G4003G vfd conversion

[Splat]

It appears my stock G4003G motor is on the way out. I replaced the capacitors and the motor still has trouble getting and maintaining anything over 500rpm. I've thought about taking the motor to a local shop to see about refurbing it but I've been thinking of just going to VFD 220v 3 phase. Dealer's Electric has this Brook Crompton drop-in replacement metric motor but I know nothing about them. For the VFD I'm considering this Teco N3-202-CS-U. The motor's a lot more than I want to spend but I can drive to Dealer's Electric which negates shipping charges. Any opinions or recommendations? Thanks.

 

[LEEQ]

Check their motor/drive packages. I got lucky there twice. When they have what you need in a package the prices can't be beat. I'm happy with the vfd's and they were both tecos.

 

[Splat]

So far I've ordered a Leeson 192205.00 motor, Hitachi WJ200-015SF drive, and this 50ohm 500W brake. I've removed the contactors, relay, and transformer from the G4003G circuit box and the controls and indicators from the main switch panel on the front of the lathe. I'll be basing my build on Mark's (MKSJ) attached pdf which was for another brand of VFD so the VFD's inputs on the Hitachi are labeled differently and the schematic might need to be slightly reworked. I'm investigating. I'm also going to be basing VFD parameters and setup off of Mark's suggestions in the other attached PDF. Mark, I hope you don't mind me using your work here. If you want me to take anything, or all of it, down just let me know.

So next is ordering the controls and indicators. I already have a 110V led worklight that is fabulously bright but would need to work that into the circuit controls. Or, go with 24VDC low voltage items and just run the worklight off an ext/cord plugged into another outlet. Gonna be a fun ride.

 

[LEEQ]

I was told a lot of people get higher hp motors when doing the 3phase vfd conversion. This is supposed to help you maintain the torque you need when slowing the motor down. Unfortunately I received this insight after I pulled the trigger. I kept my new 2hp weg motor and forged on. Surely the weg motor was closer to its hp rating than the original Chinese grizzly motor. That's what I tell myself to feel better anyway. Just a quick thought, wish I brought it up earlier so wiser minds could weigh in. I look forward to following your build.

 

[Splat]

I was told a lot of people get higher hp motors when doing the 3phase vfd conversion. This is supposed to help you maintain the torque you need when slowing the motor down. Unfortunately I received this insight after I pulled the trigger. I kept my new 2hp weg motor and forged on. Surely the weg motor was closer to its hp rating than the original Chinese grizzly motor. That's what I tell myself to feel better anyway. Just a quick thought, wish I brought it up earlier so wiser minds could weigh in. I look forward to following your build.

You don't lose torque with a VFD. A three phase motor develops full rated torque at full load amps whether its on a VFD or across the line. If you want full HP cuts you HAVE to use the belt speeds or the gear changes to keep the motor at or near 60 Hz. Light cuts you can use whatever VFD and mechanical speed setting that works but if you want stock removal you have to use the mechanical reduction to keep the motor in its sweet spot. That's my understanding.

 

[Mitch Alsup]

I was told a lot of people get higher hp motors when doing the 3phase vfd conversion. This is supposed to help you maintain the torque you need when slowing the motor down. Unfortunately I received this insight after I pulled the trigger. I kept my new 2hp weg motor and forged on. Surely the weg motor was closer to its hp rating than the original Chinese grizzly motor. That's what I tell myself to feel better anyway. Just a quick thought, wish I brought it up earlier so wiser minds could weigh in. I look forward to following your build.

A G4003G has enough settings in the gear box, that one uses the motor in a rather limited range of RPMs when operating with a VFD. This should ameliorate any concerns on the <lack of> Torque at low RPMs.

 

[mksj]

Torque for the most parts remains constant below the motor's base speed (60 Hz) and Hp drops off in a linear fashion down to 0 RPM. When you decrease the VFD to say 30Hz, you decrease the mechanical advantage of the gearbox vs. using a single phase motor and changing the gearbox ratio to get the same speed. Still a VFD is able to deliver ~150% overload to the motor for up to a minute, and running sensorless vector control also improve motor control. I would recommend a usable VFD speed range of 30-90 Hz.

See attached documents. The WJ200 logic inputs use a separate 24VDC power supply in the VFD, the default is what as known as "Source Logic" where the inputs are at +24VDC and they are activated when connected to the L terminal which is the negative supply of the VFD power supply this is completely independent of the power supply that operates the relays.

On the light I would suggest using a 12V or 24V bulb and powering it from the external power supply. You can buy an inexpensive 24VDC to 12VDC step down converter to get 12VDC to use for lights, tach., etc.

https://www.ebay.com/itm/24V-to-12V...or-Car-Step-Down-Reducer-US-Ship/321641171884

See schematics and recommended programming parameters for using the WJ200 for the G4003G lathe. I would add 2 stage braking so that you normally use 3 second braking (2 stage, 3 second) and only use 1 stage (1 second) for slow speed work like threading. These are provided as is and untested, so use at your own risk.
Mark

 

[LEEQ]

"Torque for the most parts remains constant below the motor's base speed (60 Hz) and Hp drops off in a linear fashion down to 0 RPM. When you decrease the VFD to say 30Hz, you decrease the mechanical advantage of the gearbox " So if I put the lathe in its lowest speed and reduce the motor freq. to 30 hz, I lose hp, not torque? Maybe I chose the wrong terms. I was made to understand that running the motor below 60hz cost me cutting power(whatever the exact terminology) and that a common choice was to use a bit more motor to make up for this. I'm pretty sure I will be ok with my 2hp 3 phase motor. That money is already spent. I'll dig(research) a little deeper the next time a vfd conversion comes up before I spend the money. As for the OP's build, I look forward to seeing it come along.

 

[dsymes]

Any news on how this conversion has gone? Also, one specific question - is the Leeson 192205.00 motor a "drop in", or does it require fitting?

 

[mksj]

Leeson should be a drop in replacement as far as the footing since it is a metric frame motor, you can review the specs and compare to your motor. You might need a different pulley for the motor, in particular if you want to overspeed the motor and keep the same top speed on the spindle. Several people have done VFD conversions on the G4003G with very good results. In addition you get less motor cogging and the poor finish often seen with single phase motors. I would review these older threads.

https://www.hobby-machinist.com/threads/g4003g-going-3-ph-vfd.34549/#post-296192
https://www.hobby-machinist.com/threads/vfd-setup-brook-crompton-motor-teco-vfd.66696/#post-556794