26-02-2013, 10:50 AM
Calibration of Wattmeter by Phantom Method.
Calibration of Wattmeter.docx (Size: 11.74 KB / Downloads: 65)
APPARATUS:
•LVHI T/F 1
•HVLI T/F 1
•Ammeter 1
•Voltmeter 1
•Wattmeter 2
•Current controlling resistor (CCR)
•Connecting wires
THEORY:
The wattmeter is an instrument for measuring the electric power (or the supply rate of
electrical energy) in watts of any given circuit.
Calibration of wattmeter is done by various methods. Here we will calibrate wattmeter by
Phantom Loading.
The phantom loading is that no external load is connected in actual sense and the current
and pressure coils are connected seperatly so that it will consume only less power. In this
connection the voltage across pressure coil will be supply voltage.
OR
Method by which energizing the pressure coil circuit and current coil circuits separately
is called phantom loading.
PROCEDURE:
1. Connect the circuit as shown in circuit diagram.
2. For the calibration of current coil of wattmeter, vary the voltage while keeping the
current at a constant value of 5A.
3. Note the corresponding readings of both wattmeters and calculate %Error.
4. For the calibration of potential coil of wattmeter, the current is varied by using
current controlling resistor while voltage is kept constant at a fixed value of 220V.
5. Repeat step 3.