Schaublin 135 - Help upgrading electrical system

[ballen]

Reply from my guru re k1..
It´s mounted to reduce the contact-fire at the relay contact and the brake comes a little bit faster.
Remember: You have direct current at the brake.

Yes, that is what I had suspected. The main issue: I do not understand how this reduces arcing at the contacts.

 

[ballen]

I've done some reading about contactor timing: whether the auxiliary contacts open or close before or after the main contacts.

The schematics for your lathe indicate that the contactors being used are standard ones. These are "early break, late make". It means that when the contactor is turned on:

the NC aux contacts open (break) BEFORE the main contactor contacts have closed
the NO aux contacts close (make) AFTER the main contactor contacts have closed

When the contactor is turned off, it works in time-reverse order:

the NC aux contacts close (make) AFTER the main contactor contacts have opened
the NO aux contacts open (break) BEFORE the main contactor contacts have opened

In the Schaublin design, if the contactor is working correctly, this time-ordering guarantees that the NC aux contacts d2 11/12/13/14 can not generate a short circuit in the DC power supply. So, if the contactor is working correctly, disconnecting d2/12 and/or d2/14 should not make a difference.

If disconnecting either/both d2/12 and d2/14 makes no difference in the behaviour that you describe, then I think the most likely issue is that your external PS current overload is being tripped by the inductive spikes from the brake coil being turned off. So if everything else checks out it might be high time to shift to using the built-in DC power supply. Keep alert (eyes/nose/ears) for short circuits or other signs of trouble so that you can quickly shut off the lathe power (best) or to hit the emergency power off button (almost as good).

 

[ballen]

...

Any news?

 

[marcsO]

Any news?

Busy day today so hopefully will get some time on this tomorrow.

 

[marcsO]

Hi, there has been a few post recently with a lot of discussion and suggestions so wanted to clarify if possible what you suggest the next say 5-6 tests should be, should the capacitor be replaced and should the soft start be wired in as suggested as well before the next batch of testing?

I also have another PS however this one is a 24VDC 6.5A unit and does not have a pre-set button to set max current, could this be used or should I as you suggest wire up the rectifier (I do have spare 6A fuses BTW).

 

[ballen]

Hi Marc,

I'm going to need more feedback and info to do this. If I was there it would probably take me about fifteen minutes to figure out what was wrong, because I could try things and see what happened. The back and forth is very slow, and I often have trouble understanding what you are seeing or experiencing.

Here are step by step instructions. But if things are not going as I describe, you have to try and observe what is actually happening and then write it down clearly for me.

0) Replace the capacitor. It can't hurt, and eliminates one variable. Observe polarity.

1) Hold off on the soft starter for now. Let's finish the brake, since we are close.

2) Turn off lathe

3) Connect multimeter (set to VDC) to PS

4) Turn on PS, set to max voltage 32V, set current limit to 3A, verify that you have 32VDC. Keep an eye on this voltage, it should never drop. If it does, is it because the CC light is turning on? If so, can you reset it by disconnecting the load from the PS then reconnecting?

5) Connect PS to the 6A fuses in the lathe

6) Verify that the current draw is (say) less than 1 amp. This is turning on the solenoid.

7) Push in the d2 contactor by hand. This should close the brake, and the current draw should increase by (say) another ampere, to a total of 2A. If this does not work reliably, is something wrong with the PS? Does the voltmeter show less than 32V? Does the CC light turn on? If that happens, disconnect and reconnect the PS load to reset it.

8) Release the d2 contactor and turn on the lathe with control lever in the 0 position. This should engage the brake and disengage the safety lock. If this does not engage the brake, has something gone wrong with the PS?

9) If the brake is not turning on reliably when the lathe is on and the control lever is zero, because the PS is shuttting down because of the current limit, then try disconnecting d2/12 and d2/14. Does that help?

If the brake is working some of the time but not all of the time, try to gather some clues to help me figure out why.

 

[marcsO]

Hi Marc,

I'm going to need more feedback and info to do this. If I was there it would probably take me about fifteen minutes to figure out what was wrong, because I could try things and see what happened. The back and forth is very slow, and I often have trouble understanding what you are seeing or experiencing.

