An Introduction to Dielectric Withstand Testing with the HT-10000P
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-10000P 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-10000P 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-10000P. 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-10000P 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 or component problem in the circuit.
The leakage current is also monitored by the HT-10000P to ensure that excessive leakage does not keep the tester from developing full voltage required for the high voltage test. The HT- 10000P will provide full voltage at any leakage current level up to 5mA in DC and 10mA in AC. Set the acceptable leakage current limit using the Shutdown Limit Potentiometer on the front panel. The Shutdown Limit Switch must be set to ON or the HT-10000P keep testing regardless of Leakage Current. Voltage output may sag under these conditions.
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 breakdowns by applying a high voltage between the Output and Return receptacles on the front panel. The HT-10000P 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-10000P will test only while the Test Button ispressed. The minimum test time is one second regardless of the setting of the Timer Control Switch.
If the green Hipot Pass indicator lights, the test cycle has been successfully completed, meaning there was no dielectric breakdown. If the red Hipot Fail indicator lights, a breakdown arc has been detected.
High Voltage Discharge
The HT-10000P has an internal ramp down circuit designed to discharge the high voltage after completion of the dielectric withstand test. The HT-10000P should remain connected to the circuit until the front panel meter shows that the output voltage has dropped to a safe level.
Controls, Indicators, Connectors - Model HT-10000P ac/dc Front Panel
ITEM NO. |
NAME |
FUNCTION |
1. |
HIPOT switch |
When ON, Dielectric breakdown detect will be activated. When in DEFEAT position, test will continue regardless of a dielectric breakdown, but it can be stopped by the excess leakage limit. NOTE: The RAMP switch, and TIMER switch must also be in the DEFEAT position, otherwise the buzzer will sound. The test will continue only as long as the TEST button is pressed. Minimum test time is approximately one second. |
2. |
TIMER switch |
When ON, test duration is set by TIMER ADJUST, Item 5. When in DEFEAT position, testing continues only as long at TEST button is pressed. Minimum test time is one second. NOTE: TIMER Switch position must be DEFEAT when HIPOT Switch is in the DEFEAT position. |
3. |
RAMP switch |
When ON, Voltage ramp up time is controlled by RAMP ADJUST, Item 6. When in DEFEAT position, high voltage is applied immediately when TEST button is pressed. NOTE: RAMP Switch position must be DEFEAT when HIPOT Switch is in the DEFEAT position. |
4. |
LEAKAGE ADJUST |
Adjusts the shutdown point for the Leakage Current Test. For details see “Leakage Current Adjust.” |
5. |
TIMER ADJUST |
Adjusts the test duration. For details see “Test Time Adjust”. |
6. |
RAMP ADJUST |
Adjusts the delay between time TEST button is pushed and time desired output voltage is attained. For details see “Ramp Time Adjust”. For no delay, DEFEAT Ramp Time Switch, Item 3. |
7. |
AC/DC Switch |
Selects AC or DC output. Operates only when RESET or TEST switch is lit – does not function during a test. |
8. |
RESET Button |
When lit, indicates that the HT-10000P ac/dc is unarmed. When the RESET Button is pressed, the TEST switch is lit. PRESSING THE RESET BUTTON AT ANY TIME IMMEDIATELY STOPS TESTING. |
9. |
TEST Button |
When lit, indicates the HT-10000P ac/dc is ready to test; press to begin testing. |
10. |
VOLTAGE METER |
Connected to the output. Reads actual output voltage. Adjust meter with VOLTAGE ADJUST Knob, Item 19. |
11. |
HIPOT PASS LED |
Indicates test conclusion with satisfactory results. |
12. |
FULL VOLTAGE LED |
Lights when output voltage has ramped up. Test time starts when this indicator lights. |
13. |
HIPOT FAIL LED |
Lights when arcing or insulation flashover has occurred. |
14. |
EXCESS LEAKAGE LED |
Actual leakage current has exceeded the leakage point set with Leakage Limit Potentiometer, Item 4. |
15. |
CURRENT METER |
Connected to the output. Reads the current flowing through the return lead of the HT-10000P ac/dc during the test. |
16. |
AC OUTPUT Receptacle |
Connect high voltage lead here to conduct an AC test. |
17. |
DC OUTPUT Receptacle |
Connect high voltage lead here to conduct a DC test. |
18. |
RETURN Receptacle |
At chassis ground reference level. Connect black return lead here. |
19. |
VOLTAGE ADJUST Knob |
Voltage is continuously adjustable during testing with this knob. |
20. |
AC POWER Switch |
Energize the HT-10000P ac/dc. |
21. |
FUSE |
Mains fuse. Replace only with type and rating of fuse specified on the front panel label. Turn off power switch, Item 20, before servicing fuse. |