Part 4 - Final electrical testing and operational checks.
In this final video, the device is tested.
Initially, a multimeter is used to confim earth continuity between all of the metal parts on the variac, metal case and handwheel.
The device is then tested using a Clare A255 appliance tester. This checks the earth connection with a current of approximately 25 amps - far more than the multimeter, and enough to identify any weak connections.
It also applies 1250V between the L&N conductors and the metal case to confirm the insulation resistance.
Inrush current is demonstrated and output voltages are checked.
The output voltage appears to be too high - however this is a result of the mains voltage input being at the very upper range of what is permitted.
The ratio of input/output voltage is correct.