushes are basically electricallyThe brushes are basically electricallypositioned on the commutator betweenpositioned on the commutator betweenthe areas of main pole flux so commutationthe areas of main pole flux so commutationcan take place at the right time and in ancan take place at the right time and in anarea where no electrical work ( torque ) isarea where no electrical work ( torque ) isbeing produced.being produced.
NeutralNeutralUsually it is best to look for Usually it is best to look for ““factory markfactory mark””and set brush yoke to this position after and set brush yoke to this position after reassembling the motor.reassembling the motor.
The OEM has the benefit of knowing the The OEM has the benefit of knowing the electrical design and how previous motors electrical design and how previous motors were adjusted. They also have more test were adjusted. They also have more test equipment than the typical motor repair equipment than the typical motor repair shop, for running the motor under load at shop, for running the motor under load at various speeds.various speeds.
Factory Neutral MarkFactory Neutral Mark
Shifted off the factory markShifted off the factory mark
If armature has been changed, or brush If armature has been changed, or brush arms moved on yoke, correct setting may arms moved on yoke, correct setting may not be on not be on ““factory markfactory mark””..
Methods For AdjustingMethods For Adjusting
DC Machines DC Machines
AdjustmentsAdjustments
1. Brush Position1. Brush Position
2. Commutating Field Strength2. Commutating Field Strength
Factory MethodFactory Method
Field MethodField Method
Excavator MG SetExcavator MG Set
Black BandBlack Band
A test where you intentionally misadjustA test where you intentionally misadjustthe magnetic strength of the magnetic strength of interpoleinterpole( ( commcomm field ) by adding or subtractingfield ) by adding or subtractingcurrent to find the limits of sparking.current to find the limits of sparking.
Also use this data to adjust neutral settingAlso use this data to adjust neutral settingand and interpoleinterpole shimming for good shimming for good commutation over the range of speedscommutation over the range of speedsand loads.and loads.
Black BandBlack Band
•• ProcedureProcedure–– Connect buckConnect buck--boost power supply (low boost power supply (low
Voltage high current) in parallel with the Voltage high current) in parallel with the commutating fieldscommutating fields
–– Operate the machine at various loads (0% to Operate the machine at various loads (0% to 150%), apply buck150%), apply buck--boost current and observe boost current and observe sparkingsparking
–– Adjust brush rigging position or shim Adjust brush rigging position or shim commutating poles as shown from recorded commutating poles as shown from recorded and plotted dataand plotted data
DC Machine and LoadDC Machine and Load
ARMARM LoadLoad
CommCommFieldField
FieldField
Black Band Set UpBlack Band Set Up
ARMARM LoadLoad
CommCommFieldField
FieldField
Buck Boost GenBuck Boost Gen
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
5050 100100 150150
No LoadNo Load
ARMARM LoadLoad
CommCommFieldField
FieldField
Buck Boost GenBuck Boost Gen
IIA A = 0= 0
No Load BoostNo Load Boost
ARMARM LoadLoad
CommCommFieldField
FieldField
Buck Boost GenBuck Boost Gen
IIA A = 0= 0
ii
ii
No Load BuckNo Load Buck
ARMARM LoadLoad
CommCommFieldField
FieldField
Buck Boost GenBuck Boost Gen
IIA A = 0= 0
ii
ii
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
Band at No LoadBand at No Load
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
XX No Load Band No Load Band Center on Buck Center on Buck Side (Strong)Side (Strong) Corrective action Corrective action –– shift shift
brush rigging with rotation brush rigging with rotation (motor) or against rotation (motor) or against rotation (generator)(generator)
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
XXNo Load Band No Load Band Center on Boost Center on Boost Side (Weak)Side (Weak)
Corrective action Corrective action –– shift shift brush rigging against brush rigging against rotation (motor) or with rotation (motor) or with rotation (generator)rotation (generator)
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150XX
No Load Band No Load Band CenteredCentered
OK OK –– Proceed with load Proceed with load testtest
Loaded BoostLoaded Boost
ARMARM LoadLoad
CommCommFieldField
FieldField
Buck Boost GenBuck Boost Gen
