VFD for a 3hp 2 speed 3phase motor on a mill...will it work ??

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metalmole

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I have an Enco mill with a 3hp 2 speed motor, could I run it with a VFD
 
Sure, but I'd recommend disabling the dual speed selection at the motor and run exclusively off the VFD. You could choose either the high speed range wiring scheme, or the low. That would depend on what type of work you would do most of. Obviously, the VFD is designed to give you basically from zero RPM to whatever the over-driven motor will do (90Hz anyone?), so if you need the higher speed more than the lower, wire the motor to the VFD using the diagram to make motor connections for the high speed range, and vise-versa. If you need more low end torque, you'd probably be better off with the VFD wired to the motor with the low speed connections selected.
 
A variation on Tony's response would be to wire it up so that you could switch between high and low speeds, but ONLY when the VFD is off or at zero RPM. Could be done with relays, but would take some careful thought.
 
Agreed. That would be one instance of a reason to violate the normal "no switch between the VFD and motor". I would wonder though, about any parameters on the VFD setup that would be acceptable for both. Maybe, maybe not. That's not something I have done myself, nor seen done.
 
Ok, my input...
I have a VFD driving a 3-speed motor, with an interlock on the 3-speed switch that disables the VFD output (GATE BLOCK input), works well. Most VFDs nowadays can be configured with two or more sets of motor parameters, so if the full-load amps is different for the speeds amother microswitch can select appropriately. On mine the currents are close enough to get away with a single set, YMMV.
An alternative is to stick to one motor speed and use.the VFD as.a.continuous speed.controller, usually the low.speed winding will deliver more torque, so perhaps run that to.a.higher frequency? I run my 4/6/8 pole motor up to 80Hz (50 standard) connected as 4-pole, to get my lathe's spindle speed.up to 2500 rpm for *short* periods, more from sympathy for the headstock plain bearings than the motor - the BTH motor's finely balanced.and can take it (and a.coin on edge balances on the headstock at 2500...)

Dave H. (the.other one)
 
Hey thanks for the responses, here is some info from my motor, 1720/3440 rpm, 8.3/9.7 amps, 2.0/2.4 kw....does it look like I could run it with a VFD hi/lo with the same parameters, I guess it wouldn't be no big deal to set one up for both loads, has anyone got any advise for a good FVD brand/model that would work for my application that wont break the bank too much....
 
I have Automation Direct units -like them. Also have a Huanyang. It's OK but some models (the one I have) do not have built-in rheostats for speed control which may or may not be an issue if you want to locate the speed control on a separate panel. The TECOs look good but I haven't tried one yet.
 
I'm running two machines from a Teco FM50. The mill is 1725 RPM while the lathe is 3450. Both are 1 1/2 HP, 240 V. The VFD has a zero-output interlock, which I use to prevent switching from one machine to the other unless the output has dropped all the way.

I have had no trouble with either machine running off the one VFD, so it may work well for switching between motor speed ranges.
 
metalmole said:
I have an Enco mill with a 3hp 2 speed motor, could I run it with a VFD
Click to expand...

Yes. I have a Hardinge TM, with a two speed, 3 phase motor. Just DON't switch speeds while the motor is running and VFD connected! (Same as switch- VFD's do like them)

I let the motor stop, switch speeds, and start again no issues. 3/4 HP.


Bernie
 
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