Inverter control of fridge and freezer.

[JohnW2]

I have to say that (in case it hasn't been obviously from my previous posts ), I am rather sceptical as to whether what eric said is correct (particularly given the small amount of space in which to 'hide' an inverter in many of these fans) - at least for 'run-of-the-mill computer fans !! - but I am frequently wrong

Well, I did say that I am often wrong - and it seems that I am (and eric right ) - take at look click here . As for how they fit in an inverter:

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Very interesting - and thanks to eric for the education!

Kind Regards, John

 

[ericmark]

Thanks I was looking for a picture of one I had taken to bits however I was only talking about the PC fan to say maybe it is the same idea with a freezer motor.

I know there was a problem with air conditioning units and I would assume same with a freezer that if the power is removed for just a short time then there is too much pressure in the line for the motor to restart. They have an overload device which heats up and removes power then as it cools down it will retry starting the motor one hopes the pressure has dropped enough.

There is also a problem with under voltage in Algiers when I worked there in the 80's the supply was three phase 110 so the Dutch electrician had connected the air conditioning unit to two phases which gave around the 190 volt and the air conditioner was failing due to under voltage.

Inverter control would likely remove both those problems. So I can see why even not using variable speed an inverter could help.

But I am only guessing.

 

[JohnW2]

Thanks I was looking for a picture of one I had taken to bits however I was only talking about the PC fan to say maybe it is the same idea with a freezer motor.

Yes, I realised that but, as I said, I found it hard to believe (clearly wrongly!) that they could could even a crude approximation of an 'inverter' into the space available in a PC fan - but I've been proved wrong! There's obviously a lot more space in a freezer motor, so no problem at all to fit some electronics in.

Inverter control would likely remove both those problems. So I can see why even not using variable speed an inverter could help. But I am only guessing.

That's true - but almost everything one reads about 'inverter fridge/freezers' seems to indicate, suggest or imply that they do use variable speed compressor motors, the main alleged advantage being 'economy' (although, as you and others have said, I'm suspicious about the arithmetic of that!).

Kind Regards, John

 

[JohnW2]

Thanks I was looking for a picture of one I had taken to bits however I was only talking about the PC fan to say maybe it is the same idea with a freezer motor.

I've just read that article properly, and also the one it links to about brushless DC motors ( click here ).

It seems that it's not an 'electronic inverter' at all, and doesn't create a "3-phase supply" to drive an AC-type brushless motor. It seems that the only rotating parts ('the rotor') are a number (usually 2 or 4) of permanent magnets. A Hall sensor attached to the stator coils then senses these magnets as they move, and the signal from that sensor then switches the current between coils. I suppose one might think of that as an 'electromechanical inverter' as far as the coils are concerned, but that's not really how I would think of it!

Kind Regards, John

 

[ericmark]

Be it a generator or motor there are two ways to work with DC. One is a mechanical converter (Commutator) the other is electronic from simple diode to very complex true sin wave production.

I see that using the motion to switch the electronics may be considered as a half way point but it only raises the question as it if a rotatory converter or an inverter and since there is no output I would tend to use the word inverter as a label rather than rotatory converter.

I clearly got the squirrel cage bit wrong but all I was doing was pointing out how small motors that used inverters could be.

At one time production line conveyors would be powered by DC motors today in the main they are three phase motors driven by inverters and even star/delta starters are being replaced by soft starts which to me is a problem as every make seems to have a different way to program them so one needs a library of books to show one how to program them.

How long the single phase and brushed motor will continue to be used I don't know washing machines and now refrigeration pumps have gone to some sort of electronic drive at the moment electric drills, vacuum cleaners, sewing machines, food mixers still use brushed or single phase motors but for how much longer I don't know.

But touch controls for example were used as a plus when selling goods but manufactures took them too far with for example induction hobs where using knobs gives a far better human machine interface than touch controls. I wonder if it is going to be the same with inverter where manufactures see it as a selling point to write in big letters "Inverter Control" across the front even when the inverter control is really to make production cheaper rather than give the user any advantage?

 

[bernardgreen]

~~~ is really to make production cheaper rather than give the user any advantage?

PRECISELY

 

[JohnW2]

Be it a generator or motor there are two ways to work with DC. One is a mechanical converter (Commutator) the other is electronic from simple diode to very complex true sin wave production. ... I see that using the motion to switch the electronics may be considered as a half way point but it only raises the question as it if a rotatory converter or an inverter and since there is no output I would tend to use the word inverter as a label rather than rotatory converter.

Same here.

I clearly got the squirrel cage bit wrong but all I was doing was pointing out how small motors that used inverters could be.

Yes - and, to my surprise, you were right. However, as we now know, computer fans do not use an inverter to produce a 3-phase supply to drive the motor.

... even when the inverter control is really to make production cheaper rather than give the user any advantage?

I'm sure we'll see plenty of that - for example, given the negigle cost of the electronics, the design of the computer fans, with the only moving parts being permanent magnets, presumably makes for cheap manufacture. However, as I said, everything one reads about 'inverter control' in fridges/freezers seems to talk about variable speed (which allegedly results in some economy), which is somewhat different.

Kind Regards, John