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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum ( )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Posted by: Cichocki ( )
Date posted: Thu Jul 5 22:43:41 US/Eastern 2001
Subject: Electric drives
We are looking for any information in respect to electric motors with "soft" start and electric motors with variable speed drives, concerning failure rates, reliability, and maintenance lost time.


Subject: Electric drives
Reply Posted by: Gary Sunada ( )
Organization: Reliability Analysis Center
Date Posted: Wed Jul 11 11:46:49 US/Eastern 2001
Failure rates of motors with soft start or variable speed drives vary widely depending on a number of factors: AC or DC, type of motor, environment, voltage and so forth. Generally, attempting to construct a failure rate table of most combinations of motor specifications would require substantial time and resources to gather such data; most needs are covered by doing a study on one motor design, or multiple related ones. One particular study for a frequency-modulated motor, for example, yielded a failure rate of 4.0 E-6 failures per hour (80% confidence value) with one failure count due to a capacitor; the motors operated in a factory environment, where some were protected from dust, grease and other contaminates (the failure was on an unprotected unit) in a temperature range of 15-32 deg. C.

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