Common Motor Control Power Transformers -Grounded or floating.
Common Motor Control Power Transformers -Grounded or floating.
(OP)
I'm helping on an IEC project in Africa and want to know if ungrounded control power is typical for IEC MCC's. MCC's were built in China.
Each 690V MCC has a 690V-230V, single-phase control power transformer that feeds a distribution panel with single pole breakers, one breaker per MCC bucket. The 230V winding is floating ungrounded on four of the transformers and is grounded on two of them. One has the hot leg grounded so the control circuit is still energized when the CB is open. The two grounds appear to be unintentional, (haven't located them yet).
I told the electricians to find and fix the unintentional grounds and then ground the neutral side - the one not connected to the breakers.
Is there a good reason to leave the control power ungrounded? I couldn't come up with one. BTW there is no ground detection circuit.
Each 690V MCC has a 690V-230V, single-phase control power transformer that feeds a distribution panel with single pole breakers, one breaker per MCC bucket. The 230V winding is floating ungrounded on four of the transformers and is grounded on two of them. One has the hot leg grounded so the control circuit is still energized when the CB is open. The two grounds appear to be unintentional, (haven't located them yet).
I told the electricians to find and fix the unintentional grounds and then ground the neutral side - the one not connected to the breakers.
Is there a good reason to leave the control power ungrounded? I couldn't come up with one. BTW there is no ground detection circuit.






RE: Common Motor Control Power Transformers -Grounded or floating.
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If we learn from our mistakes I'm getting a great education!
RE: Common Motor Control Power Transformers -Grounded or floating.
An anecdote from the same plant;
One of the electricians was sent to one of our plants because a ground detector lamp was out on a 440V ungrounded MCC. two or three days later he came into the shop and threw his tools on the bench and announced. Well;
"It's fixed."
The supervisor asked where the ground was.
"No ground. The damm light was burned out."
My first thought was;
"Thank god that wasn't me!"
Bill
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"Why not the best?"
Jimmy Carter
RE: Common Motor Control Power Transformers -Grounded or floating.
RE: Common Motor Control Power Transformers -Grounded or floating.
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