Looking for info on VFD for a single phase motor

Shigs · Apr 12, 2018

Hey guys! I've looked through this subject and as I am not the most experienced with the electrical side of things, I'm a little baffled as to what type, if even possible, of VFD is compatible with my motor.

I have a 1/2HP MARATHON 3450RPM 56 115/208-230V TEFC 1PH MOTOR, model # G393 that I'm looking to control the speed on......

rklopp · Apr 12, 2018

Shigs said:
Hey guys! I've looked through this subject and as I am not the most experienced with the electrical side of things, I'm a little baffled as to what type, if even possible, of VFD is compatible with my motor.

I have a 1/2HP MARATHON 3450RPM 56 115/208-230V TEFC 1PH MOTOR, model # G393 that I'm looking to control the speed on......

A couple of years back we bought a single phase output VFD from the UK. I do not recall the brand, and it was not cheap. We used it to vary the speed of a pool pump as part of an accident investigation. The VFD worked fine for us. Beware that if the motor has a centrifugal start switch, you will need to keep the speed above the speed at which the switch changes state.

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Frederick Harvie · Apr 12, 2018

It is likly cheaper to replace the motor with a 3 phase motor and use a single phase in 3 phase out VFD. Dealers electric has a half hp motor VFD package for $167 http://dealerselectric.com/item.asp?cID=2&scID=132&PID=40875

L Vanice · Apr 12, 2018

Frederick Harvie said:
It is likly cheaper to replace the motor with a 3 phase motor and use a single phase in 3 phase out VFD. Dealers electric has a half hp motor VFD package for $167 http://dealerselectric.com/item.asp?cID=2&scID=132&PID=40875

And you may see a benefit from getting a 1750 RPM three phase motor. If you set the VFD to 120 HZ, the motor will run as fast as your 3450 RPM single phase motor, but you will have more power at the low speeds.

Larry

Strostkovy · Apr 12, 2018

I've had great luck with these guys: http://www.gohz.com/vfd

I ended up using it for testing a product with 50hz motors on a 60hz supply and had no issues.

I think these are just reprogrammed 3 phase VFDs so you can actually cut the lead to the start capacitor and connect it to the third phase and run your motor at any speed.

HuFlungDung · Apr 13, 2018

Strostkovy said:
I think these are just reprogrammed 3 phase VFDs so you can actually cut the lead to the start capacitor and connect it to the third phase and run your motor at any speed.

Say what? You just blew my theories of how motors work right out the window

3t3d · Apr 13, 2018

I've done that with a capacitor motor, just connected it to three phase, remove the cap...

Replacing the motor with the three phase motor looks like the best recommended way to go, 1750 at 120 Hz for max power, torque and flexibility, and least cost.

Shigs · Apr 13, 2018

Frederick Harvie said:
It is likly cheaper to replace the motor with a 3 phase motor and use a single phase in 3 phase out VFD. Dealers electric has a half hp motor VFD package for $167 http://dealerselectric.com/item.asp?cID=2&scID=132&PID=40875

Wow that's a great deal. Looks like im.going to sell my current motor and go with this setup. Thanks!

Shigs · Apr 13, 2018

That motor VFD combo looks like the way to go! I'm going to sell my current motor and put the funds towards that, thanks!

Lakeside53 · Apr 13, 2018

Strostkovy said:
I've had great luck with these guys: http://www.gohz.com/vfd

I ended up using it for testing a product with 50hz motors on a 60hz supply and had no issues.

I think these are just reprogrammed 3 phase VFDs so you can actually cut the lead to the start capacitor and connect it to the third phase and run your motor at any speed.

Interesting. Good to see someone actually doing this. I've though it was possible for years, but never saw anyone market a reprogrammed unit. If there is sufficient flexibility in "parameter definition" for various motors it could work well.

JST · Apr 13, 2018

Lakeside53 said:
Interesting. Good to see someone actually doing this. I've though it was possible for years, but never saw anyone market a reprogrammed unit. If there is sufficient flexibility in "parameter definition" for various motors it could work well.

The phase difference is wrong, unless re-programmed, but if reprogrammed it would work for some of the "run capacitor" type motors. You would have to bypass the start switch, of course, or take it out entirely.

Problem with many single phase motors is that the start winding is made with smaller wire, and it cannot take the continuous current without overheating. Capacitor start motors usually have a start winding that is not quite as high resistance, and those can work better, especially those using a run capacitor as well.

I also have thought of that, but have not had a VFD that I could conveniently reprogram.

depending on exactly how the start winding is "mechanically phased" (exactly where in the stator it is placed as to poles), it might be very similar to a "two-phase" motor. That is exactly equivalent to a 3 phase motor, and 2 phase power can be converted to 3 phase, and back, without anything but transformers used.

L Vanice · Apr 13, 2018

Shigs said:
That motor VFD combo looks like the way to go! I'm going to sell my current motor and put the funds towards that, thanks!

Don't get the 3600 RPM motor combo. Learn about the HP and torque curves vs. speed when using a VFD. Think about what work your motor is going to be doing when you slow it down. It is pretty simple, but most people do not understand. Much depends upon the application. A fan is different from a circular saw, for instance.

Larry

dian · Apr 20, 2018

even some of the unexpensive vfd can run single phase. i have one, 1.5 kw. however you cannot slow down the motor substantially without loosing most of the torque.

JST · Apr 20, 2018

single capacitor motor, like many gearmotors, will run fine in many applications.

Regular single phase no capacitor motors? Nope..... forgetaboutit

thermite · Apr 20, 2018

JST said:
The phase difference is wrong, unless re-programmed, but if reprogrammed it would work for some of the "run capacitor" type motors. You would have to bypass the start switch, of course, or take it out entirely.

Problem with many single phase motors is that the start winding is made with smaller wire, and it cannot take the continuous current without overheating. Capacitor start motors usually have a start winding that is not quite as high resistance, and those can work better, especially those using a run capacitor as well.

I also have thought of that, but have not had a VFD that I could conveniently reprogram.

I could certainly be wrong, but I'd bet half a stale lemon cake that at least some of the VFD shown on that website are H******g - or same "grade".

Even if not, we'd probably expect lesser risk if one of more of the top five makers with long and respected track-records were to be represented in the "1-P output" category.

Sort of "blesses" it, AS a category, probably brings a few useful "white papers" on do and don't tips, too.

Anyone had sight of such?

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