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Problems With Stepper Motors

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The biggest difference between a stepper motor and a standard DC motor is the stepper motor does not have any brushes. The stepper motor's rotation position can be precisely controlled. The differences in the stepper motor makes the motor develop different problems than the problems found on a standard motor. A stepper motor can be found in CNC machines, high-speed pick and place equipment, floppy disk drives, printers, scanners and slot machines, just to name a few commercial uses.

Motor Not Turning

A stepper motor will not turn if there is not enough current being sent from the power supply. The motor will not turn when current is being sent, but does not have enough torque to turn the shaft of the stepper motor. The required torque must be capable sufficient as the desire speed setting. If the speed setting is too high for the torque requirement, the stepper motor will not turn, no matter how much current is being sent to the circuits.

Driver Failure

Driver failure is a common problem on a stepper motor. If the peak voltage is not controlled from the power supply, the stepper motor driver will fail. The correct clamp diodes must be selected for the application. The diode selected must match the speed switch on the stepper motor. The component limits the peak voltage sent to the motor from the power supply. A stepper motor's clamp diode must have the same switching characteristics as the switching time used by the output transistors.

Short Circuit

One of the major problems with a stepper motor is complete motor failure. This problem is caused by excessive current being sent to the device by the power supply. A short circuit in the wiring from the power supply to the motor cause this problem with the stepper motor. Some application will cause this short circuit. So if an application is prone to short circuits, an overload protection device can be installed to correct this stepper motor problem.

Audio Noise

Audio noise from the motor is a high-pitched squeal. The noise can affect the chopping controls of the stepper motor. Most of the time, the audio noise will only affect the control circuits because of a stability problem within the circuits. The effective chopping frequency changes from the required frequency to a sub-harmonic frequency. Excessive electrical noise and voltage spikes can also shift the motors control circuit frequency. Once the frequency changes the control circuits, the stepper motor will slow down or not turn.

References

About the Author

Mitchell Brock has been writing since 1980. His work includes media relations and copywriting technical manuals for Johnson & Johnson, HSBC, FOX and Phillip Morris. Brock graduated from the University of Southern California in 1980, earning a Bachelor of Arts in English.