Can I run a Harrison 3 phase milling machine off a VFD?

[angusb]

Hi, I have a Harrison milling machine which is 3 phase. Can I run it off a VFD if I don't use the VFD to vary the motor speed? The milling machine has a 3 phase motor which drives the spindle and another which drives the power feed for the table and a third for the suds pump. I'd just like to use a VFD to provide a 3 phase supply at a constant frequency so all 3 motors will run as if they were on a normal 3 phase supply.

I was thinking of using this VFD: https://inverterdrive.com/group/AC-Inverter-Drives-230V/WEG-CFW500B10P0S2DB20C2y2H00/

I found a couple of threads on here where people seem to be doing this but it wasn't clear to me if they were varying the frequency the VFD output so they could vary the motor speeds.

Cheers,

Angus

 

[zzr1200]

Can you take a photo of the data plate on the motor, plus a photo of the connections in the motor terminal box, Harrisons data plate.

Then upload them here.

 

[Guineafowl]

It would normally be one VFD per motor. You might get away with piggy-backing the suds pump onto the main motor, as it’s so low-powered.

 

[RobCox]

I use 2 VFDs to run the motors on my mill. One VFD drives either the horizontal spindle motor or the vertical spindle motor (switched at the VFD output, but never when the motor is running), the other drives the feed motor. The feed motor gets turned on and off while the spindle motor is running, which may upset a VFD if only one is used. The coolant pump just needs a Steinmetz capacitor, much cheaper!

What you're trying to do can be done but the "VFD" is a much uprated beast capable of dealing with switched loads and will almost certainly cost more than 2 VFDs. The WEG ones BTW are very good, all of my machines use them.

 

[Mark Davison]

I had to dig out the star point on my Harrison vertical Mill. The original 2hp Alpac motor wasn't dual voltage. I ditched the original 3 phase AC table travel motor and swapped to a stepper as part of a CNC conversion.

 

[m_c]

What you want to do should be doable.
The main motor load should provide a relatively stable load with the other two fractional motors switching in/out not causing any issues.

However, you'll likely need to use a 'boost' VFD that outputs full 380/415V 3 phase, as the suds and table feed motors aren't dual voltage motors.
You could run them at lower 240V 3 phase, but you won't get full power out of them, and run the risk of overheating them.

 

[Wedg1e]

It would normally be one VFD per motor. You might get away with piggy-backing the suds pump onto the main motor, as it’s so low-powered.

That works until you drop the spindle speed using the VFD, when the suds pump stops generating enough lift.
My Boxford does that, at any rate...

 

[RichardM]

Use a capacitor on the suds pump to allow it to run off single phase.

Thread 'Run a 3 phase lathe coolant pump on single phase.'

May 18, 2017

Here's a trick I learned from John Stevenson a while ago. 3 phase coolant pumps are quite happy to run on single phase using the same principle as rotary converters. All you have to do is wire a small capacitor like the ones you find in the old strip lights to the third phase and it'll work just fine. To demonstrate, I quickly lashed-up a small pump I have here with a 10uF 250v capacitor. My pump here is dual-voltage but I am pretty sure it would work just as well if it were 415v only. They don't use a lot of power and there's no starting load.



Anyway, here's the vid of it...

• Pete.
• Replies: 52
• forum: Machining Techniques and Materials

• 

 

[minimutly]

What you want to do should be doable.
The main motor load should provide a relatively stable load with the other two fractional motors switching in/out not causing any issues.

However, you'll likely need to use a 'boost' VFD that outputs full 380/415V 3 phase, as the suds and table feed motors aren't dual voltage motors.
You could run them at lower 240V 3 phase, but you won't get full power out of them, and run the risk of overheating them.

They will run fine at lower voltage and slightly lower speed and power, the table feed is just fast traverse so not continuos ? A restrictor on the suds pump output will reduce its load, but I would echo @Pete. And @RobCox comments on running suds pump with a capacitor. If you are doing production work then ignore this advice, if it's for hobby just go a little slower.
My horizontal an my vertical mills run this way. No problems at all, and you can actually hear if the motor is being overloaded, the rpm changes, so you'd have to be a gorilla to damage it.

 

[minimutly]

Use a capacitor on the suds pump to allow it to run off single phase.

Thread 'Run a 3 phase lathe coolant pump on single phase.'