Here are step by step instructions. But if things are not going as I describe, you have to try and observe what is actually happening and then write it down clearly for me.

0) Replace the capacitor. It can't hurt, and eliminates one variable. Observe polarity.

Done see picture

1) Hold off on the soft starter for now. Let's finish the brake, since we are close.

2) Turn off lathe

3) Connect multimeter (set to VDC) to PS

4) Turn on PS, set to max voltage 32V, set current limit to 3A, verify that you have 32VDC. Keep an eye on this voltage, it should never drop. If it does, is it because the CC light is turning on? If so, can you reset it by disconnecting the load from the PS then reconnecting?

Connected the multimeter to the PS and set the max amps to 3, multimeter shows 31.4VDC while the PS shows 13.9VDC.

5) Connect PS to the 6A fuses in the lathe

Done

6) Verify that the current draw is (say) less than 1 amp. This is turning on the solenoid.

Current draw is 0.42A and voltage on multimeter still holding at 31.4VDC

7) Push in the d2 contactor by hand. This should close the brake, and the current draw should increase by (say) another ampere, to a total of 2A. If this does not work reliably, is something wrong with the PS? Does the voltmeter show less than 32V? Does the CC light turn on? If that happens, disconnect and reconnect the PS load to reset it.

Current draw rises to 1.14A and voltage remains at 31.4VDC. No cc light.

8) Release the d2 contactor and turn on the lathe with control lever in the 0 position. This should engage the brake and disengage the safety lock. If this does not engage the brake, has something gone wrong with the PS?

Current draw goes to 0.7A and voltage remains at 31.4VDC (notice the PS display voltage has now risen to 26.9VDC - something obviously very wrong with that!)

9) If the brake is not turning on reliably when the lathe is on and the control lever is zero, because the PS is shuttting down because of the current limit, then try disconnecting d2/12 and d2/14. Does that help?

Brake seemed reliable so have not tested by disconnecting d2/12 and d2/14

If the brake is working some of the time but not all of the time, try to gather some clues to help me figure out why.

In this test mode it seems to be working all of the time, tested 10 times every 20 seconds or so.

 

[ballen]

It sounds like the brake is now working as it should. If that is correct, then replace the PS with rectifier and retest.

PS: any idea why the brake is now reliable? what has changed??

If the brake is working correctly when operating with the rectifier in place of the PS, then

(a) measure the DC voltage across the +/- terminals of the rectifier with your voltmeter, and report that here
(b) measure the DC voltage across the brake when the brake is turned on (terminals 16/17 of the terminal block) and report that here

[These are so that I can add those values to the schematic.]

(c) wire in the soft starter according to the last schematic that I provided, so we can test if this stops the d1 contactor drop-out problem.

 

[marcsO]

It sounds like the brake is now working as it should. If that is correct, then replace the PS with rectifier and retest.

PS: any idea why the brake is now reliable? what has changed??

If the brake is working correctly when operating with the rectifier in place of the PS, then

(a) measure the DC voltage across the +/- terminals of the rectifier with your voltmeter, and report that here
(b) measure the DC voltage across the brake when the brake is turned on (terminals 16/17 of the terminal block) and report that here

[These are so that I can add those values to the schematic.]

(c) wire in the soft starter according to the last schematic that I provided, so we can test if this stops the d1 contactor drop-out problem.

I currently have no idea why the brake did not work on some occasions, I wondered if the system which it mounted to the motor which is via bushes (brass) may snag and jam preventing the brake from working but other than that it has to be a quirk somewhere in the electronics, contactors, capacitor etc.

The one change since the last testing is a new capacitor so maybe it might just be as simple as that?

Will hook up the rectifier and soft starter today and see what happens and report back, be nice to finally get the dodgy PS out of the equation too.

