140 degree temperature rise
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NEMA Insulation Classes
Electrical insulation systems rated by standard NEMA classifications to maximize allowable operating temperatures.
www.engineeringtoolbox.com
So it considered a continuous use rated motor if the rise is 140 degrees C? I don't understand why it's stated class H and 140 degree rise.
NEMA Insulation Classes
Electrical insulation systems rated by standard NEMA classifications to maximize allowable operating temperatures.
This is a kind of sneaky way of rating motors without actually rating them. You can make as much power as you want to, as long as the temp doesn't go over x. You choose the application and load vs operating time to meet the temp requirements rather than the motor maker going to the effort of supplying data on what to expect for given loadings. It gets frustrating after a while because you are the RnD department in what should be an engineering project. /rant
Ha ha. You nailed it. That's how I've been feeling while searching for a motor for my project. They'll state a few specs but don't want to make any guarantees or proclamations.
This is unfortunately very much intentional... The difference between the claimed figures and the reality are sometimes an order of magnitude apart when it comes to steady-state op. This is entirely down to motor makers putting very little effort into the cooling system. I took a motor that was rated like this and spent a year just on the cooling system. The end result was almost 50kW/kg steady state at 45kW output. Didn't change any magnetics, just cooling. Out of the box it was about 1 or 2kW and then only for a few minutes. Tired old ideas go a long way in the electric motor industry. sorry still in rant mode.
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The nameplate is the guarantee and most of these companies have been around long enough to know what kind of abuse within the nameplate costs them money with replacements and warranty claims.
Get jiggy with it and put some refrigerant through it in a closed loop with a condenser and pump, water cool it, oil cool it... whatever gets the heat off the rotor, laminates and wires efficiently for your particular application. Most motors are absurdly under-loaded steady-state because the cooling, or lack of engineered cooling system doesn't allow them to take a load for very long.
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Notice, he did not list "air" cooling.
So a fan won't help much? It's a $250 tractor. That's why I'm trying to figure out a way to use a $100 motor. I wouldn't want to spend too much on cooling a 50 year old pump motor. I'm pretty sure I can get the ME1004 for just over $600.
If two motors have class H insulation, why is one rated for continuous and the other just intermittent. Is it just the size difference? More surface area to dissipate heat?
Almost every motor is air cooled, it is just how efficiently the heat gets to the air that defines the engineering of it. A wire has a small surface area and so direct forced air cooling will allow only a small current for the temperature rise as air is a terrible heat transfer fluid. It'll help, a bit.
Water has more than 3000 times the ability to absorb heat than air for the same volume and so a small amount of water moving the heat to a much larger radiator will result in a much higher current in the wire for the same Tmax. In this sense, the water is only moving the heat to the air more efficiently than direct air cooling. You can substitute just about any other liquid for water with varying effect.
It depends on your end application. If your primary objective is to save money then put a gas engine on it, it'll be considerably cheaper if you have to buy batteries. You say tractor, is it going to suck in a load of dust with air cooling? This is the engineering of a project, optimise it for what your primary goals are.
Water has more than 3000 times the ability to absorb heat than air for the same volume and so a small amount of water moving the heat to a much larger radiator will result in a much higher current in the wire for the same Tmax. In this sense, the water is only moving the heat to the air more efficiently than direct air cooling. You can substitute just about any other liquid for water with varying effect.
It depends on your end application. If your primary objective is to save money then put a gas engine on it, it'll be considerably cheaper if you have to buy batteries. You say tractor, is it going to suck in a load of dust with air cooling? This is the engineering of a project, optimise it for what your primary goals are.
This project started because I have almost 8 kwh of Chevy volt batteries left over from a solar storage project. I'm trying to go fairly inexpensive because it's just a little tractor that needs an engine and my trails need to be maintained -- nothing urgent or really even necessary.
I was under the impression that the guy who built the old forkenswift metro used a pump motor from an old forklift and I don't remember any mention of extra cooling but maybe I overlooked it. I wouldn't mind adding some water cooling to the project. Do you know of anything I could look into as a reference?
Thanks for all the help so far.
I was under the impression that the guy who built the old forkenswift metro used a pump motor from an old forklift and I don't remember any mention of extra cooling but maybe I overlooked it. I wouldn't mind adding some water cooling to the project. Do you know of anything I could look into as a reference?
Thanks for all the help so far.
The simplest approach is to suck it and see. You'll learn a whole lot by just trying. A forklift pump only operates temporarily for lifting so maybe has a peak duty cycle of 50%. A lot of its heat will be conducted to the pump and taken away by the oil so an uncooled 100% duty cycle application isn't going to do very well. You could make a water jacket around the outside of the motor and thermo syphon it to a radiator above with a fan, you could build it and put a temp probe on the motor windings and let it cool off when it gets to temp, you could burn up a few motors if you have spares and see how hard it can really run. All of these are valid approaches, depending on your resources and willingness to do your own RnD
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Class H is the insulation class, class F is a standard most common, H is a little heavier.... the slot paper and sticks that hold the winding's in the stator.....
There are currently four electric motor insulation classes in use: A, B, F, and H (although there are also N, R, and S classes).
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The duty rating would be directly related to the insulation.....
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No. Duty cycle is more related to the copper mass in the motor.
I found this report https://www.nrel.gov/docs/fy14osti/61083.pdf
"Passive Two-Phase Cooling of Automotive Power Electronics" and was thinking one could adapt it to cool the motor instead of automotive power electronics .
later floyd
"Passive Two-Phase Cooling of Automotive Power Electronics" and was thinking one could adapt it to cool the motor instead of automotive power electronics .
later floyd
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The coolant is expensive AF and the system has to be CLEAN and free of all leaks. It was used in such machines as the Cray Supercomputer.
I just don't see this being applicable in a brushed forklift motor application - at all.
I just don't see this being applicable in a brushed forklift motor application - at all.
It has nothing to do with Cray supercomputers altho the concept is near to a liquid cooling system on a normal pc. Yes the system has to be leak free and clean.
The passive system in my post eliminates the pump and fan but is basically the same. A closed loop system would need to be clean and leak free. pressure tested/vacuum tested
Common automotive anti freeze, Ammonia water, water alcohol mix, hfc's all could be used. Whether effective or not is another topic
Definitely a more expensive solution to the problem than the motor it would be cooling.
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