SiC CAB006A12GM3 MOSFET keeps heating up

ankitdesh92

I am building an ANPC Inverter with 3 SiC MOSFET Module CAB006A12GM3 .I am switching one half bridge(SiC Module) at a higher switching frequency of 25kHz using half bridge gate driver CGD1700HB2M-UNA gate driver. I am checking the temperature using inbuilt NTC Sensor. It was observed that the high switching frequency MOSFET was getting way hotter than expected even when no load was connected at the output of ANPC Inverter and the NTC reading in kohm kept on reducing indicating the temperature of MOSFET is not stable. Please let me know, if you have any suggestions for the MOSFET heating up even at no load and temperature keep on increasing problem?

Forum_Moderator

Thank you for your post, it has been approved and we will respond as soon as possible.

AustinC

Hi ankitdesh92,

Was a bus voltage applied during this testing? There are switching losses associated with the charging and discharging of the output capacitance of the devices even when no load is connected. These losses will generate heat in the system.

Best Regards,

Austin C.

ankitdesh92

Hiiii Austin,

The bus voltage was applied during testing. Yes, there will be switching losses. My primary concern is that, why the temperature keeps on increasing as per NTC thermistor and not remains stable.

Regards,

Ankit

AustinC

Hi Ankit,

Are the modules properly installed on a coldplate or heatsink? There will be a thermal time constant of the system where the modules are heating to a steady state value. Depending on your cooling system and the amount of losses, this could take many minutes to reach steady state.

Austin C.

ankitdesh92

Hiii Austin,

The modules are installed on heatsink. I was checking the value for several minutes. The modules are not supposed to get this hot like 10C above ambient at no load and temperature not stabilizing. I am still figuring out the reasons for this temperature increase.

AustinC

Hi Ankit,

10°C above ambient doesn't sound out of the realm of possibility for these conditions. Have you simulated the converter with PLECS or LTspice?

Thanks,

Austin C.

ankitdesh92

Hiii Austin,

Thanks for the feedback. For No Load condition PLECS Model does not predict any temperature rise.

Regards,

Ankit Deshpande