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Calibration of LPF wattmeter by phantom loading?

Answer:

Aim: To Calibrate LPF wattmeter by Phantom Loading.

Apparatus:

1) Voltmeter - 300V Digital --> 1 2) Ammeter - 10A Digital --> 1 3) Phase shifting Transformer - 415V/15A --> 1 4) Auto Transformer - 240V/0-270V,10A --> 1 5) Power Factor meter - 230V,10A-Dynamometer --> 1 6) Wattmeter(LPF) - 230V,10A-Dynamometer --> 1 7) Connecting wires

Procedure:

1) Keep connections as per circuit diagram. 2) Keep Auto Transformer in minimum position and On toggle Switch. 3) Vary the transformer at Power coil till voltmeter reads rated value. 4) Vary phase shifting transformer to set power factore at 0.2 lag. 5) Now slowly vary the auto transformer at Current coil in Steps. 6) Note the values of wattmeter at each step of current. 7) Repeat the above step till Ammeter reads rated current. 8) Calculate percentage of error. Plot the graph between current and percentage of error, keep current on X-axis and % error at Y-axis.

Calculations:

Wa = VxIxCosQ watts. Wm = watts. % error = [(Wa-Wm)*100]/Wm.

Precautions:

1) Avoid loose connections. 2) Avoid parallax errors.

  • 3) Keep wattmeter and P.F meter in parallel.

Result:

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