10
Leakage Test
The HT-S leakage test uses a low-frequency circuit to check for excessive leakage between
primary power components and ground. There is not a specific leakage current level pass/fail requirement
at this time for most equipment, however, higher than normal leakage current on a particular part may
indicate an assembly or component problem in the primary circuit.
The leakage current is also monitored by the HT-S to ensure that excessive leakage does not keep
the tester from developing full voltage required for the high voltage test. The HT-S will provide full
voltage at any leakage current level up to 20 mA AC (HT-2000S & HT-3000S), up to 10mA AC (HT-
4200S) or 5mA DC (HT-2800S, HT-3000S & HT-4200S). The leakage current trip level is adjustable on
the rear panel.
The leakage test is conducted by shorting the line and neutral conductors of the power supply cord
and applying high voltage between them and the exposed dead metal of the chassis of the equipment being
tested.
Excessive leakage current is not grounds
for failure of the dielectric withstand test. Leakage
current is a normal result of capacitance in the primary circuit between neutral or line conductors and
ground. (In dielectric tests of some larger electric motors, leakage currents of as high as 95 mA are
considered acceptable by safety agencies.) However, leakage currents higher than normally anticipated for
a particular model should not be ignored. This indicates problems of low resistance up to a short circuit
between line/neutral and ground, and failures should be investigated. Failure modes are discussed below.
If the green
Full Voltage
LED light is on and the test continues, the leakage current is below the
limit set by the rear panel adjustment.
Sporadic Leakage Current Failures
If the red
Excess Leakage
LED light is on, the buzzer sounds, and the test is terminated, the
leakage current delivered to the equipment being tested was over the limit set by the rear panel adjustment.
If other equipment of the same type routinely passes this test, there may be a problem with the primary
circuit of the example being tested. The unit should be checked and reworked if necessary.
Chronic Leakage Current Failures
AC Dielectric Withstand testing, charges all primary circuit capacitors connected line to ground or
neutral to ground. The current flowing through these capacitors is defined as leakage current. If almost all
examples of a model of equipment are not passing the leakage current test, we recommend that the leakage
current limit be increased by resetting the leakage current level on the rear panel to a higher level.
If the leakage current adjustment of the HT-S is set to 20mA AC and almost all examples of the
model being tested are still failing, the primary circuit capacitance of the equipment may be too high to
allow the AC dielectric withstand test to be used. This is due to the AC voltage charging all capacitors
connected between primary voltage and ground. If the overall value of these capacitors cause a leakage
current of more than 20mA to flow at the desired test voltage, the HT-S cannot generate full voltage, and
cannot successfully conduct the dielectric withstand test.
However, a DC dielectric withstand test is acceptable for most categories of equipment and will
not charge the primary circuit capacitors. The DC test can be conducted by switching the front panel
switch to DC (only HT-3000S or HT-4200). If the problem was due to high leakage current on the
capacitors of the circuit, the test should now be successful.
