EE301 Lesson 27 Power Factor Correction

Lesson 27 Power Factor Correction

Learning Objectives 

Define power factor correction and unity power factor correction.



Calculate the inductor or capacitor value required to correct AC series parallel networks to the desired apparent power.



Compare currents voltages and power in AC series parallel networks before and after power factor correction.

!hy is "ower #actor $mportant% 

Consider the following e&le' A generator is rated at ()) * and supplies one of two possible loads. Load +'  P = +,) k!  F  P  - + Load ,'  P = +,) k!  F  P  - ).(



ow much current / I 0 is the generator required to supply in each case%

!hy is "ower #actor $mportant% 

#or the load with  Fp = ).( the generator had to supply +11 more amperes in order to do the same work / P 02



Larger current means larger equipment /wires transformers generators0 which cost more.



Larger current also means larger transmission losses /think  I 2 R0.

!hy is "ower #actor $mportant% 

3ecause of the wide variation in possible current requirements due to power factor most large electrical equipment is rated using apparent power  /S 0 in volt4amperes /*A0 instead of real power / P 0 in watts /!0.



$s it possible to change the power factor of the load%

"O!564#AC7O6 CO665C7$O8

FIG. 19.28 Demonstrating the impact of  power-factor correction on the power triangle of a network.

"ower #actor Correction  

 Almost all loads are inductive. $n order to cancel the reactive component of power we must add reactance of the opposite type. 7his is called power factor correction .

Capacitor bank in shipboard power panel for #" correction

"ower #actor Correction 

$n practice almost all loads /commercial industrial and residential0 look inductive  /due to motors fluorescent lamp ballasts etc.0.



ence almost all power factor correction consists of adding capacitance .

"ower #actor Correction 9olution 9teps +.

Calculate the reactive power /:0 of the load

,.

$nsert a component in parallel of the load that will cancel out that reactive power e.g. $f the load has : LD-;+, *A6 insert a capacitor with :C-4;+, *A6.

1.

Calculate the reactance /.

Calculate the component value /# or 0 required to provide that reactance.

Example Problem 1 7he ()) * /() ?0 generator is connected to a load with  P  LD - +,) k! and Q LD - +() k*A6. a.

Determine the power factor of the load.

b.

Determine the Capacitance /in #arads0 required to correct the power factor to unity.

"ower factor correction capacitors for A 3 and C phases at the Crofton  @D substation 6ating' ,1) k* 1() @*A6

size comparison

Capacitor banks

Example Problem 2 a.

Determine the value of the capacitance /in #0 required to bring the power factor up to unity /freq of () ?0.

b.

Determine generator current before and after correction.

8otice that