Help on fault finding on a C3-31 Hammer combination machine

Attachment 23296
Not a CNC problem, but hopeing someone can point me in the right direction.
This is an electrical drawing of my C3-31 Hammer (Felder) combination machine.

A few days ago it started tripping the MCB32A trip, which progressively got worse, on
any of the motors (Saw, planner, spindle moulder) until it would not work at all.

Suspected contactors, on enquiring with manufacturer was informed they only supply
complete enclosures A1 item 2 on drawing at £500.

So decided to purchase equivalent contactor and axillary contactor and fit.
Result was it would work if I unplugged the motor. (Contactor would pull in)
But if motors plunged in would sometimes work on Saw, but most of the time contactors "chattered"
some times holding in and sometimes tripping MCB332A trip.

The safety limits and stops are the same as a cnc machines so they should not be a problem.
I have tried bypassing the overload protection - no effect.

My suspicions are the braking circuit board, as I believe this works by injecting current back into
the motor to produce a magnetic field to stoop the motor quickly. Has this broken?
Causing some load to prevent the contactors working correctly?

Any help greatly appreciated before I fork out the £500.

Robert

Break the connection of the braking circuit to the motor and test.

Fault finding is a process of logical elimination, not speculation, the fact that multiple motors suffer the same issue suggests it isn't the motors but it can still be any other common component.

Are the motors single or 3 phase?
I'm sure it's clear on the schematic and DC injection braking is a 3-phase technique but you should post the schematic the right way up and at good resolution if you expect anyone to examine it closely, if you can't be bothered......... ;-)
Regards,
Nick

It looks like it's 3 phase, I have a single phase version of this machine but it still has an electrical braking system.

Does it trip when you start a motor or when you press a stop button ?

It could be the rotary switch S7 (10), saw/moulder/planer, maybe it's losing a phase to the motors ?

Attachment 23306
Drawing any better Nick?
Translation from German:
1 Home
2 Switching Unit
3 On Off Switch
4 Overload Protection
5 Contactor
6 Auxiliary Contactor
7 Braking Circuit
8 Transformer
9 Fuse
10 Selector Switch
11 Limit Switch
12 Emergency Stop
13 Emergency Stop
14 Motor – Saw
15 Motor – Spindle Moulder
16 Motor – Planer
17 Plug
18 Limit Switch
19 Limit Switch
20 Terminal Strip

Yes the motors are 3 phase run from a Transwave inverter.

So disconnect wire R7 from the contactor to eliminate the Braking circuit?

Does it trip when you start a motor or when you press a stop button ?

It trips or won't start when you press the start button. Contacts flash, chatter. But it does run on all three motors once it decides to hold the contacts in.
But I don't think the contactor will last long if I keep using it like this.

Thank you for your suggestions I will have another look at it tomorrow.

Is the coil voltage correct on your replacement contactor ? it shows 230v AC on the drawing, have you checked the voltage at the coil with a meter while it's chattering ?

Is the MCB332A which is tripping running the transwave and have you checked the output of the transwave as cack 3 phase into your machine will cause it to play up as various control bits are powered by single phases.

With those symptoms, as Nick mentions, I'd be checking the power supply.

If the power supply is dropping enough to cause the contactor to drop out again (and enter a continual cycle causing the chattering), then the cycling high current draw can easily start tripping MCBs/blowing fuses.

Quote:

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Originally Posted by magicniner

Is the MCB332A which is tripping running the transwave and have you checked the output of the transwave as cack 3 phase into your machine will cause it to play up as various control bits are powered by single phases.

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Nick I have a Wadkin planer and a Speed Sander I run off the transwave and they are both running fine.

Quote:

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Originally Posted by EddyCurrent

Is the coil voltage correct on your replacement contactor ? it shows 230v AC on the drawing, have you checked the voltage at the coil with a meter while it's chattering ?

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Here is the replacement contactor details https://chaloncomponents.co.uk/produ...oltage=230v-ac
I will check while chattering.

Quote:

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Originally Posted by OMLCNC

Nick I have a Wadkin planer and a Speed Sander I run off the transwave and they are both running fine.

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It may be down to how each machine is connected. Do you have this machine connected, so the two legs (2 & 3) that power the control circuits, are connected to the non-generated leg on the converter?

