HMT or K-Rated transformers? (non-linear load)

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JasonCo

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I'm stumped on this homework question of mine. The question is:

Non-linear loads supplied from a ___ system would require the installation of an HMT or K-Rated transformer.
1. 120/240v, 3phase, 4W
2. 277/480v, 3phase, 4W
3. 120/208v, 3phase, 4W

A. 1 only
B. 3 only
C. 1,2,3
D. 2,3
E. 2 only

I an an electrical apprentice, I know little to nothing about this subject... I have read all over and searched the internet and I cannot come up with a definitive answer. I wish I could just understand the theory behind all this and able to pick the answer out instantly. This is sort of what I am hoping I could get out of posting this thread! I appreciate all your help and time
 
infinity said:
I can give you a hint the nonlinear system would be WYE.
Click to expand...

Ah! Okay so a non-linear load will have to have a Wye system, and a linear load will have to have a Delta system?

So answer is D.

Non-linear loads will have example: 277/480, 120/208 and Linear loads will be for example 120/240 Delta
 
It is completely possible to connect a non linear load line to line on a delta system. If you do that and there are third harmonic currents you will not get a problematic non cancelling high current in the neutral.
In a delta you can have problematic high circulating currents in the transformer.
 
JasonCo said:
Ah! Okay so a non-linear load will have to have a Wye system, and a linear load will have to have a Delta system?

So answer is D.

Non-linear loads will have example: 277/480, 120/208 and Linear loads will be for example 120/240 Delta
Click to expand...

2 and 3 are WYE systems, although we typically note them as 480Y/277 and 208Y/120 for 3Ø, 4 Wire.
 
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