2 speed motor

[nizak]

I've got a 2 speed electric motor(1 phase 1.5HP 240V). Am looking to set it up so that that it can be switched from high speed to low speed with a conventional wall type switch. The scenario would be motor running on high, flip the switch and it goes to low, flip the switch back and it resumes high speed. Does this sound like something that can be accomplished with a switch, rather than having to add relays into the mix? Would the type of switch to use be the same as a 3-way style? Any help appreciated.

 

[Jraef]

A typical "wall switch" has 2 positions; up and down. For a 2 speed switch, you have 3 positions; High, Low and Off.

So either use 2 switches side-by-side, Hi-Lo and On-Off; the Hi-Lo would need to be SPDT but that's readily available, the On-Off can just be the standard SPST switch.

Or find a 3 position switch and I don't know of one other than a rotary selector switch.

 

[ptonsparky]

You can find double pole toggle switches with center position off.

On-Off-On or Hi-Off-Low, maybe even Low-Off-Hi.

 

[nizak]

So my On/Off could be the actual disconnect(molded case breaker style) and I could wire the SPDT ahead of it for the speed control? Would the configuration of the SPDT be a 3 terminal device? Ran across some part #'s which I believe to be the correct style switch.Bryant4922, or Hubbel HBL1385.

 

[philly]

Out of curiosity how does a 2 speed motor work. Are there two contactors that connect to a different winding arrangement on the motor? Are the two winding arrangments configured with different poles?

 

[dicklaxt]

It can be done with switch arrangement but there should be inhibit contacts to keep one winding from being allowed to be energized while the other is coasting down.If you were to put a low spd NC contact in the high winding feed(hot) wire and a high spd NC contact in the low winding feed(hot) wire this would do it.If the low winding is energized it disables the high winding and vice versa,I guess these would be centrifical switches of sorts in this case where you had across the line starting without starters,this would be a single pole double throw center off or shortened to SPDT, 3 position center off,,,,,,,,It is also sometimes done with a rotary drum switch often used in operator controlled conveyer loading lines.

dick

 

[nizak]

Would motor damage occur if the contacts were not installed? I had an individual tell me that they used a standard 3 way switch to accomplish this task and that it's working fine. Do you see anyway that this could work?

 

[nakulak]

It can be done with switch arrangement but there should be inhibit contacts to keep one winding from being allowed to be energized while the other is coasting down.If you were to put a low spd NC contact in the high winding feed(hot) wire and a high spd NC contact in the low winding feed(hot) wire this would do it.If the low winding is energized it disables the high winding and vice versa,I guess these would be centrifical switches of sorts in this case where you had across the line starting without starters,this would be a single pole double throw center off or shortened to SPDT, 3 position center off,,,,,,,,It is also sometimes done with a rotary drum switch often used in operator controlled conveyer loading lines.

dick

I have a 2 speed motor in my furnace and it doesn't have any of that crap attached, just high and low (and of course off) run off the board.

 

[dicklaxt]

If its a low torque motor and is rated for the low speed winding to be used as a brake then it can be done,,,,,,,,,,industry recommended control schematics will support my opening post .

With out going to some resources I believe the switch would have to be DPDT center off as you need to break both legs of a 240V

dick

 

[LarryFine]

The thing to do is feed a SP switch, then to the common of a 3-way switch, taking each speed's wire from one traveler terminal.

If the motor proteste being switched from one speed to the other while running, turn off the SP switch before flipping the 3-way.
​

 

[dicklaxt]

Here is a sketch of the control logic schematic I spoke of earlier.The centrifical switch is used to keep the low speed winding disabled until the high speed winding coasts down to a predetermined point.This as others have noted is not always a requirement.This schematic could have many variations.The start winding,capacitor and cutout are not shown for clarity.


dick

 

[John120/240]

The thing to do is feed a SP switch, then to the common of a 3-way switch, taking each speed's wire from one traveler terminal.

If the motor proteste being switched from one speed to the other while running, turn off the SP switch before flipping the 3-way.
​

Larry's method is common for use with whole house attic fans.
Have not encounterd any problems with this setup.