 

[ballen]

Hi Marc,

I currently have no idea why the brake did not work on some occasions, I wondered if the system which it mounted to the motor which is via bushes (brass) may snag and jam preventing the brake from working

I don't follow what you mean here.

but other than that it has to be a quirk somewhere in the electronics, contactors, capacitor etc.
The one change since the last testing is a new capacitor so maybe it might just be as simple as that?

It's hard to see how the capacitor could have this effect. I think it's in the circuit to make a critically-damped RLC circuit from the resistance r1, the inductance of the brake, and the capacitor. This shortens the response time of the brake by tens of milliseconds, but has no effect on whether it turns on or off.

Another possibility is that somewhere in the wiring was a screw connection that wasn't tight or that was oxidised. In the process of tracing and testing you redid that flaky connection.

Will hook up the rectifier and soft starter today and see what happens and report back, be nice to finally get the dodgy PS out of the equation too.

I suggest one step at a time. First hook up the rectifier, test that brake is working, check voltages. If the voltage at the brake is too high, you can adjust resistor r1 to decrease the voltage. Make small changes not large ones! To decrease the voltage at the brake, adjust the resistor in a direction which increases the length of resistance wire in between the two connections to the resistor. Some contact cleaner on the resistor contact slider would also be a good idea (oxide).

Move on to the soft starter only after you are satisfied with the operation of the brake. For the soft starter:

(0) Check that we have not mixed up the c3 and c4. My understanding is that c3 is the low speed contactor and that c4 is the high speed contactor. To check this, switch the motor from zero into low speed mode, and verify that c3 closes.

(1) In wiring the soft starter, you will see that one of L1/L2/L3 is just a "straight wire". The other two currents are controlled. The "straight wire" connection should be used on the S/V pair of the c4 RST/UVW three-phase wires. This is so the soft starter is controlling the currents in the RT/UW wires, which are the same pair that feed the control transformer.

The Siemens documentation says "The SIRIUS 3RW30 and 3RW40 soft starters are two-phase controlled soft starters, in other words they are designed with two antiparallel thyristors in each of phases L1 and L3. Phase 2 is an uncontrolled phase, which is merely guided through the starter by a copper connection."

So in wiring the soft starter, use the L2/T2 pair of the soft starter in series with the S/V pair of contactor c4.

Cheers,
Bruce

 

[marcsO]

It sounds like the brake is now working as it should. If that is correct, then replace the PS with rectifier and retest.

PS: any idea why the brake is now reliable? what has changed??

If the brake is working correctly when operating with the rectifier in place of the PS, then

(a) measure the DC voltage across the +/- terminals of the rectifier with your voltmeter, and report that here

25.1VDC

(b) measure the DC voltage across the brake when the brake is turned on (terminals 16/17 of the terminal block) and report that here

9.1VDC

[These are so that I can add those values to the schematic.]

(c) wire in the soft starter according to the last schematic that I provided, so we can test if this stops the d1 contactor drop-out problem.

I wired in the soft start as per the last drawings however did not test it because when I tried to start the motor the brake was still on preventing it from starting. When you turn on the lathe now d1, d2 and c3 contactors all engage (with handle in zero position) which I am sure was not the case before, it appears when the lathe is asked to be turned on the brake circuit is not instructed to release.

 

[ballen]

Marc,

WAS THE RECTIFIER/BRAKE WORKING CORRECTLY WITHOUT THE SOFT STARTER. OR DID YOU DO BOTH THE RECTIFIER AND THE SOFT STARTER TOGETHER??

Something is wrong at the rectifier end, 25.1VDC seems too low, because you previously reported that the control transformer was providing 30VAC. This means that the rectifier output should be about 30 x 1.414 - 1.4 volts = 41VDC. (Important: be sure you are measuring VDC and not VAC. If your meter selects the wrong one automatically, figure out how to override that setting. If in doubt measure BOTH the AC and the DC voltage at both sets of connections.)

(0) One step at a time. If you did both rectifier and soft starter at the same time, get the soft starter out of there, since you may have misconnected it, thus messing up the rectifier/brake end.

Check the wiring of the rectifier. Did you connect the transformer 30V secondary to the correct terminals of the rectifier? It should go to the contacts labeled "AC" or with a wavy symbol next to them.

