Transformer Cooling Fans

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curt swartz

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Location
San Jose, CA
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Electrical Contractor
Yesterday I received a shipment of GE150kva 480-208/120 transformers for a project I?m working on. My supplier told me they would be either GE or MGM so I made sure the conduits were installed in the slab so they would work with either one. I noticed through the front went what appeared to be a terminal strip with quite a few very small wires attached. I decided to pull the front panel off and directly behind it was a 400 amp molded case shunt trip switch. Then I looked down to see 6 fans at the bottom right where my conduits are located. Luckily the conduits have only been installed for one transformer so far and they will now have to be run across the wall. I don?t install that many transformers but this is first time I have seen a small dry transformer with fans. Are others finding cooling fans a common item in the newer transformers?

Happy holidays to all!
 
Re: Transformer Cooling Fans

It would have surprised me too. As a former application engineer for a major electrical distribution protection and control equipment manufacturer supporting drytype distribution transformers we never have any transformers with fans or an option to add them.
 
Re: Transformer Cooling Fans

If they are taking advantage of the presence of the fans, in order to be able to achieve the 150KVA rating, then I think you have a mis-application. I would see if you can compel them to send you transformers that meet the specs.
 
Re: Transformer Cooling Fans

What I've noticced about these is:

they are noticably smaller on the outside then a conventional XFMR, in other words a 150kVA is about the same size as a 75kVA. I don't know about the core and coil

They have ventilation openings all around the bottom (on the sides), so the layout changes to provide clearance for the vents.

They are insulated with mineral wool on the inside.
 
Re: Transformer Cooling Fans

I don?t have the model number of transformers I received but just found a link to them at GE?s site.

http://www.geindustrial.com/products/brochures/DET389.pdf

The diagram shows the cable entrance area in the bottom but this must only apply to the 225-1000 kva sizes. There is only a few inches between the fans and the bottom of the 150?s I have so there is no way to bring conduits into the bottom.
 
Re: Transformer Cooling Fans

Larry, it sounds like you are familiar with them. You are correct that the sides are fully insulated. I guess the insulation has to be cut away in the area the conduits are connected.
 
Re: Transformer Cooling Fans

Well, that's a new one to me. I've dealt with many xfmrs. But the G.E. link shows it is a new concept.

Like the rest of you, I'd never seen a dry type so small in KVA & with less than 600V. primary with fans & sec. OCPD built-in.
 
Re: Transformer Cooling Fans

Originally posted by kiloamp7:
Well, that's a new one to me. I've dealt with many xfmrs. But the G.E. link shows it is a new concept.

Like the rest of you, I'd never seen a dry type so small in KVA & with less than 600V. primary with fans & sec. OCPD built-in.
Click to expand...
The cooling fans help to give the transformer a smaller footprint. Also, there is a terminal strip for control wiring that can be used to monitor the fans, and internal temperature. The switch is not an ocpd, it is just a built in disconnect (at least the 6 I installed were)

Gerry
 
Re: Transformer Cooling Fans

Raceway/cable entry into these fan cooled transformers is quite limited. The last one we installed has the dimensions to follow. I suggest you take a marker (we did it like that so the men would have no excuse when they actually cut/entered the unit) and mark the location for entry. Entry locations are not the same as standard transformers. These seem to be pretty nice units, and they are smaller and lighter.
 
Re: Transformer Cooling Fans

I would be very suspicious of the fans. GE says they have a minimum life of 20 years - based on accelerated life tests. Since GE's 2000 hour light bulbs seem to last a week, I give the fans 3 years at most.

And what if you put these fans in a dirty enviroment? Think of all the crap they would pull into the transformer.

I need to double check our spec. to make sure some supplier isn't going to suprise me with these.

Steve
 
Re: Transformer Cooling Fans

I am inclined to agree with Steve in regards to atmosphere xfr is mounted in. Most pieces of equipment we deal with have filters if they require cooling fans.
 
Re: Transformer Cooling Fans

I agree steve66. Smells of NEMA vs IEC starters to me.
Anyway, the life of the DTDT is greatly dependent upon the load, ref. ANSI C57.96-01.250 which talks about the short term overload capability.
This is not to be considered as a black and white issue because there as so many variables. My application notes state that a common 150degC DTDT is expected to have a life of some 30 years based upon a 35% avg loading per accepted industry standards. Push that to 100% and expect a 3-5 year life. This is all based upon 30degC amb with 40deg max. For each 10degC above 30degC expect the life to be reduced by 50%.
That sounds pretty serious but that's pushing it tp the ragged edge.
Then consider the 115 and 80degC energy efficient DTDTs which one would expect to have a longer life because they run cooler and can carry a 15-30% overload without a reduction in life expectancy.
Now add fans and where does this go? Smaller transformer can be used but must rely of fans to remove heat. So one may gain some space with a smaller footprint but is that required? Or, is it more cost effective for the manufacturer to build a smaller transformer and just add fans? Has the manufacturer optimized the design by using fans and still maintain overall transformer life? There there is the energy required to run the fans. The installer gets the privilege of being punished with a smaller interior in which to make terminations in.
With new insulation that may have been developed this may change.
 
Re: Transformer Cooling Fans

The Transformore product from GE was an attempt to provide a TP-1 compliant transformer.
When the GE rep told me about it last year, I suggested the fans in such a small transformer are dumb!
The trick is that the criteria of TP-1 is dependent on a low load, so they can get good performance with this particular model because of the arrangement.
 
Re: Transformer Cooling Fans

If they are meant for low load, I wonder if the fans run 24-7, or if they just come on when the transformer starts getting warm?

Steve
 
Re: Transformer Cooling Fans

The TP-1 criteria is meant for low load, I think 40% or something like that.
GE was able to meet the TP-1 criteria with the fans, and reduce their construction cost. At least that is my understanding of why GE did it. I know that my specifications for relatively small transformers now state "To achieve the full rating of the transformer, fans are not permitted".
 
Re: Transformer Cooling Fans

Just thought I?d post an update.

These transformers were shipped direct from GE but my supplier said they will order an MGM transformer to replace the one going where the conduits were previously installed in the slab. I will use the GE?s at the other locations.

I also called MGM to ask about the TP1 rating. They said cooling fans are one option but they decided to use a higher grade steel in the core to get the higher efficiency rating.

These GE Transformore transformers may be lighter and smaller in some sizes but not the 150KVA. Compared to MGM or SquareD they are slightly narrower but are deeper and weigh about the same.
 
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