Page 93 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

Important observations:
1 If the load power factor is unity, both watt meters W & W shows equal readings. Then total power of 3 Ph.
2
1
Load is P= W + W watts
1
2
2 If the load power factor is lies between 0.5 & unity, watt meters W & W shows unequal readings. Now also,
1
2
total power of 3 Ph. Load is P= W + W watts.
1 2
3 If the load power factor is exactly 0.5, only one watt meter W or W shows reading and other doesn’t. Now,
1
2
total power of 3 Ph. Load is P= Reading of one watt meter.
4 If the load power factor is less than 0.5, the needle of one of the watt meter kicks back. In that case Interchange
the terminals of CC or PC of that particular watt meter and after which reading recorded by that wattmeter
should be taken Negative value. In this case the total power P= W - W watts.
2
1
5 The power factor (PF) of the circuit / load is determined by the equation,

OR

Tabular column:
Cos ϕ=
Power (P) in
Type of Line Line current (I) watts Total power
load voltage (V ) P= W + W
L 1 2
(I ) (I ) (I ) W 1 W 2
B
Y
R
Resistive
Balanced

Resistive +
inductive
Unbalanced

Circuit Diagram:

76

CITS : Power - Electrician & Wireman - Exercise 38