Spintend single 85V/240A controller

[AdR]

Untapped potential or misunderstanding on my part.
There are four mosfet per phase

• Key Parts Spec:
  • Mosfet Part No: JMSH1001ATL-13
  • Current amplifier PN: INA240A1

 

[amberwolf]

Untapped potential or misunderstanding on my part.
There are four mosfet per phase

• Key Parts Spec:
  • Mosfet Part No: JMSH1001ATL-13
  • Current amplifier PN: INA240A1

I don't understand if it's a question, a statement, or just a partial post, given the post content and title.

Could you clarify?

 

[scianiac]

I had the same thought, my guess is he looked at the mosfet's max amp rating vs the controllers max amp rating and thinks the controller can push more amps than it's rating. The answer is well that depends, can you push it a bit harder than it's spec, probably if you're careful but the FET rating definitely should not be used to calculate that, that's is a way way way over simplified way to look at things.

 

[lnanek]

I guess he's saying that with 4 FETs per phase, and each capable of 290A continuous drain current, why can't he do 4*290A phase amps:


The temperature goes straight up even at 10V and 20A, though, so I think you'd have heating issues:


Heat generated is a function of resistance and putting more FETs in parallel reduces that. A 12 FET controller isn't even super beefy. There's 18 FET ones out there from decades ago.

 

[neptronix]

These spintend ESCs have very poor cooling compared to something with 2-4lbs of aluminum on it, so the continuous rating is going to be very low relative to what you can push in a burst.

The limit is mostly thermal.

 

[AdR]

To clarify: It is a question.
@Inanek, that is my question.
@neptronix, if the limit is mostly thermal, then better packaging/cooling/bigger heat sink could possibly unlock more performance?
Cute neat packaging is way over rated. LOL
For the record, more fets does not necessarily mean better performance.

 

[amberwolf]

if the limit is mostly thermal, then better packaging/cooling/bigger heat sink could possibly unlock more performance?

Depends on how they mounted the FETs. if they are small tabless packages soldered to the PCB, it's harder to cool them better than if they are tabbed packages standing free of the PCB.


That said: keep in mind that the current the FETs see is phase current, not battery current, so make sure whatever you're comparing it to is also using a phase current rating.

 

[neptronix]

@neptronix, if the limit is mostly thermal, then better packaging/cooling/bigger heat sink could possibly unlock more performance?

Yep, maybe not 4x more though, your absolute limit will be the power bus' wiring thickness, then the associated electronics.

Maybe 50% more is doable

 

[amberwolf]

Yep, maybe not 4x more though, your absolute limit will be the power bus' wiring thickness, then the associated electronics.

Side note for those that don't know how phase bridges are wired / used: With 4 fets per phase, there are only one pair in the current path at any moment, either upper or lower.

So having 4 fets doesn't get you 4x the current of one fet, at most it gets a *peak* of 2x. Since the fets are PWMed, currents flow in spikes, so the average phase current will always be lower than what the fets are "rated" for.

 

[AdR]

@amberwolf: yea, one phase is connected to the low side and another phase to the high per cycle.