With most common single to three phase converters, two legs are supplied directly from a step-up transformer, then the 3rd leg is generated using purely capacitors (in the case of static converters), or by a combination of idler motor and capacitors (in the case of rotary converters).
If you connect one of the control legs to the generated leg, then it is very likely to sag under motor starting loads, which would explain your symptoms. If you have had it connected this way, then there is a possibility that converter is the problem, which is why we're asking about voltages. It could be the converter has either developed a fault (some will try and boost the voltage under high load conditions), or it could just be a combination of capacitors getting a bit weaker as they age, a bit extra load on the motors, and the cold weather making things a bit sluggish, that have pushed things to the point the problem has become apparent.

And if your other machines are connected so their control circuits are powered from the non-generated legs, it would give the impression the convertor is working fine, as although the generate leg would sag while starting, you probably would not notice any difference unless really pushing the machines to their maximum loads.

So in short, check what voltages you're getting into the control, especially the voltage at the transformer that is supplying the 230V for the controls.

Quote:

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Originally Posted by m_c

It may be down to how each machine is connected. Do you have this machine connected, so the two legs (2 & 3) that power the control circuits, are connected to the non-generated leg on the converter?

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I will find the Transwave manual and have a look, do you mean L2 and L3 on the drawing?

Quote:

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Originally Posted by m_c

With most common single to three phase converters, two legs are supplied directly from a step-up transformer, then the 3rd leg is generated using purely capacitors (in the case of static converters), or by a combination of idler motor and capacitors (in the case of rotary converters).
If you connect one of the control legs to the generated leg, then it is very likely to sag under motor starting loads, which would explain your symptoms. If you have had it connected this way, then there is a possibility that converter is the problem, which is why we're asking about voltages. It could be the converter has either developed a fault (some will try and boost the voltage under high load conditions), or it could just be a combination of capacitors getting a bit weaker as they age, a bit extra load on the motors, and the cold weather making things a bit sluggish, that have pushed things to the point the problem has become apparent.

And if your other machines are connected so their control circuits are powered from the non-generated legs, it would give the impression the convertor is working fine, as although the generate leg would sag while starting, you probably would not notice any difference unless really pushing the machines to their maximum loads.

So in short, check what voltages you're getting into the control, especially the voltage at the transformer that is supplying the 230V for the controls.

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So using test meter on Hv setting I get 237v on a workshop socket outlet (just checking I'v got the correct range) then 160v over the low side of the transformer and 364v over the high
side. 160v seems too low?

The contacts made well some times and chatterd others. Going to look for manual for Transwave.

I was taught that 'rule' no1 when fault finding is, "check the supply" :friendly_wink:

A contactor needs more voltage to close than it does to retain but 160v is only about 70% of required, plus, as the motor applies load it is going to drop a lot further.

The other to watch is phase rotation, you don't want to be swapping phases around willy-nilly otherwise the motor direction could reverse.

You should test a supply in both no load conditions and with a load of a significant percentage of that with which you are having problems.

160V does seem low. It's not unknown for transformers to fail, but as Nick says, check what happens to the voltages when you try starting the motors. Test the high and low sides to see what happens.

Also test between the other legs when starting, to see if you any sag more.

Quote:

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Originally Posted by magicniner

You should test a supply in both no load conditions and with a load of a significant percentage of that with which you are having problems.

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No desire to be pedantic about this but,
That's not what I meant about 'rule no1' , I meant if there was nothing there when you pressed "start". In other words, "check there is the required voltage at the machine".
The quality of the supply comes later after pressing "start" does it's job.

Sorry :apologetic: but I made a mistake when testing the voltage on the transformer, wrong connections.
Now get readings of 464v and 260v.
Also get 242v over the contactor.

What to check next?

What happens to the voltages while the motors are starting, and the contactor chattering?

Quote:

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Originally Posted by m_c

What happens to the voltages while the motors are starting, and the contactor chattering?

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From putting the meter over A1, A2 on the contactor and pressing the start button the voltage is not instant ie it climbs to 240v while it chatters,
same if you put it over any of the other contacts. When it pulls in it is 240v. So readings might be 50, 70, 130, 170 then 240v (all while chattering)

Is there a way of wiring out the braking board item 7 on the drawing and still making the machine work to eliminate it from being the problem?
I can disconnect wire 24 from the contactor to stop it breaking, but there are 5 other wires still connected.

Then I can happily spend the £500 knowing that that is the cause.

Testing is not proceeding in a logical manner.

