Single phase input and output VFD

Moper361

Moper361

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Hello all
I have just purchased a mill it is running a single phase 220volt motor .Is there anyone familiar or had experience in using single phase in and single phase out VFDs as I have been looking online and there are a few suppliers of them now and seem to be slowly becoming more available
I know I could go single in 3 out and change the motor as I converted my lathe however if I can run the original motor of a single phase out VFD i would save on a motor and maybe an easier option for variable speed .
Any input appreciated
 
Normally, the speed of single phase motors is fixed. If you want to vary the speed you will have to change the motor to 3 phase and buy an appropriate VFD or a DC motor and controller
-mark
 
Your mill probably has a capacitor start motor on it. If you operate it at a low frequency the centrifugal switch won't activate, the start winding will remain connected and quickly overheat. You may be able to operate it over 60 Hz if it doesn't have a run capacitor.

Greg
 
I'm not really sure what the advantage would be to use a VFD on a single phase motor. If the motor rpm dropped below maybe 60-70% , the start windings are coming back into the circuit and it can't be operated that way.
 
I would also be interested in a single phase out vfd. In principle, induction motors run in sync with the AC input so varying the frequency of the AC input should vary the motor speed.

I think the problem arises because a second winding is require to start the motor turning in the desired direction. Usually, that winding is disengaged when the motor reaches a certain minimum speed by means of a centrifugal switch. A capacitor is also used to shift the AC phase. This would be problematic with a VFD.

At least one video that I viewed essentially rewired the motor, removing the centrifugal switch and start capacitor and having the VFD control the start winding. I had seen other videos where this wasn't done but if I recall correctly, the motor speed wasn't dropped down enough to kick in the start winding.

I would expect that a smart VFD could emulate the start winding function electronically. The ones that I have seen are usually three phase output run as single phase out. It also appears that the largest use is for controlling fan motors and I'm not sure what the implication is regarding low speed torque.
 
There are different variants, most applications are for motors that do not use a start capacitor and/or just a run capacitor. If a motor does have a start capacitor, it and the start switch are eliminated and the starter coil is used as a second phase of the motor. The timing/current of the starter phase coil is adjusted relative to the run phase coil. I have not seen any comparative performance curves, and you would assume that since the start coil is run continuously as a second phase that this would result in a higher total current draw. Essentially the output power I would expect to be greater with the same size motor frame, how this equates with heat dissipation and motor longevity is not known. If the motor is an easy replacement then you may be better with a more tradition 3 phase conversion.

How to use VFD for single phase motor? | ATO.com

www.ato.com www.ato.com
 
mksj said:
There are different variants, most applications are for motors that do not use a start capacitor and/or just a run capacitor. If a motor does have a start capacitor, it and the start switch are eliminated and the starter coil is used as a second phase of the motor. The timing/current of the starter phase coil is adjusted relative to the run phase coil. I have not seen any comparative performance curves, and you would assume that since the start coil is run continuously as a second phase that this would result in a higher total current draw. Essentially the output power I would expect to be greater with the same size motor frame, how this equates with heat dissipation and motor longevity is not known. If the motor is an easy replacement then you may be better with a more tradition 3 phase conversion.

How to use VFD for single phase motor? | ATO.com

www.ato.com www.ato.com
Click to expand...
Yes from what limited info ive seen this appears to be the case .It would be nice to gather some clear and precise info .The units are out there but information seems limited .However with new technology always moving in it does not seem out of the relms off possability for it to work .Ill keep hunting for info as there is no hurry and i have done one single to 3 phase mod on my lathe already and its not to difficult .Just if i could go this way maybe a good option to
 
I'm interested to hear some real-world results on this. I have been looking at that same drive. I have nice German-made 3hp 220V single phase motor I plan to put in a lathe I bought that runs on a 440/550V motor.
If anyone tries this single/single VFD, please post about it.
 
luxige said:
I'm interested to hear some real-world results on this. I have been looking at that same drive. I have nice German-made 3hp 220V single phase motor I plan to put in a lathe I bought that runs on a 440/550V motor.
If anyone tries this single/single VFD, please post about it.
Click to expand...
Im trying to gather more information from ATO vfds and GOHZ as these two manufacturers make 2.2 kw units and by all accounts from reading the manual they sent me it should be okay.however like you say real time experience would be nice to know
 
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