Single Phase 2 Speed Pool Pump Motor Question

[Lucien Nunes]

So it always starts and runs initially in low speed.

The problem with that is that if your timings are set so that the T104 switches on while the T106 is at high-speed or you twist the dial on the T104 to cause the same effect, or the power is briefly interrupted while at high speed, then the motor won't start and will sit stalled on high speed. That is why the motor has to contain an internal switching arrangement to forcibly select the speed that has the start winding first, then once started it can transition to the other speed as required.

In the A.O. Smith patent it specifically states that it is the high-speed that has the start winding. Therefore the switching arrangement energises the high speed start and run windings from the low speed input until the centrifugal switch operates. This makes sense because high speed has fewer poles so the start winding takes up less space on the stator, and also because the changeover speed on the centrifugal switch can be made higher.

is there a schematic of it

Yes, follow the link in post 7 to the Espacenet site where you will see the schematic in the patent document.

I've also found a pic showing a dual speed motor where the extra contacts on the centrifugal switch are clearly visible:

 

[Poolworx]

The problem with that is that if your timings are set so that the T104 switches on while the T106 is at high-speed or you twist the dial on the T104 to cause the same effect, or the power is briefly interrupted while at high speed, then the motor won't start and will sit stalled on high speed. That is why the motor has to contain an internal switching arrangement to forcibly select the speed that has the start winding first, then once started it can transition to the other speed as required.

In the A.O. Smith patent it specifically states that it is the high-speed that has the start winding. Therefore the switching arrangement energises the high speed start and run windings from the low speed input until the centrifugal switch operates. This makes sense because high speed has fewer poles so the start winding takes up less space on the stator, and also because the changeover speed on the centrifugal switch can be made higher.



Yes, follow the link in post 7 to the Espacenet site where you will see the schematic in the patent document.

I've also found a pic showing a dual speed motor where the extra contacts on the centrifugal switch are clearly visible:

So the motor would always start om Start winding and Hi speed winding

On initial start up the T104 timer clicks in and energizes the start winding and Hi speed winding. Once the motor gets up to speed the centrifugal switch opens and drops the start winding circuit so now its running only on the Hi speed winding. So it always starts and runs initially in Hi speed. Lo speed can bet set to where when the pump has primed and the pool water is at a constant flow you wouldnt need Hi speed then so it could at that time run on Lo speed and save energy?

https://drive.google.com/file/d/1eibQpKDDMnoy_PLS3ies48hj72vPYjKh/view?usp=sharing

 

[Poolworx]

So the motor would always start om Start winding and Hi speed winding

On initial start up the T104 timer clicks in and energizes the start winding and Hi speed winding. Once the motor gets up to speed the centrifugal switch opens and drops the start winding circuit so now its running only on the Hi speed winding. So it always starts and runs initially in Hi speed. Lo speed can bet set to where when the pump has primed and the pool water is at a constant flow you wouldnt need Hi speed then so it could at that time run on Lo speed and save energy?View attachment 101316

any idea why the pics are all blacked out

 

[Lucien Nunes]

So it always starts and runs initially in Hi speed. Lo speed can bet set to where when the pump has primed and the pool water is at a constant flow you wouldnt need Hi speed then so it could at that time run on Lo speed and save energy?

No, check out my diagram in post 6 and note how the centrifugal switch has two sets of contacts. When the motor is at rest, the lower (normally closed) contacts complete the circuit to the start winding in the usual way. The upper (changeover) contacts divert the low speed input to the high speed winding.

Suppose the motor is stopped and you apply power to the low speed input. The changeover contact routes the power to the high speed and start windings, and the motor starts. As soon as the centrifugal switch trips, i.e. before the motor even reaches high speed, the changeover contact re-routes the power back to the low speed winding. You would not even be aware from the outside that the motor had used the high-speed winding to achieve the start, it would seem to have gone straight to low speed.

The A. O. Smith patent shows a different switching circuit that does exactly the same thing. I would guess they did it that way either because the simpler centrifugal switch saves a few cents over the cost of the triac, or to work around a patent on the changeover contact held by another manufacturer, or even to prevent another manufacturer working their way round Smith's own patent on the changeover contact.

 

[Poolworx]

No, check out my diagram in post 6 and note how the centrifugal switch has two sets of contacts. When the motor is at rest, the lower (normally closed) contacts complete the circuit to the start winding in the usual way. The upper (changeover) contacts divert the low speed input to the high speed winding.

Suppose the motor is stopped and you apply power to the low speed input. The changeover contact routes the power to the high speed and start windings, and the motor starts. As soon as the centrifugal switch trips, i.e. before the motor even reaches high speed, the changeover contact re-routes the power back to the low speed winding. You would not even be aware from the outside that the motor had used the high-speed winding to achieve the start, it would seem to have gone straight to low speed.

