Reducing motor speed ?

[m_c]

It is possible to run single phase motors slower using a suitable VFD, but there is a limit on just how slow you can run them.
Torque drops off much quicker, and the slower they go, the more noticeable the acceleration/deceleration is between poles. Single phase mostly rely on inertia to carry the rotor past the points where no current is flowing, and is why things like single phase bandsaws often leave a wavy cut pattern in bars, whereas the equivalent 3 phase machine while leave a consistent cut.

I would guess at the aimed 700RPM, which is below 50% of the rated 1450RPM (makes it a 4 pole motor), available torque will be less than 50%. An equivalent three phase motor would still produce near 100% of torque, but reduced power (induction motors produce fairly linear torque up to the rated speed, but power is the result of torque and speed, so power produce drops of fairly linearly from rated speed).

The VFD might try and compensate by powering the capacitor coil, but that will probably risk burning out the start coil. You can also risk burning out the main coil due to reduced cooling at lower speeds, but that takes a bit more effort or a grossly mis-configured VFD.

 

[W.olly]

The wiring diagram I posted says you can use it with or without a capacitor. I have a motor I will try it over the weekend and let you know.
If you want to borrow mine to see I will send it to you.

I am not to up on electrical stuff but i read it as it will work, but then folk say no so i cant argue the toss wit them. The next biggest problem i will have is how to wire and set it up to run the gear i have on that contraption i have made. .

If you can either find out if it will work or send it me that will be brilliant kida thanks.

 

[W.olly]

It is possible to run single phase motors slower using a suitable VFD, but there is a limit on just how slow you can run them.
Torque drops off much quicker, and the slower they go, the more noticeable the acceleration/deceleration is between poles. Single phase mostly rely on inertia to carry the rotor past the points where no current is flowing, and is why things like single phase bandsaws often leave a wavy cut pattern in bars, whereas the equivalent 3 phase machine while leave a consistent cut.

I would guess at the aimed 700RPM, which is below 50% of the rated 1450RPM (makes it a 4 pole motor), available torque will be less than 50%. An equivalent three phase motor would still produce near 100% of torque, but reduced power (induction motors produce fairly linear torque up to the rated speed, but power is the result of torque and speed, so power produce drops of fairly linearly from rated speed).

The VFD might try and compensate by powering the capacitor coil, but that will probably risk burning out the start coil. You can also risk burning out the main coil due to reduced cooling at lower speeds, but that takes a bit more effort or a grossly mis-configured VFD.

the motor here only runs for a less than a minute then stops to refill the holder with new tube to be ground/profiled. not continuos running but will be used for a couple of hours maybe profiling around 250 tubes at a time.
i mention that as you mention the motor heating up and damage etc.

 

[My Old Landy]

I am not to up on electrical stuff but i read it as it will work, but then folk say no so i cant argue the toss wit them. The next biggest problem i will have is how to wire and set it up to run the gear i have on that contraption i have made. .

If you can either find out if it will work or send it me that will be brilliant kida thanks.

I will run it up on the 1hp single phase motor I have then send it to you if it works. As for the controls, I can help you with the wiring no problem.

 

[My Old Landy]

the motor here only runs for a less than a minute then stops to refill the holder with new tube to be ground/profiled. not continuos running but will be used for a couple of hours maybe profiling around 250 tubes at a time.
i mention that as you mention the motor heating up and damage etc.

The temperature is something I can check with an infra-red thermometer

 

[W.olly]

I will run it up on the 1hp single phase motor I have then send it to you if it works. As for the controls, I can help you with the wiring no problem.

if you can ensure the AT2 works then its all i need to know kida so i can find one. before i get one an AT2 i just want to know it will do the job. dont want to spend out on one then it dont work.

 

[My Old Landy]

if you can ensure the AT2 works then its all i need to know kida so i can find one. before i get one an AT2 i just want to know it will do the job. dont want to spend out on one then it dont work.

