Why not permanent split capacitor motors?

[Chetlaham]

Why didn't older washers like the GE filter flo and belt driven Whirlpools use permanent split capacitor motors? Same with older dishwasher like Maytag RR and D&M. Why centrifugal start or relay start? The way I see it using a PSC motor greatly simplifies wiring and eliminates a known failure point. Apply power Red to white and the motor spins one way, Yellow to white and the motor spins the other- exactly how new vertical modular washer do it. Greatly simplified and much improved.

 

[henene4]

I think that those motors need a voltage control to change speeds, or even an active management of the static magnetic field by the means of switching windings. These systems were not avaible until the 90s AFAIK.

Further, I don't see where the eliminate a point of failure. The boards used to control these are highly delicate for situations of overcurrent, for example a stalled motor.
They still need a cuppling system to switch between agitating and spinning, so a form of transmission would still be there.
And just wiring is actually pretty resiliant as long as its properly managed. If nothing rubbs against it, it should outlive most any other thing about the appliance.

 

[tolivac]

PSC motors don't have the start torque that Cap start split phase motors have.PSC motors that I have seen are used in fans and blowers-low start torque.

 

[Chetlaham]

Whaaaa?

I think you are thinking about front loads. GE FF only used a single speed motor (across all models), as most BOLs, and if dual speed is needed, there are PSC motors that come in multi speed (think table top fans). Further none of these machines had control boards. An over loaded motor be it centrifugal start or PSC would/can simply kick-off an internal overload. Also what do you mean by coupling system? PSC motors can easily be made to reverse, the remaining parts would take care of the rest much like a centrifugal start motor. The point of failure that would be eliminated is the centrifugal switch.

 

[Chetlaham]

Start torque

"PSC motors don't have the start torque that Cap start split phase motors have.PSC motors that I have seen are used in fans and blowers-low start torque."

This is true and now that you mention it you might be on to something. But, how much start torque did most top loaders require? Is there not a clutch?

 

[henene4]

But how does a PSC motor then either handle speed control or the switching of the stator fields? There has to be some mode of controll if they are (in contrast to what was used in the 'normal' TLs) not just motors constructed to run at a certain speed by construction (most fixed speed systems use the number of stator coils to create a certain speed, which then is influenced by the AC frequency).

 

[Chetlaham]

For GE FFs, BOLs and dishwashers you do not need any type of speed control. The stator field for reversing direction is switched simply by applying power directly to the other lead of the motor, or by reconnecting (flipping) one winding.

 

[henene4]

But what does the flipping? Either some active switching component or the frequency of the supply. If the supply does it, their basic operating principle is the same as in the others motors you suggest they replace, thus the wiring has to be the same.

If they have active switching, then they aren't more resiliant.

 

[Chetlaham]

All switching is done via the timer. Here are two examples. In the first pic applying power to the red wire and not the orange makes the motor spin clockwise, and if power is applied to the orange and not the red wire, the motor spins counter clockwise. Very elegant and simply with only 3 wires leading to the motor. (Yes the first one is electronically controlled, but it will work with a mechanical timer as well.) In the second pic the motor is a bit more complicated, but if you look closely it has no centrifugal switch. Simply changing the polarity of each leg of the start winding relative to the run winding causes a change in direction. Both these motors lack a centrifugal switch.

 

[Chetlaham]

Oppps

Pic of the GE is a bit blurry, here is the link:

Wiring Diagrams and Schematics - Samurai Appliance Repair Man

GE washer Mod# WDSR2080D5WW Schematic

appliantology.smugmug.com

 

[henene4]

You can't controll a motors speed without either a) having the motor speed coupled to AC supply frequency or b) changing the voltage (works for AC and DC, depending on design).

The early washers used method a). Their motors had several sets of windings for different speeds, reversing polarity reversed the direction. Frequency was set by supply from the socket. For example a lot of dryers use that system as they only need 1 speed for the most parts, and barely ever need to reverse.

