how a single phase energy meter is calibrated ?
Answers
Explanation:
Give the connections as per the circuit diagram above.
Apply 220V A.C to the pressure coil circuit by means of phase shifting transformer.
Apply a load of 2 Amps by switching on the load.
Note down the reading of two meters in a given period of time, say 2 minutes.
Find out the percentage error at this load.
Now rotate the rotor of phase shifting transformer so that the working power factor (p.f) of the meter is varied.
For this power factor repeat steps 4 and 5.
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.No Current I(A) Power Factor Wattmeter (w)x2 Time (T) in Hours Measured Power (Whr) % error
1. 5 UPF 1160 0.0105 12.18 23.87
2. 5 0.8 lead 720 0.0180 12.96 19
3. 5 0.8 lag 1120 0.0105 11.76 26.5
4. 4 unity 920 0.0136 12.512 21.8
5. 4 0.8 lead 560 0.0227 12.712 20.55
6. 4 0.8 lag 880 0.0133 11.704 26.85
7. 3 unity 680 0.0177 12.036 24.775
8. 0.8 lead 440 0.0297 13.068 13.068 18.32
9. 3 0.8 lag 680 0.0180 12.24 23.5
Percentage Error in Power and Actual Power formulae
Thus we’ve done the testing and calibration of a given Single-Phase energy meter.