Single Phase 2 Speed Pool Pump Motor Question

[Poolworx]

Hi everyone

I came across a single phase 230v 2 speed pool pump motor the other ay and became obsessed with how they work and are internally connected , but cant seem to find a diagram/pic of the anywhere. I decided to do my own from what i found on line

My question is have i interpreted the connection of the windings correctly

are they in series or parallel

Thanks in anticipation

 

[Lucien Nunes]

Hello and welcome. It's an interesting question. I am not familiar specifically with pool pump motors, but dual-speed induction motors are generally pole-changing motors using one of two configurations; separate winding or consequent-pole.

In a pole-changing motor with separate windings, the stator slots are wound with two completely independent sets of windings, only one of which is energised at a time. These are wound with different numbers of pole-pairs which can be in any ratio. I see for example, a pump motor with speeds of 1725 & 1170 rpm, corresponding to 4-pole and 6-pole. I am not sure what dodges the manufacturers might use to simplify the connection of the start winding and centrifugal switch.

The consequent-pole configuration produces a 2:1 speed ratio e.g. 3450 & 1725 rpm, corresponding to 2-pole and 4-pole. In a consequent-pole motor all the windings are used for both speeds, but they are split into two groups of alternate poles. To change speed, one group is reversed relative to the other, creating adjacent pairs of like poles for high speed (NNSS = 2-pole) or adjacent pairs of unlike poles for low speed (NSNS = 4-pole).

Because pool pump motors generally only require either the high or low speed hot connection at any one time, I infer they have separate windings, as a consequent-pole machine needs both ends of both windings connected.

One type of dual-speed induction motor that is quite well documented on the WWW is the Dahlander 3-phase consequent-pole motor, which switches a multi-group winding between star and delta at the same time as reversing one group relative to the other.

I need to do more research on the single-phase kind though.

 

[Poolworx]

So are the internal start, and 2 run windings wire in parallel lie this sketch? Thanks

 

[Lucien Nunes]

In your sketch the high and low speed windings are not in parallel, only one is energised at a time, but the start winding is in parallel with the high speed. I don't know how the start winding is actually configured in these motors.

 

[Poolworx]

I believe that start winding is wired in series with the centrifugal switch and capacitor. So that when the motor gets up to speed the switch opens and drops the starting circuit. This is when the run widing takes over with the the low speed winding and wired in parallel it would be running at say 1725 rpm now if you needed it at full speed 3450 rpm also independently wired in parallel it could be switched to hi speed winding via a set of time clockd

 

[Lucien Nunes]

In a single-speed capacitor-start motor, the start winding, capacitor and switch are connected in series, and that string is in parallel with the run winding. That much is standard. But for a two-speed motor, a single start winding could only have the right number of poles for one of the speeds.

You could have two separate start windings for the low and high speeds with the correct number of poles on each, but that is rather wasteful of cost and size. It would also need separate centrifugal switches and capacitors for both start windings to avoid back-feeding the unselected run winding via the two start windings.

A more practical arrangement would be to use the centrifugal switch to force the motor always to start in high-speed mode. The motor has start and run windings for high speed, plus a run winding for low speed. The centrifugal switch has two sets of contacts: an N/C contact that controls the start winding in the usual way, plus a changeover contact that diverts the low-speed input to the high-speed winding until the motor reaches low speed.

If the high-speed input is energised, the motor starts and runs using the high-speed start and run windings. If the low-speed input is energised, the motor starts using the high-speed start and run windings, then as it reaches low speed the high-speed start and run are disconnected and the low-speed run engages instead.

A search of patents might reveal whether makers have implemented this system on pool pumps. TBH I've never seen a motor wired like this and just worked it out myself, but it's so logical and straightforward that I would be very surprised if something extremely similar was not used for this application. If I get time tomorrow I will search the patents.

 

[Lucien Nunes]

I had a quick look and found patent US4623829A from 1986. Applicant was A.O. Smith who happen to make 2-speed pool pumps. It's very similar to my description, but instead of a 2-pole centrifugal switch it uses a dual-make N/C for the start winding and to link the low-speed input to the high-speed winding. A triac, triggered by the voltage across the start contacts of the centrifugal switch, serves in place of my N/O contact to connect the low-speed winding to the low-speed input once the switch operates. It also shows transformer-connected start windings.

The patent references others which I expect will show a purely switch-based solution without the triac, but I don't have time to look at those now.

Espacenet – search results

Espacenet: free access to millions of patent documents. Find out if your invention is unique or if other inventors have filed patent applications that are considered to be prior art.

worldwide.espacenet.com

 

[jozefbehr]

Informational Thread , thank you for sharing your views here.

 

[Poolworx]

In a single-speed capacitor-start motor, the start winding, capacitor and switch are connected in series, and that string is in parallel with the run winding. That much is standard. But for a two-speed motor, a single start winding could only have the right number of poles for one of the speeds.

You could have two separate start windings for the low and high speeds with the correct number of poles on each, but that is rather wasteful of cost and size. It would also need separate centrifugal switches and capacitors for both start windings to avoid back-feeding the unselected run winding via the two start windings.

A more practical arrangement would be to use the centrifugal switch to force the motor always to start in high-speed mode. The motor has start and run windings for high speed, plus a run winding for low speed. The centrifugal switch has two sets of contacts: an N/C contact that controls the start winding in the usual way, plus a changeover contact that diverts the low-speed input to the high-speed winding until the motor reaches low speed.

If the high-speed input is energised, the motor starts and runs using the high-speed start and run windings. If the low-speed input is energised, the motor starts using the high-speed start and run windings, then as it reaches low speed the high-speed start and run are disconnected and the low-speed run engages instead.

A search of patents might reveal whether makers have implemented this system on pool pumps. TBH I've never seen a motor wired like this and just worked it out myself, but it's so logical and straightforward that I would be very surprised if something extremely similar was not used for this application. If I get time tomorrow I will search the patents.

I think i have something similar

I had a quick look and found patent US4623829A from 1986. Applicant was A.O. Smith who happen to make 2-speed pool pumps. It's very similar to my description, but instead of a 2-pole centrifugal switch it uses a dual-make N/C for the start winding and to link the low-speed input to the high-speed winding. A triac, triggered by the voltage across the start contacts of the centrifugal switch, serves in place of my N/O contact to connect the low-speed winding to the low-speed input once the switch operates. It also shows transformer-connected start windings.

The patent references others which I expect will show a purely switch-based solution without the triac, but I don't have time to look at those now.

Espacenet – search results

Espacenet: free access to millions of patent documents. Find out if your invention is unique or if other inventors have filed patent applications that are considered to be prior art.

worldwide.espacenet.com

is there a schematic of it

 

[Poolworx]

Meantime heres some more i came up with

On initial start up the T104 timer clicks in and energizes the start winding and low 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 low speed run winding. So it always starts and runs initially in low speed. Now if you need to step up the speed the T106 timer drops the low speed winding and energizes the hi speed winding

 

[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?