Ah yes, Thank you. I forgot about eddy currents. Actually both are at play. The following article speaks of permeability, but that's just another (inverse) way of saying reluctance.Being picky, the reason is eddy currents, not reluctance. Otherwise you are right. Higher frequencies cause loss unless the motor is designed for that frequency. Same with transformers.
Interesting! Thanks for the link, I am glad to finally learn that it is "a thing." Now I really want to try it. I am a little confused about the paragraph at the end where they apply the concept to American motors. They get the 1.74 factor from European mains voltages (400V/230V = 1.74) and then apply 1.74 to 60Hz, resulting in 104Hz. But our mains are 480V/240V, so our factor should be 2.00 not 1.74, unless I'm missing something.I believe I read somewhere that Haas runs their machines that way.
The centrifuge company I worked for ran one of the motors on the machine that way, but used a delta-wye motor wired for 230v and 50 hz (it was a European company) on a 400 volt design feed into the VFD. Instead of typing it out, this article describes how it works.
87Hz motor control for Delta Wye VFD operated motors - KEB
This article gives an overview of the 87hz motor operation for delta/wye motors. The trick allows a motor to be oversped while keeping the torque constant. Effectively increasing the available motor power.www.kebamerica.com
They are referring to a delta-wye motor, the 1.74 ratio is the same between the wye and delta windings with a 50hz or 60hz motor, so in the US with our 60hz frequency, the motor would be 277/460v instead of 230/400v on 50hz. With that kind of motor, you would need to program the VFD with a motor base voltage and frequency of 277/60hz and that would give you the maximum frequency of 104hz at 480v. If you used a 230v motor with a rated 60hz frequency, then you could run that up to 120hz, but you can’t do that with a delta-wye motor without overspeeding it.Interesting! Thanks for the link, I am glad to finally learn that it is "a thing." Now I really want to try it. I am a little confused about the paragraph at the end where they apply the concept to American motors. They get the 1.74 factor from European mains voltages (400V/230V = 1.74) and then apply 1.74 to 60Hz, resulting in 104Hz. But our mains are 480V/240V, so our factor should be 2.00 not 1.74, unless I'm missing something.
Thank you, you revealed a blind spot in my knowledge and prompted me to go illuminate it. The crucial thing I never realized is that America is unique in having two different 3-phase supply voltages (or, "many," if you want to count all the variations on "low" voltage 3-ph). I was aware of the sqrt(3) factor between wye and delta but it never occurred to me to question why I've never needed to permanently wire an American motor for a "low" voltage of 138V, or a "high" voltage of 277V (apart from wye/delta start) despite 12-wire motors availing those options. Meanwhile working on European equipment I do have to choose 230V or 400V. Europe (broad brush, I know) only has one 3-ph supply voltage. So, back to the point, they don't have the option for anything over 1.74x.They are referring to a delta-wye motor, the 1.74 ratio is the same between the wye and delta windings with a 50hz or 60hz motor, so in the US with our 60hz frequency, the motor would be 277/460v instead of 230/400v on 50hz. With that kind of motor, you would need to program the VFD with a motor base voltage and frequency of 277/60hz and that would give you the maximum frequency of 104hz at 480v. If you used a 230v motor with a rated 60hz frequency, then you could run that up to 120hz, but you can’t do that with a delta-wye motor without overspeeding it.
Ok then you need to compare the 220V (and 50Hz?) To the parameters that are entered in the drive.Update, I took the drum switch apart and cleaned the contacts, no change. I did some milling today, as usual the motor acted up for 2 tries than ran flawlessly. When the motor acts up the VFD makes a bit of a hum and I immediately return the lever to N and wait for the hum to stop (a second or two) before moving the lever back to F, usually the motor will then go forward normally and will continue to operate normally. The motor has never acted up when the drum switch is turned to R.
Drum switch only supplies a signal (F-N-R) to the VFD which is wired directly to the motor. Wired per instructions. Motor is a GE 1hp, 1150 rpm, 220-440 3 phase, it is listed in the Millrite spec sheet at 1200 rpm with spindle speeds of 250, 430, 725, 1160, 2300, 3400 which matches the spindle speed tag on my machine.