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[How do I?] Speed Control.

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strantor

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#31

Downunder Bob

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#32
You can run it off single phase. You need to make sure you get a 240v 3 phase motor. You can run that motor from a suitable vfd but you can't create 400v from a 240v power supply. Well that's my understanding.
That might be a bit difficult here in Australia all single phase motors are 220/ 240 v and 3 phase is 415 / 440 v .

i think i'll try the PWM setup, if it works, end of problem , if not I'll go to a 3 phase motor get more HP and a VFD That is if I think I still need the reduced speed, by then I might decide I don't need it.

Thanks for all your help.

Bob.
 

master53yoda

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#33
The original motor in question was a single phase and by description is a capacitor start motor. It will have a centrifugal end-switch as Ulma Doctor mentioned. When you slow down the motor more than about 20% it will bring the start capacitor back into the circuit and it will blow the capacitor in about 10 seconds. These motors are not designed to be speed controlled without modifications to the internal wiring they normally will have different sets of run windings for each speed.

the fan type speed controls vary the delivered voltage, the motors that they are designed to work with will either have brushes or be fractional HP shaded pole motors.

AC motors whether single or three phase are speed controlled by varying the frequency. The voltage drops as the freguency goes down but the voltage isn't the controlling factor

VFDs take the incoming power convert it to DC and then convert it back to the varied frequency AC power. the VFD if run on single phase power the input amperage will be approximately 153% of the delivered output AC amperage.
 

Str8jacket

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#34
That might be a bit difficult here in Australia all single phase motors are 220/ 240 v and 3 phase is 415 / 440 v .

i think i'll try the PWM setup, if it works, end of problem , if not I'll go to a 3 phase motor get more HP and a VFD That is if I think I still need the reduced speed, by then I might decide I don't need it.

Thanks for all your help.

Bob.
http://au.rs-online.com/web/p/inverter-drives/8325304/

Single in 3 phase out.

http://au.rs-online.com/web/p/ac-motors/8777354/

230v 3 phase. 2 pole 3000rpm

http://au.rs-online.com/web/p/ac-motors/8777373/

4 pole

All in Straya mate. 12 month warranty and decent quality. Not cheap to do. But if you want things to be able to do bells and whistles nothing is cheap I've found. I have been buying 3 phase gear from the states as 400v stuff is cheap over there as no one wants it at a hobby level. I can't even get a consistent result with a pwm control on a ceiling fan not sure how you will manage on a lathe. Once set up on a vfd with your lathe you won't look back. So much nicer to use.
 
Last edited:

Downunder Bob

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#35
The original motor in question was a single phase and by description is a capacitor start motor. It will have a centrifugal end-switch as Ulma Doctor mentioned. When you slow down the motor more than about 20% it will bring the start capacitor back into the circuit and it will blow the capacitor in about 10 seconds. These motors are not designed to be speed controlled without modifications to the internal wiring they normally will have different sets of run windings for each speed.

the fan type speed controls vary the delivered voltage, the motors that they are designed to work with will either have brushes or be fractional HP shaded pole motors.

AC motors whether single or three phase are speed controlled by varying the frequency. The voltage drops as the frequency goes down but the voltage isn't the controlling factor

VFDs take the incoming power convert it to DC and then convert it back to the varied frequency AC power. the VFD if run on single phase power the input amperage will be approximately 153% of the delivered output AC amperage.

Thank you, One of the things I like about this forum is that people with better knowledge than me can and will offer their advice. I feel secure that my adventure is in good hands. I think you have collectively talked me out of trying to vary the speed of the single phase motor that will come with the lathe, when it comes, ETA about early August.

So it's back to speed pulleys and or a 3 phase motor with VFD. I will reassess all this when the lathe arrives and is set up.

Thanks again,

Bob.
 

Downunder Bob

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#36
http://au.rs-online.com/web/p/inverter-drives/8325304/

Single in 3 phase out.

http://au.rs-online.com/web/p/ac-motors/8777354/

230v 3 phase. 2 pole 3000rpm

http://au.rs-online.com/web/p/ac-motors/8777373/

4 pole

All in Straya mate. 12 month warranty and decent quality. Not cheap to do. But if you want things to be able to do bells and whistles nothing is cheap I've found. I have been buying 3 phase gear from the states as 400v stuff is cheap over there as no one wants it at a hobby level. I can't even get a consistent result with a pwm control on a ceiling fan not sure how you will manage on a lathe. Once set up on a vfd with your lathe you won't look back. So much nicer to use.
Thanks, Yes I know nothing worth having is cheap. When the lathe arrives and is installed, I'll have to reassess my desire for a lower speed control and see if I really need it. The 12 speeds on the headstock gears should be sufficient for most needs.

maybe I just make a set of change over pulleys to reduce the speed by half, and leave the motor as is.

Thanks again.

Bob.
 
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