ECN Forum Forums General Topics of the Trade General Discussion Area transfomer taps

Hello everybody
I`m new to this site and what I`ve seen so far I think this is a great forum.

I was having a discussion with another student of the trade and we couldn`t agree on the following statement.
" Taps are usually provided on the secondary low-voltage side at 2 1/2 percent incraments to correct the phase angle of the secondary voltage"
Would you`ll say that this is a true or false statement?

I thought they where there to dial in the secondary voltage if the primary voltage consistently runs high or low.

Answering off the top of my head. (In this group a good way to lose your head.) I think the answer for the test would be False. The taps are for voltage not angle of phase.
A transformer is rated with a fixed primary voltage which is not always available. that is 480 delivered by the utility may be 470 or 490 volts. If you want 240 on the secondary you would use the taps to get 240 volts. Make Sense ?
Alan--
Looking again I just repeated what Iwire said.

[This message has been edited by Alan Nadon (edited 09-06-2005).]

Thanks guys for the quick response and clearing this up for us.

For low voltage distribution transformers (eg. 480V delta to 208V/120 wye), is it more common to see the taps on the primary or secondary side?

I was under the impression that taps were often on the primary side, so that the core would not be excessively saturated if the supply voltage was a tad high. But I don't have a large sample of transformers to go by.

-Jon

Jon


Much more common to see the taps on the front side.

Sorry....

Seroiusly I have not paid that much attention to remember if the taps are primary or secondary.

Taps are on the primary side. If your voltage is low you need to select a lower voltage tap (take some of the primary winding out of the circuit). If your voltage is high you need to select a higher voltage tap (add some primary winding to the circuit) It is just the opposite of what you think you would do . It's all about turns raito. If you have a chance to look at a high voltage transformer like 13200/480V it should have a nameplate with a diagram it will be easy to see what is happining with the primary taps.

any transformer 35 KVA or larger useally have a primary tap in the front and it will marked 4 points above and 2 points below but some have more than that so double check the nameplate to make sure

i do check transformer lead both " unloaded and loaded to make sure it correct voltage most of my time i set at least one step above the normal voltage by time it loaded up it get to correct level

Merci , Marc

Taps can also be on the low side. You can have one primary voltage and taps for different out-put voltages. But can we all agree that taps Do Not correct the phase angle of the SECONDARY voltage?

Quote:
"But can we all agree that taps Do Not correct the phase angle of the SECONDARY voltage?"

That is correct, taps are for voltage adjustment, NOT phase angle or power factor correction.