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Old 10-29-2010, 11:02 AM   #3933 (permalink)
Mark Weisheimer
Join Date: Aug 2009
Location: Columbus Ohio
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Darlington Power Modules

Originally Posted by snakub View Post
Yes I have almost exactly what blackpantherst does. ....I am using an 8 amp hour twelve volt battery and a battery charger powered off of the traction pack to power B not Bx which would take a lot more drive current I measured the current going to B and it is only about 2 amps so all in all my power section took 8 amps.
The battery is being called upon to deliver 8 amps now, though I think it might work for a test,
You are looking at 96 watts of drive already and you haven't even kicked it in the butt yet!
I'd be looking to up the size soon.
I'd add a .1uf 50v ceramic cap from the collector of the driver MOSFET to common too.
I'd also keep a close eye on that battery while testing too.
You may have more blown module issues if it starts going flat.

Are your BX lines tied together as in BlackPanthers schematic?

Originally Posted by snakub View Post
But can I put the fuse in as one of the series connection to my batteries or would it be better to have it connect to the positive going out?
You can put the fuse anywhere in series with the battery loop.

I have a fuse at the most positive battery, a circuit breaker at mid pack
(because it is convenient and in between the seats for easy reach)
and another fuse in the negative lead of the pack.
You'd be fine with one fuse at any point in the loop.
Just put it in a convenient spot to check and replace if needed.

Originally Posted by snakub View Post
I wasn't really talking about if the mosfet shorted I was just trying to say that if I have the current sensor hooked up to motor negative wouldn't that still limit my current by resetting the PWM at appropriate times by turning off the mosfet? What did tesseract mean by hard saturate?
The control board is only going to be able to limit current when it has proper control of the modules.
I'm not so sure that you're there yet.

And this is important to understand:
NO CONTROL BOARD can limit the current through an Emitter-Collector short in a module.

That is part of what the fuse is for.
It is also why I am fond of multiple disconnects.
You won't plow yourself into a tree if you can get the power turned off after that kind of a failure!

Take a look at:

Baker clamp - Wikipedia, the free encyclopedia

It speaks to the issue of saturation and turn-off.
A couple of high speed diodes are used in a baker clamp
and would keep the module from reaching saturation
which will help with the turn-off time.

I'll see if I have a spare rev C board that is populated enough
to compare with your measurements. I know mine is missing
the DC-DC converter, but I think it is mainly intact otherwise...
It will be tonight before I do that.
I've got to move along to log splitting for now!
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