Calibration of single phase energy meter by phantom loading
AIM:
To calibrate the given single phase wattmeter by phantom loading at UPF and at 0.5pf.
APPARATUS REQUIRED:
- Voltmeter
- Ammeter
- Wattmeter
- Lamp load
- Energy meter
THEORY
When current rating of the meter under test is high, a test with actual loading arrangements involves considerable waste of power. Phantom loading consists of supplying the pressure circuit with required normal voltage and the current circuit from a low voltage supply. the total power required for testing the meter with phantom loading is comparatively very small.
PROCEDURE:
At UPF
- Connections are made as shown in diagram
- The rated voltage applied across pressure coil
- Keep the autotransformer at its minimum position and switch on the power supply.
- Adjust the autotransformer for various values of current from minimum to maximum
- Take all meter readings and time taken for 5revolution of E/M disc
- Plot error and calibration curve
At 0.5pf lag
- Connect the pressure coil across N&Y and CC in R phase
- Repeat the same procedure mentioned above
- Plot the error and calibration curve
CIRCUIT DIAGRAM:
OBSERVATION:
| PF | v/m | A/m | Time for 5 rev of E/M disc | Recorded power = (5/t)*(3600/N) KWH | Actual power( VI cosΦ/1000) | Error = RP-AP | % Error = (RP-AP)/RP |
| UPF | |||||||
| 0.5 LAG |
RESULT:
The given single phase energy meter is calibrated at UPF and 0.5 lag by phantom loading
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