Castle - Make A Special Edition Monster

[GriffinRU]

Originally Posted by Pdelcast

You know, I've been thinking about this --

It wouldn't be too hard to do a 400V MOSFET based 3 phase controller for an EV. And it wouldn't be hard to do a PM motor for it either (expensive magnets though...) Both ST and Infineon have some nice 500V MOSFETs now (that don't have 1000nC charges.)

Need to sleep now, but I'm thinking about it.

Too bad we are far from each other,
I am less concern about cooling, can fix that.

If you can get me some ESC's already pre-fabbed with caps and tvs, I would like to share with you one more aspect of this tuning. I am sure you aware of that, but still. Pushing 30V fet's towards 6S is not great and we have seen more than one catastrophic fet's failure. What I was trying to add to MM, but didn't find a good place, is tvs per phase, not across H-bridge. 3 TVS total, no TVS across power leads required if caps are good and leads are short.
Concern - V=L*di/dt
With higher Kv motors, motors inductance and fast high current switching can exceed fet rating pretty quick. It would be the best to place clamp that would be before fet's diodes.
If you have any catastrophic fet's failures (I had one unit from DickyT) than it might be related to that.
Neu 1515 1.5D has about 2.3uH @ 50Amps and 1us it can hit 115V, your are not clamping phase - but just a thought.

Need to go, see you next weekend,

[Pdelcast]

Originally Posted by GriffinRU

Too bad we are far from each other,
I am less concern about cooling, can fix that.

If you can get me some ESC's already pre-fabbed with caps and tvs, I would like to share with you one more aspect of this tuning. I am sure you aware of that, but still. Pushing 30V fet's towards 6S is not great and we have seen more than one catastrophic fet's failure. What I was trying to add to MM, but didn't find a good place, is tvs per phase, not across H-bridge. 3 TVS total, no TVS across power leads required if caps are good and leads are short.
Concern - V=L*di/dt
With higher Kv motors, motors inductance and fast high current switching can exceed fet rating pretty quick. It would be the best to place clamp that would be before fet's diodes.
If you have any catastrophic fet's failures (I had one unit from DickyT) than it might be related to that.
Neu 1515 1.5D has about 2.3uH @ 50Amps and 1us it can hit 115V, your are not clamping phase - but just a thought.

Need to go, see you next weekend,

You'll find there are much better (faster and more robust) solutions than TVS.

Notice you never see those high voltages (115V) in a MMM or MM, because the body diodes clamp WAY before avalanche occurs. But there are several improvements that can be made beyond what the MMM has. First -- the body diodes do clamp to rail +- 1.5V or so, but they are slow. The snubbers are faster, but can't handle enough power -- bigger snubbers make a huge difference.

The whole idea is giving that energy a place to go that is LOW resistance path, not a high resistance path like a TVS. That energy of the inductor doesn't have to be wasted in a resistive part -- it can be recaptured, re-routed, restored.

[GriffinRU]

Originally Posted by Pdelcast

You'll find there are much better (faster and more robust) solutions than TVS.

Notice you never see those high voltages (115V) in a MMM or MM, because the body diodes clamp WAY before avalanche occurs. But there are several improvements that can be made beyond what the MMM has. First -- the body diodes do clamp to rail +- 1.5V or so, but they are slow. The snubbers are faster, but can't handle enough power -- bigger snubbers make a huge difference.

The whole idea is giving that energy a place to go that is LOW resistance path, not a high resistance path like a TVS. That energy of the inductor doesn't have to be wasted in a resistive part -- it can be recaptured, re-routed, restored.

That is where software comes to play...
Hundreds of ps are not that slow (it is possible to get faster devices but then substrate size (to maintain current capacity) will increase capacitance, thus slow you, limit you) , and there is no need to clamp all the way to zero, just to the safe Fet's level, and fet's are not that fast. But overtime both of them degradate, TVS first (easy to replace) fet second. Temp also change their response. Diodes are also rated to max Fet’s voltage, they are by-product of Fet. So you will exceed diode ratings if you do not clamp it earlier with something rated at higher voltage. You got the idea.
There is no much energy there to recuperate, but plenty to damage. Just switching fronts I am talking, nothing else.