Ac theory : - power factors

[daiplayer]

Has any body got a simple sheet or site in which it explains ( in simple terms) on how to calculate power factors, pf angles, relationship between trianlges (impedance/power/ voltage) etc ....?

I am trying to get my head round the year 2 math, most is fine, just cant seem to understand this for some reason...., doing some revision ...n this is the q ive been asked :

Xc is given as 18 ohms...and R = 42 ohms.....calculate the power factor of the circiut.

????????????

 

[sparky2011]

First u must find out the impedence (Z) of the circuit ... Equation is ...Z = square root of r squared + xc squared
( 1764) + ( 324) = 2088
Z = square root of 2088 Z = 45.69

power factor equation is R divided by Z
(42) / (45.69) = 0.92

Hope this is clear enough to follow

 

[daiplayer]

cheers mate. I got the same answer, however i somehow followed a differnt method...lol

So in the theory.. real power..is in the resistor only ? ...ie..Xc is reactive power ( Kvar ) ??

 

[pushrod]

cheers mate. I got the same answer, however i somehow followed a differnt method...lol

So in the theory.. real power..is in the resistor only ? ...ie..Xc is reactive power ( Kvar ) ??

You have to be very careful about getting your terms right as a lot of questions are based on that

power is dissipated only in the resistor... Xc is the capacitive reactance

 

[daiplayer]

right...ok...so power disapated...= Watts ...correct...? ....reactive power = Kvar....(useless power) ...??

Thanks mate ur a star.

 

[pushrod]

right...ok...so power disapated...= Watts ...correct...? Yep....reactive power = Kvar....(useless power) Yep also called wattless power...?? Common multiple choice exam question to ask how many watts of power used by a capacitor or inductor.. answer zero
]

and kVA is apparent power.

 

[daiplayer]

thankyou very much