control and balance
control and balance
(OP)
I have a 3 hp @ 208/230v 3P nameplate motor with a control circuit with various items in it.
For much of the control circuit, 120v is needed, so he (the previous eng.)was using one leg of the 3 phase to neutral. However, after some investigation, the control circuit is consuming nearly the current of the motor. So, I thought I'd balance the load out as best I could. My problem now, is that there is no way to determine whether the customer will have a 3phase/neutral wye supply or one with a high delta leg. I need to make it so that either is acceptable.....without using another transformer or anything remotely costly or realestate greedy. Any suggestions? I am unable to tell the customer beforehand that he should use a supply with a WYE configuration.....
For much of the control circuit, 120v is needed, so he (the previous eng.)was using one leg of the 3 phase to neutral. However, after some investigation, the control circuit is consuming nearly the current of the motor. So, I thought I'd balance the load out as best I could. My problem now, is that there is no way to determine whether the customer will have a 3phase/neutral wye supply or one with a high delta leg. I need to make it so that either is acceptable.....without using another transformer or anything remotely costly or realestate greedy. Any suggestions? I am unable to tell the customer beforehand that he should use a supply with a WYE configuration.....





RE: control and balance
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: control and balance
RE: control and balance
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: control and balance
RE: control and balance
What about making the control/auxillary circuits all line-line loads and balance it across the 3 phases as much as possible. If that's not possible, leave it all on one leg, mark that clearly and document it in all literature for the installer.
RE: control and balance
Everything has its cost. Specifying a neutral and the voltage of L1 to neutral is not problematic. The fact that a 3phase power source of 208 - 230 VAC 60Hz is required and specified better not be a problem!
Wye is easier for (some) people to deal with when it comes to single phase loads. It is not better than wye for 3-phase loads, and not necessarily better than wye for single phase loads either.
It sounds as though you fully realize that bringing in a separate neutral conductor and not using a control xfmr is,,, well,,, kinda cheesy. I did it too a time or two, before I knew any better. At least use a control circuit fuse (or circuit breaker).
Please let us all know how this works out for you! and don't forget FAQ731-376