IIA A
ii
IIAA + i+ i
IIAA
Loaded BuckLoaded Buck
ARMARM LoadLoad
CommCommFieldField
FieldField
Buck Boost GenBuck Boost Gen
IIA A
ii
IIAA -- ii
IIAA
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
xx
xx
Take data with machine Take data with machine loaded, beginning at 50% loaded, beginning at 50% loadload
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
xx
xx
xx
xx
xx
xx
Band CenterBand Center
Band Center on Boost Side Band Center on Boost Side (Weak)(Weak)
Corrective Action Corrective Action –– Remove Remove nonmagnetic shims, add magnetic nonmagnetic shims, add magnetic shimsshims
No sparking in black area, sparking outside black area
Buck Boost CurveBuck Boost Curve
xxLoad Amps (%)Load Amps (%)
Corrective Action Corrective Action –– Remove Remove magnetic shims, add non magnetic magnetic shims, add non magnetic shimsshims
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
XX
XX
5050 100100 150150
xx
xx
xx
xx
xx
Band CenterBand Center
Band Center on Band Center on Buck Side Buck Side (Strong)(Strong)
Sparking with no buck or boostSparking with no buck or boost
Buc
k A
mps
Buc
k A
mps
Boo
st A
mps
Boo
st A
mps
00
Load Amps (%)Load Amps (%)
Buck Boost CurveBuck Boost Curve
XX
XX
5050 100100 150150
xx
xx
xx
xx
xx
xx
Near perfect black band Near perfect black band ––centered at centered at all loadsall loads
Black BandBlack Band
• Advantages– Adjusts both neutral and commutating
pole shimming– Tests over complete load range or can
adjust for specific load and speed
Black BandBlack Band• Advantages
– Adjusts both neutral and commutating pole shimming– Tests over complete load range or can adjust for specific load
and speed
• Disadvantages– Requires field supply and armature
supply capable of 1.5 to 2 times rated armature Amperes
– Need control of loading, voltages, speeds,etc.
– Need buck-boost power supply (low voltage and high current)
Kick Inductive NeutralKick Inductive Neutral
•• ProcedureProcedure–– Connect an analog DC voltmeter Connect an analog DC voltmeter
between shunts of brushes on adjacent between shunts of brushes on adjacent arms (brushes need to be well seated)arms (brushes need to be well seated)
–– Repeatedly apply and remove DC Repeatedly apply and remove DC voltage from shunt fieldsvoltage from shunt fields
–– Shift brush yoke for minimum deflection Shift brush yoke for minimum deflection (kick) if meter needle (kick) if meter needle
++
--
SwitchSwitch
A1A1
A2A2
AnalogAnalog DC VoltmeterDC Voltmeter00
++--
Shift brushes for minimum needle deflectionShift brushes for minimum needle deflection
Shunt Shunt FieldField
Kick Inductive NeutralKick Inductive Neutral
•• AdvantagesAdvantages–– Static TestStatic Test–– Little equipment requiredLittle equipment required
Kick Inductive NeutralKick Inductive Neutral•• AdvantagesAdvantages
–– Static TestStatic Test–– Little equipment requiredLittle equipment required
•• DisadvantagesDisadvantages–– Best compromise neutral for reversible Best compromise neutral for reversible
machines. Best for motors that could machines. Best for motors that could run either rotation.run either rotation.
AC NeutralAC Neutral•• ProcedureProcedure–– Connect an AC voltmeter between the Connect an AC voltmeter between the
shunts of brushes of adjacent arms shunts of brushes of adjacent arms (brushes well seated)(brushes well seated)
–– Apply 120 Volt AC to the shunt fields, Apply 120 Volt AC to the shunt fields, connected where the DC field supply connected where the DC field supply would normally connectwould normally connect
–– Shift the brush yoke to get minimum AC Shift the brush yoke to get minimum AC voltage on the voltmetervoltage on the voltmeter
A1A1
A2A2
Analog or Digital AC VoltmeterAnalog or Digital AC Voltmeter00
120 120 VoltVoltACAC
Shift brushes for minimum AC VoltageShift brushes for minimum AC Voltage
Shunt Shunt FieldField
AC NeutralAC Neutral
•• AdvantagesAdvantages–– Static testStatic test–– Little equipment requiredLittle equipment required
AC NeutralAC Neutral•• AdvantagesAdvantages
–– Static testStatic test–– Little equipment requiredLittle equipment required
•• DisadvantagesDisadvantages–– Best compromise neutral for reversible Best compromise neutral for reversible
machines. Not as good for single rotation machines. Not as good for single rotation machines. Really only gets you in the ball park machines. Really only gets you in the ball park for large machines with pole face windings.for large machines with pole face windings.
