3.4.26 HPAC - AC HI-Pot (EHT)
The ac high-pot (or EHT) test is used to check for safety isolation between windings, or between windings and the core or screens.
During the test, an ac 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.
On selecting ‘HPAC High-Pot ac’ from the Available Tests window, a dialogue box will be displayed:
To program the test :
- Enter the test voltage, the test frequency, and the ramp-up and dwell times.
- Enter the terminal names for the High and Low Terminals.
Click with the mouse to select a terminal from the Available list; then click the ‘Add >‘ button to transfer it to the Used list.
(To correct a mistake, click with the mouse to select a terminal from the Used list; then click the ‘< Remove’ button to transfer it back to the Available list.)
- Enter the maximum current value in the bottom section.
Note that the current is the peak value, not an rms.
- Select OK. The test specification will then be displayed in the program window.