Possible motor for mill

[Joeman77]

Thanks @ttabbal
I’ll keep my eyes open for a suitable 3ph motor


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Since you're probably going to have to make an adapter anyway, if it was me I'd take this opportunity to bump the HP up on the motor a bit, more available power won't hurt at all. 1-1/2 to 2hp 220v, 3 phase 1725rpm motors aren't terribly expensive. Try for an "F" rating in insulation if possible (especially if you're buying new) but that's not a deal breaker by any means. Lots of us are running 50 year old motors on VFD's.
All that being said a new motor & a shiny new VFD doesn't mean you won't have to change belts, it'll just be much less frequent and will probably for that rare occasion when you're down on the RPM's & up on the DOC trying to hog something crazy! The sky (or your wallet) are the limit. Have fun with this!

 

[graham-xrf]

When I went to variable speed on my mill drill I installed a 2 hp Dc motor
Not sure how the torque at low speed with a VFD on a 1 hp 3 phase would be
Maybe someone who has done this can verify the performance
My mill will go from 120 to 1500 rpm without changing belts on the pulleys
Have not had to change pulleys since installing 15 years ago
You may have to look at a bigger motor to get low speed torque
I agree changing pulleys for speed control is the pitts

@Nigel123 : You may have a really good drive control. It may be using PWM drive electronics, and may have a control response faster than the changes in load can collapse the voltage. It sounds like you have a useful power range there. 120RPM is slow enough for most folk, except those into CNC control who want stuff like automatic tapping with stops and reversals and all the stuff you would be doing manually.
BUT..
A "bigger" motor does not simply deliver more low speed torque. If it is an induction motor, with capacitor, instead of being a 8-pole servo-motor with encoder and permanent neodymium magnets, and a smart servo drive, then all that will happen is "big" motor simply fails to spin up to enough revs to deliver it's "bigger" power.

Go slow with your kit, and note the revs. Then give it a bit of load. Does the speed stay exactly unchanged? One can take this test all the way to stall and trip-out, but in most folks shops, that is not something to be casually trying out.

 

[graham-xrf]

they are not magic boxes

Honestly, when I first encountered them, I thought they were (magic boxes).

I think that despite the name "VFD", the good ones have do more than simply alter the frequency. Changing the frequency alone cannot to the trick. The simple inductance is a frequency dependent thing that evaporates as the revs slow down, and inductance is important to limiting the AC current.

We still call them "VFDs", but now, the actual internal operation of variable speed control in AC motors no longer uses simple AC induction motor speed rotating field in relation to frequency in the traditional way. The currents are switched on an off at kilohertz frequencies, and the energy is varied by controlling the ON time compared to the OFF time in a complex waveform. That these techniques can then, at another level, be used to make bolt-on kit that can usefully work "traditional" motors with "artificial AC" is remarkable, and perhaps it was inevitable.

When these technologies are mated up to servo motors specifically built for this kind of control, then we have a whole new game, like robotic CNC. One can, and I have, also explored going faster than the 50Hz or 60Hz related maximum revs. It works well!

I have to appreciate that there are esoterics, and I can't just casually use the term "VFD control" anymore.

 

[Nigel123]

When I setup this system VFD were expensive and not without problems
I had a surplus of cheap DC motors and drives
By reading threads on this site VFD's and 3 phase are the way to go just have no machines with them installed
Set up a few on drives before I retired almost 20 years ago wash down was a killer
Set the DC drive with max and min trim pots to get RPM stable when loaded
Yes quick reversing is not an option found that out when I hit the reverse switch by mistake lucky 10 amp fuse blew
If I remember rightly the motor bolted on to the mill with little trouble maybe had to drill a couple of holes
Just wanted to suggest a slightly bigger motor might be less belt changing not that DC is the way to go

 

[ttabbal]

If you have the gear, nothing wrong with DC from what I can tell. Perhaps permanent magnets attracting swarf, but not a big deal. People use treadmill parts which are usually DC motors with PWM speed controllers for this sort of thing all the time. They are popular with the DIY belt grinder crowd too. I think they have some areas on the torque curve they are better and 3ph has some in different areas. I haven't worked with them much, even though I have one in the garage from a treadmill my brother was trashing. I was going to do a grinder with it, but ran into a perfect 3ph, brand new for a killer price.

 

[luxige]

This is a very educational thread!

David, I highly recommend this 8-part YouTube series, starting here:

 

[DavidR8]

Thanks @luxige!


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[DavidR8]

This is a very educational thread!

David, I highly recommend this 8-part YouTube series, starting here:

I watched the video series last night.
What a great explanation for visual learners like me.
Thanks to everyone that contributed, I feel like I am much better informed now.


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[DavidR8]

I might have found a decent Canadian source for a new 3-phase motor.
Conversion might be around $325 all in.


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[DavidR8]

So the motor supplier had a 'free shipping' sale so I have ordered a 1.5 hp 220v/440v 3 ph motor and a Teco VFD.
Watching Clough42's videos he is using a contacter between the line input and the VFD. I can't make out what model it is though.
Ideally I'd like to end up with fwd, rev and variable speed.

In lieu of the contacter, can I simply install an on/off swith on the incoming line? Not to start or stop the mill as I understand frequent power cycles are hard on the VFD internals, but to power on the VFD at the start of the day and off at end of day?