On 03/21/2013 08:08 PM, Scott Dorsey wrote:
In article , jim beam wrote:
On 03/21/2013 07:23 PM, Nate Nagel wrote:

*why* is it overheating?

because it's linear, retard. if you don't know what they means, ****
off until you find out.

Nothing wrong with linear motor control, it's just inefficient and
produces a lot of heat. I used to work in a place with a 1.2 MW DC
motor

that must have been interesting - what did that motor do?


whose field coil voltage was controlled by a couple rooms full
of cast-iron resistors.

that must have been a sight to see too.


The resistance array lasted nearly 80 years
before the whole facility was taken down.

shipped to china? or replaced by pwm controllers?



As long as you keep within the safe operating area of the semiconductors,
you're fine. If you exceed them, bad things happen. But we don't know
if the semiconductors are failing on these things, or if it's just
ordinary RoHS solder failures; the RoHS crap doesn't like thermal cycling
so well.
--scott



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fact check required