VFD, DFC?? Wiring a 3 phase Mill

[lukeshotrods]

First off, I'm not an electrical person at all, I purchased a Bridgeport Series 1 mill that's 3 phase and want to get it wired up but my shop is only single phase. From my research I believe I need either a VFD or a Digital Phase Converter. My questions are-

Which is the best option?
Will my on/off and speed controls still work on the mill?

Thanks for any help

 

[mm08822]

What is the the mill incoming voltage? and current requirement?
How many motors are 3 phase and their respective voltages?
What is the existing on/off hardware now?
What is the existing speed control(s) method?

Pics and schematic would help.

 

[whateg01]

It likely can be wired for 240 3 phase so as long as you have 240, I like the vfd option. Mine is a Newport but a good clone. I've been using the OEM motor with a vfd and like it, keeping in mind the motor life might be cut short using it on an inverter. I do still use the two speed switch on the motor but all of the on/off fwd/rev is handled at the vfd which also allows me variable speed. Much easier than reaching up to the motor for those things.

If you really want to turn it on and off from the motor, I would avoid a vfd. In general, they don't like having loads applied or removed while they are running.

 

[Gokart]

I would use a phase converter from Ronk Electrical. Give them a call Monday, and they will walk through all the options

 

[dscheidt]

If you really want to turn it on and off from the motor, I would avoid a vfd. In general, they don't like having loads applied or removed while they are running.

the existing controls can be rewired to send signasls to the vfd, instead of the motor directly. Requires some work, but there are plenty of people that have done it (and made videos about it...).

 

[whateg01]

the existing controls can be rewired to send signasls to the vfd, instead of the motor directly. Requires some work, but there are plenty of people that have done it (and made videos about it...).

I did that on my 10ee. On the mill, because there are several wires between the hi/lo and fwd/rev switches, I think it's easier to leave those at the motor. You only need the hi/lo switch that way. Fwd/rev is easy on the vfd.

I hate having to reach to the motor anyway so having the controls on the arm next to the dro is way more convenient.

 

[wyliesdiesels]

It likely can be wired for 240 3 phase so as long as you have 240, I like the vfd option. Mine is a Newport but a good clone. I've been using the OEM motor with a vfd and like it, keeping in mind the motor life might be cut short using it on an inverter. I do still use the two speed switch on the motor but all of the on/off fwd/rev is handled at the vfd which also allows me variable speed. Much easier than reaching up to the motor for those things.

without knowing what the rated voltage is not good to say likely

If you really want to turn it on and off from the motor, I would avoid a vfd. In general, they don't like having loads applied or removed while they are running.

thats why you wire the existing controls to the VFD controls.

 

[whateg01]

without knowing what the rated voltage is not good to say likely

Ok, I should have said possibly.

thats why you wire the existing controls to the VFD controls.

How are you going to wire the two speed switch to the vfd such that you maintain the ability to switch between both speeds, effectively giving you two ranges?

 

[wyliesdiesels]

How are you going to wire the two speed switch to the vfd such that you maintain the ability to switch between both speeds, effectively giving you two ranges?

most VFDs have inputs that can be programmed to different Hz (speeds) for motor control.

 

[RoninB4]

-The post by @mm08822 asked the right questions. Additional questions to consider:

1) How many more machines/motors do you intend to add in the future?

2) How many machines/motors will be run simultaneously?

3) Will any present/future machines be a surface grinder or use CNC controls?

4) What will your budget allow?

 

[whateg01]

most VFDs have inputs that can be programmed to different Hz (speeds) for motor control.

Yes but I use low range on the motor to avoid running it at 15 hz since it's probably not inverter rated. If op has a factory motor, it's most likely not inverter rated either. I don't know for sure but I believe running at low speed also provides more torque, probably roughly double, than on high speed.

 

[alfredeneuman]

On the mill, because there are several wires between the hi/lo and fwd/rev switches, I think it's easier to leave those at the motor. You only need the hi/lo switch that way. Fwd/rev is easy on the vfd.

Any switching between the VFD and the motor will cause damage to the output transistors of the VFD. Repeated switching will cause premature failure of the VFD.

 

[mm08822]

It likely can be wired for 240 3 phase so as long as you have 240, I like the vfd option. Mine is a Newport but a good clone. I've been using the OEM motor with a vfd and like it, keeping in mind the motor life might be cut short using it on an inverter. I do still use the two speed switch on the motor but all of the on/off fwd/rev is handled at the vfd which also allows me variable speed. Much easier than reaching up to the motor for those things.