(1) Disconnect the DC (+/-) terminals of the rectifier
(2) Check that you have 30VAC on the AC terminals of the rectifier
(3) Check that you have about 40VDC on the DC terminals of the rectifier
(4) Now reconnect the DC terminals of the rectifier and check the DC voltage again. Has it dropped??

 

[marcsO]

Hi Marc,


I don't follow what you mean here.

Sorry can't make it much clearer, the brake unit is mounted on brass bushes which are new these allow the electromagnet to slide backwards and forwards when the magnet is energised, MAYBE these bushes are binding or preventing the brake releasing or engaging from time to time - is that any clearer?

It's hard to see how the capacitor could have this effect. I think it's in the circuit to make a critically-damped RLC circuit from the resistance r1, the inductance of the brake, and the capacitor. This shortens the response time of the brake by tens of milliseconds, but has no effect on whether it turns on or off.

Another possibility is that somewhere in the wiring was a screw connection that wasn't tight or that was oxidised. In the process of tracing and testing you redid that flaky connection.



I suggest one step at a time. First hook up the rectifier, test that brake is working, check voltages. If the voltage at the brake is too high, you can adjust resistor r1 to decrease the voltage. Make small changes not large ones! To decrease the voltage at the brake, adjust the resistor in a direction which increases the length of resistance wire in between the two connections to the resistor. Some contact cleaner on the resistor contact slider would also be a good idea (oxide).

Move on to the soft starter only after you are satisfied with the operation of the brake.

In wiring the soft starter, you will see that one of L1/L2/L3 is just a "straight wire". The other two currents are controlled. The "straight wire" connection should be used on the S/V pair of the RST/UVW three-phase wires. This is so the soft starter is controlling the currents in the RT/UW wires, which are the same ones that feed the control transformer.

From the photo I'm not sure which of the wires is the "straight through" one. Perhaps it is the L2/T2 pair. But this should be clear in the Siemens documentation for the soft starter.

Cheers,
Bruce

25.1VDC

9.1VDC

I wired in the soft start as per the last drawings however did not test it because when I tried to start the motor the brake was still on preventing it from starting. When you turn on the lathe now d1, d2 and c3 contactors all engage (with handle in zero position) which I am sure was not the case before, it appears when the lathe is asked to be turned on the brake circuit is not instructed to release.

Hi Marc,


I don't follow what you mean here.



It's hard to see how the capacitor could have this effect. I think it's in the circuit to make a critically-damped RLC circuit from the resistance r1, the inductance of the brake, and the capacitor. This shortens the response time of the brake by tens of milliseconds, but has no effect on whether it turns on or off.

Another possibility is that somewhere in the wiring was a screw connection that wasn't tight or that was oxidised. In the process of tracing and testing you redid that flaky connection.



I suggest one step at a time. First hook up the rectifier, test that brake is working, check voltages. If the voltage at the brake is too high, you can adjust resistor r1 to decrease the voltage. Make small changes not large ones! To decrease the voltage at the brake, adjust the resistor in a direction which increases the length of resistance wire in between the two connections to the resistor. Some contact cleaner on the resistor contact slider would also be a good idea (oxide).

Move on to the soft starter only after you are satisfied with the operation of the brake. For the soft starter:

(0) Check that we have not mixed up the c3 and c4. My understanding is that c3 is the low speed contactor and that c4 is the high speed contactor. To check this, switch the motor from zero into low speed mode, and verify that c3 closes.

(1) In wiring the soft starter, you will see that one of L1/L2/L3 is just a "straight wire". The other two currents are controlled. The "straight wire" connection should be used on the S/V pair of the c4 RST/UVW three-phase wires. This is so the soft starter is controlling the currents in the RT/UW wires, which are the same pair that feed the control transformer.

The Siemens documentation says "The SIRIUS 3RW30 and 3RW40 soft starters are two-phase controlled soft starters, in other words they are designed with two antiparallel thyristors in each of phases L1 and L3. Phase 2 is an uncontrolled phase, which is merely guided through the starter by a copper connection."

