# MES liquid cooled AC motor



## leejohnson (Jun 9, 2011)

Would it be sensible to use the heater matrix of the car with a small radiator and a water heater with a water cooled motor. 

In hot weather, just the rad is used. In cold weather the heater is turned on and and the hot air thrown into the cab and circulated through the heater. The water would be 70 degrees celcius controlled by heat from the motor and heater. Is that too hot for the motor, will it be more or less efficient?


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## Jan (Oct 5, 2009)

I wouldn't do that. Why not place an air heating element just behind the liquid heat exchanger? So, the motor stays cool. And you get maximum efficiency, by not heating up -totaly unecasary- the motor and inverter.


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## leejohnson (Jun 9, 2011)

Jan said:


> I wouldn't do that. Why not place an air heating element just behind the liquid heat exchanger? So, the motor stays cool. And you get maximum efficiency, by not heating up -totaly unecasary- the motor and inverter.


Would I not then loose some of the valuable heat through the exchanger, they aren't too efficient. I was just trying to use any heat that the motor generates.


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## Jan (Oct 5, 2009)

leejohnson said:


> Would I not then loose some of the valuable heat through the exchanger, they aren't too efficient. I was just trying to use any heat that the motor generates.


I don't see what you loose. Maybe I don't understand you, or I am very unclear. Probably the last.

On top of the heat exchanger inside your heater assembly you construct an aextra electric powered air heater. Ceramic, or from old hair driers. Whatever.

Cool outside air -> Heater Heat exchanger -> pre warmed air -> New (ceramic) air heater -> You and your co pilot.

Motor -> Warm Water -> Heater Heat exchanger -> cooled off back to motor

In my project this is a prety simple solution. Thats one of the pro's of using an old timer.


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## Nathan219 (May 18, 2010)

We do just what you are mentioning, we have a small radiator from a motorcycle and heat exchanger from a Firero as our cooling system for our MES DEA motor controller we have a valve to switch another heater core in our vintage air system into the loop when it gets colder. The system will make heat but not much, unless you use a small radiator. Machines had a different opinion on what is hot than we humans do. 70C is not too extreme in my opinion.


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## leejohnson (Jun 9, 2011)

Jan said:


> I don't see what you loose. Maybe I don't understand you, or I am very unclear. Probably the last.
> 
> On top of the heat exchanger inside your heater assembly you construct an aextra electric powered air heater. Ceramic, or from old hair driers. Whatever.
> 
> ...


I'm with you now, are you the old timer, or the car?
Thanks for you help


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## steven4601 (Nov 11, 2010)

Keeping the water for the motor low is a must in my conversion...Dumping 100kW through a motor does not take much time to heat up the windings.

See the motor name plate. It has an insulation class. Usually it is F (150C) for traction motors or performance oriented motors. That describes the quality of the Polyurethane insulation layer on the copper windings. If you stress the rated insulation class temperature you're going to weaken the enamel (polyurethane) and produce shorts. It is Nr 1 failure of AC motors. 

150C is not a hard limit but a gradual slope. If you'd run the motor so the copper windings become 120C often, you will likely run into trouble. Keep it down far south of 100C as much as you can. Reason is AC motors due to the higher voltages often are also stressing the dielectric properties of the insulation. Once an ARC is produced it is basically toast.


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## leejohnson (Jun 9, 2011)

steven4601 said:


> Keeping the water for the motor low is a must in my conversion...Dumping 100kW through a motor does not take much time to heat up the windings.
> 
> See the motor name plate. It has an insulation class. Usually it is F (150C) for traction motors or performance oriented motors. That describes the quality of the Polyurethane insulation layer on the copper windings. If you stress the rated insulation class temperature you're going to weaken the enamel (polyurethane) and produce shorts. It is Nr 1 failure of AC motors.
> 
> 150C is not a hard limit but a gradual slope. If you'd run the motor so the copper windings become 120C often, you will likely run into trouble. Keep it down far south of 100C as much as you can. Reason is AC motors due to the higher voltages often are also stressing the dielectric properties of the insulation. Once an ARC is produced it is basically toast.


I'm not going to be stressing the motor that much! I presume that the cooler the motor runs, the more efficient it works?


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## steven4601 (Nov 11, 2010)

I dont know at which temperature the motor runs most efficient, but generally cooler is better yes.

Get a 2nd waterpump, a cheap brushless pump can be bought new on ebay for 20 or less. 

Perhaps it is an option to use a ceramic heater?


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## leejohnson (Jun 9, 2011)

steven4601 said:


> I dont know at which temperature the motor runs most efficient, but generally cooler is better yes.
> 
> Get a 2nd waterpump, a cheap brushless pump can be bought new on ebay for 20 or less.
> 
> Perhaps it is an option to use a ceramic heater?


I think that is sounding like a good idea. I will take your advice, it would be interesting to know what the optimum temperature is for a motor though as it would make sense to try and run it at it's most efficient.


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## steven4601 (Nov 11, 2010)

Lower temperatures produce lower copper losses. But also the iron permeability & resistance drops. Lower permeability means more current is required to produce the same torque. Lower iron impedance probably produce more eddy-current losses..... At which temperature this happends is unknown. Its even frequency dependant. 

To be safe try to keep it cool as you can without taking it into the extreme . The old ICE radiator is perfectly suited to keep the AC motor and inverter cool.


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## leejohnson (Jun 9, 2011)

It's a mine field out there. Thanks for your input, I had no idea it was so complicated. Might it be worth setting the water pump to switch off at 0 degrees c? In winter it can get to -18c here.

Cheers

Lee


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## steven4601 (Nov 11, 2010)

There is no risk in turning the pump off if the temperature sensor indicates its 'cold'. Afaik all watercooled AC motors are cooling their stator through the outside contact area of the laminations. The temperature sensor is also placed there.

But what about your inverter controller? Doesn't it need cooling also? Converting 40kw you'll likely loose a kilowatt during the process. That heats up the chill plate in less than a minute.


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## leejohnson (Jun 9, 2011)

The project is next year, I'm just getting all the ideas together and picking peoples brains. If the inverter generate more heat than the motor then I suppose it would make sense to route the water through the motor first, then the inverter


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## steven4601 (Nov 11, 2010)

almost but it will work 

In a high flow setup it does not matter in which order you place the components. 
But in a regular setup wtih a small pump (pump wattage under 15watts) you should cool your inverter first then the motor. IGBT's (the power switches in the inverter) are heat intolerant. 

If I recall correctly the mes dea manual clearly describes the water cooling order/routing.


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## leejohnson (Jun 9, 2011)

Great cheers


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