According to UL FUS Procedure (Inspection Report), Hipot tester on production-line test shall have 500VA capacity, what does it mean?
What action should be taken if the tester doesn’t comply with the requirement?
The VA rating of hipot tester describes its output power, it can be calculated by taking the hipot tester’s max. output voltage and max. output current. For instance, a hipot tester’s max. output voltage 5K Vac, max. output current 100 mA, its max. output power is:
5000V x 100mA = 500VA
If the max output current is only 80 mA, the max output power is:
5000V x 80mA = 400VA
Then it doesn’t comply with the 500VA requirement. However for the situation, UL does have alternative way to verify the output capability of hipot tester.
Alternative way to verify output capability
Taking UL60950-1/UL60065 Procedure for example, all inspection requirements for production-line tests are addressed in the “Generic Inspection Information” of the FUS Procedure. There is addressed “If the output of the test-equipment transformer is less than 500 volt-amperes, the equipment shall include a voltmeter in the output circuit to indicate the test potential directly.”. This is to make sure that there is no voltage drop due to insufficient power capacity.
Above figure is the internal measuring circuit block diagram of eec all series hipot testers. Voltage output is from T2 high voltage transformer and a sensor is connected to the secondary side of T2 to measure output voltage/current and feedback signals to mainboard performing A to D signal converting, then display the measured result on LCD panel. This design does comply with UL Procedure requirement that the equipment include a voltmeter in the output circuit to indicate the test potential if the output of hipot tester is less than 500VA.