If you really want to turn it on and off from the motor, I would avoid a vfd. In general, they don't like having loads applied or removed while they are running.

If the motor is not dual voltage and let's say straight 460v, then not happening with a vfd fed from 240vac. Hence, the reason to ask for more info.

Switching the motor pole configuration while running is the same as adding a disconnect between motor and vfd. Easily blown the vfd output circuit.

 

[mm08822]

Yes but I use low range on the motor to avoid running it at 15 hz since it's probably not inverter rated. If op has a factory motor, it's most likely not inverter rated either. I don't know for sure but I believe running at low speed also provides more torque, probably roughly double, than on high speed.

Unless the drive has a torque boost feature (and enabled), the torque will be reduced at lower Hz. This is one reason why belted mill spindle drives exist and mfr recommends its use for low speed tooling operations.

 

[whateg01]

Unless the drive has a torque boost feature (and enabled), the torque will be reduced at lower Hz. This is one reason why belted mill spindle drives exist and mfr recommends its use for low speed tooling operations.

That's part of why I switch to the low range on the motor. It keeps the frequency higher.

 

[mm08822]

That's part of why I switch to the low range on the motor. It keeps the frequency higher.

I hope not on the fly.....

 

[whateg01]

Speed selection via programmed input

I hope not on the fly.....

Did I not say, and did you not quote me saying vfd doesn't generally like having loads applied or removed while running?

 

[mm08822]

Did I not say, and did you not quote me saying vfd doesn't generally like having loads applied or removed while running?

Yes, but it does not mean you aren't doing it. Reconfiguring the pole configuration and disconnecting the motor are about the same impact of the vfd output hardware.

 

[Firebrick43]

Did I not say, and did you not quote me saying vfd doesn't generally like having loads applied or removed while running?

It will destroy the VFD's power transistors (IGBT) if disconnected under power

What mill do you have?

Hi and Lo range are typically a lever that physically engages a lower gear in the drivetrain, and rarely actually changes anything with the motor. Although in a bridgeport this reverses direction of the spindle by putting it in low gear.

There are ways to put switches on the hi/lo lever so the VFD will always run the spindle in the correct direction. We did this with all the bridgeports that we converted to VFD and removed the reeves drive.

 

[whateg01]

It will destroy the VFD's power transistors if disconnected under power

What mill do you have?

Newport. It's a series 1 clone.

Hi and Lo range are typically a lever that physically engages a lower gear in the drivetrain, and rarely actually changes anything with the motor. Although in a bridgeport this reverses direction of the spindle by putting it in low gear.

That's the back gear. I'm talking about a two speed motor.

There are ways to put switches on the hi/lo lever so the VFD will always run the spindle in the correct direction.

I have an on/off toggle that goes through a second switch that connects to either fwd or rev on the vfd. I just set it to reverse when it's in back gear.

 

[Firebrick43]

Newport. It's a series 1 clone.

That's the back gear. I'm talking about a two speed motor.

On Bridgeport's I haven't seen a two speed motor, which is why I am asking. Two speed motors are pretty rare. Of all the machine tools I have worked on over the years I have only seen it once or twice and it was an old lathes.

Is it a two winding motor, or does it cut out half the poles, or does it switch the windings from Star to Delta configuration?

 

[whateg01]

On Bridgeport's I haven't seen a two speed motor, which is why I am asking. Two speed motors are pretty rare. Of all the machine tools I have worked on over the years I have only seen it once or twice and it was an old lathes.

I've had a couple other people use it and both commented it was a close copy, but it's not a pancake motor. I've never used a real Bridgeport so I guess I just assumed that meant they all had a two speed motor. My bad.

Is it a two winding motor, or does it cut out half the poles, or does it switch the windings from Star to Delta configuration?

Based on what I remember when I looked at moving the control switches to a more convenient location, I don't remember. But since I have it in my head that it's producing more torque, I'm thinking it's not just cutting out poles.

 

[Firebrick43]

Based on what I remember when I looked at moving the control switches to a more convenient location, I don't remember. But since I have it in my head that it's producing more torque, I'm thinking it's not just cutting out poles.

It probably switching from star to delta then. I have personally never seen it on a spindle motor but it’s a popular way to start high inertia loads on industrial dust collectors, via contactors switched by timer.

