Electric Eel, twin 3phase "6 phase" controller build

[Electric Eel]

I am in great awe of many contributors here, I have learnt a huge amount reading through stuff for hours and hours
I am building up a reliable twin three phase controller ( possibly with the ability to parallel the outputs to drive a single three phase motor) .... But it might take me a while to get there.

The controller will be driven by AVR architecture, and the software will be a project in its self. At first, I am going to focus of the power stages. I really like what Lebowsky is doing with the low inductance 6 FET units. Hell, I really like what everyone is doing!
I have an already built an 18fet power stage, and 2186 driver board, which ended in smoke, bangs and excitement due to the Fets being counterfeit items off aliexpress... It was a lesson to me, and let it be a lesson to everyone.
I went there as shipping from the US to Japan only makes sense for big orders. Any suggestions for (legitimate!) component suppliers to Japan would be appreciated, I have found 1 so far, and they appear to have the irfb4110 at a good price. I have yet to order from them, so I see how that turns out.
Also, I have two young kids and a wife, all of whom I like to see and speak to. So my resources are going to be a bit limited for my project. Expect it to be a slow build!


So I am going to start out with some really dumb questions to try to get some stuff ordered so I can begin.

I see most people are using the square polyester caps for snubber caps. Would a ceramic smd cap not be better? ( if you can find one!)

 

[bearing]

MLCC's are better, but they are fragile in comparison. But I would use MLCC for sure, and change them to the (more expensive) "soft termination" type if it turns out that they crack.

 

[Electric Eel]

MLCC's are better, but they are fragile in comparison.

Thanks, I was wondering if that was what it was about. Most people on here seem to use about 1uF... I guess it is better to have several small capacitors spread around as close to the sources of noise as possible.

I ordered a 24 FET greentime controller, so It can be the test case as I am pretty sure they have no snubbers out of the box.

 

[bearing]

One thing you should know about MLCC's is that their capacitance decreases when they have a DC bias. They can loose as much as 90% if they are biased close to their rated voltage. So a 100V 10uF could have only 1uF at 90VDC. The better quality (X7R, for example) and bigger sizes will loose less capacitance.

I use this site to compare DC bias curves. I'm sure the other manufacturers provides similar info.
http://product.tdk.com/capacitor/mlcc/search_by_characteristics.php?lang=en&ref=us

 

[Electric Eel]

Thanks for that heads up.
I was reading on Wikipedia about the voltage rating methods for mlccs and thought it might be O.K... you may have saved me a lot of grief !!

 

[Punx0r]

Have you considered buying FETs from Australia? I understand there is a lot of trade between Japan and Australia and from what I have read I am confident genuine IRF FETS are available from several sources there.

 

[Electric Eel]

Chip1stop has the TO-220 irfb4110 for $1.69, which seems a pretty good price. I have just ordered $ixty plus some 250v 0.5uf mlcc and gate drivers etc etc..

I spied this the other night too. Some interesting stuff on "Active Freewheeling" which sounds interesting, but the controller concerned seems to have dedicated fets for it, which seems a bit over the top.

http://www.helifreak.com/showthread.php?t=443322

Gotta love anyone who does testing!
"After 3 mins the case ONLY warmed up to 70C..." No suprises why RC controllers blow on ebikes...