> I would like to test with a load, but haven't figured out 
> a way to do that yet. (The cart is not ready yet.)
> Anybody know how to put load on a 500W motor sitting on a desk?
 
If it's a real problem just skip straight to the stall test, which will likely be highest 
current draw. Beware the hazards, but you need to know the stall current so you 
need to do this test. Lock the motor solid with the rotor prevented from turning in a 
suitably secure and safe fashion. Make sure your batteries are new and fully 
charged, cables are short, good connections etc. Measure the current with 100% 
direct battery power (for just a few seconds) measure current with a DC clamp on 
ammeter. Expect more than you were expecting. Spec your controller accordingly, 
then build it.

Test with your controller also with the locked motor. Try it for a second or two, if no 
smoke, good. Continue tests at various power settings 0 -100%. Carefully monitor 
heat rise over time, with appropriate cool down periods to avoid damage to 
controller or motor. Check heat rise in your MOSFETs and heat sink agrees with 
your calculations.

-- 
Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
eMail:  brent.brown@clear.net.nz


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