Micropositioning Stepper Motors

[GDN]

I have developed a micropositioning stepper motor system in which the magnitude of the current can be changed in each phase proportionally.

Therefore, when the system is not in use, I can decrease the current and not loose positon. The system is always stopped on a 90 degree boundary(the most stable state). Therefore, one phase will be off, and the currrent is reduced in the other phase to 150-200ma. Once again the main reason to do this is that I do not want to loose the current position.

My main question is: What will happen to the motor if the following condition exists in the system. Phase A is shut off and phase B has a small hoding current 150ma-200ma. If the system is in this condition for a year or more before someone used it, would there be any damage to the motor?

Thanks,
GDN

 

[tiki]

Hi GDN,
There should be no "electrical" failure at the motor caused by infinite time current flowing in one or two phases. Assuming, all parameters inside specifications, including worst case temperature risings, caused by I^2xR winding losses. Conceivable: Grease of botor bearings will get resinous, and a small amount, not significant degradation of the magnet power. This is because the normal statistic thermal reversal of several elementary magnets will be supported by the magnetic force of the winding and especially by temperature. But I believe, you won't be able to measure this effect, permanent magnet dc motors are functioning over decades of years without degradation also.
If you want to to the best for your system, take a stepper from a aerospace manufacturer, for instance Phytron. They are experts for highly reliable steppers.
tiki