Testing electric motors with high voltage AC test

The question regularly arises as to what the requirements are for the high voltage AC test to be carried out on electric motors. Here we refer to the IEC 60034-1:2017.

This standard defines the requirements for new electric motors and rewound electric motors.

Basically, everyone knows the rule of thumb 2x Unominal + 1000 volts.

What is not always highlighted is the time duration of the measurement. The standard for new machines defines a time duration of 60 seconds. This can possibly (for example, for a production where time pressure is important) be reduced.

When adjusting the measurement time, apply an increase to the test voltage and thereby reduce the measurement time to 1 second.

There are several references in the standard where it is desirable to apply a current of >100 mA at test voltages <100 kV. The ramp up time (ramp time) of the test voltage can also be specified in the standard.

The above data are based on the high voltage AC test for new electric motors.

If you have cleaned motors or partially rewound motors, you can apply a reduction to the test voltage. In our experience, people usually omit this.

There are various requirements in the standards governing the high-voltage test and also many exceptions for DC machines, powers < 1 kW and rated voltages < 100 volts, among others.

As one can see, testing according to the standard is not as basic as the rule of thumb 2 x U nominal +1000 volts.

For detailed information, please refer to standard IEC 60034-1:2017

Suitable high-voltage testers for AC testing on electric motors:

• GLP1g – compact safety tester
• GLP2-Basic – modular safety tester
• GLP2-Basic HV – high-voltage tester up to 6 kV

For more information or advice, contact IONIO.