Speed ReversibilitySpeed Reversibility
•• ProcedureProcedure–– Apply known DC field Apply known DC field currentcurrent–– Apply known DC armature Apply known DC armature voltagevoltage–– Measure rotational speed (RPM)Measure rotational speed (RPM)–– Keep field Keep field currentcurrent the same, but reverse the the same, but reverse the
armature armature voltagevoltage polarity and measure RPMpolarity and measure RPM–– Shift brush yoke as required to equalize speed Shift brush yoke as required to equalize speed
in both directions within 1%in both directions within 1%
A1A1
A2A2
DC VoltmeterDC Voltmeter
DC DC Power Power SupplySupply
DC DC Field Field
SupplySupply
00
DC AmmeterDC Ammeter
VVAA
IIff
RPMRPM
0
Set ISet Iff, Set V, Set VA, Measure RPM. Reverse Polarity of VA. Measure RPM. Shift until RPMs agee within 1%.
Speed ReversibilitySpeed Reversibility
•• AdvantagesAdvantages–– Good technique for reversible machinesGood technique for reversible machines–– Armature supply does not need to supply very Armature supply does not need to supply very
much currentmuch current
Speed ReversibilitySpeed Reversibility•• AdvantagesAdvantages
–– Good technique for reversible machinesGood technique for reversible machines–– Armature supply does not need to supply very much currentArmature supply does not need to supply very much current
•• DisadvantagesDisadvantages–– Requires both field and armature DC supplyRequires both field and armature DC supply–– Machine must be uncoupled or able to rotate Machine must be uncoupled or able to rotate
unloaded or with controlled loadunloaded or with controlled load–– Best compromise neutral for reversible Best compromise neutral for reversible
machines. Best for motors that could run machines. Best for motors that could run either rotation.either rotation.
•• ProcedureProcedure–– Apply DC current through armature and Apply DC current through armature and
commutation fields onlycommutation fields only–– If on neutral, machine will not rotate. If off If on neutral, machine will not rotate. If off
neutral, machine will rotate in one direction or neutral, machine will rotate in one direction or the other depending on which way it is off the other depending on which way it is off neutralneutral
–– Shift brush yoke as required so motor does Shift brush yoke as required so motor does not rotatenot rotate
•• WarningWarning --Do not use this method on Do not use this method on series motors as they will overseries motors as they will over--speed!!speed!!
DC Current In Armature DC Current In Armature CircuitCircuit
DC VoltmeterDC Voltmeter
A1A1
A2A2
DC DC Power Power SupplySupply
VVAA
IIA
CommCommFieldField
Armature Will Not Turn Armature Will Not Turn on Neutralon Neutral
00
•• AdvantagesAdvantages–– Only armature supply is requiredOnly armature supply is required
DC Current In Armature DC Current In Armature Circuit (Shunt Machines Circuit (Shunt Machines
Only)Only)
•• AdvantagesAdvantages–– Only armature supply is requiredOnly armature supply is required
•• DisadvantagesDisadvantages–– Limited to smaller antiLimited to smaller anti--friction bearing friction bearing
machinesmachines–– Limited to shunt machines (series or Limited to shunt machines (series or
compound machines will overcompound machines will over--speed)speed)–– Best compromise neutral for reversible Best compromise neutral for reversible
machines. Best for motors that could run machines. Best for motors that could run either rotation.either rotation.
DC Current In Armature DC Current In Armature Circuit (Shunt Machines Circuit (Shunt Machines
Only)Only)
Pencil Volt NeutralPencil Volt Neutral
•• ProcedureProcedure–– Place special template on the Place special template on the
commutatorcommutator–– Run machine at 100 Volts, no loadRun machine at 100 Volts, no load–– Measure voltage through holes in the Measure voltage through holes in the
template with a special probetemplate with a special probe–– Plot readings on graph paper and adjust Plot readings on graph paper and adjust
yoke accordinglyyoke accordingly
PVN TemplatePVN Template
Installing PVN TemplateInstalling PVN Template
PVN TestPVN TestPointsPoints
PVN PVN AnchoringAnchoring
PointPoint
PVN VoltmeterPVN Voltmeter
Pencil Volt NeutralPencil Volt Neutral
RotationRotation
VoltmeterVoltmeter
Pencil Pencil ProbeProbe
Brush StudBrush Stud
Brush Brush BoxBoxTemplateTemplate
Warning!!Warning!!Working around rotating electrical machineryWorking around rotating electrical machinery
can cause serious or fatal injury due to can cause serious or fatal injury due to electrical shock hazards or contact with electrical shock hazards or contact with
rotating parts. Contact the manufacturerrotating parts. Contact the manufacturer’’s s service engineers for performing adjustmentsservice engineers for performing adjustmentson electrical motors and generators. These on electrical motors and generators. These
people have the necessary training and people have the necessary training and information available to properly adjustinginformation available to properly adjusting
DC machines.DC machines.
