Partial discharge in inverter applications

[User17668]

Dear Infineon,
I am wondering what is partial discharge and how should this be considered in inverter applications? Thanks

[schmoelb · Accepted solution]

What is partial discharge and why is it important for inverter designs?
Partial discharge is a flashover in between two insulation materials if the electric field exceeds a certain number. Root cause of this negative effect are voids within the insulation leading to a concentration of the electric field through the void.
Voids are small air gaps with much smaller (50-100 times) breakdown field strength than the insulation.
It damages the insulation over time and must be therefore prevented. Motor windings suffer from this effect especially if the voltage transients dV/dt are exceeding the limit.
Therefore, inverters are in average limited to an dV/dt below 10 V/ns which must be set via controlling the semiconductor switch within the inverter (IGBT, SiC, GaN). This is in general done through the gate resistor.
Drawback is, that the switching losses are therefore defined by the allowed dV/dt and especially wide bandgap devices cannot show their full capabilities.

[Apic1]

schmoelb wrote:
What is partial discharge and why is it important for inverter designs?
Partial discharge is a flashover in between two insulation materials if the electric field exceeds a certain number. Root cause of this negative effect are voids within the insulation leading to a concentration of the electric field through the void.
Voids are small air gaps with much smaller (50-100 times) breakdown field strength than the insulation.
It damages the insulation over time and must be therefore prevented. Motor windings suffer from this effect especially if the voltage transients dV/dt are exceeding the limit.
Therefore, inverters are in average limited to an dV/dt below 10 V/ns which must be set via controlling the semiconductor switch within the inverter (IGBT, SiC, GaN). This is in general done through the gate resistor.
Drawback is, that the switching losses are therefore defined by the allowed dV/dt and especially wide bandgap devices cannot show their full capabilities.

May I´d add that length of the cables (inverter-->eMachine) play an important role therein.

e.g. https://ieeexplore.ieee.org/document/4147875