Motor reverse switch 3 phase

[Me.Participant @me1]

I want to fit a new rotary 3 phase motor reverse switch to my Mill.

Ive found a switch which is suitable but need advice on how to wire it.

The switch is an on-off-on rotary with 12 positions.

I have my 3 wires coming from the contactor, what goes where into the switch and what positions goes to the motor to enable it to run forward and then to reverse.

[Me.Participant @me1]

[Martin ConnellyParticipant @martinconnelly55370]

The usual way 3 phase motors are reversed is to swap two of the phases feeding the motor. Without full details of the switch that is all that can be said for definite. There are probably lots of wiring diagrams for dedicated switches but since the dedicated switches will be likely be just 2 or 3 positions (forward/reverse or forward/off/reverse) they will not help. Can you confirm if the switch is 12 positions and not 12 connections. 12 position rotary switches are available but would usually not be suited to switching motor wiring.

Martin C

[DC31kParticipant @dc31k]

Posted by Martin Connelly on 23/01/2021 09:10:54:

There are probably lots of wiring diagrams for dedicated switches but since the dedicated switches will be likely be just 2 or 3 positions (forward/reverse or forward/off/reverse) they will not help.

If we take the concept of a three phase reverse switch and the number '12', a good possibility is a fwd/off/rev/off cyclic mode of operation*. That would correspond to a 4 position switch in your terminology above so the diagrams for a 3-position one might at least give a starting point.

In the absence of a proper wiring diagram, use a continuity meter and make up a truth table for all terminals and all switch positions. Publish it here for review and we can tell you how to connect it.

Why not publish a link to the switch you have bought? Or if the source of your switch breaches the rules here, find an identical one from a 'clean' seller and point us in its direction.

* That is how the classic Santon ones work, even if the legend plate only has three marked positions.

[John HaineParticipant @johnhaine32865]

Do you have a true 3 phase mains supply? If not and you're using a VFD it is usually a programming option to select reverse, no need to do anything in the wiring,

[Me.Participant @me1]

This is the switch – sorry i meant 12 connections – the description in the blurb says its for a motor F&R switch. I just need to know what connections to use – The truth table indicates which connections make and brake but I can't work out what is what in layman's terms.

[Me.Participant @me1]

Yes true 3 phase supply 400v supply

[DC31kParticipant @dc31k]

If it has a truth table, you are halfway there. Use your continuity meter to translate into layman's terms what the truth table is telling you.

Martin has already told you all there is to know on the subject: to reverse, swap any two of the three phases.

In the off position, the three incoming connections, call them U, V, W, will not connect to anything at all.

In the forward position, U, V, W will make to A, B, C respectively.

In the reverse position, U, V, W will make to B, A, C (or similar).

It is very important for your own safety and peace of mind that you understand what is going on rather than just follow a recipe that says 'connect this to that'.

[Les Jones 1Participant @lesjones1]

It looks like there is information on the left hand side of the switch between the connections. there is probably the same on the other side. If you post pictures of both sides it may avoid you having to meter out the connections.
The make and model number of the switch may enable use to find the data on the switch.

Les.

[Brian MorehenParticipant @brianmorehen85290]

The last one i fitted had a handle in the middle on the side which was of . Pushed up gave you one direction and down the opposite direction you the needed a separate Switch for on and off because the first one was just for rotation , I think this was a MEM switch.

Good Luck Bee,M

[J HancockParticipant @jhancock95746]

Looks like a Blue Line switch.

Google 'Blue Line' , all the information you need is in their catalogue/ pdf page.

[Martin CargillParticipant @martincargill50290]

Can you give us a picture of the truth table? It may be possible to use the switch to drop out the contactor (I assume your using a contactor/overload in the circuit) as this will prevent you from making a forward / reverse selection while the machine is running. Motors and mechanical bits tend not to like being changed from one to the other while running.

Martin

[Me.Participant @me1]

Thanks – Ive already had a look at the blue line page but still means nothing.

All I know is I have 3 wires from the contactor – 12 connections on the switch – 3 wires going to the motor (not including the earth).

If i connect the feed from the contactor to 1 3 5 where do the wires that feed the motor go ?? 2 4 6 ?? what are the other 6 connections for ???

[Alain FooteParticipant @alainfoote90915]

One phase say Red goes straight to the motor not via the switch! Then use the switch to reverse the other two phases round to reverse the motor.

[EmgeeParticipant @emgee]

Posted by Me. on 23/01/2021 13:04:34:

If i connect the feed from the contactor to 1 3 5 where do the wires that feed the motor go ?? 2 4 6 ?? what are the other 6 connections for ???

