Vfd and motor recommendations

Hi,

I have done countless searches and read a lot here I want to thank you guys in advance for all your patience answering the same questions over and over again hopefully mine is slightly different.

Ok I have an old 16” Harrison lathe, they came with a 3,5 and dual speed motor. I’m replacing the motor and installing a vfd for motor control and to update the old nasty wiring.

I have found a great deal on a new 5hp 200-240vac Baldor unit, great! Purchased. Searching for sutable motor now. First thought would be 5hp (bigger the better right) Now I have a 5hp RPC I run everything else in my shop no issues. My intentions are to run the vfd off single phase. After more though here are my questions. Mainly to avoid vfd motor derating , let me know opinion for best combo

5hp vfd and 5hp motor using single phase in (2.5hp net hp)

5hp vfd and 3hp motor using single phase in 2.9???? net hp??? not sure if this would make more power or not

5hp vfd and 5hp motor using rpc 3 phase??

I’m not going to running the lathe at max capacity so I’m looking for max energy efficiency and max hp. Not looking to do this twice so I had to ask. Thanks

I don't quite understand what motor you found but if you buy a 4KW three phase 220 delta motor and a 4KW single to three phase inverter there will be no derating whatsoever. I usually install a 4 pole motor instead of a two and a 6 pole instead of a 4 pole. That give better ( double ) low end torque and one uses the inverter to speed up things when needed. I just did something like this over the weekend and the motor cost around $350 and the inverter $250. I think but have no real evidence to back it up that more poles at the motor gives better finish when turning.

Sorry I found a 5hp 200-240vac Baldor VFD. 200$

Factory motor speed is 1750-3450

I assumed I would use high speed motor so I can reach max spindle speed. But I understand you can over ride the rpm of the low speed motor with the vfd. Also a bonus because the 1750 motors are a lot cheaper that I have found.

Best combination would be a 5Hp motor with a fully rated 5Hp VFD.You lose Hp below the base speed of the motor, most factory installed VFD lathes 14" and 16" oversize the motor to compensate for this and use a 2 speed headstock. I would go with a (4 pole) 1750 RPM motor. Although a 6 or 8 pole motor has more torque at it's base speed, when you factor in the final drive ratio to achieve the same spindle RPM, the torque will be the same as a 4 pole. One can also adjust the motor pulley ratio (going smaller on the motor) so that you achieve the same spindle speeds in each gear as previously, but the motor is spun up to say 90 or 100Hz. Given the motor to spindle drive ratio, you will achieve more effective Hp at the spindle over a wider operating range.

If you have a 5Hp RPC, then the maximum recommended motor size that can be run by it is ~3Hp. You would need a 7.5Hp RPC to run a 5Hp motor or 5 Hp 3 phase VFD.

Single phase input VFD rated at 5Hp, are few.
Invertec ODE-3-320153-1042, 5 HP, 230V Phase Converter
ODE-3-32153-142, 23V 1 Phase input, 23V 3 Phase output


Yaskawa, CIMR-AU2A0018FAA
Yaskawa CIMR-AU2A18FAA, 5 HP, 2-24V, VFD

Going to a larger 3 phase VFD (probably a 10Hp, or 7.5Hp with a DC choke) and derating for use on single phase, gets costly quickly because the input side needs to be rated for the full Hp rating of the VFD and not the derated output. The other alternative, would be to switch out/convert the RPC to 7.5Hp and use a 3 phase 5Hp VFD for the lathe. Cost wise it probably will come out a wash if you need to purchase a new RPC motor and up size everything for the increased current. Have not used the Invertek VFDs, but Drivewarehouse is very positive about them. There are previous discussions as to who makes them. I have done a number of installs with the Yaskawa VFD mentioned, they work very well with no issues, but cost more.

I have tried to do several VFD installations with dual speed motors with the VFD programmed for each speed setting/motor parameters, but have not had good success with the motor operating smoothly. On a number of lathe installs I have used vector duty motors going to 120Hz, and belting down the drive pulley ratio to give similar or slightly higher speeds in each headstock gear setting. This gives a very wide variable speed range, about 20-120Hz, but you would do just fine with a standard 1750 RPM 3 phase 5Hp motor and spinning it up to ~90Hz with a smaller motor puley. The motor you are describing, unless a constant Hp would have less Hp at the low speed setting. If constant Hp, then I use the lower RPM (4 pole configuration). You would be better off with a single speed 1750 RPM motor.

To confirm I have no interest in using the factory 2 speed motor as it’s 440v and my phase converter and transformer are too small to run it. It was just a thought.. They run everything else fine. Keeps it simple to leave that setup alone and make the lathe happy with 1phase input.

Baldor VS1MD25 VFD V19 - Variable Frequency Drive 28-24V 3 Phase Input, 23V 3 Phase 5 HP 16 Amps Output

Here’s a link to the drive I have found locally. It does derate a 5hp motor to 2.5hp that’s why I was considering putting a 3hp motor so I may actually have more power and possibly less amperage draw..

Agreed 1750rmp motor it is, bonus there half the price too..

That Intertek unit is very nice, no hp loss it seams. Very nice.