4-Speed Electric Motor: What are the Speeds?

[gitano]

Attached are two pictures of the data plate for an electric motor (F48Y 14A50) I just bought. It says the motor rpm is 1075, but it's also a 4-speed motor depending in the wiring. I cannot find out what the other three speeds are, or, whether the 1075 rpm is the "hi" one or the "lo" one. (I am assuming it's the high one.) Can anyone tell me what the other speeds are, OR, where I can find out what they are?

Of course, I could just run it and tach the shaft, but I'd rather wire it closest to the speed I want first. Plus, why aren't these values just spec'd for goodness' sake?

Thanks in advance,
Paul

 

[johnoder]

Attached are two pictures of the data plate for an electric motor (F48Y 14A50) I just bought. It says the motor rpm is 1075, but it's also a 4-speed motor depending in the wiring. I cannot find out what the other three speeds are, or, whether the 1075 rpm is the "hi" one or the "lo" one. (I am assuming it's the high one.) Can anyone tell me what the other speeds are, OR, where I can find out what they are?

Of course, I could just run it and tach the shaft, but I'd rather wire it closest to the speed I want first. Plus, why aren't these values just spec'd for goodness' sake?

Thanks in advance,
Paul

3B P&W Jig Bore had 1800 / 1200 / 900 and 600. Or the usual somewhat less. In other words 1750 or so on down

To answer your question - here is my guess
Its a 60 cycle motor and we have to assume its normal speeds would be 1200 / 900 / 600 / 300. These are synchronous speeds and actual speeds are always less - like the 1200 would be 1150.

Additional guesses on the three lower speeds would be 806 / 538 and 269

we don't know why this motor is somewhat slower at 1075

 

[Phil in Montana]

Thats a fan/blower motor, not a real 4 speed motor, just a 1200 rpm with very high slip, works well for a fixed load , but is worthless for a machine tool

 

[SomeoneSomewhere]

Yup. 1075 RPM full speed - so a six pole 60Hz motor.

Reduced speeds are just some kind of quasi-reduced-voltage operation, I think via autotransformer effect. When fitted with a predictable load like a blower wheel, the lower torque of the motor leads to a stable operation at a lower speed. Permanent-Split Capacitor (PSC) motors are designed to be safe to operate 'overloaded' like this, down to about half speed.

It's like driving a car by leaving your foot at 30% throttle rather than cruise control. Fine as long as the road stays exactly the same...

If you use it for machine tool use, you'll find that at the lower speed taps, it will run near 1200RPM while unloaded, but will rapidly collapse under load.

 

[gitano]

Thank you all very much for your answers! The use I have planned for this motor is driving a grain mill. This mill is normally hand-powered, but built with the handle attached to a 12" pulley so that it can be motorized if so desired. I so desire.

A 1/2 HP electric motor is sufficient to the task, but the best rpm for grinding, is around 120. Therefore, I need to build a transmission. Obviously, the rpm values of the motor I use dictate what set of pulleys I need to purchase. The lower the motor's speed, the fewer pulleys I need to get the mill's speed down to 120 rpm.

With respect to the nature of the load: The load should be fairly constant/uniform.

Thanks again for your replies and explanations.

Paul