Small single-phase VFD for 120V? (2023 Update)

The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:

And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:

And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Thu, 14 Oct 2021 16:33:25 -0000 (UTC) in message-id <sk9m4k$qvd$ snipped-for-privacy@dont-email.me.

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ceiling fans are often capacitor run as this setup provides an easy way to reverse them. (reversing a shaded pole motor is harder) the series capacitor just makes a current limit reducing the torque and thus the speed. if you unbolt the blades you'll see that they always run at the same speed unloaded.

capacitor should work too.

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** The ** TOPIC* is speed control of a small fan motor - you ASD f***ed POS !! ================================================================

** Funny how that IS is the ** FUCKING TOPIC ** you ADD MORON =======================================================

Go save us from f****ng Google monkey idiots like this 1/3rd wit.

.... Phil

Jasen Betts wrote: =================

** Yes it will, but is not so stable.

Q. Why does nobody here ever trim ??

...... Phil

tried an RC to reduce variac idle current? ... plus some series variable/switched R to get it all upto voltage without tripping

The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:

And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:

And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Thu, 14 Oct 2021 20:47:17 -0000 (UTC) in message-id <ska50k$ta4$ snipped-for-privacy@dont-email.me.

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Tabby meeowed: ==============

** Huh ??

** The OP may need to use a NTC thermistor in series with the Variac's primary to reduce inrush current and asymmetry offset effects at switch on. Bout 200 ohms might be right.

...... Phil

But a 40W pedestal fan with a 13" diameter is along way from the muffin-type fans that Jeorg was trying to deal with.

For one thing. it is a lot bigger. For another it is a mass-market consumer item, engineered for minim cost, when the muffin fans are manufactured in much lower volumes, for a more demanding market.

Phil does seem to exemplify the breed.

Not the topic I was addressing, which was AC induction motors, like the one that blows air through my furnace. It's the internals of an AC motor that determine what it does with oddball power supply, not the 'fan motor' application. 'Small' wasn't mentioned, but is likewise... uninformative. What is 'small' for an aviation turbofan?

1/3 wit trolling maniac

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** THEN FUCKING STOP POSTING YOUR GOOGLED UP SHITE UNDER MY WORDS !! ===================================================================== =================================================================== = You illiterate idiot.

piglet wrote: ==========

** There is none from the rotating parts.

** The fan motor is resistive at all voltages, PF of unity. Winding resistance dominates the 50Hz impedance. The current waveform matches with the AC supply voltage. The impedance curve has a broad peak around 50/60 Hz.

The 3 way speed control fitted to the fan uses tappings on the motor's windings. Interestingly, a Variac reduces the blade speed over a much wider range while using a far less current.

...... Phil

Not so in an AC induction motor: those inductors transformer-couple and there's a resistive short circuit; the 'just inductors' assertion ignores the 0 ohm load resistor on the secondary.

But those are measurements on an unknown motor; it could, for all we know, be a rectifier/DC motor, or universal type, or reluctance motor (AC but with high resistivity in the rotor). Testing tells us it's not an AC induction motor, or stepper, or synchronous type. If you want to buy a fan, and power it for speed control, the differences matter.

The next 'fan motor' isn't represented by that one example.

I don't know for sure how a fan-rated speed-control would work, but given that motors don't like harmonics[*], the continuous speed-control would pretty have have to produce a sine wave at reduced voltage. That's what the controllers with a few positions achieve by putting capacitors in series.

Running something designed for 60Hz at a different frequency does not seem like a good idea.

Sylvia.

[*] I once tried running a fan off a modified-sine-wave inverter. The burning smell quickly alerted me to the issue.

That's Phil's assertion. Since he doesn't seem to have an example of Jeorg's muffin fan - a Pabst all-metal muffin fan with a shaded pole motor (which is still pretty unspecific) he does seem to be lying. "Over-confident" is a nicer way of saying the same thing, but who'd bother being nice to Phil?

<snip>

[snip]

Hi Joerg, whatever variable-drive- speed control method you go with, consider one that provides: (a) initial full power, for ~5 seconds, to ensure fan gets up to speed (b) closed-loop control, like a tachometer (optocoupler, etc.) since for some motors (those not designed to be varied) the drive isn't predicable or linear formula... cheers, RS

Unfortunately, any UPS that's not really true sine wave is a design flaw.

Manufacturers will even pass square waves off as "modified sine wave". While a VFD should rectify this ugly input and make a new AC wave for the motor, but good luck finding one speced to take input from a dubious UPS and work correctly.

Cydrome Leader wrote: =================

** Nonsense - that never happens. You must have some other issue going on.

** Is an insane idea.

** Yawnnnnnnnnn....... wot drivel,. ** Works just fine with SMPSs. ** Nut case idea.

but good luck finding one speced to take input from a dubious UPS

** Bet any one you find will work just fine.

...... Phil

The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:

And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:

And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Fri, 15 Oct 2021 19:36:53 -0000 (UTC) in message-id <skcl8k$h9d$ snipped-for-privacy@dont-email.me.

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The John Doe troll stated the following in message-id <sdhn7c$pkp$ snipped-for-privacy@dont-email.me:

And the John Doe troll stated the following in message-id <sg3kr7$qt5$ snipped-for-privacy@dont-email.me:

And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Fri, 15 Oct 2021 19:37:38 -0000 (UTC) in message-id <skcla2$h9d$ snipped-for-privacy@dont-email.me.

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