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Applianc testing

Applianc testing

Applianc testing

When single phase appliances are to be tested for insulation resistance, advice is to connect phase and neutral together and test at 500vdc between these two and earth.Thus no voltage will be present between phase and neutral.I would have thought that this is ok when appliance has old style isolating transformer. However, many modern appliances have filtering circuits upstream of their switch mode power supplies and connection with earth is present.
What I want to know is, just how vunerable to damage are these filtering circuits when the test described above is applied?



RE: Applianc testing

They should be sufficiently hi-pot tested or designed to handle that type of voltage, since it's a common-mode input.  Proper electrical design should have no connection to external chassis or ground.

The only caveat is to run up the hi-pot voltage reasonably slowly to avoid capacitive displacement currents that could couple through internal circuitry.


RE: Applianc testing

dwayned (electrical)

Some products may have MOV's or filter capacitors connected between line and ground which will cause a hipot or dielectric withstand tester to fail. Some product safety standards will instruct you to test with these items disconnected as to prevent damage to them. While other safety standards may instruct you not to test.
My suggestion would be contact a third party Product Safety Testing Agency for their recommendation.


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