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Old 05-10-2010, 04:37 PM   #8 (permalink)
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I cannot quite remember which sepex you got but the reasons it is hot are:

1) Your motor is rated for triple the voltage you are using. Being at 48V means ventilation is not 3 times worse - it is 4-5 times worse as it varies exponentially with rpm. It is not a coincidence that we put a lower voltage spec on our motors...
2) Your motor is wound for much higher voltage. Operating as low as 24-48V results in lower efficiency which produces more heat.
3) Class H insulation allows the coils to get to 160-220C which feels quite hot even on the outside case. Even 60C feels quite hot to touch.
4) Running a sepex motor at 1/3 the voltage does not allow you to overload properly - your armature will witness increased amps, while the field will barely increase its amps. This is very bad for commutation and heats up the comm.

Why do you use 48V anyway?!?

Originally Posted by ExplodingDinosaurs View Post
Actually it's the opposite for my motor. Allegedly my Kostov motor is spec'd for 144 Volts, but at 1/3 that (48 V) the fields get pretty hot after 10 or 15 minutes. At 144 Volts I would expect the field to overheat in about 1 minute. One reason to run the field at less voltage is you can ramp it up for regen, down for accelerating, and have some overhead for higher or lower rpm.

I'll parrot what I've heard: There is some difference between shunt and sepex. The field and armature are run in parallel for both. The shunt field is wound with finer wire, and is designed to run at full voltage. This is what you'd do for a constant speed motor, like a conveyor belt or elevator. It would be harder to get regen on a shunt motor, practically speaking you could only do it by physically speeding up the motor as it would be hard to give it higher than pack voltage. A sepex field is wound with somewhat thicker wire, and the field meant to generally run at less than the full armature voltage -- this gives some voltage overhead for regen.
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