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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

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

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Original Message:

Posted by: Cichocki (artur.cichocki@worley.com.au )
Organization:worley
Date posted: Thu Jul 5 22:43:41 US/Eastern 2001
Subject: Electric drives
Message:
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.


Reply:

Subject: Electric drives
Reply Posted by: Gary Sunada (gsunada@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Wed Jul 11 11:46:49 US/Eastern 2001
Message:
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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