Basic PF

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Basic Power Factor Correction

What are the different types of loads?

Ohmic loads

Lighting bulbs

Iron

Resistive heating

Capacative loadsCapacitors

Underground cables

Overexcited

synchronous

generators

Inductive loads

Electrical Motors

Transformers

Reactors/chokes

Overhead lines

Under excited

Synchronous

generatorsDischarge lamps

Power electronic

GRID

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Three different types of loads: 1. OHMIC-LOADS

Ohmic loads

U and I in phase

Phase shift = 0

No penalty

In resistive circuits the voltage and current

waveforms reach their peaks and troughs as

well as the electrical zeros at the same

instant of time.

The voltage and current are said to be in

phase ( = 0) and the entire input power is

converted into active power. Thus, resistive

circuits have a unity power factor.

The ohmic resistance does not depend onfrequency.

U - Voltage

I - Current =0

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Three different types of loads: 2. INDUCTIVE-

LOADS

Inductive loads cause

a phase shift between

current and voltage.

A positive as well as a

negative power can be

observed.

Phase shift

t

U,

Iandpower

+ ve + ve

-ve

Power

Current

Voltage

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Three different types of electrical power

Reactive Power ( kvar)

22 PSQ -

Active Power

QSP -

[ KW]

Apparent Power

QPS +

[kVA ]

cos= P/S = phase displacement anglesin = Q/S S

1= uncompensated apparent power

Q = S sin S2= compensated power withcapacitors for compensationQ = P tan

Q1

QCQ2

2

1

S1

S2

S = Apparent Power

P = Active Power

Q = Reactive Power

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What is Active Power?

The amount of input power which is converted into output power, is

termed as activepower and is generally indicated by P.

The active Power is defined by the following formula.

[W]

Ideally, entire input power i.e. apparent power should get converted

into the useful output, i.e. heating of an oven, movement of an motor,

light of an bulb.

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What is Reactive Power?

Electrical machines work on the principle of conversion ofelectromagnetic energy.(e.g. electric motors, transformers). A

part of input energy is consumed for creating and maintaining

the magnetic field. This part of the input energy cannot be

converted into active energy and is returned to the electrical

network on removal of the magnetic field. This power is known

as reactive power Q and is defined as follows.

[VAr]sin3 IUQ

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What is Apparent Power?

Applications of electrical equipment are based on conversion ofelectrical energy into some other form of energy. The electrical

power drawn by an equipment from the source is termed as

Apparent Power, and consists of active and reactive power.

The current measured with a clamp amp indicates the apparentpower. It is defined as follows:

[VA]IUS 3

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What is the power factor?

Power factor = cos

cos-phi = P (kW) / S (kVA)

Phase shift

t

U,Iandpower

+ ve + ve

-ve

Power

Current

Voltage

Category

Typical

uncompensated PF

Breweries 0,6..0,7

Cement plant 0,6..0,7

Compressor 0,7..0,8

Cranes 0,5..0,6

Data Centre - Computer 0,8..0,9

Drying-Plants 0,8..0,9

Hospitals 0,7..0,8

Machinery, big sized 0,5..0,6

Machinery, small sized 0,4..0,5

Office Building- General 0,7..0,8

Plywood 0,6..0,7

Sawmill 0,6..0,7Steel factory 0,6..0,7

Suggar 0,8..0,85

Tobacco 0,6..0,7

Water pumps 0,8..0,85

Welding transformer 0,4..0,5

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Power Factor Correction

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What is the power factor?

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Why to improve the power factor?

Reduction of power bill (short pay back time: 6-18 month usually)

Reduction of ohmic losses

Power Quality improvement (harmonics, voltage sags..)

Higher kW loading of transmission and distribution equipment and/or

smaller dimensioning of this equipment (cable, transformer, bus bars..)

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Industrial. Commercial and domestic customers

want to get most effective electrical installation toserve their machinery. Low PF can mean extralosses and penalty payments to utility for excessivereactive power.

Power production and transmission companieswould like to sell as much active power as possibleto their customers. Low PF can reduce thegenerating and transmission capacity.

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Why to improve power factor?

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What does this mean in reduced losses and saveenergy?

The losses in the power line, transformers , and cablesare proportional to the square of the current.

