900V DC bus with 1200V SIC module

Duclair

I am designing a three phase rectifier with the requirement to reach 900V on the DC Bus. As I can see, most of the tests on the application notes for wolfpack modules are with 800V on the bus, same for some specs on the datasheet. Also, the gate resistor populated by default on wolfspeed gate drivers seem to be 1Ohm, I would like to know if it is required to increase this value for a DC bus of 900V, even if a good DC bus layout is assumed, and that I will include snubber capacitors on the PCB. I would also like to know if some of the reference designs from wolfspeed have been tested at 900V operational, with 1200V modules.

Forum_Moderator

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ArunA

Hello Duclair,

Figure 19 in the datasheet depicts the SOA (Safe Operating Area) for this module. Here SOA curves are given for 2 different gate resistance values 1 ohm and 4 ohm. These curves show that it is required to increase your gate resistance values, if the bus voltage is increased to 900V, subject to your Ids current and bussing stray inductance values.

Currently we do not have any 900V operation data for our 1200V module reference designs. But there is no reason why they should not work at 900V, provided that the operational limits are strictly adhered to, in this case especially the voltage rating of the DC link capacitors.

Let me know if you have any further questions.

Duclair

Hello,

Thank you for your reply.

does the gate resistance used for SOA estimation in the datasheet include the internal resistance of the gate driver IC ? so, for example, in a scenario where RgIC_on = 0.7Ohm, should I assume an RgExt_on = 3.3Ohm may provide similar result as the ones indicated in the SOA for Rg_on = 4Ohm, provided (approximately) the same stray inductance values ?

ArunA

Hi Duclair,

The external gate resistance mentioned in the datasheet is the discrete resistance used on the gate driver PCB and does not include the IC internal resistance.

Thanks.

TBhatia

Hi, I hope that this answered your question. I will close this discussion for now but if you have a follow up question, please "Start a New Discussion" and we would be glad to support you further.