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Section 2
An Introduction to Dielectric Withstand Testing with the HT-20KVPac
The dielectric withstand test is a test which is recognized by safety agencies worldwide as
a valid criterion of safe assembly of end-use equipment. The HT-20KVPac is designed as a
research instrument to determine the dielectric properties of component assemblies of end-use
equipment. It applies a high-voltage potential between Output and Return test leads and monitors
Leakage Current, and watches for Dielectric Breakdown during the test. To aid in testing, the
HT-20KVPac can be configured with or without voltage ramp time, with or without a test
duration timer, and can be set to deliver high voltage after an arc has been detected to pinpoint an
area of arcing.
The dielectric withstand test involves high voltage, and caution should be exercised when
using the HT-20KVPac. The Return Receptacle on the front panel is connected to ground
potential, and setups should be designed with this in mind, to guard against the operator
contacting high voltage. Always make sure the return lead is firmly connected.
Leakage Test
The HT-20KVPac leakage test uses a separate low-frequency circuit to detect excessive
current between the Output and Return receptacles on the front panel. 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 sample may indicate an assembly, and or a component
problem in the circuit.
The leakage current is also monitored by the HT-20KVPac to ensure that excessive
leakage does not keep the tester from developing full voltage required for the high voltage test.
The HT-20KVPac will provide full voltage at any leakage current level up to 5mA. Set the
acceptable leakage current limit using the Shutdown Limit Potentiometer on the front panel.
If the green Full Voltage indicator lights and the test continues, the leakage current was
below the acceptable limit.
If the red Excess Leakage indicator lights, the buzzer sounds,
and the test is terminated; the leakage current was above the acceptable limit.
High Voltage Dielectric Withstand Test
This test checks for insulation system breakdown’s by applying a high voltage between
the Output and Return receptacles on the front panel. The HT-20KVPac uses a separate high-
frequency circuit to detect arc breakdowns.
Set the test duration with the Timer Control Potentiometer on the front panel. The test
time is counted from the time the Full Voltage indicator is lit to the completion of the test. The
Timer Control Switch must be set to ON, or the HT-20KVPac will test only while the Test Button
is pressed. The minimum test time is one second regardless of the setting of the Timer Control
Switch.
