Hi, I did the two wattmeter experiment in a lab in order to work out the power in a balanced three phase system of which the loads were resistive. I recorded the power using the two wattmeters and obtained a total power of 1.41kW. I had to compare this to calculate power which I worked out by the following equation: rt3* Line current*Line Voltage* Power factor. This came to: rt3*5.16*134*0.83 = 994kW.

As you can see the calculated power is significantly less, is this because it only calculates true power and the wattmeter method measures total power?

I also got a VA power reading of 706VA for line one an 726VA for line three. Line 2 was used as a reference. I thought this was strange in itself seeing a neutral line was used. Could anybody shed any light on this?

Cheers

 

It's curious that you have a power factor of 0.83 with a purely resistive balanced 3-phase load.

A total power of 1.41kW gives a per phase power of 470W. Even with a power factor of 0.83 this does not square with your per phase VA values.

Unfortunately, none of your results are consistent.

You probably need to post a schematic and all values of the measurements made and their locations.