Seems you have a 4 pole switch so as said earlier you can use the 4th pole to switch the starter coil off to help reduce chance of going from fwd to rev without any delay.

You need to upload the schematic drawing recd with the switch to get sensible advice, or inform of the make and model of the switch.

Emgee

[SillyOldDufferModerator @sillyoldduffer]

Posted by Me. on 23/01/2021 13:04:34:

…

All I know is I have 3 wires from the contactor – 12 connections on the switch – 3 wires going to the motor (not including the earth).

…

That's all we know too! It's not enough. Can you identify the switch and share the truth table & diagrams please?

Dave

[J HancockParticipant @jhancock95746]

This from the Blue Line on-line catalogue F071 plate, like yours.

Line Connection is terminal 2 (say red phase supply )

Switch Position 1 , term 2 will connect to term 3

Position 0 + off

Position 2 , term 2 will connect to term 1)

Line Connection is terminal 6 (say yellow phase )

SW pos 1 , term 6 will connect to term 7

SW pos 0= Off

SW pos2 , term 6 will connect to term 5

Line Connection is terminal 10 ( say blue phase )

SW pos 1 term 10 to 11

SW pos 0 = Off

SW pos 2 term 10 to 9

FOURTH POLE

14 to 15

OFF

14 to 13

[not done it yetParticipant @notdoneityet]

An interesting thread, with a comprehensive set of instructions from JH! I sorted out mine from scratch (about 6 years ago). Not too difficult when you have the right number of connections available (and a multimeter, or other circuit tester).

[Me.Participant @me1]

Many thanks for the very precise instructions. Exactly what I needed.

[Me.Participant @me1]

For those that asked the truth table for the switchI want to use.

[noel shelleyParticipant @noelshelley55608]

So, L1 to Ter 2, link 1 & 3 to A

L2 to Ter 6, link 5 & 11 to B

L3 to Ter 10 link 7 & 9 to C Correct ? Noel.

[Martin ConnellyParticipant @martinconnelly55370]

You are close to correct but not all the way there. Connect L1 and link to 1 and 3, connect and link L2 to 5 and 7, connect and link L3 to 9 and 11.

Connect and link A to 2 and 4, connect and link B to 6 and 12, connect and link C to 8 and 10.

Check this out on a bench first with a meter or continuity tester first to be sure it works as expected. Make up the link wires (6 off) to join the terminals 1-3, 5-7, 9-11, 2-4, 6-12, 8-10,

In position one note what L1, L2 and L3 connect to, and check for continuity or not between the L1, L2 and L3 positions. I would expect them to connect to A (2), B(6), C(10) respectively and no continuity between them.

In position two repeat as above, I would expect them to connect to A(2), C(8), B(12) respectively and once again no continuity between them.

In position 0 I would expect no continuity between any terminals except where linked.

Note this system is for use with a 3 phase supply that is not being fed by a VFD as stated above. They don't like switching the terminals when on.

Martin C

PS this is with the advantage of the table, up to then there was some guess work going on so it is important to have full information before going ahead with this sort of wiring.

Edited By Martin Connelly on 24/01/2021 09:08:27

[Les Jones 1Participant @lesjones1]

From the truth table Noel's instructions will only work in position 1. (Post 23/01/21 at 23:33)
It needs the following three links adding. 2 to 4, 6 to 8, and 10 to 12.

Edit. I see Martin has beat me to replying. His information will also work
Are you using a contactor and thermal overload ? If so the point made about arranging the wiring to make the contactor drop out in the middle off position is a good one. It would be even better is a delay circuit was added so that the contactor could not be activated for several seconds after it dropped out. This would prevent switching straight from forward to reverse.

Les.

Edited By Les Jones 1 on 24/01/2021 10:32:42

[Martin CargillParticipant @martincargill50290]

Good to see that this has been cleared up

Just a word of warning regarding Alain Foote's solution. Connecting a switch in the way that has been suggested will certainly work BUT this leaves the motor connected to one live phase even with the switch on the off position. Thus its possible to receive an electric shock from the motor terminals even when its not running (assuming that the contactor is still energised)

I once realised that some 3 phase DeWalt saws are connected in a similar manner. Their motor control switchgear only controls two of the three phases. The third phase is connected to the motor all of the time, so if the saw is connected to the mains the motor is live…….

Martin

[Me.Participant @me1]

Thakns again for all this info. Just to clear this in my mind – where you say "link" you mean add a link wire between the terminals. ?

My machine has an On Off Button which controls a contactor which then send the power to the old switch – No VFD.

Is there any chance of a small schematic diagram ?

Just to note I had already Rulled out the "one line directly to the motor" option as I don't really want the motor to be live all the time its switched on.

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