Need a three Phase Motor

This topic has 19 replies, 8 voices, and was last updated 23 July 2014 at 21:02 by Muzzer.

Viewing 20 posts - 1 through 20 (of 20 total)

Author

Posts
21 July 2014 at 22:13 #23422
Oompa Lumpa
Participant
@oompalumpa34302
Advert

21 July 2014 at 22:13 #158438
Oompa Lumpa
Participant
@oompalumpa34302
I am going to do Neils conversion of my small Chester lathe to 3Phase with VFD.

In order to accomplish this I need a motor and despite looking I can't find what I want. I need a 1HP 3 Phase 1800rpm 240volt compact frame motor. Do we know of a reputable supplier of such a thing?

graham.
21 July 2014 at 22:34 #158448
Mike Poole
Participant
@mikepoole82104
Most motors in the UK are specified for 50Hz , so a 4 pole machine will have a theoretical speed of 1500rpm, the plate will have a value like 1430rpm. The frame size will fix the shaft size, height from base and mounting dimensions. If your current motor is a standard size it should be possible to match a 3 phase one.

Mike
21 July 2014 at 22:41 #158450
Oompa Lumpa
Participant
@oompalumpa34302
Just to refresh everyone's memory, I will be mounting the motor like this:

Fourth post down.

1430 rpm will work just fine.

I am not trying to match the motor as you can see Michael. I am re-engineering the lathe.

graham.

Edited By Oompa Lumpa on 21/07/2014 22:42:23

Edited By Oompa Lumpa on 21/07/2014 22:44:18
21 July 2014 at 22:48 #158452
blowlamp
Participant
@blowlamp
Have you seen these?

Martin.

Edited By blowlamp on 21/07/2014 22:50:03
22 July 2014 at 11:04 #158477
Neil Wyatt
Moderator
@neilwyatt
Hi Graham,

The TEC motor I used is rated 50/60 Hz so I set the base frequency at 60Hz instead of 50Hz to get constant torque up to 1640-rpm.

That also ups the power rating to 0.44kW instead of 0.37kW.

You could use a similar 'trick' to allow you to use the 'next size down'. The penalty is the lubrication life drops from 40,000 hours to 32,000 hours, so if you use the lathe eight hours a day the motor might only last ten years before it needs new bearings…

Neil
22 July 2014 at 11:12 #158478
Oompa Lumpa
Participant
@oompalumpa34302
Oh, I don't know whether that will work Neil, I need it to work 10years 4months………….

I have found a company: motors direct, pretty self explanatory, so I will give them a bell this afternoon. I really would like one horse in a 71 frame. Usually they are 80 size from my research.

Martin, I have seen the Seig motors and now they are sorted out the brushless DC motors are getting good reviews. But that is not what I want at all.

graham.
22 July 2014 at 12:15 #158487
blowlamp
Participant
@blowlamp
Posted by Oompa Lumpa on 22/07/2014 11:12:16:

Oh, I don't know whether that will work Neil, I need it to work 10years 4months………….

I have found a company: motors direct, pretty self explanatory, so I will give them a bell this afternoon. I really would like one horse in a 71 frame. Usually they are 80 size from my research.

Martin, I have seen the Seig motors and now they are sorted out the brushless DC motors are getting good reviews. But that is not what I want at all.

graham.

I don't understand what you're looking for, Graham.

The motor & controller that I linked to is 1000W or 1.3hp, has a variable speed range of 100-3500rpm and has motor dimensions of 92x92x146mm. I can't see where you'd get a more compact system.

Is this to convert a mini-lathe?

Martin.
22 July 2014 at 14:30 #158501
Oompa Lumpa
Participant
@oompalumpa34302
Martin, at the risk of labouring on I need exactly as the title: 1HP 3 Phase 1800rpm(or thereabouts) 240volt compact frame motor

Now I do appreciate you pointing me in the direction of the Seig conversion but I am not looking for one – All I need is a three phase motor.

I have Inverters, a Mig welder and plenty of material. I am going to do a three phase conversion exactly the same as the one Neil did and for the avoidance of doubt it is going to look like this:

Since everyone is trying to advise me in all directions except the one I am going I will give you my reasons.

If I ever sell the lathe (not really likely but you never know) all I have to do is take the motor and frame off the back, swap the pulley back and then all you need do is plug it in and you have a working lathe as it was originally.

If I buy a bigger lathe (looking likely) all I need do is take the motor off, swap the pulley back and then you have a fully functioning variable speed lathe AND a 1HP motor with VFD to go straight on the new lathe.

IF I sell the Chester I can imagine the conversation. "Yes, I took a perfectly functioning lathe, took the motor and controller off – it's over there in the corner – and replaced it one supplied by Seig for their lathe cutting everything up in the process and drilling a load of holes everywhere. No I don't know why either."

So you see, it's not complicated, all I want is a compact frame 1HP motor – and I am happy to say that Drives-Direct have them on the shelf, they are a stock item. The difference is about 25mm or an inch in old money on the diameter. More importantly they are a constant run motor which the DC motor is not.

Oh, and they are £79

graham.

Edited By Oompa Lumpa on 22/07/2014 14:31:27
22 July 2014 at 17:42 #158511
blowlamp
Participant
@blowlamp
Sorry to have got your goat, Graham.

Good luck with your conversion.

To anyone else that may be interested, I did a similar conversion to my mini-lathe about a year ago.
I bought a 550W brushless D/C motor and combined driver (from a well known auction site), intended for use with industrial sewing machines. To keep things as simple as possible, I used the pulleys and drive belt, sold as spares for the Super C3, from Arceurotrade.

Performance is now very similar to a Super C3 lathe, with the same superb low speed torque.

There are some pictures in my album.

