VOC (voltage open circuit) testing
Voltage open circuit testing is a high voltage version of the turns ratio test. Instead of returning a ratio result i.e. 2:1, 1:2 etc. a voltage result is returned that is proportional to the number of turns on the primary versus the number of turns on the secondary.
The test parameters provided range from 1V to 270V with a measurement range from 100mV to 500V. Phase is also catered for and can be selected as positive (in phase) or negative (anti-phase).
Figure 3 shows the parameters required for VOC on the primary and secondary windings of the sample transformer.
The voltage and frequency levels have been selected as U.S line frequency mains 110V @ 60Hz with the voltage limits selected as a minimum of 52V and a maximum of 60V. Phase has been set for a +ve.