Technical informationReason for not indicating of Quantity electric charge amount in high frequency corona discharge test (partial discharge test)

As you know, as parts used in high frequencies and motors driven by inverters are increasing in recent years, Corona (partial) discharge occurs at the surge and high frequency / high voltage generated, which may damage the insulation layer and the windings.
In particular, there is an IEC document (IEC 61934 TS) that specifies the test method of the motor by inverter driving, but because there are insufficient contents, the joint research by the research meeting of 「The Institute of Electrical Engineers of Japan 」is carried out and a new proposal to IEC.

That committee
Technical report No. 1218 of The Institute of Electrical Engineers of Japan “Partial Discharge Measurement and Inverter Surge Isolation in Repeated Impulse” issued by the Technical Committee on Partial Discharge Measurement Investigation in Iterative Impulse issued in April 2011.
Recent literature is introduced in this.

Unlike the partial discharge tester to be tested at the conventional commercial frequency, in order to detect the partial discharge signal superimposed on the applied impulse voltage, since a method of detecting only the high frequency is usually adopted, the signal is integrated and the charge You can not ask for it.

Also, in the report of「The Institute of Electrical Engineers of Japan」 (March, 2010, p. 70), it is reported that charge calibration in pC (pico coulomb) unit prescribed by partial discharge measurement method IEC 60270 with AC voltage is impossible in principle.
The calculation formula is shown in the partial discharge standard of the Institute of Electrical Engineers of Japan (JEC) – 0401-1990 (page 21), but because the true charge can not be measured, the measured value is referred to as the apparent discharge charge.
We do not know the real electric charge amount.

We recommend that you refer to Technical Report “Partial Discharge Measurement and Inverter Surge Isolation in Repeated Impulse” and refer to the reference documents as necessary.

Method of detecting corona discharge by Adphox

• When corona discharge occurs, a discharge signal ranging from low frequency to 3 GHz is generated.
  The corona discharge tester CORONA-i of Adphox detects the presence or absence of corona discharge by detecting a signal of 10 MHz to 50 MHz.