Modern motors that have a variable speed controll and use either method a) by the means of an inverter that can put out AC at variabe frequencys or method b) via a voltage divider of some form.

The wiring diagramm for the GE shows that the machine with that model number is a single speed machine, so it uses the fixed frequency of the wall supply to determine its motor speed. (See screenshot I attached). Clutch/Transmission are used for shifting from agitation to spin.

The second pic just shows a circuit. That circuit can verry well be part of the MCU (Motor Control Unit) or conected to a MCU. The main PCB can communicate with the MCU via a protocoll simmilar to the USB protocolls used, and USB 2.0 only uses 4 wires: Power +/- and data +/-. GE did this on their Hydrowave washers, which, if you search the trouble shooting videos for, have a board mounted on top of the motor, with a indicator LED. That board checks the mode shifter position and controlls motor speed.

So, to achieve multiple speeds with a PSC motor, you have to go the same direction as any other mutiple speed washers: Either MCU or different windinings for different speeds.

 

[Chetlaham]

Motor Speed

As Ive said GE filter flo washers were single Speed. As are most BOL top loaders. A PSC motor can achieve the same (approximate) 1600 RPMs as a centrifugal start motor- via the 60Hz wall supply. And to be clear- I never said a PSC would eliminate the transmission in a filter flo or any vintage washer for that matter. You would still need it to achieve agitation. And a clutch if the washer is a spin drainer.

My point- and my question- why didn't they simply drop a PSC motor directly in the place of those centrifugal/blow-out coil motors?

 

[Chetlaham]

Clutch/Transmission are used for shifting...

...from agitation to spin. Yes and no. To clarify that shifting is achieved via the motor reversing direction, something that a PSC can do. Yes the belt driven Whrirpools were an exception, but the rest used a reversing motor.

 

[henene4]

Yeah, but PSCs are not simpler then the other motors then.

You still have a motor. That can break.
You still have a transmission/clutch. That can break.
You still have cabeling. That still can break.
You still have a timer. That still can break.

Every part of the drive system is still there, they are just differently designed. Don't even think you'd necessaryly loose any cabeling, and even if you had 3 instead of 5 or 7 wires, as long as they are somehwat well managed, they won't break.

So it dosen't matter which kind of fixed-speed motor that is capable of reversing they used, making your question a moot point.

If it was simpler and avaible, it would be used.
But it wasn't.

 

[Chetlaham]

I never said the cabling will break- just that its simpler. Eliminating the centrifugal switch is one failure point out of the picture. Clutch can go on neutral drain models as GE latter did.

But my point is still not moot- there has to be reason for choosing one over the other- hence why I am asking.

 

[henene4]

Yeah, you asking is totaly valid.

But how is the PSC simpler? You take the centrifugal switch, but add a capacitor. Either you switch fails, or the capacitor. Same amout of failure points.
Early electronic components were expensive, and verry delicate. Thus, centrifugal switches were choosen.
Now, the PSC are choosen, as the capacitors are cheaper (which, btw, are verry special once which can resist high voltage and are not of fixed polarity) and you can convert them to variable-speed motors by adding active switching components which, by now, are cheaper then creating new windings for each speed you need.

 

[Chetlaham]

But what is more likely to fail? And lets not forget that 2/3 of centrifugal motors came with a capacitor. Why both when you can just have one?

 

[Chetlaham]

And to add

Air conditioning units for decades had a very beefy capacitor which held up well over all.

 

[tolivac]

PSC motor capacitors are oil-paper or oil -film caps which are HIGHLY reliable-better than the electrolytic caps in Split phase cap start motors.The PSC caps don't need to be as high a capacitance value as those in Cap Start spit phase motors.I rember a PSC motor used as a blower motor in an FM transmitter I worked on.The blower stopped-Tx went off air.The blower stopped because the PSC cap failed-only one I had seen do this and the blower maker as well-They sent me a FREE replacement by overnight shipping.The station did have a spare blower-so I was able to make the blower I took out a ready spare.The blower cooled the base of the PA tube and tube socket.