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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: Shanta
Date posted: Mon Mar 5 15:36:45 US/Eastern 2007
Subject: HALT test motors
Does anybody know how to perform a HALT test on motors? We are trying to simulate the wearout of bearings and brushes. The motor manufacturer data sheet claims the MTBF of bearings is 50000 hours under nominal load conditions at 10000rpm. There is no description of what "nominal load condition" is. We would like to test this claim. How do we set up the test? Thanks for all the help in advance.


Subject: RE : HALT test motors
Reply Posted by: Rushabh
Date Posted: Mon Mar 5 17:14:40 US/Eastern 2007
Hi Shanta, One thing I can say from my exp. that HALT test would not be useful to validate the MTBF of 50K hours. HALT test is typically to find the destruction limit it would not give any MTBF figures. You may try for accelerated life test with increased RPM or Increased load level. Typically this type of test involves at least 9 samples considering 3 stress levels and 3 samples for each test level. Based on acclerated test results it may be possible to have infrence of MTBF figures. Imp points for test plan 1 ) Decide what type of failure distribution bearings follow.Mostly it follows log normal or weibull. 2 ) If mfd. has not specified any nominal load condition then use your application nominal load condition as nominal stress level for your test. In case your company can afford nearly 10 to 20 samples for testing then you can go for Life test and cover reasonable amount of your application life time in to the test at nominal stress level and can validate Mfd. claim.


Subject: Motor Reliability Testing
Reply Posted by: bwd
Date Posted: Mon Mar 5 17:16:26 US/Eastern 2007
The nominal load conditions are usually stated as the 50% loading point for most motors. This load point is generally derived by use of 50% of maximum current. This 50% current condition sets the maximum life point which in your case is 50,000 hours. By increasing the load current to 100% or near 100% you will stress the motor and accelerate your testing. The level of acceleration requires research on the failure mechanisms and modes of motors, which is one of the technical areas that SRC performs.

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