208 3 phase motor on 240V 3 phase supply

[DSrader]

I have an RTU rated for 208 V 3 phase being fed 240 V 3 phase with 2 compressors, both are showing unbalanced current draw. One is reading 30-31 amps on L1 and L3, 41 amps on L2, the other is 51 amps on L1 and L3, 71 amps on L2. My first thought was motor windings, but highly unlikely that both would have the same problem. I've never had issues this severe before, and I know there would be no wild leg on a Y wound transformer, which I think is common for 208V, but even on a delta wound transformer I've never seen where a wild leg causes current unbalance. The voltage reads 241V to 243V across on all 3 legs. Is there something I'm missing here?

One more thing, this Mfr. makes distinct units for either 208V or 240V, not both.

 

[Dennis Alwon]

I am not sure that it is good idea to feed this with a delta 240v when the unit calls for a Y 208V . I suspect that is the reason for the wacky reading but I am not certain. I am sure there will be more knowledgeable members who will respond.

 

[ptonsparky]

Open Delta seems to have issues with current imbalance. Usually it can be minimized by rotating the leads. A to B, B to C, C to A. Repeat until you have the least imbalance. Your system seems to be a bit high even for Open Delta. Make sure you don’t have a single phase load mixed in there somewhere.

 

[hillbilly1]

Usually the condenser fans are single phase, but that would make two phases higher than the third, and you have the opposite. With an open delta, the second transformer is quite a bit smaller than the main one, but you say your voltage is pretty consistent between phases.

 

[DSrader]

I asked the owner if the transformer had been replaced, as the unit has been in for 15 years, indicating a new problem, he wasn’t aware that it had. I appreciate the responses, I’m thinking that the solution will be to have the 208V Y transformer put in.