Question about usage of snubbers in CRD300DA12E-XM3

ak47

Hello Experts,

In the CRD300DA12E-XM3 inverter, we don't see the usage of any snubber capacitors across the Power modules.

Could you please shed some light on how the ringing is controlled?

Thanks

AK

Forum_Moderator

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

AustinC

Hello AK,

The ringing is reduced by minimizing the parasitic inductance in the inverter's power loop. Starting with the module, the XM3 has a very low stray inductance of approximately 6.7 nH. Next, the system is designed to have high mutual-inductance between the DC+ and DC- layers through a tightly-coupled, laminated bussing structure. This mutual-inductance cancels out much of the self-inductance resulting in a low overall parasitic inductance seen by the system (roughly 10 nH total including the module & system).

The bussing design mates to the module in a unique manner as shown below by the red (DC+) and blue (DC-) bus bars, which eliminates the need for bends in the bussing structure and reduces the cost of the design.

The full cross-section including the DC-link capacitors and module internals is shown below.

We've also selected low-ESL capacitors to further minimize the stray inductance of the power loop. When care is taken in the design of the system with regards to minimizing parasitic inductance, a snubber circuit is not necessary as the overshoot and ringing is minimal.

Best Regards,

Austin C.

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.