Hardinge HLV motor and speed control question

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30 Mar 2020 09:55 - 30 Mar 2020 10:23 #162087 by jools
Hi All

I've just picked up a Hardinge HLV lathe which has an infinitely changeable gearbox for speeds. From what I see the motor just spins at 1500RPM all the time and to change speeds at the spindle you turn a hand wheel on the front of the lathe while it is spinning.

Converting it to CNC I'm pondering which route to take.

Swap out 3 phase 440v motor to single phase of same or smaller power and control with VFD.
Benefits are infinitely controllable speed with feedback directly from the spindle, plugs into the garage wall.
Downsides: Will the motor overheat at lower speeds when the fan isn't blowing so fast.
Question: Can VFD's be controlled through PWM from a mesa?

Swap out motor and have linux CNC turn the speed handwheel
So I can put a single phase motor in and have it running at 1500 RPM constantly. If there were cooling issues with the VFD this would overcome them.
Have a stepper or servo, getting feedback from a spindle encoder, attached to the hand wheel adjusting 'manually' the speed

Just change it all for an A/C servo
Downsides: What kind of torque levels would be needed for a lathe; could be expensive. Possibly low torque at low revs??

run 440v three phase motor at 240v three phase through VFD and lose 40% of top speed

Any comments appreciated or even other idea's I haven't thought of.

Cheers

Jools
Last edit: 30 Mar 2020 10:23 by jools. Reason: adding fourth option

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30 Mar 2020 10:29 #162093 by cmorley
What hp is the motor?
440 volt motors often can be run on 220volts (not sure what you have available).
Do you need to change the motor for power or voltage reasons?

If not, I would consider buying a VFD, leave the variable gearbox in the machine if it's in good shape and use the original motor.

Chris
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30 Mar 2020 10:54 #162095 by jools
Hi Chris

The motor is 1.5hp. Not sure I need all that power.

I have 240v single phase available in the garage.

Looking to change the motor for powering reasons; the cost of a step up transformer, that I can see, would be very prohibitive. I did read a web page that said they can be run on 220v or there about as long as the frequency was kept in sync. Think it said 400v at 50Hz you could run at 220v and 29Hz.

That would lower my top spindle speed from 3000RPM to about 1700RPM. Not having had a lathe before I'm not sure how that would affect turning small parts and SFM requirements.

If I did do this, which is a good option for cost, is there any special requirement for the VFD? I've read things about rotary converters but aren't really sure what they are or if I would need one.

Cheers

Jools

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30 Mar 2020 11:06 #162097 by cmorley
got specs on the motor? or a pic of the name plate?

Lots of motors can be rewired to run from 220volts - no transformer needed.
You would need a VFD or phase converter.
!.5 hp is really small - you could buy a nice VFD off ebay for not too much.

i run a 10hp 3 phase motor off 220v in my shop and my drill press is probably 1.5 hp off a VFD i got off ebay for about $100 delivered (for the small vfd).

Just need to know if the motor can be rewired.

Chris

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30 Mar 2020 11:14 #162098 by jools
Motor plate attached.

inverterdrive.com/howto/240V-Supply-to-a-400V-AC-Motor/ is the link that said about running 440v motors at lower voltage.

Jools
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30 Mar 2020 11:31 #162100 by cmorley
By the name plate it seems to be a single voltage motor - if you open the motor wiring box on it if it has 6 or 9 wires then it surely can be wire for different voltage.
(but I'm not an electrician either)

Interesting read in the link - but it does make sense.
setting the frequency ifs basically what a vfd does.
According to that link you'll lose some power at full rpm -not a big deal for at home.

let the post sit for a bit and see if other guys with other experience chime in.

Chris
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30 Mar 2020 11:51 #162103 by jools
Thanks Chris.

If I can do as it says in the link and run from a 240v VFD I think as you say, for the home workshop small commercial it would be awesome.

Stay safe.

Jools

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30 Mar 2020 11:58 #162104 by tommylight
that is some bad info there on that link, damn.
400V motor will work at 220V, but it will be pretty much useless as the torque will be very low.
inductive motors need some power for the physics of it to function properly, not in the mood to explain all that as there are plenty of good info about inductive or inductance motors, but unfortunately there is much more bad info on the net.
Buy a VFD, a single phase one for 220V, wire it see if it has enough torque for what you need.
If it does not, get a motor for 220V and you already have the VFD.
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30 Mar 2020 12:03 #162106 by cmorley
fo reference this is the type of VFD I use:
www.ebay.com/itm/ONE-Mitsubishi-inverter...9:g:MToAAOSwC2VbPfa7

This one is big enough for your motor. this one isn't made for single phase input but it works fine - you tend to want to get a bit bigger capacity then you need to compensate. you need 3 amps this is capable of 11 if it had 3 phase power.

They also make ones specifically for single phase input -just harder to find.

You can run this depending on the model,l from the panel, using analog +-10 volt and over a type of modbus.

Chris

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30 Mar 2020 22:54 #162178 by andypugh
Is there a speed-change switch too? That motor plate seems to suggest 1500/500 rpm. ie it might be a Dahlander wound two-speed motor.

The advantage of the variable speed thingy is that you get increased output torque at lower speeds. Whereas with a VFD speed control you get lower torque at lower speeds.

If it's a Dahlander motor then rewiring for 240V is difficult, and it won't run nicely off of a VFD. Given that it is a 1.5hp motor and those aren't expensive I would be tempted to swap the motor for one that will run off 240V, but probably a three-phase with a VFD as three phase is just better. Then you could run at two different frequencies and keep the speed range using both VFD and variable speed unit.

This is exactly what I didn't do when I CNC-ed my Holbrook Minor. I removed the variable speed drive but kept the motor. (but that was a rewirable single speed motor, with a 2-speed electrically-controlled gearbox after the Kopp Variator.
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