Martin.
22 July 2014 at 20:32 #158528
Oompa Lumpa
Participant
@oompalumpa34302
Martin, you didn't "get my goat" but I did make it quite clear in the first sentence of my first post what I intended to do.

Although I think it is great that we have such a diversity of knowledge and experience I just struggled a little. I had asked for recommendations for a supplier of a three phase motor that people may have had experience of and we seemed to go everywhere but. Made interesting reading though for those that were unaware of the Brushless DC motor options out there. Since the driver boards have been sorted out they really are a terrific option. Just not sure how that would work out if connected to the 3 phase Inverter

graham.
22 July 2014 at 21:31 #158531
Martin W
Participant
@martinw
Graham

It would work like magic, a loud bang, a puff of smoke, all the lights go out and its all over except for the shouting .

Cheers

Martin
22 July 2014 at 21:56 #158533
Oompa Lumpa
Participant
@oompalumpa34302
Posted by Martin W on 22/07/2014 21:31:14:

Graham

It would work like magic, a loud bang, a puff of smoke, all the lights go out and its all over except for the shouting .

Cheers

Martin

LMAO!

graham.
23 July 2014 at 00:19 #158539
blowlamp
Participant
@blowlamp
The Sieg system is 3 phase.

Martin.
23 July 2014 at 08:47 #158544
Michael Gilligan
Participant
@michaelgilligan61133
Posted by blowlamp on 23/07/2014 00:19:14:

The Sieg system is 3 phase.

Martin.

.

Martin,

Technically correct … but I think you needed [for the sake of safety] to highlight a few more points
- The system is 3 phase
- The motor is Y connected [i.e. Star]
- The motor has Hall effect sensor
These features combine to suggest that the motor is actually "Brushless DC" and, if so, it would be totally unsuitable for connection to the "common or workshop" Inverter … The drive circuitry in Seig's system would be a dedicated unit, similar in concept to the ESC used for the R/C models.

MichaelG.

.

Edit: There is a useful introduction to BLDC in the first post on this page.

Edited By Michael Gilligan on 23/07/2014 08:56:13
23 July 2014 at 09:18 #158548
blowlamp
Participant
@blowlamp
Posted by Michael Gilligan on 23/07/2014 08:47:25:

Posted by blowlamp on 23/07/2014 00:19:14:

The Sieg system is 3 phase.

Martin.

.

Martin,

Technically correct … but I think you needed [for the sake of safety] to highlight a few more points
- The system is 3 phase
- The motor is Y connected [i.e. Star]
- The motor has Hall effect sensor
These features combine to suggest that the motor is actually "Brushless DC" and, if so, it would be totally unsuitable for connection to the "common or workshop" Inverter … The drive circuitry in Seig's system would be a dedicated unit, similar in concept to the ESC used for the R/C models.

MichaelG.
Hi Michael.

Yup, it already says that in the information in the picture, and that's why I wrote "The Sieg system is 3 phase.", as that is what I wanted to highlight.

Interested parties should indeed make further enquiries, before entering territories they are not familiar with.

Martin.
23 July 2014 at 09:45 #158551
John Stevenson 1
Participant
@johnstevenson1
They will NOT run on an invertor – Don't ask.
23 July 2014 at 10:02 #158555
Neil Wyatt
Moderator
@neilwyatt
BLDC motors have magnets in their cores.

AC motors use induction in a 'squirrel cage' armature.

Clearly with fixed polarity magnets, the BLDC motor will only run on DC…

Neil
23 July 2014 at 11:19 #158558
blowlamp
Participant
@blowlamp
One system uses a 3 phase A/C inverter and the other system uses a 3 phase D/C inverter.

Martin.
23 July 2014 at 21:02 #158589
Muzzer
Participant
@muzzer
The terminology is a bit confusing but:
- BLDC (brushless DC) drives and AC inverters all operate from a DC source internally and generate an AC voltage as seen by the (3-phase) motor. Inverters that operate from an AC source (mains) actually convert the AC to DC first.
- Most AC motors are induction (asynchronous) machines. The torque generated is proportional to the slip frequency ie the difference between the unloaded speed and the loaded speed. The more you load them, the slower they turn until they reach breakover torque. The nameplate tells you what the speed would be at rated torque.
- The unloaded speed for 50Hz machines would usually be 1500 or 3000 rpm depending on how many pole pairs it has. For 60Hz machines that would be 1800 or 3600rpm.
- BLDC aka AC brushless are synchronous machines and need to be driven by a drive waveform that is synchronised to the position of the rotor. You can drive some of them open loop but generally you need a position sensor to do it. The simplest position sensor is a Hall effect device or devices that responds to the passing magnetic rotor.
- AC synchronous machines are pretty much similar to BLDC but are generally driven by a sinusoidal current (BLDC require a "6-step" trapezoidal waveform). They give a more constant torque output than BLDC but unless you are doing something clever with the position signal, you also need a higher resolution absolute position sensor like a resolver or encoder.
- There are inverters that can drive synchronous machines as well as asynchronous but I doubt any of us would have the need for one.
- Most inverters drive the motors with a PWM (high frequency on-off voltage with variable duty cycle) voltage but the current is smoothed by the inductance of the motor. It's the current that ultimately generates torque, so the PWM shape of the drive voltage has little effect on the performance, even though it results in a higher voltage stress on the insulation and can induce some nasty currents in bearings etc.
- If you spin up a synchronous machine (careful!) and look at the back EMF with a scope, you will see that some are designed for a sinusoidal drive voltage and some for a trapezoidal voltage. So as well as needing a position sensor, you need to provide the correct waveform shape.
- Proper DC motors are a different beast.
Hope that helps.

Murray
Author

Posts