Assume the average load on the 55kW is 35kW, then

motor current is 65A. The AC drive input current underthis condition is 60A

The AC drive reduces the input current from 65A to60A. The reduction of losses is described:

If the losses on the supply side are 5% of the averageload, the AC drive can reduce these losses to about 4%.

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How to improve the power factor?

PFC Capacitors (HV or LV, automatic or fixed)

Reduce amount of inductive load

Over-excited synchronous generators
http://d/fotos/Photos%20aus%20PFC%20Katalog/klk16651.jpghttp://d/PRODUKTE/Active%20Power%20Factor%20Correction%20LV/EBEHAKO/TSM-ENGL.DOChttp://d/fotos/Photos%20aus%20PFC%20Katalog/klk16651.jpg

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Power Factor Correction

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Principle of Power Factor Correction

Mechanical orthermal work

Generation of

magnetic field

Active Energy

Reactive Energy

Capacitor

Supply

Current

0

Load

95

CurrentCurrent

65

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Principle of PFC

S = Apparent Power

P = Active Power

Q = Reactive Power

P

Q1QCS1

Q2 = Q1 - QC

1

S2

2

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Methods of PFC

Individual compensation

Group compensation

Centralised automatic compensation

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Methods of PFC: 1. Individual (fixed)Compensation

M h d f PFC 1 I di id l (fi d)

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Methods of PFC: 1. Individual (fixed)Compensation

Advantages at a glance

kvar produced on the spot

Reduction of line losses

Reduction of voltage drops

Saving of regulator

Disadvantages

Many small capacitors are more

expensive that one central one

* Low utilization factor of

capacitors or equipment

not often in operation

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Methods of PFC: 2. Group Compensation

M M M


Reduction of capital investment

Loses reduced in distribution lines

Voltage drops reduced in distribution lines

Higher utilization factor of capacitors

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Methods of PFC: 3. Centralized Compensation

M M M

controller

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Methods of PFC: 3. Centralized Compensation

In factories with many loads of different output and operating

times fixed compensation is usually too costly and non-effective.The most economic solution for complex applications is usually

a centralized automatic capacitor bank, controlled by a automatic

PF controller. Point of connection is usually in the main

distribution panel close to the transformer.


Best utilization of the capacitors

Most cost effective solution

Easier supervision

Automatic control

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Methods of PFC: Summary

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Example of power factor correction calculation

Capacitor bankQc = ?? kvar

HV Grid

Transformer630 kVA, uk = 5 %

300 kWcos = 0.65

M

3 ~

Question:A building with a total load of 300 kW shows an actual power factor of 0.65

The customer asks for a target PF=0.96

What capacitor output is required to avoid surcharges for low PF?

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Solution:

Qc = P * K) = 300*(0.88) = 252 kvar

For a proper fine tuning of the target PF, a capacitor bank design:

25 + 50 + 50 + 50 + 50 + 50 kvar

Depending on types of loads, e.g. frequency converters, de-tuned

capacitor banks should be used

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M M M SSB 1 SSB 2

?

TCL = 1200kW

Office Building

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Ic = kVAR / system voltage

Qc = 2 x 3.14 x 50Hz x Cp x V2

E l f f i l l i

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MCCB = 1.5 X Reactive Current

CONTACTOR = AC-6b RATING

E l f f i l l i

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P f t ti t t

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Power factor correction at motor

V lt i

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Voltage rise

V lt i

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Voltage rise

R b C it h l

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Remember Capacitor has losses

Utili ti C t

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Utilization Category


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PF Capacitor Inrush Current

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Contactor for Switching

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Contactor for Switching

Power factor capacitors various brands

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Power factor capacitors various brands

Power factor capacitor specifications

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High over current loading possible

Longest life cycle: 115 000 hours

Highest ambient temperature, up to 55

Highest impulse current: 300 * In

No Corona effect

Highest safety by Triple Safety System

Highest reliability


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-3000,0

-2000,0

-1000,0

0,0

1000,0

2000,0

3000,0

4000,0

73,2 73,8 74,5 75,1 75,7 76,3 77,0 77,6

Time [ms]

Current[A]

5 steps parallel

Highest impulse current withstandcapability: > 300 * In

Inrush current of app. 3500 Aby energizing a PFC capacitorwith 20 A rated current!



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Power factor capacitor Installation

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Power factor capacitor Installation

Power Factor - Metering

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Power Factor - Metering

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Basic PF

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