i'm running a .5 hp 12v dc motor. it works fine until i put a load on it. with the load i am using, the initial current spike exceeds the rating of my power supply so the power supply shorts. my power supply is rated for 52a surge, 40a constant. is there a device or some sort of circuit that i could utilize to solve this problem?
It would depend on the characteristics of the load and load application. Also, what kind of DC motor is it (series, shunt, etc.). What is the time duration for that power supply 52A surge rating?
Typically, the worst case inrush current will be the locked rotor level experienced when the motor starts. However, if it starts unloaded, the motor will accelerate rapidly and the current will decrease with increasing motor speed. It seems that your power supply is capable of providing this current-time envelope successfully. However, the load inertia is such that it exceeds this, which the power supply treats as an overload.
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Paul Hovnanian mailto:Paul@Hovnanian.com
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The large print giveth and the small print taketh away.
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The best thing to do is to use a power supply or amplifier that will current limit gracefully. This may make the motor take longer to recover from a load change, but it'll keep your power supply happy.
Are you driving the motor with an amplifier, or just a switch? If you're using an amplifier, you should be able to find one that'll current limit.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/
It doesn't short, it shuts down >my power supply
With full load yor motor will probably draw already more than your continuous 40A rating, when stalled maybe 120A. just measure the DC resistance and you will know. :-) To supply such a current, your power supply is not sufficient. The only possbility would be to connect a car battery across the output and set your supply to 13.8V, to recharge the battery.
-- ciao Ban Apricale, Italy
Flywheel and or one of those Farad capacitors that they use in car audio. Make sure that you power supply can charge such cap.
Regards,
Boris Mohar
Got Knock? - see: Viatrack Printed Circuit Designs (among other things)
void _-void-_ in the obvious place
I don't think it's a spike. I think what you have is a simple overload - at start up, the motor draws more current than the supply can provide. I'll bet the LRA exceeds the power supply capability.
So it seems your first step has to be to determine the LRA rating of your motor. If it exceeds the supply rating, you'll need to increase the supply or decrease the load on the motor at startup. Or maybe "kick start" the motor with a battery, then switch in the supply to handle the continuous run and to recharge the battery.
Ed
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