Associated Research HypotULTRA II 7500DT, Руководство по эксплуатации и обслуживанию

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INTRODUCTION
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current reaches the leakage threshold during the initial charging of the product under
test.
2. Since a DC hipot does charge the item under test it becomes necessary to discharge
the item after the test.
3. DC testing unlike AC testing only charges the insulation in one polarity. This
becomes a concern when testing products that will actually be used at AC voltages.
This is a key reason that some safety agencies do not accept DC testing as an
alternative to AC.
4. When performing AC hipot tests the product under test is actually tested with peak
voltages that the hipot meter does not display. This is not the case with DC testing
since a sinewave is not generated when testing with direct current. In order to
compensate for this most safety agencies require that the equivalent DC test be
performed at higher voltages than the AC test. The multiplying factor is somewhat
inconsistent between agencies which can cause confusion concerning exactly what
equivalent DC test voltage is appropriate.
The Insulation Resistance Test....
Some "dielectric analyzers today come with a built in insulation resistance tester.
Typically the IR function provides test voltages from 500 to 1,000 volts DC and resistance
ranges from kilohms to gigaohms. This function allows manufacturers to comply with
special compliance regulations. BABT, TÜV and VDE are agencies that may under
certain conditions require an IR test on the product before a Hipot test is performed. This
typically is not a production line test but a performance design test.
The insulation resistance test is very similar to the hipot test. Instead of the go/no go
indication that you get with a hipot test the IR test gives you an insulation value usually in
Megohms. Typically the higher the insulation resistance value the better the condition of
the insulation. The connections to perform the IR test are the same as the hipot test. The
measured value represents the equivalent resistance of all the insulation which exists
between the two points and any component resistance which might also be connected
between the two points.
Although the IR test can be a predictor of insulation condition it does not replace the need
to perform a dielectric withstand test.
TYPES OF FAILURES DETECTABLE ONLY WITH A HIPOT TEST
·
Weak Insulating Materials
·
Pinholes in Insulation
·
Inadequate Spacing of Components
·
Pinched Insulation