Exactly, I bought this one just before I got sick. It has been sitting in its box waiting for me to revamp the mill with the 3ph I bought for it and use the 1ph in a similar thing to your contraption!

 

[W.olly]

Unless you want to sell your AT2 kida

 

[My Old Landy]

Unless you want to sell your AT2 kida

If it works for you then you can buy it. I will let you know then we can go to pm

 

[m_c]

the motor here only runs for a less than a minute then stops to refill the holder with new tube to be ground/profiled. not continuos running but will be used for a couple of hours maybe profiling around 250 tubes at a time.
i mention that as you mention the motor heating up and damage etc.

Continuous stopping/starting is worse for motor coils in terms of overheating them.

The temperature is something I can check with an infra-red thermometer

You can cook the coils long before the outside gets hot enough to show any issue.
Case temperature can lag behind in the internal temperature quite a bit. The coils can potentially be a smouldering lump of copper long before the case warms up.

 

[My Old Landy]

Continuous stopping/starting is worse for motor coils in terms of overheating them.

You can cook the coils long before the outside gets hot enough to show any issue.
Case temperature can lag behind in the internal temperature quite a bit. The coils can potentially be a smouldering lump of copper long before the case warms up.

It is a fair point, I have been designing motorised systems for many years. It will be an interesting experiment and will save @W.olly from burning out his motor

 

[W.olly]

So would a motor like this being a 6 pole and less reduction on speed as in % be better.

https://www.ebay.co.uk/itm/255534145588?var=555486245015

fitted with an AT4

 

[My Old Landy]

So would a motor like this being a 6 pole and less reduction on speed as in % be better.

https://www.ebay.co.uk/itm/255534145588?var=555486245015

fitted with an AT4

3ph will always be better for reducing the speed

 

[W.olly]

3ph will always be better for reducing the speed

So that 3ph will be smoother as its 6 pole. Can run from a single phase supply as its
Nominal Rated Input Voltage:
230V, 690V, 400 V

 

[W.olly]

and use

1 phase Variable Frequency Drive VFD Speed Controller for 3-phase 2.2kW AC Motor | eBay

Power Source Phase: Single-phase. Designed with large heat sink for better heat dissipation. Output Frequency: 400Hz. Filter: Built-in filter. CI External current signal input 4-20mA current signal input.

www.ebay.co.uk

 

[My Old Landy]

Yes, then wire in the controls via the analogue terminals, a bit of adjusting the settings and away you go

 

[Guineafowl]

Assuming that motor is centrifugal switch type, running it at less than about 75% of rated speed will mean the start circuit will be permanently engaged, and will quickly burn out.

I’ve not used an AT2 VFD setup, but I assume it involves bypassing this switch. Bear in mind that 1ph motors have quite limited starts per hour. For intermittent operation, it’d be best to leave it running.

Go for 3ph. It’s almost always better.

 

[W.olly]

Yes, then wire in the controls via the analogue terminals, a bit of adjusting the settings and away you go

well sod tis motor, not knowing how long it will last ill just get that 3ph then can run off 240v to make it easy aswell were it will be used. Just hope now i can find a 24mm spindle, always something when faffing about.

Thanks kida, ill be in touch on how to wire the CVFD now lol

 

[My Old Landy]

well sod tis motor, not knowing how long it will last ill just get that 3ph then can run off 240v to make it easy aswell were it will be used. Just hope now i can find a 24mm spindle, always something when faffing about.

Thanks kida, ill be in touch on how to wire the CVFD now lol

If you need a spindle adapter making let me know and I can turn one up for you. I'll do a schematic when comes time to wire it up. I have had a lot of help on this forum so it's time to pay it forward

 

[W.olly]

If you need a spindle adapter making let me know and I can turn one up for you. I'll do a schematic when comes time to wire it up. I have had a lot of help on this forum so it's time to pay it forward

I am just being lazy on the spindle as i can turn one up myself lol. well making life easier than it is haha. It amazing ow much you can use a lathe and mill when you have one. Makes me wonder what i did when i didnt have one.

And thanks for the offer kida,