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Unread 12-02-2006, 13:08
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Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
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Re: FisherPrice Problems

Quote:
Originally Posted by CyberWolf_22
We have monitored the current in the motors and they are steady at about 20 amps till right before they shut off and they ideally with out going through any other value go to zero.

Allen,
I question what you are using for current monitoring. If you are at anything less than full power, most current meters will not be able to accurately measure the changes in current from a PWM output. If that is the case you are running more closer to stall (64 amps) then you think. Even at 34 amps (max power) you are asking the motor to dissipate over 360 watts, at about 41% efficiency you are dumping over 200 watts in heat inside the motor. That is a lot of heat. You also may have loose connections on the motors (FP motors are very difficult to terminate properly). Heat generated at the connection migrates inside the motor and raise the temp on the thermal cutout.
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Al
WB9UVJ
www.wildstang.org
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Storming the Tower since 1996.