Discussion:  Most product designers can relate to issues on obtaining a compliant design when it comes to electrical safety.  Standards and approving agencies require that selected tests be accomplished on 100% of units produced prior to shipment.  These aspects are considered so critical to operator safety that all are tested.  Insulation is a part of the critical tests evaluated by a dielectric strength test.  The idea is that if the insulation is compromised, it will be revealed in the test.  During the qualification testing rigorous tests are accomplished but the factory test allows a little relief (shorted duration, no conditioning, etc.).  In the example below a manufacturing flaw was noticed during a random sample inspection.  Note that the insulation is damaged because a cable tie was tightened to a corner reducing the insulation thickness.  Results provide for arcing to metal parts of the unit.  Would this be detected during factory testing – hopefully but atmospheric influences could allow a pass condition and shipping vibration makes this unsuitable for use.  Root cause – inadequate manufacturing instructions on placement or application of the tie.  The design must be supported by manufacturing.

Insulation Squeeze Play

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Article Reference ID: DYK00004

Posted in: Did You Know? Electrical Safety