Associated Research 7700, Руководство по эксплуатации и обслуживанию

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which will indicate failure almost immediately if the total current reaches the leakage threshold
during the initial charging of the product under test.
Since a DC hipot does charge the item under test, it becomes necessary to discharge the item
after the test.
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 an important
reason that some safety agencies do not accept DC testing as an alternative to AC.
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.
1.6.2. 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.
1.6.3. Ground Bond Test
The Ground Bonding test determines whether the safety ground circuit of the product under
test can adequately handle fault current if the product should ever become defective. A low
impedance ground system is critical in ensuring that in case of a product failure, a circuit
breaker on the input line will act quickly to protect the user from any serious electrical shock.
International compliance agencies such as CSA, IEC, TÜV, VDE, BABT and others, have
requirements calling out this test. This test should not be confused with low current continuity
tests that are also commonly called out in some safety agency specifications. A low current
test merely indicates that there is a safety ground connection. It does not completely test the
integrity of that connection.