TRANSFORMER TESTS VOLTECH AT3600 USER MANUAL
PAGE 7.1.46. VPN 98 - 024 TESTS AND TEST CONDITIONS
1.27. HPDC - DC HI-POT (EHT)
WHERE USED
Hi-Pot or EHT testing (to check for insulation breakdown between windings or
between windings and the screen or core) is often specified for power line
transformers or for switched mode power transformers in applications where safety is
important.
It is typically performed between all primary windings connected together, and all
secondary windings plus the screen connected together.
SPECIFYING THE MEASUREMENT
During the test, a dc voltage is applied across two groups of windings with the
windings in each group being shorted together. The voltage and current are
monitored throughout the dwell time; if either the test voltage cannot be maintained,
or the current is too large, then a failure will be recorded.
In programming the tester you may select the voltage (from 100V to 7KVdc), the
current trip level (1µA to 1mA), and the ramp up and dwell times, all to suit the
specification of the transformer under test.
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