VFD on Variable Speed Lathe

maybe I'm getting dense, but your question doesn't make any sense. I have a logan/powermatic with a reeves drive and a VFD. the VFD is wired directly to the motor as it MUST be. this is electrical and in no way affects the operation of the reeves drive. I removed the contactors and barrel switch and let the VFD do that work.

If this didn't answer your question, please clarify a bit......

The output of a VFD should be wired directly to the motor with no contactors, switches, or other circuit breaking elements between the two. I'm told that VFDs don't like being run to an open circuit. You can run wires from the lathe run/off/reverse switch to the control inputs on the VFD to provide those functions and most VFDs have inputs for an external potentiometer should you desire to control motor speed that way.

Not too long ago we had a LONG thread from guy attempting to use all the existing wiring and he wondered why it didn't work well. He wanted to set the VFD and then put switchs between the VFD and the motor ie use all the existing wiring in spite of the fact that the manual says very clearly not to do this. Hook the motor directly to the VFD. Do not put any switchs between the motor and the VFD!

If you want to use the existing controls; you will have to look at the manual and figure out how to interface the existing controls to your VFD. I have found that "3-wire" control interfaces well with push buttons. Other schemes work better for drum switchs.

The sensitivity of the vfd to "plugging" the motor on and off is design dependent.

I don't have electronic controls hooked up on mine yet, I just use the original BP isolator switch. My vfd idles until it sees the motor load, then spins it up. When the load goes away, it switches back to idle. I specifically asked the vendor about this, they indicated the unit will handle it just fine- I'm just not fully taking advantage of its motor accelerate/decelerate features.

Better check with your vendor- and especially confirm how your unit will behave if there is a short to ground. Some vfd's will fail catastrophically if any of the phases conduct appreciable current to ground. For those that do, the situation can be mitigated by constructing a chassis ground which leads thru a resistor and gfi breaker so the vfd 3 phase can be cut out to prevent damage to the personnel and equipment.

Gregm

Well William, my Sheldon has a mechanical variable speed drive and it is adjusted via a gear motor. The gear motor is run from circuit box off of a transformer apparently. So if I run the motor directly from the VFD how to you suggest that I operate the gear motor without running another run of wires to the transformer which is impractical??? Please let me know. Thanks, Steve

I am not familar with your lathe, but mechancial VS drives on clausing and rockwell must be adjusted when the spindle is running. If your little gear motor is 3ph, I would put in parallel with the main motor. If the little gear motor is single phase, it might not like low frequency or running from VFD power, so I would figure out a way to connect it to single phase AC but try to interlock it with the spindle motor so that it won't run unless the spindle is running. Some VFDs have outputs indicating the drive is "at speed" that could be connected to relays that enable power to the gear motor.

chuck

Well ourname.... That was a smart a@@ed answer from someone who hadn't even read the question.... Sheesh. Looks like Chuck understood the question.. Pete

actually, yes I did. What it looks like is the guy wants to know if there is an easy way out.

the short answer is 'no' come to think of it the answer is almost always no

One has to wonder if the mechanical variable stuff is going to want to spin much faster than it does now...

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