Transformer with wierd test results
Transformer with wierd test results
(OP)
We tested a small, 3-phase, dry type, 20kVA transformer that is delta to wye and 1000V/416/240V. We took a multimeter and measured from from Phase A to ground and phase B to ground on the low side and measured 416V. When we measured from phase C to ground we measured 0V. This told me that phase C and ground were at the same potential. If the transformer was energized shouldn't it have been damaged if this was occuring? I'm wondering if anybody else has ever observed something like this before.
I only ask because someone wants to hook this XFMR up to a small distribution panel. There are no 3 phase loads in the distribution panel but I'm almost positive that something will get damaged if we do.
I only ask because someone wants to hook this XFMR up to a small distribution panel. There are no 3 phase loads in the distribution panel but I'm almost positive that something will get damaged if we do.






RE: Transformer with wierd test results
Bill
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"Why not the best?"
Jimmy Carter
RE: Transformer with wierd test results
RE: Transformer with wierd test results
RE: Transformer with wierd test results
As Bill said, also be sure you are checking your phase to (ground) voltages to the neutral point, not to ground because it appears your neutral is not tied to ground.
If the neutral point is tied to the transformer case (because you said it was grounded) and the case is not tied to ground, you need to be sure you clear the ground on phase C FIRST, and then tie the transformer case firmly to ground......All to be done with the transformer de-energized! Very dangerous to have the neutral tied to the case and not also to ground.
Alan
Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin
RE: Transformer with wierd test results
Alan
Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin
RE: Transformer with wierd test results
RE: Transformer with wierd test results
If the neutral were grounded and you had a C-G fault, your A-G and B-G voltages would be much closer to 240V than to 416V. If the neutral were floating, you would have had something close to the same value from phase-ground; generally around 240V each, but could be more or less depending on couplings and meter impedance.
RE: Transformer with wierd test results
Were the original voltage tests routine or was there a suspected problem?
Alan
Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin