Where to buy transformer oil?

Status
Not open for further replies.
O

Open Neutral

Senior Member
Location
Inside the Beltway
Occupation
Engineer
We're experimenting with various coolants on our electric car's cooling system. [The loop cools the motor controller heat sinks.]

One possibility is transformer oil. But unlike PEPCO, we need but a liter or two, not a kiloliter. None of us are young, agile, & foolish enough to shinny up a pole with a bucket; are their any sources of same in small quantities?
 
A decade or more ago, there was a collage level electric race car competition. They would race in conjunction with CART races. The idea was take a 30hp, 3 phase AC motor and a souped up VFD. They would get maybe 200 hp out of a 30hp unit. To make that work they had a large oil cooling system. Maybe you could find out what they used.

This was one:
http://connection.ebscohost.com/c/articles/9512092010/lincoln-electric-races-motor
 
Last edited:
I would try a transformer supplier. Large transformers are often shipped without oil, this being added on site, so the suppliers should have drums or kegs of it.

Proper transformer oil is selected for high voltage withstand properties, but in your application with presumably modest voltages, any light, fluid, and not too flammable oil should serve.
What about engine lubricating oil, the lightest available grade.
 
Open Neutral said:
We're experimenting with various coolants on our electric car's cooling system. [The loop cools the motor controller heat sinks.]

One possibility is transformer oil. But unlike PEPCO, we need but a liter or two, not a kiloliter. None of us are young, agile, & foolish enough to shinny up a pole with a bucket; are their any sources of same in small quantities?
Click to expand...

You need to look a little bit closer of what you're trying to accomplish. Transformer oil is a compromise between insulation properties, heat transfer capability and maximum exposure teperature. It may not be the most suitable for your application if the heat sinks are operating at a higher teperature than what is expected in transformers. There are heat transfer oils such as Marlotherm or Dowtherm that have a higher breakdown temperature and may suit your needs better. This could be a rather complex thermal design issue where more expertise maybe in order.
 
weressl said:
You need to look a little bit closer of what you're trying to accomplish. Transformer oil is a compromise between insulation properties, heat transfer capability and maximum exposure teperature. It may not be the most suitable for your application if the heat sinks are operating at a higher teperature than what is expected in transformers. There are heat transfer oils such as Marlotherm or Dowtherm that have a higher breakdown temperature and may suit your needs better. This could be a rather complex thermal design issue where more expertise maybe in order.
Click to expand...

There's lots of that kind of learning going on. We need low viscosity, fair electrical insulation {200V}, good thermal conductivity, and no propensity to absorb water. We're considering a variety of options, including Fluorinert {One of the team has lots of CRAY-II time, so he had to suggest it....} as unlikely as that is.

We want things cooler than 100C, so high temp is not an issue. And, oh, it better not ruin the paint when spilled, so no DOT4 brake fluid, but I have some DOT5 to try.
 
Power Steering Fluid

Power Steering Fluid

My dual 160kw 360v Delphi frameless PM brushless motors and 600amp cont(IIRC) Rinehart drives use Power Steering fluid as the cooling agent. I am told its thermal capabilities is much better than lots of other fluids. This decided by the company with some good hotshot engineers who design & build these conversions and are building for some of our countries largest commercial delivery vehicles.....
 
How about ethylene glycol or mineral oil. Both are readily available in small quantities, low cost, and have relatively high flashpoints. Not so sure about ethylene glycol's insulation capabilities, but it should be easy enough to find out.
 
Hi folks ... I've read through post 9 and there are some interesting and scary thoughts. I'm involved in industrial and mobile hydraulics, electro-hydraulics especially. Occasionally, we will submerge electric and electronic assemblies in oil, virtually always conventional hydro-carbon based fluids. As fluid breakdown is greater at higher temperatures (that rule of thumb that chemical reactions double every 10 centigrade degrees), temperatures are not usually very high ... 130F is good, 180F is not good, between there are engineering evaluations made.

We make regular suggestions ...

NEVER use a fluid optimized for automobiles or transmissions ... they have an additive package which intentionally encourages solution of water in the fluid rather than the water settling.

