The Sajo mill is here

[spuddevans]

One side of the 220v secondary is connected to frame earth it seems.

I dont know about 3ph systems, but isnt it true that on single phase systems protected with ELCB, if you short the neutral to earth it will trip the ELCB?

Could that be happening with the mill's emergancy stop system?


Just a thought.

Tim

[Bluechip]

Tim

Shouldn't really trip as earth and neutral are the same connection at the sub-station. Or even at you own consumer unit if you are on PME ( Protective Multiple Earth) as I am.

Will try to post a c-o-c.


Beware of ELCB and RCD. Not same. ELCB's are (IIRC) voltage operated whereas RCD's are current. Most in UK are RCD's .. Lot of stuff in earth faults and various means of knocking off the power under fault conditions.

Dave BC

c-o-c herewith ..

This should be read with some caution, it may NOT apply to every distribution system



It'a a damn long time since I did any of this for real, but ...

The (IIRC) High Voltage distribution is 3-wire Delta ( AKA Mesh ) and goes into the local Sub Station  transformer and gets stepped down in voltage and also connected Star ( AKA Wye ), as per LH diag. Which is where the Neutral and Earth appear.

RCD's
On the RH diag, we have a magnetic core, attached to which is some means of mechanically opening the breaker. Like a solenoid. So, assuming we have no fault, all the current goes from line thro' the top coil, load, lower coil, thence down the neutral return. The two coils are contra wound, and, as the currents are identical the magnetic pull generated by one coil is negated by the other. One is pushing the same amount as the other is pulling. Nothing happens. If we close the test switch, we get If (fault current) to ground. Both the load and fault current go thro the top coil, but only the load current thro lower coil. Not equal and opposite any more. Device will trip. Lights go out. Telly packs up. Women folk squawk piteously 'cos no Eastenders etc.
There are all sorts of ways of doing this, just one of many. Lots are 'transistor aided' or whatever.

Suggest you Google stuff like Star/Delta  RCD  PME etc.

That 220v on Trion's Mill should not trip any RCD if earthed. BUT, it may be the machine has been modified, with greater or lesser competence, at some time, and thus may not be to the cct.  It' s not possible to tell, I think he needs an Electrician ON SITE ...

Remote theorizing is fun, but has it's limits ..

Dave BC

[Bernd]

Andy,

I think you might be right.

Bernd

[andyf]

Andy,

I think you might be right.

Bernd

If I am, that'll be a first 

Andy

[Trion]

I must admit, I dont understand squat of the drawings and stuff posted. 3-phase is still just a word to me

But I had a lot of spare time this weekend, so I brought the wiring diagram with me. Long story short, the only place where the emergency stop switch is shown in the diagram is as a holding switch PB1 on the control current diagram. It seems to have no other function than to hold the current for the rest of the switches, so if it is pressed nothing will work. Why this causes current to go to ground is rather confusing. Will just have to see what my electrician has to say to it..



On another note, I have made a small investments during the recent days


Yup, it's a 2mm thick rubber foil which is going to be my combined y-z-axis way cover!

[Bernd]

This is a bit amazing to me. They are using 220volt control circuit. One would think that they would have used some smaller voltage. But anyway I ramble.

It looks like your PB1 should only have two wires on it. If there are more than I'd say there is a wiring problem. The parts labled OL1, OL2, etc. are the motor overloads. If the amparge is exceeded on any of these the machine goes into "emergency stop". I would find one of those OL's in the panel box. They should be able to be tripped manually. If they can try one. The machine should shut down. If it does and nothing else turns off, like you descibrd before then I'd say your PB1 is the sorurce of your problem.

One of the reasons I'm so interested in this is that I used to do a bit of trouble shooting on the machines in the place I worked at. Used to do it over the phone sometimes. So I want to see if I can trouble shoot a machine via the internet. Call it a challenge. 

Bernd

[AdeV]

Is it possible that when PB1 is released, it's causing a spike in transformer T1, which is tripping the ELCB? Or, maybe PB1 is faulty, and is (briefly, perhaps) connecting live to earth as it disconnects, again tripping the ELCB. I presume that PB1 is earthed on its chassis.

[andyf]

I must admit, I dont understand squat of the drawings and stuff posted. 3-phase is still just a word to me...
On another note, I have made a small investments during the recent days .....
Yup, it's a 2mm thick rubber foil which is going to be my combined y-z-axis way cover!

