Do I need a magnetic contactor with a VFD?

[Wedg1e]

VFDs I've worked with wouldn't sanction a contactor on the outlet side, but you CAN use contactors/big switches on the outlet to switch one VFD between two or more machines as long as the programmed parameters are OK for all of them.
As long as the contactors are only switched when the VFD is idle it's not a problem.
I use spare poles or accessory contacts of the contactors to interlock the start/stop for each machine so you can't start one accidentally from the other, for example.

 

[Wedg1e]

Might take you up on that - 3 phase motors are a bit of a black art to me!
Cheers

Generally easier to reverse a 3-phase than a 1-phase motor though.

 

[eLuSiVeMiTe]

VFDs I've worked with wouldn't sanction a contactor on the outlet side, but you CAN use contactors/big switches on the outlet to switch one VFD between two or more machines as long as the programmed parameters are OK for all of them.
As long as the contactors are only switched when the VFD is idle it's not a problem.
I use spare poles or accessory contacts of the contactors to interlock the start/stop for each machine so you can't start one accidentally from the other, for example.

This is the way il be going with the mill and two lathes. 3 identical motors and a magnetic control box to move to each machine.

 

[Wedg1e]

This is the way il be going with the mill and two lathes. 3 identical motors and a magnetic control box to move to each machine.

Yeah, I keep meaning to make a remote speed control for mine; the Perrin has 16 spindle speeds but you always seem to need one in between any two.
The Boxford VSL has speed control by expanding pulleys (think DAF Variomatic ) so doesn't technically need the VFD to alter... but as it can go down to 50rpm on the pulleys at 50Hz drive, there might be some need to go even slower

 

[eLuSiVeMiTe]

The Boxford VSL has speed control by expanding pulleys (think DAF Variomatic

Managed to get a similar setup on a raglan little John working again earlier this year. Simple but effective.
Not just speed control though. Ramp up and down. Breaking jog
Only ended up going that route as the sp motor I had was upsetting the neighbors.
Wish I'd done it sooner

Have 3p in the garage (no DB a throwback to electric heating) but not going to utilise it. 4 years and il be moving. Don't need to add 3p onto an already awkward requirement list

 

[skotl]

Ah poop. You'll never guess, but the lathe that I'm picking up on Sunday isn't three phase after all!

So the good news is that I don't need to learn how to speak 3phase-star-and-delta, and I don't need to buy a VFD, and I don't need to build an electrical enclosure.... yay...

I was quite looking forward to that, to be honest Oh well - just need to hope that the motor on the lathe or mill burns out then I will be "forced" to buy a 3-phase replacement.

Many thanks to all for responding and for helping me up my meagre knowledge of triple-phasing. Special shout out to @rikrobson for his kind offers of assistance - would still be good to pop in one time

 

[eLuSiVeMiTe]

Ah poop. You'll never guess, but the lathe that I'm picking up on Sunday isn't three phase after all!

So the good news is that I don't need to learn how to speak 3phase-star-and-delta, and I don't need to buy a VFD, and I don't need to build an electrical enclosure.... yay...

I was quite looking forward to that, to be honest Oh well - just need to hope that the motor on the lathe or mill burns out then I will be "forced" to buy a 3-phase replacement.

Many thanks to all for responding and for helping me up my meagre knowledge of triple-phasing. Special shout out to @rikrobson for his kind offers of assistance - would still be good to pop in one time

Doesn't mean you can't replace the sp with a 3p and vfd.
I did.
No regrets

 

[Hopefuldave]

Doesn't mean you can't replace the sp with a 3p and vfd.
I did.
No regrets

Did you find, apart from the expected VFD benefits (variable speeds, dynamic braking, reversing etc.) you also get better surface finish due to the more-constant torque from the 3-phase motor? I've seen that on a few lathes I've converted.

Dave H. (the other one)

 

[eLuSiVeMiTe]

Did you find, apart from the expected VFD benefits (variable speeds, dynamic braking, reversing etc.) you also get better surface finish due to the more-constant torque from the 3-phase motor? I've seen that on a few lathes I've converted.

Dave H. (the other one)

Indeed. Not fair to the so though. Damaged shaft was causing an evil knock.

 

[Seadog]

So the good news is that I don't need to learn how to speak 3phase-star-and-delta, and I don't need to buy a VFD

Believe me, you do.

 

[skotl]

Believe me, you do.

I knows it Just don't need to do it in the next two weeks!

 

[Wedg1e]

Did you find... you also get better surface finish due to the more-constant torque from the 3-phase motor? I've seen that on a few lathes I've converted.

Dave H. (the other one)

I had a Colchester Student MK2 that came with a SP motor already fitted, the original 3P was included. The surface finish with the SP was shocking, a sort of helical patterning, even on very light cuts. Having checked everything I could think of I swapped the 3P motor back in and the problem disappeared.

 

[Seadog]

The surface finish with the SP was shocking, a sort of helical patterning, even on very light cuts. Having checked everything I could think of I swapped the 3P motor back in and the problem disappeared.

There are lots of vibrational harmonics generated with a single phase motor.

 

[eLuSiVeMiTe]

There are lots of vibrational harmonics generated with a single phase motor.

Mine sounded like a breaker. Slight damage to the shaft caused a knock every rotation.

Now repaired ready to do duty on the Whitehead. Well. Once I've out it back together. Only been 6 months

 

[rikrobson]

Ah poop. You'll never guess, but the lathe that I'm picking up on Sunday isn't three phase after all!

So the good news is that I don't need to learn how to speak 3phase-star-and-delta, and I don't need to buy a VFD, and I don't need to build an electrical enclosure.... yay...

I was quite looking forward to that, to be honest Oh well - just need to hope that the motor on the lathe or mill burns out then I will be "forced" to buy a 3-phase replacement.

Many thanks to all for responding and for helping me up my meagre knowledge of triple-phasing. Special shout out to @rikrobson for his kind offers of assistance - would still be good to pop in one time

You're more than welcome any time. 3ph really isn't that scary and its also not that expensive considering the benefits.

What size motor has that Colchester got? It looked a bit of a beast when I saw it in the flesh.

 

[skotl]

You're more than welcome any time. 3ph really isn't that scary and its also not that expensive considering the benefits.

What size motor has that Colchester got? It looked a bit of a beast when I saw it in the flesh.

Yeah - it is quite a beast. There's a lot of serious looking electrical hardware on it, so I can completely understand why @Rannsachair thought it was 3 phase - so did I right until I took the wall plate off

 

[rikrobson]

its possible it could have been, the air compressor was meant to be 3 phase. it was onlt a small garage on a housing estate, so unless he had phase converter its unlikey.
The drill press was single phase.
you'll be looking for a 3ph motor and VFD for it soon

 

[skotl]

its possible it could have been, the air compressor was meant to be 3 phase. it was onlt a small garage on a housing estate, so unless he had phase converter its unlikey.
The drill press was single phase.
you'll be looking for a 3ph motor and VFD for it soon

The compressor (which is GIGANTIC!) is definitely 3 phase