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28 Oct 2008

How to use high power diodes

Hello everyone. I apologize for such a long post.

I'm trying to design a 1000A, DC motor controller. Basically, I'm chopping a 300V battery source into a DC motor, and I'm trying to identify a freewheeling diode to put across the motor. I'm relatively new to high power design, and I'm confused by the form factor of the diodes that are rated at this current level.

Almost all of the diodes at this rating are in different "PUK" packages. These look like hockey puk's and some have one or two smooth surfaces for the electrical connection (i.e. no lug connections).

My question is, how are these diodes typically mounted? It appears they have to be sandwiched somehow between two conductors, and apparently the conductors have to act as the heat sink as well.

I was anticipating using a module that has lug contacts, and bolts to a heat sink (similar to IGBTs). I really don't want to have the heat sink electrically connected, and I also don't want to have to setup some sort of clamp with bus bars.

Am I missing something? Is there an easier way to use these diodes?



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