Personally, I would install the original contactor first.
With the machine disconnected from supply, manually operate the contactor and confirm, using an ohmmeter, that all the contacts operate as expected.
Then I would remove the load, i.e. disconnect the selected motor, e.g. saw
Plug the machine in and press start and see if the contactor pulls in and holds
Now with a voltmeter I would test to see if we are getting 3 phases (full voltage) at the disconnected motor leads.
If not, I would start at the supply end and work my way through to find the reason.
If yes, then it suggests the wiring and contacts are okay, on no load at least.
If you then press stop, there should be DC across 2 of the motor wires for several seconds (it makes a loud humming noise under normal conditions)

If your machine works in a similar way to mine, if an e/stop button is pressed and you press 'start', then the braking system energises for several seconds just as during a normal stop.
This means that if the contactor, and it's contacts, are not working correctly it may be possible to initiate the brake during startup. This is the main reason
I would refit the original contactor and auxilliary as there may be some time delay involved here.
The drawing is one of the worst I've seen and it's not easy, for me anyway, to determine exactly what's going on, and I've used some complex drawing in the past.

I've attached a copy of the single phase version if it helps sort this out, (not studied it yet though)

Quote:

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Originally Posted by EddyCurrent

No desire to be pedantic about this but,
That's not what I meant about 'rule no1' , I meant if there was nothing there when you pressed "start". In other words, "check there is the required voltage at the machine".
The quality of the supply comes later after pressing "start" does it's job.

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If I'd been referring to your suggestions I'd have quoted you.
When looking for the source of a fault in a 3 phase electrical system where components such relays and actuators are commonly run from one phase with different components running from different phases then if you don't check what you have before applying any load at all then you can make things harder for yourself.
Just saying ;-)

Quote:

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Originally Posted by OMLCNC

From putting the meter over A1, A2 on the contactor and pressing the start button the voltage is not instant ie it climbs to 240v while it chatters,
same if you put it over any of the other contacts. When it pulls in it is 240v. So readings might be 50, 70, 130, 170 then 240v (all while chattering)

Is there a way of wiring out the braking board item 7 on the drawing and still making the machine work to eliminate it from being the problem?
I can disconnect wire 24 from the contactor to stop it breaking, but there are 5 other wires still connected.

Then I can happily spend the £500 knowing that that is the cause.

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The readings are what I suspected you'd get, especially with a multimeter.
What about the input voltage to the transformer?
If they also drop, what about the main supply into the machine?


What I can't really make out from the wiring diagram, is are the top right wires, and lower left side wires on the braking module directly connected (I'm guessing each wire has a separate terminal, but are the terminals paired together? - A photo might help)

However, I think if you remove the link between R8 and 4 on the contactor, it'll be enough to break the circuit for the braking.
Do you have a diagram for the selector switch, as it would help understand exactly what's going on?

Assuming the selector switch is just a switch, with no relays/contactors to control things, then the key to the braking circuit is how the 3rd leg is handled. It is controlled via the auxiliary contact (other two legs go via the main contacts, with the third main contact used as the latch for the start button - the start button second contact also bypasses the aux. contact, which I assume also ensures the braking module remain inactive until the contactor is fully energised), but goes to the braking module, before heading to the selector switch, unlike the other two legs that go straight to the selector switch.
The braking module is also connected to the 2nd leg output from the contactor (terminal 4), via the NC contact (R8), so when the contactor is energised, the braking circuit is broken, but once the contactor is de-energised, the braking module is connected to the 2nd and 3rd legs on the motor side. By breaking the 4/R8 link, it should prevent the module from braking (which I'm assuming is done either via DC injection braking, or controlled shorting of the legs).

Quote:

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Originally Posted by EddyCurrent

Testing is not proceeding in a logical manner.

Personally, I would install the original contactor first.
With the machine disconnected from supply, manually operate the contactor and confirm, using an ohmmeter, that all the contacts operate as expected.

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No they do not.

(1 and 2) and (3 and 4) closed all the time (NO) even if you manually opperate contactor.
ONLY when Planer and Spindle Moulder selected.

When Saw selected all contacts operate as expected.

Quote:

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Originally Posted by EddyCurrent

Plug the machine in and press start and see if the contactor pulls in and holds
Now with a voltmeter I would test to see if we are getting 3 phases (full voltage) at the disconnected motor leads.

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Yes it pulls in and holds.
Yes 440v - 460v out of three wires at plug to motor.