The A. O. Smith patent shows a different switching circuit that does exactly the same thing. I would guess they did it that way either because the simpler centrifugal switch saves a few cents over the cost of the triac, or to work around a patent on the changeover contact held by another manufacturer, or even to prevent another manufacturer working their way round Smith's own patent on the changeover contact.Hoping i interpreted you correctly?

No, check out my diagram in post 6 and note how the centrifugal switch has two sets of contacts. When the motor is at rest, the lower (normally closed) contacts complete the circuit to the start winding in the usual way. The upper (changeover) contacts divert the low speed input to the high speed winding.

Suppose the motor is stopped and you apply power to the low speed input. The changeover contact routes the power to the high speed and start windings, and the motor starts. As soon as the centrifugal switch trips, i.e. before the motor even reaches high speed, the changeover contact re-routes the power back to the low speed winding. You would not even be aware from the outside that the motor had used the high-speed winding to achieve the start, it would seem to have gone straight to low speed.

The A. O. Smith patent shows a different switching circuit that does exactly the same thing. I would guess they did it that way either because the simpler centrifugal switch saves a few cents over the cost of the triac, or to work around a patent on the changeover contact held by another manufacturer, or even to prevent another manufacturer working their way round Smith's own patent on the changeover contact.

Hoping i interpreted you correctly?

 

[Poolworx]

https://drive.google.com/file/d/1mWK1lmh95uNuc9nIfpHnYhfJ50njeJ30/view?usp=sharing

 

[Poolworx]

For some reason my images get blacked out like a silhouette

https://drive.google.com/file/d/1mWK1lmh95uNuc9nIfpHnYhfJ50njeJ30/view?usp=sharing

 

[Lucien Nunes]

Yes that looks like the scheme in my original drawing. Note that I have no proof that this system has been used commercially, nor the triac controlled one in the Smith patent. Only that they are possible implementations.

I have found a few more patents.

US2488658 to Ronald Brennen in 1948 claims two windings of different pole numbers, each of which serves as the start winding for the other.

US2488658A - Multispeed single-phase electric motor - Google Patents

US2564633A to Peter Ziegler in 1948 uses a tricky winding configuration to re-purpose only part of the 6-pole winding as the start winding, under the control of the centrifugal switch.

Patent Public Search | USPTO

pdfpiw.uspto.gov

US2669683 to John Burdett and filed by Westinghouse in 1951 cites both of these and claims the same idea of re-purposing part of the low speed winding but with a different centrifugal switch arrangement.

US2669683A - Two-speed single-phase induction motor - Google Patents

Read column 1 lines 16-26, where it describes the setup you have just drawn (i.e. with two run and one start windings) as the prior art, also the idea of separate run and start windings for each speed. I haven't yet found these exact configurations claimed anywhere. There are various others that turn up for searches similar to 'multi-speed induction motor' that are not relevant because they are consequent-pole types, or small tapped-winding motors eg. for desk fans that don't have two true near-synchronous speeds.

Have a go searching from that one and see where it leads.

 

[Poolworx]

Yes that looks like the scheme in my original drawing. Note that I have no proof that this system has been used commercially, nor the triac controlled one in the Smith patent. Only that they are possible implementations.

I have found a few more patents.

US2488658 to Ronald Brennen in 1948 claims two windings of different pole numbers, each of which serves as the start winding for the other.

US2488658A - Multispeed single-phase electric motor - Google Patents

US2564633A to Peter Ziegler in 1948 uses a tricky winding configuration to re-purpose only part of the 6-pole winding as the start winding, under the control of the centrifugal switch.

Patent Public Search | USPTO

pdfpiw.uspto.gov

US2669683 to John Burdett and filed by Westinghouse in 1951 cites both of these and claims the same idea of re-purposing part of the low speed winding but with a different centrifugal switch arrangement.

US2669683A - Two-speed single-phase induction motor - Google Patents

Read column 1 lines 16-26, where it describes the setup you have just drawn (i.e. with two run and one start windings) as the prior art, also the idea of separate run and start windings for each speed. I haven't yet found these exact configurations claimed anywhere. There are various others that turn up for searches similar to 'multi-speed induction motor' that are not relevant because they are consequent-pole types, or small tapped-winding motors eg. for desk fans that don't have two true near-synchronous speeds.

Have a go searching from that one and see where it leads.

This is all very interesting. I used to be and electrical design engineer specializing in Electric Surface Heating Systems some 20 plus years agog when we lived in UK. Now i have Parkinsons so this is so stimulating Thanks

 

[Poolworx]

I found a 2 speed motor, that also has a hi & Lo switch on the back,. I'm assuming that would be their (manually operated) equivalent of the secondary centrifugal switch?