February 2013 Electrical Apparatus

February 2013 Electrical Apparatus

This is a summary of the Electrical Apparatus February 2013 featured technical article,  by Richard L. Nailen, P.E. 

When a motor fails, the user must decide whether to repair it or to replace it with a newer one. The choice is not a simple one. It should be based on more than a comparison of repair cost with the price of a new motor.

Because a replacement often offers higher efficiency, the actual load should be known. A single average kilowatt-hour cost won’t indicate the true energy cost for a motor operating at different times of day, or a varying load.

Users often encounter claims that the latest motor designs are more reliable because of larger or “motor quality” bearings, better insulation, or other benefits of rapid technological innovation. In fact, inverter-duty wire, epoxy insulation, and many other features common in today’s motors have been in common use for decades. Most are readily available and widely used in repairs as well.

In addition to long-term reliability, a new motor may be assumed to offer less likelihood of early failure than a repaired unit. However, ample evidence supports the widely published relationship between failure rate and age, showing a relatively high initial probability of some breakdown (the “infant mortality” period), followed by years of relatively trouble-free service, then by the increasing likelihood of trouble brought on by aging.

Thus, either new or properly repaired motors may be at least as vulnerable to breakdown soon after installation as in later life. Furthermore, the nature of such failure cannot be predicted as a function of age. Catastrophic breakdowns will occur less often than minor ones, but no single failure is any more or less likely to be one type or the other.

Anyone facing a repair-or-replace decision should evaluate the capabilities of repair shops as rigorously as those of motor manufacturers. Users should also recognize the importance of a sound predictive maintenance program in maximizing motor reliability.

To order a back issue with the full article, “Repair or replace? Not an easy decision” call 312-321-9440 or visit our online webstore.

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