Strange XFMR construction

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sandsnow

sandsnow

Senior Member
Location
Southern California
I saw a delta wye xfmr 225 kVA 208V to 480Y277 where all taps were at the front except the H0 tap which was in the back.

What's up with that??

Xfmr was MGM.

Anybody ever seen that?
 
Let's back the truck up a second. You say that you have a delta wye 208-480/277 transformer which makes it a step-up transformer. No problem with what you have said so far. Now that H0 "tap" I have a problem with.
I would like to think that you have (3) primary connection points for the 208 delta labeled X1, X2, and X3 2which represent the corners of the delta, A, B, and C phas.
I would like to think that the secondary terminations would be maked H1, H2, H3, and H0, H0 being the neutral point of the secondary wye which commonly comes from the factory with a jumper to the transformed enclosure.
I is also common for the tranfomer to include primary taps providing a means to correct for low voltage.
 
templdl said:
Let's back the truck up a second. You say that you have a delta wye 208-480/277 transformer which makes it a step-up transformer. No problem with what you have said so far. Now that H0 "tap" I have a problem with.
I would like to think that you have (3) primary connection points for the 208 delta labeled X1, X2, and X3 2which represent the corners of the delta, A, B, and C phas.
I would like to think that the secondary terminations would be maked H1, H2, H3, and H0, H0 being the neutral point of the secondary wye which commonly comes from the factory with a jumper to the transformed enclosure.
I is also common for the tranfomer to include primary taps providing a means to correct for low voltage.
Click to expand...

I don't understand your problem with the H0 tap? The X taps are primary(208V) and the H taps are secondary (480Y/277). It has voltage taps on the 208V side.
Factory bonding jumpers are not so common with XFMRs provided in my area. GE used to do it. I can't remember who else.
 
Dave58er said:
Is that 208v phase to phase? isn't that an odd voltage for a delta?
Click to expand...


Not if it's on the primary. The primary has whatever voltage is applied to it, in this case 208 volts. The delta configuration does not change the applied voltage.


And I agree with sandsnow. I haven't seen many transformers where the neutral was connected to the case by the manufacturer.
 
Larry,

I have dealt with many MGM Brand Transformers in the past, and have never seen one with any taps or terminals located "in the back" - all FCAN / FCBN taps on the windings were on the same "Side" of the assembly, which the "H" and "X" Terminations are located.
This location being the "side" which is accessed when the cover containing the nameplate is removed.

Maybe the reasons for my experiences are these Transformers were all Step-Down Transformers (480v Delta Primary - 208Y/120v Wye Secondary), and most were Non- K Rated.

Interesting though!

I will definitely keep this in mind for future installs! (AKA: "Ya' Never Know Whaddahecks Gonna Happen!!!")

Thanks for the info!

Scott
 
sandsnow,
I was going by the term "tap" which taps are commonly provided on the input side of the transformer, that is when you "tap" a winding. I misunderstood your terminology as transformers may have up to (2) taps 2-1/2% FCAN and (4)taps 2-1/2% FCBN.
I then may assume that it is the neutral "connection," that is the connection to the common point where the 3 windings of the wye come together to form the neutral of the 480y/277. With the DTDTs that I am familiar with an have sold I never had an H0 connection placed in such an odd location.
 
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