So in wiring the soft starter, use the L2/T2 pair of the soft starter in series with the S/V pair of contactor c4.

Cheers,
Bruce

I did not see this post before so whilst the original suggestion was to fit it I have now removed it again.
With the soft start removed the brake is working perfectly at 9.1VDC and I am happy to leave it there as its just below the suggested 10-11 VDC made by my contact.

 

[marcsO]

Hi I am getting frustrated with this stupid forum as posting reply to's is a PITA as it seems to make it very hard to follow the thread, find previous comments as they are hidden from view unless expanded, hopefully it's not just me but once you have hit 'reply' you cannot delete this action!

So copy and paste it is KISS ....

(1) Disconnect the DC (+/-) terminals of the rectifier
Done
(2) Check that you have 30VAC on the AC terminals of the rectifier
Yes 30.7VAC
(3) Check that you have about 40VDC on the DC terminals of the rectifier
Yes 41.4VDC
(4) Now reconnect the DC terminals of the rectifier and check the DC voltage again. Has it dropped??
Yes it has to 25.1VDC

 

[ballen]

(1) Disconnect the DC (+/-) terminals of the rectifier
Done
(2) Check that you have 30VAC on the AC terminals of the rectifier
Yes 30.7VAC
(3) Check that you have about 40VDC on the DC terminals of the rectifier
Yes 41.4VDC
(4) Now reconnect the DC terminals of the rectifier and check the DC voltage again. Has it dropped??
Yes it has to 25.1VDC

I do not understand this voltage drop. The transformer secondary is protected by a 6A fuse. Less than 2A is needed. The transformer should provide more than enough current to keep the DC voltage at 40VDC. One possibility is a bad connection or wire between the transfomer and the AC contacts of the bridge rectifier, or between the DC contacts of the bridge rectifier and the next point downstream. Check that your connections to the bridge rectifier are snug. Could the wire strands be broken inside one of the stranded wires?

After the DC voltage has dropped to 25.1VDC, what is the AC voltage at the AC terminals of the rectifier? Has it dropped well below 30VAC?

Try taking your other new capacitor and connect it across the plus and minus terminals of the bridge rectifier, plus to plus and minus to minus. Does that affect the DC voltage 25.1 VDC?

Do I understand the current status correctly? Without the slow starter installed, the brake circuit is now working correctly using the internal rectifier, but the DC voltage is lower than expected?

If you had an oscilliscope it would be a lot faster to figure this out.

 

[marcsO]

I do not understand this voltage drop. The transformer secondary is protected by a 6A fuse. Less than 2A is needed. The transformer should provide more than enough current to keep the DC voltage at 40VDC. One possibility is a bad connection or wire between the transfomer and the AC contacts of the bridge rectifier, or between the DC contacts of the bridge rectifier and the next point downstream. Check that your connections to the bridge rectifier are snug. Could the wire strands be broken inside one of the stranded wires?

The connections to the rectifier are snug, crimped terminals on fresh copper wire when I prepared the ends for the bolt fittings on the rectifier. Naturally what goes on inside any wires is not easy for me to check but overall the quality of the wiring is good with all wire ends crimped with a sleeve to ensure good contact.

After the DC voltage has dropped to 25.1VDC, what is the AC voltage at the AC terminals of the rectifier? Has it dropped well below 30VAC?

I did check this, and no still around the same 30VAC

Try taking your other new capacitor and connect it across the plus and minus terminals of the bridge rectifier, plus to plus and minus to minus. Does that affect the DC voltage 25.1 VDC?

Will try that later

Do I understand the current status correctly? Without the slow starter installed, the brake circuit is now working correctly using the internal rectifier, but the DC voltage is lower than expected?

Yes it is

If you had an oscilliscope it would be a lot faster to figure this out.

Well not being an electrician I don't own one, the fact I have two PS's is a bonus and these were only used to cut foam core rc jet wings!
If anyone on this forum owns a 135 could we ask them to check the voltages across the rectifier and report findings? Maybe it's normal especially as the resulting voltage to the brake is very close to the suggested max VDC.