Typical DataTypical Data
Pencil Volt NeutralPencil Volt Neutral836 KW Generator836 KW GeneratorTaken at 100 volts Taken at 100 volts -- No LoadNo Load
Lead VoltageLead Voltage Trail VoltageTrail VoltageHole No.Hole No.19.919.9
21.521.5
23.323.3
25.025.0
26.826.8
16.416.4
17.917.9
19.619.6
21.321.3
23.023.0
44
55
66
77
88
Note: Lead Volts Higher Than Trail Volts For SingleNote: Lead Volts Higher Than Trail Volts For SingleRotation Machine. For a Reversible Machine,Rotation Machine. For a Reversible Machine,Lead Volts Equals Trail Volts.Lead Volts Equals Trail Volts.
Neutral AdjustmentsNeutral Adjustments
•• To lower trail voltsTo lower trail voltsshift brush riggingshift brush riggingagainst rotationagainst rotation
•• To raise trail voltsTo raise trail voltsshift brush riggingshift brush riggingwith rotationwith rotation
•• To raise trail voltsTo raise trail voltsshift brush riggingshift brush riggingagainst rotationagainst rotation
•• To lower trail voltsTo lower trail voltsshift brush riggingshift brush riggingwith rotationwith rotation
GeneratorGenerator MotorMotor
Pencil Volt NeutralPencil Volt Neutral
•• AdvantagesAdvantages–– Repeatable, accurate way to set neutralRepeatable, accurate way to set neutral–– Can adjust single rotation machinesCan adjust single rotation machines
Pencil Volt NeutralPencil Volt Neutral•• AdvantagesAdvantages
–– Repeatable, accurate way to set neutralRepeatable, accurate way to set neutral–– Can adjust single rotation machinesCan adjust single rotation machines
•• DisadvantagesDisadvantages–– Requires working closely with energized Requires working closely with energized
rotating machineryrotating machinery–– Motors must be mechanically uncoupled or Motors must be mechanically uncoupled or
able to operate with little loadable to operate with little load
Other Methods Of Setting Other Methods Of Setting NeutralNeutral
There are other methods of setting neutral. There are other methods of setting neutral. It is important that neutral be set by It is important that neutral be set by somesomemethod as commutation or motor or method as commutation or motor or generator performance may suffer.generator performance may suffer.
Using Static Neutral Setting Using Static Neutral Setting Methods for Single Rotation Methods for Single Rotation
MachinesMachines
From experience, excavator generators From experience, excavator generators can be shifted about can be shifted about ½½ bar against bar against
rotation from symmetrical neutral to rotation from symmetrical neutral to approximate black band or pencil Volt approximate black band or pencil Volt
neutralneutral
Adjusting Commutating Adjusting Commutating Field (Field (InterpoleInterpole) Strength) Strength
Adjusting Adjusting commcomm field strength in the field is field strength in the field is difficult to impossible. difficult to impossible.
The machine voltage, speed and load must The machine voltage, speed and load must be controlled, which is usually impossible, be controlled, which is usually impossible, and some of the methods available, such as and some of the methods available, such as brush potential measurements, have safety brush potential measurements, have safety issues. issues.
Adjusting Commutating Adjusting Commutating Field (Field (InterpoleInterpole) Strength) Strength
Some manufacturers ( GE ) use nonSome manufacturers ( GE ) use non--magnetic magnetic interpoleinterpole bolts. These can be bolts. These can be same size as main pole bolts. Do Not mix same size as main pole bolts. Do Not mix these up. Look at bolt head markings. these up. Look at bolt head markings. Magnetic bolts will have 3 (grade 5) or 6 Magnetic bolts will have 3 (grade 5) or 6 (grade 8) radial marks.(grade 8) radial marks.
The order of the shims is also important,The order of the shims is also important,make sure to put them back like youmake sure to put them back like youfound them! Best to put tape around thefound them! Best to put tape around thewhole whole ““shim packshim pack”” and mark similar to:and mark similar to:4 o4 o’’clock pole this side toward frame IDclock pole this side toward frame ID
Properly adjusting DC Properly adjusting DC machines not only affects machines not only affects
commutation, but also commutation, but also machine performance and machine performance and
loop balanceloop balance
Properly maintained, the Properly maintained, the electrical equipment electrical equipment
used in mining used in mining machinery can perform machinery can perform
well for many, many well for many, many years.years.
And it will not end up And it will not end up like like thisthis pair!!pair!!
Rich HallRich Hall
Old broken down excavator and Old broken down excavator and old broken down engineerold broken down engineer