Switch gear for 2 speed motor

[EmgeeParticipant @emgee]

Tom

You are almost right, but not a 2 way but a 2 position switch providing High or Low speed configuration of the windings. The levers will normally provide Stop/Start also Fwd and Rev direction of spindle depending if the lever is lifted up to start or pushed down.

Emgee

[Brian MorehenParticipant @brianmorehen85290]

Tom

This souds likeca bit of a puzle , You do not want to reverse your motor only change speeds from low speed to high speed , I think we may need 2 contactors one for high speed and one for low speed a 2 position switch can operate one or the other contactor I feel we need more info to get this right

My Lathe has a single phase motor wthe a lever attached that when moved changes rotation .

I feel more details of your motor are required.

Brian

[EmgeeParticipant @emgee]

Posted by Brian Morehen on 24/08/2020 17:58:13:

Tom

This souds likeca bit of a puzle , You do not want to reverse your motor only change speeds from low speed to high speed , I think we may need 2 contactors one for high speed and one for low speed a 2 position switch can operate one or the other contactor I feel we need more info to get this right

My Lathe has a single phase motor wthe a lever attached that when moved changes rotation .

I feel more details of your motor are required.

Brian

Brian, follow the links I posted early on in the discussion, you will be able to see the schematic in the Manual, it shows what is needed.

Emgee

[Tom Walker 1Participant @tomwalker1]

Emgee, for some reason I cant open the files on the Colchester website. I will keep trying, meanwhile here is a photo of the connections on the 2 speed motor I picked up at the week-end.

Thank you for looking.

[Anonymous]

This link may clarify the connections needed:

**LINK**

Note that the switches control contactors, they do not switch the phases directly.

Andrew

[Tom Walker 1Participant @tomwalker1]

Thank you Andrew.

Emgee, I have cracked it, and found the files at the Colchester website. I presume that the wiring diagram in the lathe manual is the one you were referring to.

[Tom Walker 1Participant @tomwalker1]

Posted by Emgee on 23/08/2020 22:04:31:

Tom

You are almost right, but not a 2 way but a 2 position switch providing High or Low speed configuration of the windings. The levers will normally provide Stop/Start also Fwd and Rev direction of spindle depending if the lever is lifted up to start or pushed down.

Emgee

Emgee, my lathe has a start lever which does as you say, up to start one DOR, and down to start the other DOR

[Tom Walker 1Participant @tomwalker1]

So looking at the wiring diagrams I need the 2 speed switch and another motor overload for the second speed, wired between the 2 speed switch and the motor.

Luckily it seems the reverse switch can be left as is, but even with the wiring diagram in front of me, because I am "wiring diagram illiterate", I dont see how the reverse switch and the 2 speed switch manage to to everything.

I just need part numbers/makes for the two components.

[Brian MorehenParticipant @brianmorehen85290]

Tom

Unless my mind is playing tricks due to my age . A three phase motor that requires a a star delta starter is not a two speed motor as such . I have had 2 speed motors rewound that have been controlled by a timer with a low speed that stops and then switches to high speed , A star delta motor uses star to start and you then switch to run most of these type motors where 25 HP and above what are the details on the motor plate.

Regards Brian

[EmgeeParticipant @emgee]

Tom

My Bantam is wired to run 3 phase 2 speed motor with fwd and rev and on/off switching from the apron lever, the speed change is done by a 2 position switch mounted integral with the starter.
It is all original switchgear but only uses 1 overload which is sized to suit the max flc stated on the motor plate.

The 2 position switch when High speed is selected links out A3-B3-C3, power is fed in on motor A2, B2, C2.

When Low speed is selected the switch removes the links between A3, B3,C3, these are the motor terminals where the power is fed to for low speed operation.

The motor you have does appear to be a Bantam motor, the rating plate information , terminal box and winding ID's is exactly as my motor.

The very clear DD3 drawing that Andrew linked to show the connection method but with the addition of a shorting out contactor in place of the switch on mine, and a 2nd contactor and overload for the Reverse function, you don't need that if the apron lever is operating the contactor and providing the phases changeover.

Does your lathe have a starter fitted below the chip tray ?

Emgee

[Tom Walker 1Participant @tomwalker1]

Emgee

no, it only has an emergency stop button and the suds pump switch box" on/off" on the front.

Interestingly, because you asked, I checked all the switches. There is a main on/off box on the back, and the stop button on the front. The stop button doesnt work, neither do the safety switch on the gear cover, nor the switch on the foot brake!

