Supplying current to locked DC motor
Supplying current to locked DC motor
(OP)
I have a question about DC motors. I have some 12vdc motors that operate a pair of butterfly valves, I have a problem with them vibrating open after they have been closed so I was wondering if I made an additional circuit that kept a constant current on the motors with a lower voltage say like 3v would that be enough to keep pressure on the valves with out burning up the motors? They are small motors operating a gear reduction box that will be open to free air flow. If this is possible is there a formula to figure out what voltage to safely supply based on the regular operating amperage?
Thanks
Thanks





RE: Supplying current to locked DC motor
Do you know the gear ratio and efficiency?
Do you know the armature resistance of the motor?
Do you know the thermal resistance of the motor?
Do you know the torque required to actuate the valve?
If so, you can.
RE: Supplying current to locked DC motor
The easiest way to determine the maximum safe current is probably to directly measure the winding temperature under stall conditions. I don't think any simple formula will be forthcoming as there are so many variables.
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RE: Supplying current to locked DC motor
BK
RE: Supplying current to locked DC motor
RE: Supplying current to locked DC motor
RE: Supplying current to locked DC motor
If you can power the motor with a PWM signal you would just turn the duty cycle down to whatever is required to keep the valve closed.
I simple microcontroller could do this automatically (once closed go to low duty cycle).
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Supplying current to locked DC motor
RE: Supplying current to locked DC motor
If operation is hampered by the resistor, a simple time relay that opens a shorting contact across the resistor after the valve has closed will solve that problem.
May also be combined with a diode that bypasses the resistor when you open the valve.
Of course, the resistor will dissipate some heat. But it can be put where cooling is good and heat doesn't harm.
Gunnar Englund
www.gke.org
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