How to measure 3+ consumption of electric power

[ataslaki]

Trying to compute consumption of electric power for a 3 phase machine, which has an average currents of on a continous basis, as measured with a current loop ammeter:

phase 1 = 16A @ 120V
phase 2 = 16A @ 120V
phase 3 = 8A @ 208V

 

[waross]

Given the voltage unbalances and the 30/30/120 degree phase angles, I'm always surprised to see amachine actually working with this connection. I've seen it a few times on 3 phase welders plugged into a 120/208 2 phase receptacle usually used for single phase "Buzz box" welders. The welder didn't read english. He just kept cranking up the adjustment until he got a usable welding current.
To find the power my first reaction would be to discourage you.
My second reaction may be to sneak away.

If I absolutely had to find the power, I would turn everything off except the machine under test and measure the time in seconds for the revenue meter disk to make one revolution (or for the dots to make a complete cycle on an electronic meter). I would divide one hour (3600 seconds) by the time for one revolution. Now I have turns per hour.
Multiply the turns per hour by the Watthour Constant And you have watt hours. Divide by one hour and you have watts.
Actually, I usually time ten revolutions and divide by ten.
The WattHour constant is abreviated Kh and is shown on the face of utility meters in North America. 7.2 is a common Kh but by no means the only one. A quick check in my meter book shows Kh ratings from 1/3 to 57.6.