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My Master's thesis project works with a system that mechanically prevents a DC motor from stalling and effectively thresholds the amount of current the motor draws and removes large current spikes from sudden loads. It seems intuitive to me that removing these spikes will extend the lifetime of the components in the system (motor, motor controller, battery, etc.) but I need some sort of reference as to why this should be true; ideally some type of study or journal article that I can reference in my thesis. I am also open to personal explanations. Thank you!

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    \$\begingroup\$ I have a Pump system that runs since the 60s, several times a day, and has not yet failed. I doubt any current spikes do any harm to that thing... \$\endgroup\$ – PlasmaHH Feb 9 '15 at 17:01
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    \$\begingroup\$ @PlasmaHH has a point : the first step is going to have to be: identify a real problem (actual failures) and show that existing solutions are inadequate (complex or expensive or unreliable). A mechanical solution to an electrical problem is likely to be a hard sell. \$\endgroup\$ – Brian Drummond Feb 9 '15 at 17:37
  • \$\begingroup\$ @BrianDrummond I guess maybe some background would help. I'm designing a robotic bucket wheel excavator that will operate on the moon or mars. I'm trying to show that my solution will make the electrical system more robust to large sudden loads from rock encounters. With PlasmaHH's pump, the spikes are probably pretty consistent and well below stall current. With my application the spikes could be very random and could stall the motor (without my solution). A motor drawing stall current is obviously bad for the motor but I assume would also be bad for other components as well. \$\endgroup\$ – jkheadley Feb 9 '15 at 18:37
  • \$\begingroup\$ That establishes the need for reliability! And neat project! My impression is that limiting torque by limiting current in the driver - i.e. - allowing the motor to stall safely - is probably more reliable than adding mechanical means. (And easier to override if need be). But that's all I can offer, sorry. \$\endgroup\$ – Brian Drummond Feb 9 '15 at 18:53
  • \$\begingroup\$ @BrianDrummond That's definitely a good point. Thanks for the help! \$\endgroup\$ – jkheadley Feb 10 '15 at 18:56
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Look into "thermal cycle". Presumably any current spike would result in additional (albeit transient) power loss in the motor. Inside the motor there will likely be junctions (solder junctions ?) in the winding. The solder junction would be slightly higher resistance, thus slightly higher loss than the surrounding wiring. This would result in a temperature rise at the solder junction (again probably small). However, a rise in temperature and subsequent drop in temperature is known as a "thermal cycle". I have dealt with thermal cycling in substrate bonded semi-conductors where thermal cycling reduces the lifetime of the semiconductor by eventually tearing away of the bond.

It may take several million extreme thermal cycles to disrupt or destroy equipment, but then in an extreme environment, it might do well to at least consider thermal cycles. EDIT : add link : http://nepp.nasa.gov/docuploads/99810235-C28A-4A8D-BD52223A33EF7CDF/ASME-Hawaii993-lockeed.pdf

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  • \$\begingroup\$ Thanks! That's definitely the kind of thing I'm looking for, and good to know! \$\endgroup\$ – jkheadley Feb 10 '15 at 18:55

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