The lever on the apron starts and controls DOR with the drop rod that goes thru the chips tray to a switch which is tucked away behind the emergency stop box, on the other side of the panel. So you can see it easily from the back of the lathe, as you would expect.

[Tom Walker 1Participant @tomwalker1]

WRONG! The box on the back is the transformer for the light, not an isolator.

I took the front off the emergency stop and cant see anything obviously disconnected. It is also the overload by the look of it.

[EmgeeParticipant @emgee]

Tom

Sounds like a starter to me with the stop button on the front face, if you saw an overload did you also see the contactor, original were Crabtree BD15 units, picture would help identify the item.

What does DOR represent please ?

Emgee

[Tom Walker 1Participant @tomwalker1]

Emgee, first of all, thank you very much for hanging on in there with me.

I thought a starter would have a green "go" button, because on the farm that is what they are like.

You are saying that what I thought was just an emergency stop may also be a starter in conjunction with the switch on the apron handle.

Please assume that I have a low level of understanding then halve it.

I struggle to "read" the wiring schematic, because you need a level of knowledge to know what symbol means what.

However, I will get there in the end because the forum is a great help. I must admit I was put on the back foot by the fact that none of the off switches seem to work.

I will identify the parts of the switch as you request. I meant direction of rotation by DOR. I think I may have made that up

[EmgeeParticipant @emgee]

Tom

Iv'e looked through all your posts about the lathe, please inform me if the lathe has a motor fitted that is running and can be started to run by pushing the saddle lever down and if the lever is pulled up it runs in the opposite direction.

I believe this is the case as you say the apron lever controls DOR, that being so you most likely have a starter and overload fitted and just need as a minimum a 4 pole NO 16A rated contacts 3 position rotary switch in an enclosure with minimum IP44 protection. With the motor at rest the switch will provide High/OFF/Low and switch the starter control circuit.
You will need to check any overload fitted will adjust to the maximum FLC on the motor plate.

Emgee

[Tom Walker 1Participant @tomwalker1]

Emgee,

my lathe is up and running well on the single speed 3 phase motor.

Yes the lever on the apron starts and stops the motor, and switches the direction of rotation.

I will take a photo of the emergency stop button on the front, with its cover off.

I think it may well be an overload, as there is an adjustable thumb wheel.

Please bear with.

[SillyOldDufferModerator @sillyoldduffer]

Is it time to review the requirement?

Tom asked:

'I have a Colchester Bantam, with a single speed motor. I am looking for a 2 speed motor for it, and want to be prepared, so need to find out about how to install the switching.'

and John Haine (motor guru) quickly suggested: 'Why not just fit an inverter and have done with it?' Good question!

Some awkward technical problems to be solved fitting a two-speed motor to a lathe:

1. Two speed motors need native 3-phase – fortunately Tom has this already.
2. The control circuitry needed by two speed motors is unusually complicated and in this case there is no diagram to work from (yet). It may be necessary to design a control circuit, a task beyond the skills of many competent electricians.
3. There are two different types of 2-speed 3-phase motor and we don't know for sure what Tom has. (Though Alan Johnson said 'From your motor nameplate photograph, you have a two pole / four pole three phase motor'   I see the motor plate mentions 3350, 2800, 1740 and 1450 rpm. Important to identify the motor type, Dahlander or what, and the rpm needed from the motor, which depends on the lathe's belts / gearing. Will also be necessary to identify the windings, not always obvious on second-hand motors.
4. Once the circuit is established, the contactors, wiring, and switches have to be bought and fitted. Won't be cheap.

Tom said: 'The main reason for not going down the VFD route was that I want a higher chuck speed than the inverter delivers.' As VFDs can spin motors faster than their plate speed, Tom may be applying the wrong solution. Possibly Tom doesn't want a two speed motor, he wants a lathe capable of a certain rpm.

Digging round the web, Tom is the only example I found of anyone replacing a motor/VFD with a two speed motor. I did find examples of people going the other way, ie permanently wiring two speed motors in the fast position and speed controlling with a VFD.

As two-speed motors make life difficult, I'd want to be sure there was a really good reason for fitting one. Gut feel on this, I'd simplify the requirement, probably doing the job with a single speed motor and VFD. Cheaper and easier than a two-speed motor, plus the VFD provides fine speed control.

Always a good idea in engineering to nail the requirement if you can rather than jumping straight to a technical solution. Usually worth checking the options, including 'Do Nothing'!

