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Motor reverse switch 3 phase

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Martin Connelly24/01/2021 09:01:26
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1663 forum posts
179 photos

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 124/01/2021 10:13:58
2215 forum posts
153 photos

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 Cargill24/01/2021 11:47:43
153 forum posts

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.24/01/2021 14:36:36
97 forum posts
13 photos

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.

Bazyle24/01/2021 14:37:04
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5787 forum posts
216 photos

mmm probably very helpful thread for future fererence
but
If I were a beginner with limitted elctrical knowledge I would be well confused and a bit worried. Lots of numbers and letters but i'm not seeing nice clear statements like "mains supply" and "Motor wire". I wonder if someone could draw a nice diagram goinf from the mains pug to the motor?

Les Jones 124/01/2021 14:48:18
2215 forum posts
153 photos

Reading through the thread again I notice you do have a contactor so here is a suggestion that would ensure the contactor dropped out when the switch passed through the middle off position.

Connect L1 directly to A on the motor.

Connect L2 to 6 and link 6 to 8.
Connect B on the motor to 5 and link 5 to 11

Connect L3 to 10 and link 10 to 12
connect C on the motor to 7 and link 7 to 9

Link 1 to 3 We will call this point X

Link 2 to 4 We will call this point Y

Break the feed to the contactor coil and connect the two ends of the break one to X and one to Y
This will cause the contactor to drop out when the switch passes through the middle off position.
You will then have to press the start button again after the switch has been set to either the forward or reverse positions.
As you have a contactor all three phases will be disconnected from the motor when the switch is in the off position.
Even if the switch is set to forward or reverse if the motor has been stopped with the stop button none of the phases will be connected to the motor. If you post the exiting wiring diagram and information on the contactor one of us will be able to tell you a suitable place to break the feed to the contactor coil.

 

Les.

Edited By Les Jones 1 on 24/01/2021 14:56:22

Me.24/01/2021 15:16:33
97 forum posts
13 photos

I had thought of that option and I suppose it would be safer I suppose if I did it that way - For some reason my PC isn't allowing me to upload any photos - pictures so I can't draw out what I have got but its very basic wiring.

3 phase wires + Neurtal which goes into the coil of the contactor

1 phase wire goes into the coil of the contactor (hager - 240v coli) and into the switch - one "off" and one "on" wired in series.

When I press the "on" button it energises the coil which brings in the contactor - which then feeds my (very) old existing lever switch. Up for forward and down for reverse.

To stop the motor I bring the lever switch to the middle which kills the power to the motor and then I press the "off" button.

I was just getting my head around the Linking terminals now it looks like I'm gonna have to add more....

Ive not brought the rotary switch yet so if i need a 16 terminal switch then that's ok.

john fletcher 124/01/2021 15:42:32
669 forum posts

I have been following this discussion with interest, so would some one tell the part number for this switch and where can I get the truth table or was it included with the package. John

Martin Connelly24/01/2021 16:05:14
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1663 forum posts
179 photos

This is the basic circuit that does not involve the contactor circuit.2021-01-24.jpg

Martin C

Edited By Martin Connelly on 24/01/2021 16:06:19

Me.24/01/2021 16:06:04
97 forum posts
13 photos

Hi John I just went on Ebay and inputted - 3 phase motor reversing switch.

Me.24/01/2021 16:10:45
97 forum posts
13 photos

Wow Martin - Thanks- that is exactly what i needed - it is so much easier to understand when written down like that.

I can't thank you enough -

I wonder if you could do one with the other option with the It breaks the feed to the coil on the contactor as suggested by Les

Martin Connelly24/01/2021 16:13:47
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1663 forum posts
179 photos

This is the one where the top contacts are used to latch the contactor as described by Les. The contactor may have terminals just for this external latching with a link in place.

2021-01-24 2.jpg

Martin C

Les Jones 124/01/2021 17:00:29
2215 forum posts
153 photos

It would be better if you can provide information on the existing so we can tell you where to break the feed to the contactor coil. all of the interlocks, the thermal overload contacts and the stop button will probably be in series with the coil. Also we don't know if the contactor coil is powered between phases, between a phase and neutral or from the secondary of a low voltage transformer. Your existing wiring diagram should provide that information.

Les.

Me.01/02/2021 15:54:36
97 forum posts
13 photos

Two pictures of the contactor and switches as fitted to my Mill.

Brown Black and grey input from the mains at the top.

the 3 pairs of yellow blue and red are the feed to the two motors. Which I am fitting the new rotary switches too.

The brown leads go to two momentary switches the green one energizes the contactor and the red one turns it off.

The blue wire sticking out at right angles is the neutral.

Where do I need to break the leads to add my new switches as per Martins wiring diagram ( X - Y connection)

Or do I need to replace the momentary switches for something else.

img_5209.jpgimg_5208.jpg

Les Jones 101/02/2021 17:34:52
2215 forum posts
153 photos

Here is a diagram of how I suggest adding the reversing switch.

010221.jpg

Connect the reversing switch as in Martin's drawing posted at 16:13 on Jan 24th.
Remove the link wire between the bottom mains input (I can't read the marking on it.) and the stop button. Connect the point X on Martins diagram to bottom mains input terminal on the contactor, Connect Y on Martin's diagram to the connection on the stop button that you removed the link from.

Les.

Me.02/02/2021 08:59:20
97 forum posts
13 photos

HI Les

Many thanks again for your very easy to understand description and diagram. I will do as suggested.

As I will have two rotary switches - one to control the main spindle motor and one to control the table feed, do I take a separate feed to each X point on each switch or do I add the switches in series.

i.e "Brown (feed) - X-Y-X-Y - Stop".

Steve

larry phelan 102/02/2021 09:51:16
948 forum posts
14 photos

Just as a matter of interest, why would you need to run the mill in reverse ?indecision

Les Jones 102/02/2021 10:36:50
2215 forum posts
153 photos

Hi Steve,
The way you have show will work but it would make more sense to have a separate contactor for each motor.
Every time you change the feed direction the spindle motor will also have to stop and start.

Les.

Me.02/02/2021 10:44:53
97 forum posts
13 photos

Thanks Les _ I can do that I have a spare contactor the same as the picture.

Will I need two more on/off buttons as well ?

My Idea was

1.Press the button to turn the contactor on

2.Switch the main motor on (rotary switch)

3.Switch Table feed on (rotary switch)

4.switch to the "0" position when finished cut

5.Press the off button to turn main power off.

*i'm now in need to know the answer to Larry's Question - why does the main spindle motor need to run in reverse ???*

It has the option too on the "old switch panel" but when would you ever need to make a cut with the spindle in reverse ??

Les Jones 102/02/2021 11:54:56
2215 forum posts
153 photos

You would need an extra stop button and start button.
Your suggested switching sequence is not a good one as you are using the reversing switch to switch under load which will shorten it's life. You should set the direction then switch on and off using the start and stop buttons.

I have used my mill in reverse on a few occasions. I think it was to use a boring tool from my lathe mounted in a boring head on the mill.

Les.

Edited By Les Jones 1 on 02/02/2021 12:00:15

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