INTRODUCTION
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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 Ground Continuity Test
The Ground Continuity test is checking to verify that there is low impedance path between
the chassis and the safety ground wire of the line cord. A low impedance ground system is
critical in ensuring that in the event 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. A low current test merely indicates that there is a safety
ground connection. It does not completely test the integrity of the connection that would
be accomplished by using much higher currents in the range from 10 to 30amps. The high
current test is known as a Ground Bond test.
The Ground Continuity test verifies that the ground circuit between the Continuity and
Return panel jacks on the Hypot II is below 1ohm while test at a current of 100mA. This
function can be enabled or disabled through software, when a ground circuit is not
provided on the device under test or test requirement are not needed.
The Insulation Resistance Test....
Some dielectric analyzers 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 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
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