Never use in a (water) glycol system, whether ethylene or propylene glycol ... just like your car antifreeze, these are frequently roughly equal water and glycol. I've never seen full concentration glycol used, but would be concerned that water is miscible in them.

There is a design concept where the hydraulic fluid flows through the motor windings to cool it. This offers the advantage of smaller (typically the motor is loaded to about twice what it could be if externally air cooled) package, but the big advantage is that a much quieter assembly can be made.

Remember that PURE water does not conduct electricity. Large PoCo generators have water cooled stators. We're talking medium voltage here, often 10,000 to 50,000 volts. Of course, pure hydrogen doesn't burn either ... the generator housing is full of it, at moderate pressures (3-100 psi) for lower friction and better thermal conductivity. DON'T TRY THIS AT HOME<g>.

The silicone or chlorinated hydrocarbon fluids would be good if you can find them in small quantities. The Dowtherm family sounds good ... although way over engineered for your need, I'd expect ... and is used in industrial applications so should be readily available.

BUT ... what I'd use is a good, low viscosity, petroleum hydraulic oil which is DEFINITELY available in small quantities ... a 32 cSt from any reputable manufacturer will give you decent life for testing at your temperatures ... certainly in the 1000's of hours, then evaluate the silicone products if operating temperatures really are exceeding 180F.
 
GeorgeB said:
As fluid breakdown is greater at higher temperatures (that rule of thumb that chemical reactions double every 10 centigrade degrees), temperatures are not usually very high ... 130F is good, 180F is not good, between there are engineering evaluations made.
Click to expand...
We need to keep the FET's heat sink at no more than 60-70C, I'd say.

NEVER use a fluid optimized for automobiles or transmissions ... they have an additive package which intentionally encourages solution of water in the fluid rather than the water settling.
Click to expand...

Had not planned on it.

Never use in a (water) glycol system, whether ethylene or propylene glycol ... just like your car antifreeze, these are frequently roughly equal water and glycol. I've never seen full concentration glycol used, but would be concerned that water is miscible in them.
Click to expand...

Agreed

Remember that PURE water does not conduct electricity.
Click to expand...

All we need is a handsome prince to kiss the water and make sure it's pure of heart.

The silicone or chlorinated hydrocarbon fluids would be good if you can find them in small quantities. The Dowtherm family sounds good ... although way over engineered for your need, I'd expect ... and is used in industrial applications so should be readily available.

So my one idea is a quart of DOT5 brake fluid.

BUT ... what I'd use is a good, low viscosity, petroleum hydraulic oil which is DEFINITELY available in small quantities ... a 32 cSt from any reputable manufacturer will give you decent life for testing at your temperatures ... certainly in the 1000's of hours, then evaluate the silicone products if operating temperatures really are exceeding 180F.
Click to expand...


Our tiny 10 l/m pump is great on water, but can't handle drugstore mineral oil; way too viscous.

We're looking at http://www.amazon.com/gp/product/B004Y0RX52/ref=s9_simh_gw_p201_d0_i1 pr similar.
 
Open Neutral said:
We need to keep the FET's heat sink at no more than 60-70C, I'd say.

Our tiny 10 l/m pump is great on water, but can't handle drugstore mineral oil; way too viscous.

We're looking at http://www.amazon.com/gp/product/B004Y0RX52/ref=s9_simh_gw_p201_d0_i1 pr similar.
Click to expand...

Your temperature limits fit my experience. A quick web search on oils similar to the sewing machine oil suggests they are likely in the ISO 15 or ISO 22 range, 2 or 1 grade lower than the COMMONLY used ISO32 ... but made by all the major players. ExxonMobil DTE11 is ISO22. Penzoil has it in 22. Shell Tellus is available in 22.

I pulled these from a HYDRAULICS reference where anti-wear additives are present and very important ... not of much concern for you ... but ask any knowledgeable oil distributor for their ISO 15 hydraulic, circulating, or turbine oil. They should cost about what motor oil costs ... $10-$15 per gallon, but packaging may be an issue. RUN from anything that says "detergent" or "good emulsifying additives" or whatever.
 
Status
Not open for further replies.
Top