May 18, 2017

Here's a trick I learned from John Stevenson a while ago. 3 phase coolant pumps are quite happy to run on single phase using the same principle as rotary converters. All you have to do is wire a small capacitor like the ones you find in the old strip lights to the third phase and it'll work just fine. To demonstrate, I quickly lashed-up a small pump I have here with a 10uF 250v capacitor. My pump here is dual-voltage but I am pretty sure it would work just as well if it were 415v only. They don't use a lot of power and there's no starting load.



Anyway, here's the vid of it...

• Pete.
• Replies: 52
• forum: Machining Techniques and Materials

• 

Stick an earth on that @Pete.

 

[Guineafowl]

That works until you drop the spindle speed using the VFD, when the suds pump stops generating enough lift.
My Boxford does that, at any rate...

He’s planning to stick to 50Hz. That said, I wouldn’t be without pot speed control on my machines…

 

[angusb]

Can you take a photo of the data plate on the motor, plus a photo of the connections in the motor terminal box, Harrisons data plate.

Then upload them here.

Apologies for the cr4p photo of the motor plate but it's really hard to get to. I will take a picture of the plate off the table motor but can't do it at the moment, it is hard to see but I think it has been painted over and needs cleaning up.

 

[angusb]

Thank you all for your replies. I think I need to go and do some more reading but from what I understand at the moment it sounds like it will be best to use 2 VFDs, one for the spindle motor, one for the table motor, and a Steinmetz capacitor for the suds pump as this is just for hobby stuff.

 

[m_c]

They will run fine at lower voltage and slightly lower speed and power, the table feed is just fast traverse so not continuos ? A restrictor on the suds pump output will reduce its load, but I would echo @Pete. And @RobCox comments on running suds pump with a capacitor. If you are doing production work then ignore this advice, if it's for hobby just go a little slower.
My horizontal an my vertical mills run this way. No problems at all, and you can actually hear if the motor is being overloaded, the rpm changes, so you'd have to be a gorilla to damage it.

Table feed motor can be run for quite extended periods if you're doing long passes.
It would probably be fine, as I suspect it's not likely to be loaded that much, but I'm not wanting the blame if the lower voltage saturates and cooks the windings!

Plus, restricting the pump output will increase it's load...

 

[daleyd]

One thing to be aware of is if there are any contactors or control gear then these won’t work off a vfd supply.

Typically if you want to use a vfd then whatever control gear is currently fitted will need to be removed, it’s generally a complete rewire job - not a bad thing given the age of the machine and not particularly difficult but just some rung to be aware of.

 

[angusb]

He’s planning to stick to 50Hz. That said, I wouldn’t be without pot speed control on my machines…

Yes I was planning to change spindle speed using the levers on the machine to control the belts and pulleys.

 

[zzr1200]

View attachment 512424View attachment 512425View attachment 512426
Apologies for the cr4p photo of the motor plate but it's really hard to get to. I will take a picture of the plate off the table motor but can't do it at the moment, it is hard to see but I think it has been painted over and needs cleaning up.

Harrison data plate states the following
1.5Kw = 2HP motor at 2800 rpm, so it's 2 brush centre tapped 3ph motor to use a cheap vfd you would need to dig out the centre tap connection and split them into a 220 x 3 motor as opposed to a 415 volt motor as it is currently.
and
0.9Kw = 1HP motor is probably more awkward due to it's size so really needs a 415 volt supply.

There are other possible solutions, one is a phase convert either static or rotary but these are fairly expensive but do the job you would really need a rotary oe being as you have 3 motors to run (mill/table/coolant).

You can get 415 volt vfd's (as apposed to the cheap 220 x 3 versions) but these are really expensive

 

[RobCox]

My Elliott Omnimill has 415V motors. I run them off a 220V VFD. The only problem I've had is with the vertical spindle at high speed... when I switched it off the mass of the spindle would backdrive the motor, overvolting the VFD and causing it to shut down, so the spindle would freewheel. The cure was a 2.2kW VFD (Weg), which had the connections for a braking resistor. Problem solved.
I think the vert motor is 750W and the horiz 1.5kW.

 

[Mark Davison]

I'm curious. Is this a horizontal mill? My Harrison vertical mill had a 6 pole ~1000rpm motor. Getting the motor in and out was a pain. Finding the star point was relatively easy.

 

[waddycall]

My Startrite mercury drill and 8 inch wolf grinder are both three phase but run off single phase with a pair of capacitors. Had to dig the star point out on the grinder. Both been like that for over ten years without issue. Only evening and weekend use though.