3 Phase wattmeter
3 Phase wattmeter
(OP)
We have a wattmeter hooked up on the mains 3 phase 480V AC input to our compressor.
For each phase is a separate coil to measure the AC current.The direction of each coil was determined by the Right Hand Rule and all 3 coils for that meter were placed in the same direction.
I hooked up another exact type and model wattmeter as a test meter to check if the first meter was working ok.
It was but what I found was that when I positioned 2 coils in one direction and the third one in the opposite direction in the 2nd meter the readings from both meters were the same.
Why would the meter readings be the same if one meter has 2 of its coils in one direction and the 3rd coil in the oppostite direction to the current flow and the other meter has all its 3 coils correctly orientated but different from the other meter?
Cheers,
Roy
For each phase is a separate coil to measure the AC current.The direction of each coil was determined by the Right Hand Rule and all 3 coils for that meter were placed in the same direction.
I hooked up another exact type and model wattmeter as a test meter to check if the first meter was working ok.
It was but what I found was that when I positioned 2 coils in one direction and the third one in the opposite direction in the 2nd meter the readings from both meters were the same.
Why would the meter readings be the same if one meter has 2 of its coils in one direction and the 3rd coil in the oppostite direction to the current flow and the other meter has all its 3 coils correctly orientated but different from the other meter?
Cheers,
Roy






RE: 3 Phase wattmeter
RE: 3 Phase wattmeter
Roy
RE: 3 Phase wattmeter
Not sure of the size or type of your CT's, but I have had toroids placed in upside by the manufacturer compared with the polarity markings, etc.
RE: 3 Phase wattmeter
What happens to the second-meter readings if the third coil is "corrected"?
Specifically, how are both meters' potential leads connected? Blondel’s Theorem always gets dragged into wattmeter connections. Is that discussed in the meter application material?
Are different readings obtained connecting each mater in an identical manner?
RE: 3 Phase wattmeter
Any thoughts?
Roy
RE: 3 Phase wattmeter
Is it possible the meter(s) are operating in a 3-wire, 2-element mode and ignoring the third current?
RE: 3 Phase wattmeter