Why we use low power factor wattmeter in open circuit test?

In open circuit test the secondary winding of transformer is kept open.As the secondary side is open, the entire coil will be purely inductive in nature.So the power will be lagging due to inductive property of the circuit. So LPF(Low Power Factor) Wattmeter is used in OPEN CIRCUIT TEST of Transformer.

Why phantom loading arrangement is done for testing high capacity energy meters?

The phantom loading is used for examining the current rating ability of the energy meter. The actual loading arrangement will waste a lot of power. The phantom loading consumes very less power as compared to real loading, and because of this reason, it is used for testing the meter.

What is phantom loading in measurement?

Definition: Phantom Loading is a loading condition in which an energy meter is connected to factious or phantom load for testing of energy meter with high current rating. Such loading is favorable to avoid wastage of energy during the test of measurement instrument.

What are the special features incorporated in low power factor wattmeter?

Small Control Torque: Low power factor wattmeters are designed to have a small control torque so that they may provide full scale deflection for power factors as low as 0.1.

What is a Wattmeter used for?

The wattmeter is an instrument for measuring the electric active power (or the average of the rate of flow of electrical energy) in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements.

Why the ordinary wattmeters are not suitable for low power factor circuits?

The ordinary Wattmeter used for measuring the low power factor gives the inaccurate result. In low power factor meter, the magnitude of deflecting torque on moving coil is small even after the full excitation of the pressure and current coil. The error occurs in the reading because of the pressure coil inductance.

Why the ordinary wattmeter are not suitable for low power factor circuit?

Now there are two main situations where we should not use an ordinary wattmeter in measuring a low power factor: The value of deflecting torque is very low even though we fully excite the current and pressure coils. Errors due to pressure coil inductance.

What are the errors that might occur for measuring power by using wattmeter?

Pressure coil Inductance Due to self inductance, the pressure coil creates phase-shift in the current flowing through it. So the true angle between voltage and current slightly changed, which leads to an error in the readings. The wattmeter gives a higher reading for lagging load and lesser reading for leading pf load.