Pushing the IRFB4110's to the limit

[Arlo1]

i am not sure dp-420 or other epoxy will stick to the kapton or mylar.

No way epoxy will stick to them... I use Kapton and mylar all the time as epoxy proof release films. Peels right off leaving a nice smooth surface.

Locktight Hisol would likely work but I would like a method other then epoxy to install them!

 

[dozentrio]

Seems like we just keep finding different ways to bash our heads against the low-inductance motor problem. More FETs, bigger FETs, higher voltages... with no particularly overwhelming results.

What we need is a paradigm shift. A new approach that doesn't band-aid the low inductance problem but solves it elegantly. Something "outside of the box."

As I understand it, a low inductance motor is a good thing, because it gives you more power or efficiency. Isn't that right?

*edit: For the record, I've been running a 24fet infineon board with 4110s at 24s (4.1v/cell usually) for a while now, with no issues. Current limited to 100 battery amps, on motors wound for less speed than your typical 5303. I can't give good comparisons, but top speeds at 100v were 75 and 65 kph on the two motors I've used so far. Torque and acceleration are ridiculous, and it requires careful effort to keep the front wheel on the ground. Of course, frame geometry and weight distribution may have something to do with that, as I'm using a DH bike frame and carrying a 1kwh lipo battery in a backpack.

 

[Arlo1]

Seems like we just keep finding different ways to bash our heads against the low-inductance motor problem. More FETs, bigger FETs, higher voltages... with no particularly overwhelming results.

What we need is a paradigm shift. A new approach that doesn't band-aid the low inductance problem but solves it elegantly. Something "outside of the box."

As I understand it, a low inductance motor is a good thing, because it gives you more power or efficiency. Isn't that right?

.

There is a lot of Hi power BLDC controller work going on behind the sceens. I agree we need something out side the box. But There is already some great BLDC controllers in some of the up comeing cars. As for low inducance im not realy sure if it helps effieiency.... Inductance does not stop power from being put into a motor is just slows the ramp up of amps flowing though it. Low resistance helps efficiency. But I think too low inductance meens the pwm for the motor is going to be more short pulses which meens increased switching losses in the controller. I think you will be happy with what happens in the next year. IM going full tilt into a controller build as many other are. One big reason its a slow thing to come to market is there is no push for engineering to develop hi end electric cars for the auto industry (they make the auto and big oil less money) so its up to the little guy like you and me to get-er-done! I will show the world Hi power bldc and It will kick ass its just a matter of time. If you want to find out about companys working with Hi power bldc controller stuff look to Electric only companys they are the ones with the passion! Like Rimac http://www.rimac-automobili.com/concept_one/introduction-20

 

[Arlo1]

Oh and as far as Im concerend we dont want fets or igbts but something new that doesnt exist yeat! A new transistor or maybe not even a transistor at all! But way out of the box!

 

[Doctorbass]

Oh and as far as Im concerend we dont want fets or igbts but something new that doesnt exist yeat! A new transistor or maybe not even a transistor at all! But way out of the box!

Heah.. maybe the new flux capacitor based junction that would have ZERO rise time due to a "DTTVC", Dynamic Time Travel Variable Compensation 8)... A junction that travel in time to zero the rise time... making less heat loss and perfect sync over infinitie fets eventhough the circuit path over all junction used, making the gate capacitance problem solved

Doc

 

[gensem]

yeah... something like it Doc!

 

[zEEz]

maybe the new flux capacitor based junction that would have ZERO rise time

flux cap? maybe IXYS MMIX1F520N075T2 are a bit better, but probably still suboptimal in many applications ...
I wonder if the shy attitude in commercializing them is not a way to protect
the main company from being sued by all the unhappy company trying to implement in new designs
their shitty new silicon devices

have fun!

 

[gensem]

I really tought Doc was joking using Back to the Future movie.

 

[Arlo1]

maybe the new flux capacitor based junction that would have ZERO rise time

flux cap? maybe IXYS MMIX1F520N075T2 are a bit better, but probably still suboptimal in many applications ...
I wonder if the shy attitude in commercializing them is not a way to protect
the main company from being sued by all the unhappy company trying to implement in new designs
their shitty new silicon devices

have fun!

LOL now find one good to 200 volts with those specs!

 

[zEEz]

LOL now find one good to 200 volts with those specs!

Haha, it was ironic ... I'm not inclined to think those mosfets are any good for us ...
But I also am a bit scared of high voltages for 'personal use' ....

I'm not very inclined to use voltages higher than 70 volts on my self built things ... :?
So, I'm not really interested in high voltage mosfets or IGBTs, sorry!

have fun!

 

[liveforphysics]

The side that is capable of cooling effectively is the side that has to mount to a PCB, so no matter how good of an Rth you get to the PCB, the PCB itself is not capable of shedding heat effectively at all, and in high current situations, it's a heat source itself. All the cooling you get from the back side of the package amounts to roughly nothing, almost like it's just for looks, or just a gesture of cooling if you look at the real Rth numbers, even if you have a magic heatsink that never rises above room temp, you need a thermal pad because the installed heights on all of them are inconsistent, and when you add the pad and the back of the packages Rth, you end up with a part that just explodes into plasma temperatures while the heatsink is neatly room temp still. lol

this is a bit off-topic..

i have an idea in my head, to glue milled copper bussbars to a aluminum heatsink and insulating the copper from the aluminum with a thin layer of either kapton or mylar, i am not sure dp-420 or other epoxy will stick to the kapton or mylar. then soldering d2-pak 7lead FETS to the copper bussbars.

is this a viable idea to try, or doomed to fail?
hope to hear your opinion.

I don't see glue doing it, as all the best thermal epoxies I've ever tried has always been very disappointing, but bolting little bars across the backs would mount them with the pressure needed for good thermal conduction.

What you've got you ask yourself though, is what are you looking to gain? If you have special water-jet-cut copper bus bar PCB on an insulating layer mounted to an aluminum sink, you've spent a lot of money and mfg effort/time to accomplish something that through-hole components still do better, and lend themselves towards simple and cheap cooling.

 

[CNCAddict]

Nothing wrong with current technology. Only thing wrong is in the design area. Everything targeted towards the low end EV market doesn't have enough protection and monitoring software/circuitry and is still based around the most basic motor control theory. Things will change soon, I'm sure of that.

 

[zEEz]

Everything targeted towards the low end EV market doesn't have enough protection and monitoring software/circuitry and is still based around the most basic motor control theory.

While this is sure true, it is to admit that any actual cheap controllers have a very high efficiency ... Even making them far more complicated is not going to improve the business more than 1% in that department ....

Tangible Proof of this is that Sevcon controllers, far more advanced and complicated, using DSPs and tough algorithms, are not preferred, in normal build nor in race, against the simple and rough Kelly controller standard .... 8)

have fun!