Does this point to item 10 the selector switch?
The Saw does not operate correctly all the time, it still makes the contactors chatter.
If that helps.

Quote:

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Originally Posted by EddyCurrent

If you then press stop, there should be DC across 2 of the motor wires for several seconds (it makes a loud humming noise under normal conditions)

If your machine works in a similar way to mine, if an e/stop button is pressed and you press 'start', then the braking system energises for several seconds just as during a normal stop.
This means that if the contactor, and it's contacts, are not working correctly it may be possible to initiate the brake during startup. This is the main reason
I would refit the original contactor and auxiliary as there may be some time delay involved here.
The drawing is one of the worst I've seen and it's not easy, for me anyway, to determine exactly what's going on, and I've used some complex drawing in the past.

I've attached a copy of the single phase version if it helps sort this out, (not studied it yet though)

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Yes I get the loud humming noise when I stop the machine.
Here is a picture of the original contacts and auxiliary, I've split them apart so you can see the information.
I can not see that they have a 1 second delay, can you? Attachment 23316

Quote:

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Originally Posted by m_c

The readings are what I suspected you'd get, especially with a multimeter.
What about the input voltage to the transformer?
If they also drop, what about the main supply into the machine?


What I can't really make out from the wiring diagram, is are the top right wires, and lower left side wires on the braking module directly connected (I'm guessing each wire has a separate terminal, but are the terminals paired together? - A photo might help)

However, I think if you remove the link between R8 and 4 on the contactor, it'll be enough to break the circuit for the braking.
Do you have a diagram for the selector switch, as it would help understand exactly what's going on?

Assuming the selector switch is just a switch, with no relays/contactors to control things, then the key to the braking circuit is how the 3rd leg is handled. It is controlled via the auxiliary contact (other two legs go via the main contacts, with the third main contact used as the latch for the start button - the start button second contact also bypasses the aux. contact, which I assume also ensures the braking module remain inactive until the contactor is fully energised), but goes to the braking module, before heading to the selector switch, unlike the other two legs that go straight to the selector switch.
The braking module is also connected to the 2nd leg output from the contactor (terminal 4), via the NC contact (R8), so when the contactor is energised, the braking circuit is broken, but once the contactor is de-energised, the braking module is connected to the 2nd and 3rd legs on the motor side. By breaking the 4/R8 link, it should prevent the module from braking (which I'm assuming is done either via DC injection braking, or controlled shorting of the legs).

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See pictures - Yes the wires are connected on the PCB board, paired together as you thought, I checked them with "the tester"
Other red wire goes to 24 and brown to R7

Also see pictures of rotary switch, you may be able to work out how it works. It could be the issue if you see my other post to Mr EddycurrantAttachment 23317Attachment 23318Attachment 23319

This is the brake unit I think; http://www.klibo.com/brake_16a.html?L=1
and there are drawings etc.

So it is a DC injection brake, in which case disconnecting the link as I suggested will stop the brake from functioning, although I think you'll also want to disconnect the wire going to the Sp terminal on the braking module, as going by the diagram for it, the Sp appears to be some kind of detection signal (it only gets powered when the contactor is active).

However, I still suspect the real problem is the supply voltage sagging with the starting load.
What happens to the main phases powering the control circuit (L2 & 3 on the diagram) when everything is starting?

Quote:

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Originally Posted by m_c

So it is a DC injection brake, in which case disconnecting the link as I suggested will stop the brake from functioning, although I think you'll also want to disconnect the wire going to the Sp terminal on the braking module, as going by the diagram for it, the Sp appears to be some kind of detection signal (it only gets powered when the contactor is active).

However, I still suspect the real problem is the supply voltage sagging with the starting load.
What happens to the main phases powering the control circuit (L2 & 3 on the diagram) when everything is starting?

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I will have a look later.

But why are (1 and 2) and (3 and 4) closed all the time (NO) even if you manually opperate contactor.
ONLY when Planer and Spindle Moulder selected with no power on machine?
When Saw selected they all perform as expected with no power to machine?

I agree with m_c about which wires to remove, however it may be easier just to pull the connections from C1 and SP at the brake board.(insulate them after diconnecting)
I don't know about the switch enigma but as a starting point you should always check contacts with the wires disconnected to prevent feedback.
If it's okay in the saw position I suggest getting the machine running like that for a start.

Operation of the brake looks like this to me.

