Transformer Temperature Rise Question

[fifty60]

I have two different transformers. One is designed with UL class 180 C insulation, with a 115 C temperature rise at a maximum ambient of 40 C. The other transformer has 130 C insulation system with an 80 C temperature rise.

Can I expect the transformer with the lower rated insulation to operate at less temperature than the transformer with the higher rated insulation? At ambient the temperature rise will only be 80 C whereas the other transformer will have, or is at least rated to have, 115 C temperature rise?

Is this a positive or a negative? Obviously with the lower rated insulation I do not have much room to go above ambient condition. The higher rated insulation gives me 25 C separation from the temperature rise and the rating of the insulation, whereas the lower rated insulation only gives me 10 C for winding hotspots.

 

[mgookin]

You have two transformers to choose from?
Or you have two transformers?

 

[jim dungar]

There are three components that go into transformer temperatures.
The ambient - usually at 30?C for liquid filled and 40?C for dry types.
The insulation rise - typically 55 or 60?C for liquid filled and 80, 115, or 150?C for dry type.
The hot spot allowance - 30?C for dry type units.

If the sum of these values exceeds the ultimate insulation temperature rating, the life of the transformer is usually shortened.

For identical transformer construction and loading, you would expect a lower temperature rise unit to produce less heat. However if the construction is different (e.g. sand-filled epoxy versus air over windings) then it might be hard to predict which unit runs cooler.

 

[fifty60]

Here are the two transformers. The Dongan is part number 50-1000-059 and the Sola Heavy Duty is part number CE1000TH. The Dongan has the higher insulation rating and temperature rise.

They are both Industrial Control Transformers. The Dongan is not enclosed and has a higher insulation rating whereas the Sola is enclosed and has the lower temperature rise and insulation rating. I would think it would be the other way around and the enclosed would need the higher ratings.

I currently use the non enclosed and would like to switch to the enclosed. I am worried about the overall temperature of my equipment enclosure rising due to the new transformer. They look like identical transformers other than the temperature ratings and the enclosure vs non-enclosure. Any help on this is appreciated. Anyone else see any other differences?

Dongan:
http://www.dongan.com/Portals/0/Catalogs/Industrial Control Transformers (50 series).pdf

Sola:
http://www.solahevidutysales.com/pdf/transformers/ICE.pdf

 

[jim dungar]

I am worried about the overall temperature of my equipment enclosure rising due to the new transformer.

You need to find the losses for each transformer, then you can determine the watts lost based on your loading profile.

The insulation temperature rise value alone is not sufficient.

 

[fifty60]

Can anyone else point out any differences between the two transformers? The Sola has a center tapped transformer and is an "export" model. The Dongan does not have a center tap. The insulation and temperature rise specs are the major differences that I see. Does a lower temp rise and insulation rating indicate in any way lower quality?

 

[jim dungar]

Does a lower temp rise and insulation rating indicate in any way lower quality?

No.

Temperature rise is about heat transfer not heat generation.

Have you asked each manufacturer for their losses or heat output? This is a common issue for control panel builders, and therefore should be easy to come by.

 

[fifty60]

I will speak with the manufacturers, but I am trying to get a better understanding first. So a temperature rise of 80 C means that it will transfer 80 C into a 40 C ambient at full rated KVA?

 

[GoldDigger]

You cannot talk about "transferring 80?C".
A small object or an insulated object 80C hotter than the panel ambient will transfer less heat to it than a larger uninsulated object which is only 60C hotter then the ambient.
The transformer with the higher internal temperature rise may be reaching that temperature because it is wasting more power or because the core and shell do not transfer heat to the air as well.
You cannot generalize about the effect without knowing more about the internal construction.

Tapatalk!

 

[jim dungar]

So a temperature rise of 80 C means that it will transfer 80 C into a 40 C ambient at full rated KVA?

As Golddigger said: absolutely not.

Stop reading the marketing literature. It is full of potentially misleading information. For the vast majority of installations (but not all), temperature rise is a useless tidbit of information, yet marketing seems to focus on it.

 

[fifty60]

I read over the comments again and better understand them now. Should I compare power in to power out to understand what losses are going on inside of each Industrial Control Transformer? They are both 1KVA Industrial Control transformers. They are both approximately the same size. One is ecapsulated and one is not encapsulated. The encapsulated transformer has a lower insulation rating and temperature rise than the non-encapsulated transformer. I currently use the non-encapsulated transformer.

The prospective encapsulated also has a center tap on the secondary for 120/240 voltages. I need this center tap and that is why I am looking for a new transformer. I just do not understand how to interpret the insulation differences. I do not understand what implications the insulation and temperature rise differences will have on my design. My design is sensitive to temperature rise, so I am trying to determine if there will be any difference here if I make the switch.

 

[jim dungar]

I do not understand what implications the insulation and temperature rise differences will have on my design.

They will have no direct effect.

My design is sensitive to temperature rise, so I am trying to determine if there will be any difference here if I make the switch.

You need to find out about the transformer losses and how much heating they contribute.

 

[GoldDigger]

You need to find out about the transformer losses and how much heating they contribute.

Which includes how much heat may be directly conducted away from the inside of the panel through the transformer mounting flanges compared to heating the air inside the panel.

Tapatalk!