Variation of NTC in HM3

Hiroshi

Hi Wolfspeed Expert,

I have a customer purchased HM3 modules to develop inverter application.

When they read NTC valve, they found there's a module which has 2°C higher even at room temperature (no load applied) by comparing to other modules.

When operating inverter with HM3 modules, the temperature difference rises up to 6°C. This would be due to variation between SiC MOSFET chips, however customer can’t get why NTC value is different at room temp. 

 

Question 1: Regarding the thermal resistance Rthjc value described in the datasheet, is this the value when only high-side or low-side is heated? Or the both high-side and low-side are heated? Since NTC is placed near low-side, the customer wants to clarify how Wolfspeed heated the device during measurement.

 

Question 2: Could you please provide the document describing the method how Wolfspeed measured the thermal junction?

 

Question 3: Is the NTC value difference (2°C @ RT) within the spec? Also, please advise the reasons for the NTC variance from your perspective.

Thank you for your support.

Best Regards,

Hiroshi