If there is voltage or has been voltage at terminal SP (even briefly) and there is a circuit from C1 through the motor winding back to L3 (i.e. contactor has just been de-energised) then brake.
If there is voltage at terminal SP (even briefly) and there is no circuit from C1 through the motor winding back to L3 (i.e. contactor energised) then do not brake.
If there is no voltage at terminal SP (or a brake operation has just completed) and there is a circuit from C1 through the motor winding back to L3 then do not brake.

This also explains why the brake will activate if 'start' is pressed while an e/stop is activated. Start button contact 23/24 apply voltage to SP briefly when pressed but the contactor is de-energised.

There is nothing in the diagram that indicates why the contacts 1 & 2 would show as having continuity, however the other two main contacts could, so it's probably a discrepancy between the diagram and the actual machine.
As Eddy says, you should only be testing for continuity with the wiring removed from the contactor.

The rotary switch (10) has 4 positions.
1. Saw
2. spindle moulder forward
3. spindle moulder reverse
4. planer

It's hard to see why there should be the difference in readings across the contactor as the assumption is that switch 10 just swaps motors.

Quote:

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Originally Posted by m_c

However, I still suspect the real problem is the supply voltage sagging with the starting load.
What happens to the main phases powering the control circuit (L2 & 3 on the diagram) when everything is starting?

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Disconected brake by pulling off C1 and SP terminals and insulating

So I took multimeter set on Hv put one end in earth and other in L1, L2, L3 in turn. (at the overload 4)
L1 Black wire 330v no load no dip (because the contactors stopped chattering while testing?)
L2 Brown wire 120v no load dips to 75v on start
L3 Grey wire 361v no load dips to 330v on start

While testing on and off and rotating switch for different motors, the chattering contactor problem stoped and I canot get it to do it any more.
There are small sparks from the contactors 5 and 6 on switching on and off.
I dare not touch anything as the problem may return.
What should I do next?
Go back and see if It is still ok, then re-connect the brake?

Not your standard 3 phase voltages by any means but might be okay for a converter ? I believe there is a minimum load required for one thing but I'm not 100% on that.

I meant to ask this much earlier, was the machine working okay with the current setup, you changed nothing and then the next time you started the machine there was this fault ?

Did you actually start any of the motors during these last tests ? it should be okay to do so but you won't get any braking.

Quote:

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Originally Posted by EddyCurrent

Not your standard 3 phase voltages by any means but might be okay for a converter ? I believe there is a minimum load required for one thing but I'm not 100% on that.

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All the information is here to down load https://www.powercapacitors.co.uk/pr...ve-converters/ It states that you can not treat it the same as a normal 3 phase supply.

Quote:

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Originally Posted by EddyCurrent

I meant to ask this much earlier, was the machine working okay with the current setup, you changed nothing and then the next time you started the machine there was this fault ?

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Yes, the machine was running for a time then the MCB to the Transwave triped on the saw and the planer, got worse then would not start at all without tripping. Chattery contacts only noticed when opened the enclosure.

Quote:

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Originally Posted by EddyCurrent

Did you actually start any of the motors during these last tests ? it should be okay to do so but you won't get any braking.

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Yes ran all of the motors, no braking, but they all started and stopped, many times.

What to do next?

Quote:

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Originally Posted by OMLCNC

While testing on and off and rotating switch for different motors, the chattering contactor problem stoped and I canot get it to do it any more.

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Crikey Mate! I'd be into that switch and looking for issues like a rat up a drain pipe, you might have found the source of your problem!

Try this.

Quote:

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Originally Posted by OMLCNC

Yes, the machine was running for a time . . .

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Too vague. I meant has it been working for weeks/months/years with the current setup ?

If not, I'd be inclined to think it's something to do with how the machine is connected to the Transwave; https://www.powercapacitors.co.uk/wp...structions.pdf

It was also strange how the rotary switch influenced those tests you did earlier.

1. reconnect C1 and try to start the motors again, do this 3 times, once for each motor.

2. reconnect SP (leave C1 still connected) push in one of the E/Stop buttons, switch to saw and try to start the motor.
You should hear the motor humming as the brake applies DC. If that works okay it suggests the brake unit is working.
Repeat that 3 times, once for each motor.

3. one thing I don't like is this; when you press the start button (contact 23/24), it applies voltage to SP and for the time it takes the contactor to pull in there is also a circuit via C1 (R7/R8)
On a sample diagram from the Klinger Born website I linked to earlier, it shows the start button having a normally closed that open circuits the C1 circuit when pressed, this makes more sense especially
if it's a 'break before make' type.
It may just be that we don't fully understand the brake unit's operation.