 

[ballen]

I did check this, and no still around the same 30VAC

If you have 30VAC on the input of the rectifier, and only 25DC on the output of the rectifier, something is wrong with the input power. This is not normal.

Either the AC power has a waveform which is very non-sinusoidal, or the rectifier is broken. Maybe this is somehow related to the "ghost" power lead. Let's see if we can fix the behaviour.

Please swap your input power leads as follows:
R-> S
S->T
T->R
and see if that behavior persists. If it does, please swap a second time:
R-> S
S->T
T->R
and see if that behavior still persists. If neither of these raises the DC voltage to about 40VDC under load, then swap one more time to return to the current configuration.
R-> S
S->T
T->R

 

[marcsO]

Try taking your other new capacitor and connect it across the plus and minus terminals of the bridge rectifier, plus to plus and minus to minus. Does that affect the DC voltage 25.1 VDC?

Yes it does it now reads 33.9VDC
The input voltage from the transformer is now 30.1VAC
The voltage at 16/17 the brake terminals is now 12.2VDC

 

[ballen]

Try taking your other new capacitor and connect it across the plus and minus terminals of the bridge rectifier, plus to plus and minus to minus. Does that affect the DC voltage 25.1 VDC?

Yes it does it now reads 33.9VDC

The input voltage from the transformer is now 30.1VAC
The voltage at 16/17 the brake terminals is now 12.2VDC

OK, the waveform produced by your RPC is very non-sinusoidal. Install that capacitor permanently in place, as it will help to compensate for the bad RPC waveform. A good place to put it is across the plus-minus leads of the rectifier.

Longer term, I suggest that you order a larger capacitor, say 2000-5000 microfarads (at least a 50 volt rating) and then replace the 250uF across the bridge diode +/- by that larger capacitor. This will help to get the DC voltage up to where it should be. Below is an updated schematic with the 5000uF filter capacitor included.

In looking at the circuit further, I suggest that you add another metal oxide varistor (MOV, blue disk) across the safety solenoid. I've indicated it on the schematic below. Put it across terminal block contacts 18 and 19. This is to absorb the inductive transient generated when the safety solenoid current is switched off, preventing arcing in the d3 NC contacts.

If the brake and safety solenoid are now working correctly, let's move on to the soft starter.

First verify that c4 is indeed the high speed contactor, and that c3 is the low speed contactor.

You should install the soft starter as per the wiring diagram below, but let's do it one step at a time. First, just connect the control leads (1, A1 and A2) and verify that the lathe is still functioning as it did before the soft starter was connected. NOTE: I have changed the connection point for A1 compared with the earlier diagram. It should not matter, but this is more conservative.
A1 - terminal block 53
A2 - terminal block 50
1 - contactor c3/12

WARNING: IF THE SOFT STARTER HAS A JUMPER (WIRE) BETWEEN TERMINAL 1 AND TERMINAL A1, THEN REMOVE IT!!

If the lathe does not work as before, please give me a written description of what is happening. If the lathe still works as before, then connect the L1-3 and T1-3 terminals in series with the contactor c4 as shown below. Ensure that the the L2/T2 path in series with the S/V path.

 

[marcsO]

Added the 250uF capacitor across the rectifier for now, have ordered a 5000uF 50V (x2 for spare) capacitors to replace as suggested.

Adjusted the variable resistor for the brake down from 12.1VDC to 9.6VDC as this for me seemed a good starting point which I can adjust as required, it stops the chuck from 1000rpm in under a second.

Added the MOV across terminals 18 & 19 as suggested.

Wired in the soft start to the connection points as instructed, the small 'ready' light on the SS lights up when the lathe is powered up and the system works fine with brake still engaging and releasing as required.

No jumper present

c4 is the fast speed contactor

Next job is to wire up the SS in series to the fast feed wires from c4 using S/V across the L2/T2 terminals on the SS where S is wire number 10, on terminal 10, from c4, and V is wire number 10 from terminal 10 to motor.