VFD and 2 speed motor

[jbobb1]

I'm kind of confused as to what speed I should set my VFD for. I've read a lot of info and have gotten mixed answers. I'm leaning towards using the lower speed and run the motor above rated Hz when needed, but would really like to hear what you guys think. Thanks.

 

[JimDawson]

Connecting the motor for the low speed is exactly what I would do. Normally this will give you the best performance.

 

[jbobb1]

Thank you.

 

[f350ca]

My radial arm drill has a two speed motor. I left the selector switch in place and can run it on either speed. Just don't change speeds while the motor is running, you'll damage the vfd. Techs at Automation Direct confirmed it would be fine doing so.

Greg

 

[Ulma Doctor]

I have a 3PDT toggle switch on my 7x28 motor, it allows retention of the 2 speeds.
as Greg said, it is not switched during operation

 

[AGCB97]

Just for my own education, what is a 7x28 motor?
Thanks
Aaron

 

[cathead]

My Enco mill switch wore out some years ago so I opted for a VFD. The motor has two speeds so I picked the
lower speed and at times overclock the VFD to 130 Hertz or so. It works fine at any speed I desire. I use the back
gear when drilling large diameter holes and reverse the motor direction.

 

[jbobb1]

I have a Jet lathe that most of the electronics are pretty much shot, including the 2 speed switch, which is the obvious reason for the VFD.
As Cathead mentioned, I plan to overspeed the motor if/when needed.
I did perform the "Powerup" test today, and everything worked as it should. Next step is the "Auto Tune".

 

[jbobb1]

Also, Thanks for all the info/suggestions.

 

[mksj]

It all depends on the motor and if it is a constant Hp or constant torque and the number of poles. If it is a constant Hp, then you use the lower speed wiring (higher pole) configuration and double base frequency to 120 Hz so the speed is the same as it would be in the lower pole wiring. So if a 8P/4P you would use the 8P, and on a 4P/2P you would use the 4P. If it is what as known as Dahlander motor which usually has 1/2 the Hp on the lower speed setting I usually use the high speed wiring configuration at 60 Hz, you will have full Hp, you sometimes give up some torque at low speed setting of 30 Hz but you will have the same Hp as the low speed wiring. Since the VFD can boost torque typically by 150%, I have not seen this as an issue. So the added wrinkle, is I have done a number of VFD installs with Dahlander 2 speed motor's, tried both pole settings and frequently had issues with rougher running despite loading the different parameters and auto-tune for each motor setting. In these installs, I ultimately switched the motor out to a single speed 4P inverter rated motor with much smoother and better performance. Also, trying to use a single VFD to run both motor settings is doable, but complicated and has no performance benefit in the installs I have done. Factory VFD machines up-size their motors and fewer mechanical speeds. In some applications when retrofitting a VFD motor and going to say a direct drive with a back gear, you would want to oversize the motor and maybe consider a vector or PM (BLDC or similar) motor.

How to Install Motor Dahlander on VFD? | GoHz.com

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