3 phase motor wiring

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3 phase motor wiring

This topic has 15 replies, 8 voices, and was last updated 4 November 2022 at 15:58 by Roger Clark.

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3 November 2022 at 15:49 #619615
Roger Clark
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@rogerclark
I'm currently wiring this motor to a vfd and my query is there are 2 thin blue wires ending in a small connector as below, in the top left hand corner, are these for temperature sensing? otherwise what are they?

Thanks

Roger
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3 November 2022 at 15:49 #28905
Roger Clark
Participant
@rogerclark
TECA B3-80-IE3 1.5kw motor
3 November 2022 at 16:15 #619618
SillyOldDuffer
Moderator
@sillyoldduffer
I'd bet money the wires go to a thermistor – an optional temperature sensor. Worth connecting if the motor is going to be run flat out most of the time, I've never got the 1.5kW motor on lathe more than luke-warm. It is fitted with a permanently 'on' fan though, and I rarely do long sessions of heavy cutting.

Dave
3 November 2022 at 16:18 #619619
Roger Clark
Participant
@rogerclark
I'm using it on a 72" x 2" belt sander, I doubt it'll be running more than 10 to 15 mins max at a time.

Roger
3 November 2022 at 16:31 #619620
David Jupp
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@davidjupp51506
Could be for a temperature sensitive switch, or a thermistor as Dave suggests. Either can be used to indicate when the windings get hot.

Checking the resistance should determine which it is, if zero ohms it's a switch.
3 November 2022 at 17:31 #619628
AJAX
Participant
@ajax
I have a Tech / Techtop motor with similar wires (which I didn't use). I'm reasonably confident the user manual stated they were thermistor connections. A well known supplier of Techtop motors lists "Protective thermistors type PTC (1 per phase)" as a feature. I hope that helps.
3 November 2022 at 17:36 #619629
Hairy Pete
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@hairypete39644
It will be a thermistor – see page 14 of their catalogue.

https://tecmotors.co.uk/wp-content/uploads/2019/04/teccat.pdf
3 November 2022 at 18:21 #619638
Robert Atkinson 2
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@robertatkinson2
Is that "earth" connection actually connected to the frame of the motor? It looks like it goes to the terminal box housing which looks like it's plastic! In particular there is damage to the edge where the cover fits and it looks like gray plastic not diecast alloy.

It's worth checking with a meter. Good to see you are using SY cable and proper ring tags

Robert G8RPI.

Edited By Robert Atkinson 2 on 03/11/2022 18:22:35
3 November 2022 at 18:27 #619640
Roger Clark
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@rogerclark
Posted by Robert Atkinson 2 on 03/11/2022 18:21:56:

Is that "earth" connection actually connected to the frame of the motor? It looks like it goes to the terminal box housing which looks like it's plastic! In particular there is damage to the edge where the cover fits and it looks like gray plastic not diecast alloy.

It's worth checking with a meter. Good to see you are using SY cable and proper ring tags

Robert G8RPI.

Edited By Robert Atkinson 2 on 03/11/2022 18:22:35

No it's a cast box with full continuity to the motor and also into the sander its bolted to.
3 November 2022 at 18:43 #619644
DC31k
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@dc31k
Posted by Rockingdodge on 03/11/2022 18:27:18:

No it's a cast box with full continuity to the motor and also into the sander its bolted to.

Note the international symbol for protective earth cast into the part to the right hand side on the photo. It is somewhat unlikely that would be moulded into a plastic part.
4 November 2022 at 08:56 #619688
Robert Atkinson 2
Participant
@robertatkinson2
Looking more closely there is paint removed under two of the screws holding the frame down.. The damage to the sealing edge must have been before they painted it. There are different views on using screws to provide a primary earth path. A lot of standards won't accept using the shank of the screw, it has to be a metal to metal contact or a earth wire / strap.

Robert G8RPI
4 November 2022 at 11:31 #619717
Roger Clark
Participant
@rogerclark
Posted by Robert Atkinson 2 on 04/11/2022 08:56:36:

Looking more closely there is paint removed under two of the screws holding the frame down.. The damage to the sealing edge must have been before they painted it. There are different views on using screws to provide a primary earth path. A lot of standards won't accept using the shank of the screw, it has to be a metal to metal contact or a earth wire / strap.

Robert G8RPI

This is in my hobby workshop Robert, here's a couple of photos of a resistance test between the vfd earth and a fixing bolt and the sander table.

vfd earth to motor fixing bolt.

vfd earth to sander table.

The whole belt sander will be bolted through a steel base which is earth bonded to an earth running round the workshop and back to the mains.

Roger
4 November 2022 at 13:45 #619735
Lindsay
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@lindsaydonaldson93648
Posted by Rockingdodge on 03/11/2022 16:18:57:

I'm using it on a 72" x 2" belt sander, I doubt it'll be running more than 10 to 15 mins max at a time.

Roger

Is it the Jer Schmidt design?
4 November 2022 at 14:29 #619740
Roger Clark
Participant
@rogerclark
Posted by Lindsay Donaldson on 04/11/2022 13:45:11:

Posted by Rockingdodge on 03/11/2022 16:18:57:

I'm using it on a 72" x 2" belt sander, I doubt it'll be running more than 10 to 15 mins max at a time.

Roger

Is it the Jer Schmidt design?

It's based on the Made By Dad design Lindsay. It is really solid but I had to play with the dimensions a bit to get the belt to fit.
4 November 2022 at 15:37 #619746
Lindsay
Participant
@lindsaydonaldson93648
Posted by Rockingdodge on 04/11/2022 14:29:42:

Posted by Lindsay Donaldson on 04/11/2022 13:45:11:

Posted by Rockingdodge on 03/11/2022 16:18:57:

I'm using it on a 72" x 2" belt sander, I doubt it'll be running more than 10 to 15 mins max at a time.

Roger

Is it the Jer Schmidt design?

It's based on the Made By Dad design Lindsay. It is really solid but I had to play with the dimensions a bit to get the belt to fit.

I had a quick look – it's very similar to the JS one I made. I guess they all are to some degree. I'm in the lucky position of having made one for a friend my 'payment' was a pile of materials to make myself one so I have the opportunity to apply 'lessons learned' second time round.
4 November 2022 at 15:58 #619751
Roger Clark
Participant
@rogerclark
I had a quick look – it's very similar to the JS one I made. I guess they all are to some degree. I'm in the lucky position of having made one for a friend my 'payment' was a pile of materials to make myself one so I have the opportunity to apply 'lessons learned' second time round.

Nice one, always good when a plan comes together

Mine was more than paid for when my mini mill sold for asking price.
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