Exceeding gearhead permissible torque?

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om_tech_support_JT
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Exceeding gearhead permissible torque?

Postby om_tech_support_JT » Mon Aug 12, 2013 6:40 pm

Q: I have a PK296A2A-SG7.2 geared stepper motor. The rated current of the motor is 3A/ph. The motor is currently stalling if I only provide the rated current. I may have mis-sized this motor due to inadequate safety factor in my calculations. I'm wondering if I provide more current to the motor (I have a driver that can supply 4.2A/ph), what kind of torque should I expect? Is this safe for the motor?

A: Actually, the holding torque specification for the PK296A2A-SG7.2 geared stepper motor is the maximum permissible torque limit for that given gear ratio (7.2:1). It's not recommended to exceed this specification. Providing more current will increase torque output from the motor which in turn will produce more torque at the shaft of the gearhead. In theory, providing a stepper motor 40% more current (4.2 / 3 = 1.4) should increase its torque output by 40% as well. However, this will exceed the 44 lb-in holding torque specification of the gearhead. Overloading the motor will produce excessive fatigue and stress and shorten the life of the gear teeth or shaft; not to mention the problems with high temperature that could result from the high current. Increasing dwell time between moves may help with reducing the temperature of the motor, but it doesn't resolve the gearhead issue. To avoid potential problems, we would recommend that you select another product or gear ratio that matches your requirements better (with rated current).

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