Dave

 

 

 

Edited By SillyOldDuffer on 28/08/2020 10:09:06

[EmgeeParticipant @emgee]

Morning SOD

Tom has this morning confirmed his lathe is running with fwd and rev working off the apron switch with a 3 phase motor fitted.
To me this means he already has the starter and overload fitted and working so just as a minimum needs a switch to give the pole change for high speed running.
A few days ago Andrew provided a link to excellent schematics which suit the motor being used, 2 speed 3 phase, Tom also has copy of the original circuit as fitted by Colchester and has an electrician to do the work for him, I considered the purpose of Tom's post was to ascertain what was needed to get his lathe running a 2 speed motor on 3 phase supply.
We are now waiting for a picture and details of the starter to see if it is original equipment and suitable o/l for the 2 speed motor.
With a 2 speed motor fitted there is a good range of speeds from 32 to 1600 rpm and full torque will be available throughout the range, admittedly there is no fine tuning available.

Emgee

[Tom Walker 1Participant @tomwalker1]

Well Im not sure, Dave, that I always do things for strictly logical, sensible reasons (though I am also a hypocrite because I berate the girls in my family for their non-logical thinking sometimes!). So it can be problematical when one approaches the patient and helpful forum members with a problem, and then go off on a route which most think is possibly the wrong one. It smacks of thick-headedness.

All that said, I now have in my possession, a 2 speed motor, so am committed, if only to the tune of 80 quid.

Emgee is kindly staying with the folly, and here are the photos of the box which may contain starter and overload.

You said BD15, so we have a match. Give or take a D.

 

Edited By Tom Walker 1 on 28/08/2020 12:12:18

Edited By Tom Walker 1 on 28/08/2020 12:17:03

[Tom Walker 1Participant @tomwalker1]

This is the switch which is operated by the lever on the apron

[Anonymous]

Posted by Emgee on 28/08/2020 10:32:56:

…..full torque will be available throughout the range…..

Surely that should be full power not torque.

Although I've got a varispeed head on the Bridgeport I've never missed infinitely variable speed on my other machine tools. As long as one is in the right ball park it's fine. The exact speed isn't critical. What's the betting someone will pop up and mention chatter?

Andrew

[EmgeeParticipant @emgee]

That's good Tom, you only have to buy a switch, best get in touch with your electrician and arrange for him to have a look and order up some materials to do the job for you.
Print copies of the electrical schematics from the manual and the drawing at Andrews link so your man has ll the info needed.
The max setting on the o/load looks to be slightly below full load current but I suggest you turn it to max of the 3 range.
The mechanical linkage operates the 2 phase changing/off switch.

Emgee

[Brian MorehenParticipant @brianmorehen85290]

Looks like you are winning with all of the info that Emgee has been able to supply,

Always a problem when a problem is some way away , I believe I possibly could write a book when think of the many times I have had problems like this to solve , Where abouts is your home or works and Emgee , Myself i am in Cambridgeshire Hope to see soon all working ok.

Best regards Brian

[Tom Walker 1Participant @tomwalker1]

Yup Brian, it is looking promising. I dont know what it is with mains electrics, its not as if I am incapable. I am good on vehicle electrics, and I installed all the conduit and cabling for my workshop as per the sparky instructions, but I have never dug deep into mains and 3 phase. Probably a good thing, I have had the odd jab from farm electrics, once bitten twice shy…

I am near Market Harborough, and spend most of my time fettling vintage bikes and cars. Racing took up all my spare time, but that is a young mans game. Still doing a bit though, and rallies, hill-climbs etc.

Many thanks due to all on this forum. I will continue with the posts till the lathe is going on 2 speeds. It may possibly help others.

[EmgeeParticipant @emgee]

Posted by Andrew Johnston on 28/08/2020 13:33:09:

Posted by Emgee on 28/08/2020 10:32:56:

…..full torque will be available throughout the range…..

Surely that should be full power not torque.

Although I've got a varispeed head on the Bridgeport I've never missed infinitely variable speed on my other machine tools. As long as one is in the right ball park it's fine. The exact speed isn't critical. What's the betting someone will pop up and mention chatter?

Andrew

You're probably right Andrew but I was thinking more on practical lines, if you apply a DOC which results in stalling the lathe you can drop to a lower gear and the same motor speed will allow the same DOC to be taken at the lower spindle speed.

Emgee

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