Calibration and Testing of Single-Phase Energy Meter

Our aim here is to calibrate the given Single-Phase Energy Meter using a precession Wattmeter and stopwatch using or employing phantom loading. The main apparatus required for conducting this practical experiment include:

  • Single-Phase Induction type Energy Meter – 240V (5-10)A
  • Wattmeter 300V/10A UPF
  • Phase Shifting Transformer 440V/440, 500VA
  • Single-Phase Variac – 240V / (0-270)V
3-Φ Auto Transformer Circuit Diagram

Procedure for calibration and testing of Single-Phase Energy Meter:-

  1. Give the connections as per the circuit diagram above.
  2. Apply 220V A.C to the pressure coil circuit by means of phase shifting transformer.
  3. Apply a load of 2 Amps by switching on the load.
  4. Note down the reading of two meters in a given period of time, say 2 minutes.
  5. Find out the percentage error at this load.
  6. Now rotate the rotor of phase shifting transformer so that the working power factor (p.f) of the meter is varied.
  7. For this power factor repeat steps 4 and 5.
  8. Now increase the load current in suitable steps and repeat the steps 4,5,6 and tabulate the results. The expected example results are given in the table below:

    S.NoCurrent I(A)Power FactorWattmeter (w)x2Time (T) in HoursMeasured Power (Whr)% error
    2.50.8 lead7200.018012.9619
    3.50.8 lag11200.010511.7626.5
    5.40.8 lead5600.022712.71220.55
    6.40.8 lag8800.013311.70426.85
    8.0.8 lead4400.029713.06813.06818.32
    9.30.8 lag6800.018012.2423.5

    Percentage Error in Power and Actual Power formulae

Thus we’ve done the testing and calibration of a given Single-Phase energy meter.

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