 

[mm08822]

It probably switching from star to delta then. I have personally never seen it on a spindle motor but it’s a popular way to start high inertia loads on industrial dust collectors, via contactors switched by timer.

Agreed, it is star-to delta configuration transition. I was wrong in thinking switching number of pole pairs. Point is still valid, don't open the vfd output circuit while running.

I've seen motors rated at 2 different hp's between high speed and low speed.

 

[whateg01]

Explains why what I say about switching speeds at the motor is so confusing to everybody.

I have a motor, can't remember what it's called, maybe reluctance motor? On my old WT drill press. Starts out really show then after a certain rpm, switches to induction. Supposed to be for hard to start loads like high inertia.

 

[mm08822]

Wye-delta switching has frequently used timers to make the transition if no other means was provided. (These were not connected to vfds.)

2 speed motor np.....

 

[Firebrick43]

Agreed, it is star-to delta configuration transition. I was wrong in thinking switching number of pole pairs. Point is still valid, don't open the vfd output circuit while running.

I've seen motors rated at 2 different hp's between high speed and low speed.

There are some motors that do drop two poles to change speeds. They have a significant torque loss in doing so.

The old lathes I worked on that had two speed motors were two separate winding, one was 4 pole and the other 6 pole. The were monster in size however. The size of a 30-40 hp motor but only made 10hp

 

[theoldwizard1]

most VFDs have inputs that can be programmed to different Hz (speeds) for motor control.

this is a BIG bonus !

 

[American Locomotive]

Yes but I use low range on the motor to avoid running it at 15 hz since it's probably not inverter rated. If op has a factory motor, it's most likely not inverter rated either. I don't know for sure but I believe running at low speed also provides more torque, probably roughly double, than on high speed.

The motor's name plate will tell you. Generally most multi-speed motor's I've seen are constant torque, meaning you effectively lose power if run in the "low" speed.

 

[whateg01]

The motor's name plate will tell you. Generally most multi-speed motor's I've seen are constant torque, meaning you effectively lose power if run in the "low" speed.

The motor plate is gone. Op has removed the motor to use a single phase motor and had to dig this one out of storage. So all I have to go off of is what he told me about it which was 240v 3p. I'm not even sure about the HP, but I think 1.5 or 2. Does what I need it to do. Certainly possible I'm not getting more torque at low speed, so the only benefit I would be getting is not running the motor at super low frequency to get slow spindle speed.

 

[BillK]

First off, I'm not an electrical person at all,

Considering that I would suggest a Phase Converter instead of a VFD. That way you can just hook the mill up with no modifications. Just make sure to get one sized properly for your Mill.

 

[oldtractors]

the existing controls can be rewired to send signasls to the vfd, instead of the motor directly. Requires some work, but there are plenty of people that have done it (and made videos about it...).

Not a lot of work. Just a little bit of thinking and some small wire. I did it with mine. The VFD was about $100 on Amazon.

 

[dscheidt]

Not a lot of work. Just a little bit of thinking and some small wire. I did it with mine. The VFD was about $100 on Amazon.

I agree with you, that it is not a big project, but I have found that what I consider a trivial wiring project, many people think is a major undertaking. So I try not to attach a scope to suggestions, unless I know who it is, or they are going to hire someone.

 

[whateg01]

I agree with you, that it is not a big project, but I have found that what I consider a trivial wiring project, many people think is a major undertaking. So I try not to attach a scope to suggestions, unless I know who it is, or they are going to hire someone.

The biggest challenge I find is that either you buy a "good" vfd and get good documentation or you buy a $100 vfd from Amazon and might as well have no documentation. For basic use, there's not a lot that has to set, but acceleration and max/min freq are a couple things that do need to be set. Not sure if op can figure that stuff out or not. If the features that an inverter bring to the table are something op might benefit from, I think it's worth looking into. I have only moved the belt on my mill once in the years I've had it.

 

[micromind]

Explains why what I say about switching speeds at the motor is so confusing to everybody.

I have a motor, can't remember what it's called, maybe reluctance motor? On my old WT drill press. Starts out really show then after a certain rpm, switches to induction. Supposed to be for hard to start loads like high inertia.

Repuse - induction.

Very popular many years ago before AC capacitors were invented.

They had huge starting torque and low starting current.

 

[micromind]

If a VFD is installed and the original motor control contacts are used, the VFD inputs are very low current and the carbon build-up on the contacts might not work with low current.