When measuring voltage from a converter, always measure between the legs.

How those voltages relate to earth, depends on the kind of step-up transformer they've used, and if they've connected to the mains input or earth at any point.


If it's now working again, all you can really do is wait until it stops working again.
Personally, I'd be wanting to ensure the supply voltages are 100% before looking elsewhere, which is why I keep asking about voltages.

Quote:

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Originally Posted by EddyCurrent

Try this.



Too vague. I meant has it been working for weeks/months/years with the current setup ?

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Yes, machine and transwave and two other 3 phase machines running from the transwave set up in 2011, all worked fine untill now.

Gave it a quick run on each of the motors tonight just to make sure I wasent dreaming and it still works with no braking

Will look at and go through suggestions tomorrow.

The rotary switch.

1 - L1
3 - L2
17 - L3
10 - Saw Motor U1
12 - Saw Motor V1
20 - Saw Motor W1
6 - Moulder Motor U1
4 - Moulder Motor V1
18 - Moulder Motor W1
14 - Planer Motor U1
16 - Planer Motor V1
22 - Planer Motor W1
23 - 230v control
24 - 230v control

This is how I would expect the switching to be.
in Saw position, L1,L2,L3 will be connected to the saw motor only
in Moulder Fwd position, L1,L2,L3 will be connected to the moulder motor only
in Moulder Rev position, L1,L2,L3 will be connected to the moulder motor only, but two phases will have been swapped over
in Planer position, L1,L2,L3 will be connected to the planer motor only

in all positions terminals 23 and 24 will be connected in order to complete the 230v control circuit.
It probably goes through the switch because the contact between 23 and 24 will go open circuit between positions
thus dropping the contactor out if the switch is moved while a motor is running.

That being the case it should be fairly easy, though laborious, to test it.

1. Mark up the wires securely, you don't want a label dropping off, masking tape works okay.
2. Also take however many photos it needs to be sure all the wires will go back in the same position (there may be links from one terminal to another, leave them in place)
3. remove the wires and test the switch arrangement using terminals 1,3,17 as the reference terminals, make good notes with pen and paper.
For each position of the switch make a note of;
a) which terminals are connected to terminal 1
b) which terminals are connected to terminal 3
c) which terminals are connected to terminal 17
d) state of terminals 23 to 24
4. do the results match what we think it should be ? (using the information above)

Sorry if my instructions seem childish, I've learned the hard way (many call outs through night) that leaving easy to follow unambiguous instructions is the best way to achieve success (and let me get a nights sleep, although all that is past me now)

Given the fault seemed to affect all functions, my money would be a voltage drop in something common to all functions.

I certainly wouldn't be unwiring such a complex switch just to test how it works, when you can get far more accurate readings by testing it under load, by measuring voltages...

Plus, the fault could quite easily be with some of the other safety switches in the control circuit.
The only thing I'd do now everything is working, is double check all the connections at the switches, and work them a few times to work the contacts. If the switches haven't been operated for a while, the contacts could oxidise causing a voltage drop, and working them a couple times can be enough to get them working again for a while.

The switch information is there in case it's required, I had some time to spare last night.

Quote:

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Originally Posted by EddyCurrent

1. reconnect C1 and try to start the motors again, do this 3 times, once for each motor.

2. reconnect SP (leave C1 still connected) push in one of the E/Stop buttons, switch to saw and try to start the motor.
You should hear the motor humming as the brake applies DC. If that works okay it suggests the brake unit is working.
Repeat that 3 times, once for each motor.

3. one thing I don't like is this; when you press the start button (contact 23/24), it applies voltage to SP and for the time it takes the contactor to pull in there is also a circuit via C1 (R7/R8)
On a sample diagram from the Klinger Born website I linked to earlier, it shows the start button having a normally closed that open circuits the C1 circuit when pressed, this makes more sense especially
if it's a 'break before make' type.
It may just be that we don't fully understand the brake unit's operation.

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So carried out step 1 and 2.

Yes the brake works but the chattering has returned, no logical pattern, it can hapen in any position of the rotary switch.
First start can be fine and second and third then fourth chattering, rotate switch starts fine, second chattering...... etc.... so no logic.

Will now look at rotary switch.