Surge Current and Power in FETs

You really are struggling with this, aren't you? Yes, not worded well. I was referring to the need to limit the surge on attaching the battery, but not limiting the surge for the motor. So an NTC device has to find the Goldilocks point that works properly in both cases.

Sorry, are you the PM? There has been a discussion going on and I am listening to ideas. Someone may come up with something good yet although most of the discussion has been typical SED complaining, insulting and just general off topic side discussions.

It is funny that people here wonder why newsgroups are dying. Eevblog is a much better place to discuss such things. That is where I learned about the "anti-spark" connector. Here people just complain that I haven't defined the problem well enough.

So did you look at the schematic? I posted the link just for you! :)

I'm happy to post the simulation code as well.

I've been working on a class D amplifier too and downloaded a simulation model for an inductor from TDK. I wanted to look at the parasitic values and the durn thing is ***encrypted*** for god's sake! Why does an inductor need to be encrypted? What could they possibly be hiding?

Yes

That's the main reason why.

An NTC is typically used to limit the inrush current at power on (or when the battery is connected in your case). After that it stays out of the way by going very low resistance so the bears don't notice it.

How did you model the internal resistance of the battery when you discovered that there was a problem with excessive inrush current?

Not yet. You're on a VM known as strawberry. I'd have to switch to banana for that. I'll get to it.

Anything which the competition could use to make an equivalent part cheaper.

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** I reckon this naive code scribbler is still in his 20s.

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** What a blatant, f****ng LIE ! ** ROTFL - my insults are brutal and *spot on*.

Egomaniac, know nothing fuckheads like you are a dime a dozen.

You are NEVER going to grow up cos YOU you have no idea how to.

...... Phil

Wow, stream-of-consciousness scorn. You didn't even bother to go back and delete your previous remark when you read that sentence. Serves me right for trying to help you, I suppose.

Play around with it for a bit and see. Maybe try turning it around, thinking about how the TVS voltage, polarity, and uni/bidirectionality come into it.

Cheers

Phil Hobbs

Language like "stays out of the way" is not a useful description. To "stay out of the way" requires some minimum current to maintain the low resistance. In this case I doubt that can be provided. Alternatively it can respond quickly enough to not cause a problem with the rapid motor current spike which is essential to the motor coming up to speed quickly. So a narrow region of operation.

Now is it clear? If not, I can't help you understand your own idea any better.

I used the data sheet value for Internal Resistance. While there may be chemical effects that increase this value, that will respond slowly as the concentrations in the electrolyte in immediate contact with the electrodes change and become diffusion limited.

Like they can't get a sample of the item and measure the parameters themselves. It's a coil! Not rocket science. Anything that can't be measured from a sample can't be gleaned from a simulation model.

Anyone thinking their newsgroup insults have any impact on anyone is a f****ng moron!!!

It is so mind boggling idiotic that anyone would think their opinion posted in a newsgroup is worth a dam that it is hard to imagine that person being functional enough to not be locked away somewhere for their own safety.

You are almost as bad as P. If you want to help, help. If you don't want to help, why are you posting???

I have no idea what you are talking about with "stream of consciousness". Most likely you still dont understand what is being discussed.

Thank you, but I need to find useful solutions. Like I said, either help or please stop being a Phil and just don't post. I'm ok with that.

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** This " man " is a child... ** Major dummy spit.....

Pics up football - carries it slowly home, in tears.

..... Phil

Okay, you don't want me to try to help you. Duly noted.

Cheers

Phil Hobbs

I don't want to play your little mind games... like this one. You probably don't even know you are doing it, do you?

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** The Rick C troll is beyond all help. Better take it to the vet, put it out of it's misery.

..... Phil

Heaven in Europe is where:

the English are the policemen

the French are the cooks

the Germans are the mechanics

the Italians are the lovers

and the Swiss organize everything.

Hell in Europe is where:

the German are the policemen

the English are the cooks

the French are the mechanics

the Swiss are the lovers

and the Italians organize everything.

<snipped the usual nonsense>

So John Larkin is as silly as Phil Allison, or possibly merely just as fond of being dismissive.

I hadn't realised that polyfuses were a form of positive temperature coefficient thermistor.

They aren't, but they do behave in a similar way. They have to heat up enough to create a phase change in the polymer that separates the carbon black particles that provide the conduction path. The catch is that "It could take hours, days, weeks or even years for the device to return to a resistance value similar to its original value, if at all". Thermistor action doesn't depend on any physical movement at all, and the resistance of the device is only determined by its temperature.

Yeah I think Sartre said something about that. Gawd what an ol' fuddy-duddy. Something Trumper Scott Adams and Marxist Sartre seem to have in common these days.

So the initial surge is just the battery charging up the reservoir capacitors?

Everything depends on a lot of details, and you don't seem willing to spell out what they are. You do seem to want to find a miraculous solution that you can apply without having to bother with thinking about what is going on.

Just make it big enough. With enough thermal mass the energy that gets dumped into it won't make it hot enough to take it outside it's operating limits. Power resistors can run at up to about 200C, which lets you get rid of a lot of heat, but they do have to be kept away from less heat-tolerant components.

....

And yet your next sentence demonstrates that you did in fact clearly understand what I meant.

Which NTC thermistors have you evaluated to determine whether this is true or not?

It wasn't my idea, but it is a means of limiting inrush current which I have been aware of for decades.

Ok. What limits the inrush current for the AC derived power?

....

Sure but you still can't compare the measurements directly with the encrypted information.

I think it was in Nashua NH a long time ago with an early laptop when I wanted to filter the power to a modem. So I went into the nearest Radio Shack to ask for something suitable. Inductor got a blank look. So did coil. But choke worked.

But a much bigger subject than resistors or capacitors.

Simulation models don't go up in smoke the same way real inductors can.

+-+ Get 1,000 miles of free Supercharging +-+ Tesla referral code -

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** Or almost as smart as me.

** I think the "penny" has just dropped !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

" Polyfuse" is trade name, also known as PTCs by others.

Their operation is very different from NTCs long used for inrush limiting. They snap to a high R state at a critical temp.

Mains rated examples appeared about 12 years ago, from Raychem and Epcos. These can be use as mains inrush limiters, with additional relay by passing circuitry.

The Slowman demented f****it has never seen any of them.

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** Fake quote, no such thing is even slightly true.

..... Phil

It effect it does, once its resistance goes high I²R keeps it warm even at a smaller than normal current, so its resistance says high.

The problem is you have to turn the power off, so it's not suited for inrush limiting.

We're just throwing guesses at you. given the incomplete description we're provided.

10A is the stall current or the run current for the motor? is there a soft-start implemented?

Why is there a capacitor?

Why is the motor starting and stopping, is that going to cause lots of repeated mechanical stress?