Using AIPM-3V to monitor a 3-phase delta load from 3-phase y source


I have two rotary blowers that I am trying to monitor for energy consumption, so that I can establish some metrics i.e. kWh/lb of product.

The incoming service is 3 phase Y, 208V between phases and 120V from phase to neutral. However, the motors are connected in delta configuration through VFDs, having just 208V between the three phases.

I got two AIPM-3V modules, and wired them up as shown on page 15 of the datasheet, including the neutral wire. I put the 3 CTs on the legs going to the motors, just past the VFD output.

Here is my dilemma: If the voltage on Points 0, 4, and 8 of the module is 120 (not 208) will the module correctly calculate the power and energy consumption for the motors? Do I need to scale the phase-to neutral voltage measurement by sqrt(3) to correct it?

One thing we thought of would be to jumper all the places where neutral is normally connected to the module (Ch0 point 2, Ch4 point 2, and CH8 point 2) to kind of float that terminal, but we would like to get the OK from opto before blowing a $500 module.

Any insight would be appreciated.


Hello mjlewis22!

Welcome to the OptoForums. This sounds like a question for our Support Team, especially since you’re concerned about harming the module. Also, you mention “the OK from opto” – although I call myself OptoMary, certainly my comments here should be taken as My Option Only [disclaimer, disclaimer]. Our discussions here on the OptoForums are more about sharing and brainstorming than Official Opto Opinion.

However, as I hope you’ll find as you check out and post to the OptoForums, it’s always fun to see the wide variety of experiences and ideas that people are willing to share. But you certainly don’t my ideas when it comes to anything electrical that might potential go up in flames. (I’ve managed to cause flames in a microwave while cooking instant stuffing.)

In any case, I strongly urge to email this one to support (at) – they’re the best equipped to handle this kind of question.