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Joined: Jan 2003
Posts: 4,391
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iwire Offline OP
Moderator
Here are some photos of a transformer I am doing.

It is a GE 500 KVA 480-208Y/120 Transformer.

We did not ask for fan cooling or shunt trip molded case switches or high temp alarms, none of the cut sheets I received showed any of this.

There are temp sensors in each coil, if the temp rises the fans come on, more heat brings on an audible alarm and finally if it keeps getting hotter the shunt trip switches open.

GE says it's a benefit as the footprint is much smaller, the reality IMO is that the fans and switches cost less than using more raw material to produce a 500 KVA that does not need forced cooling.

[Linked Image]

[Linked Image]

You can click on the rest of the pictures to get a larger one, be warned the large photos are large files.

<IMG SRC=\"https://www.electrical-contractor.net/forum/iw/300KVA1SM.jpg\">

<IMG SRC=\"https://www.electrical-contractor.net/forum/iw/300KVA3SM.jpg\">

<IMG SRC=\"https://www.electrical-contractor.net/forum/iw/300KVA4SM.jpg\">

<IMG SRC=\"https://www.electrical-contractor.net/forum/iw/300KVA2SM.jpg\">

I would be happy to hear any comments, good bad or otherwise.

The job is yet to be inspected.

Bob



[This message has been edited by iwire (edited 09-16-2006).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Jun 2004
Posts: 1,273
T
Member
The install looks terrific.

I'm with GE: this design reduces hysterisis losses since the core is smaller and the reduced footprint is an advantage all the way around.

At this scale forced convection is the way to go.

The shunt trip thermal protection is terrific. It means that you don't have to get complicated when over the 112.5 kVA threshhold.

Now if only the contract permitted compact aluminum feeders instead of copper....

Then you wouldn't have needed a wire bender.


Tesla
Joined: Jan 2003
Posts: 4,391
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iwire Offline OP
Moderator
First, thank you for the kind words.

Wow this is cool I get to bend the ear of a GE guy.

Do you mind if I speak candidly about this?

Quote
Then you wouldn't have needed a wire bender

That is my primary complaint, there is darn little space for the number of conductors needed. I could not find enough space to enter all my conduits.

In the end the wireways worked well but they add work and expense and basically mean the footprint is increased back to 'normal' dimensions.

Second complaint, we have now made what was essentially a maintenance free unit into a unit that will need maintenance.

I see this as being handy for remodels when space is tight but I would rather have a maintenance free unit if space allows.

Just an opinion from a guy stuck trying to fit 600 lbs of copper into a shoe box. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Apr 2002
Posts: 558
C
Member
Hi Bob

A few months ago I posted a comment on the MH site about GE transformers with fans. I was really surprised to see them when I pulled the front cover. Unfortunately I had stubbed the primary and secondary raceways up in the slab to enter the bottom of the transformer. This wasn’t going to work! Luckily this was only an issue for on of the 4 transformers on the project. My supplier had these transformers shipped directly from GE to the job site but they were willing to have MGM ship be a replacement and put the GE in their stock.

I talked to an engineer from MGM and was told that GE was using the fans to get the TP1 rating. He said that they opted to use a higher grade steel core for their tp1 units instead of fans. I’m not sold on the idea of using fans. You now have 6 fan motors that will eventually fail.

I also don’t care for the “smaller foot print” benefit. Its hard enough making up standard transformers. You also have very limited space for cable entry and exit.

BTW…..Beautiful installation!

Curt




[This message has been edited by caselec (edited 09-16-2006).]


Curt Swartz
Joined: Apr 2002
Posts: 7,313
Likes: 7
Member
Bob:
First, NICE install!!!

Second, I have to agree that the fans will become a maintenance issue for an otherwise 'maintenance free' item. (Excluding facilities that do PM)

I also take your side on the small footprint issue; good for a retrofit, not really 'good' for a new install. Seems like some of the mfg's have adopted an 'installer UNfriendly' attitude. The 'spaghetti' going to the fans is a distraction from your quality craftsmanship.
Stay safe.
John


John
Joined: Mar 2002
Posts: 582
R
Ron Offline
Member
Fans required for full ratings on a relatively small xfmr .... BAD
Shunt trip MCS ..... BAD
I don't like it.
Now you have to consider AIC ratings when installing the transformer itself, not the just the devices upstream and downstream.
Now I have more non-adjustable protective devices to worry about when doing coordinations studies ..... BAD

The only fans that show up in my specs are very large pad mounted xfmrs that have dual ratings, in which most of the time the building will not reach the second rating anyhow.

[This message has been edited by Ron (edited 09-16-2006).]


Ron
Joined: Jun 2005
Posts: 821
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Member
Nice neat work, Bob. I haven't done much work like this but I can appreciate the fine workmanship, right down to the same length of tape identifying the conductors.

I notice that the red, blue, and black legs on the secondary are grouped in 4, not 2. I was always under the impression that parallel installations were to be in groups in two. Could u tell me which NEC article permits this?

I'm not even going to get into the shunt trip, fan cooling discussion because that really exceeds my knowledge of transformers. But I appreciate the discussion. [Linked Image]

Joined: Nov 2005
Posts: 507
M
Member
Shock, maybe one of the guys who knows the code better than I will correct me, but there has never been a code requirement for limiting paralleled conductors to 2. As long as you follow the ampacities in 310.16 and allow for derating as per 310.15(B)(2)(a) you can parallel as many conductors as you want. Heck you can even do them in groups of 3.

310.4 is the basic code for paralleling

392.8(D) gives the only place that limits the number of conductors. and this is only if you have A,B,C and a Neutral in the same conduit.

but then again, I tend to hide the code book more than look at it, so [Linked Image]

Joined: Dec 2005
Posts: 866
Likes: 4
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Beautifull job, well done.
It is amazing how compact that 500 kVA transformer is.

The fans will give troubles in future and after a certain amount of hours will fail.
It wouldn't be a bad idea to fit an hour meter on the latter to get an idea how many hours the fans are actually working.

Perhaps preventitative maintenance (replacement) can be carried out on the fans after a specific amount of hours quoted by the manufacturer, to prevent a trip on overtemperature at an inconvient time.


The product of rotation, excitation and flux produces electricty.
Joined: Jun 2003
Posts: 681
P
Member
Hello Bob
This is a nice looking installation. I have seen more and more of these transformers lately.

I do have a question about the support of the conductors terminated on the lugs. Do you have any concern about the distance they are installed without any support before they terminate to the lugs. With the vibration created in transformers, and the weight of all of the conductors per terminal, I myself do see the possible need for a bracket... maybe? It is sometimes hard to judge the distance in the photos provided.

Is the empty EMT for the GEC?

[This message has been edited by PCBelarge (edited 09-17-2006).]


Pierre Belarge
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