Until the electrical problem is solved, it might be a good idea to put the rubber mat on the floor and stand on it 

Andy

[John Hill]

Here is something you could try...

Run the machine and stop it with the emergency stop button.  

Then unplug the machine and test for continuity (i.e. resistance) between the earth pin of the plug and each of the other two lines.

There should be no circuit between earth and phase pin.

There should be no circuit between earth and neutral.

There should be no circuit either between phase and neutral when everything is turned off.

There MUST be a circuit between the earth pin and the exposed metal of the machine.

If it fails any of these tests it is unsafe and the attendance of an expert is required, in my opinion.

I suspect that whatever is happening it is just a very short spike on the earth lead which your earth leakage circuit breaker is sensitive to.  The pulse is probably coming from the collapse of magnetic fields in motors or relay coils.

An easy solution may be to put some ferrite beads on the earth lead,  you can buy these and you might have seen them moulded on to the cable to VDU displays etc.

[Darren]

Is there a neutral, how are the two transformers fed?

[Trion]

Ok, I wasn't sure if I was even going to write this. It's a bit embarassing to say the least..
I had the electrician look at the machine the other day, and he litterarely laid his magic hands on it and immediately found the problem

I had the switch panel hanging out of it's mount, to facilitate the measurement of the wires. Once the machine was powered up, all he did was to touch the panel, quickly pull his hand back and state that the error was found. At first I didn't quite understand how he could know that, so obviously I had to try it out myself too
Afterwards, we measured 230V between the surface of the panel and ground..

Then we disconnected the wires from the emergency stop switch and simply joined them together. Voila, the current was gone. So all the time, it was just a bad switch.


I'm sorry to have let you down on your error seeking challenge


I have spent the rest of my spare time putting the engine of my Nissan back together. Will post a picture when it's finished.

Oh, I've also bought a bit of new stuff. Hydraulic oil for both knee and transmissions and 5 litres of unmixed coolant


Question:
- Where is a good place online to buy proper electrical switches?

[Darren]

Glad to hear you got that sorted, in more ways then one 

[Bernd]

Hey Trion,

Glad it was a simple fix. No dissapointment here. Sometimes problems are just that simple. We always seem to lookd for more complicated answers.

Bernd

[jatt]

So live chassis eh?  Doh   

At one stage used to repair teletypewriters.  Always used to plug em into the bench switch on and then turn on the circuit breaker from a safe distance.  If it tripped u know u gotta problem in the power supply.

It wasnt uncommon to find one that had a live chassis.     

[framey]

Question:
- Where is a good place online to buy proper electrical switches?

try rswww.com they might have a branch where you are

[andyf]

Question:
- Where is a good place online to buy proper electrical switches?

try rswww.com they might have a branch where you are

RS have a presence in Norway: http://no.rs-online.com/web/
I don't know about Norway, but they have a number of branches in the UK - there's one about 6 miles/10km from me, where I call in occasioally to buy stuff over the counter. They aren't cheap, but as far as I can tell from my limited experience, it's good quality stuff from reputable manufacturers.

They started life as an outfit called Radio Spares, but don't like to be reminded of that.

Andy

[LA3PNA]

Hello. Nice milling machine.
RS in Norway don't realy like to talk to private custumers with small orders. They tend to be slow moving and not have any custumer service.
You could try Elfa: http://www.elfa.se/no/ They also have an outlet in Oslo.

Where in Norway are you located?

Br.
Thomas.

[LA3PNA]

An other ting to note:
Norway have an IT grounding network instead of the TN network used elswhere. So as long as you don't have 400V then the machine seems correct.

BR
Thomas.

[Bluechip]

Hi Folks

Maybe this outfit have a presence in Norway ?

Some pics. to look at anyway ...   

http://uk.farnell.com/jsp/search/results.jsp?N=500006+1000192&Ntk=gensearch_001&Ntt=emergency+stop&Ntx=mode+matchallpartial&isGoback=false&isRedirect=false

Dave BC

[Trion]

Thanks for the replies guys
I have had quite a bit of bad experience buying from larger norwegian companies, and have found buying online to be both cheaper and faster, even if I buy the parts in the USA. The farnell site looks good, after a bit of research of what I need, I should be ready to order a few bits. I might even add a emergency stop to the lathe while I'm at it!

LA3PNA: I live just south of Stavanger. You know, where we are supposed to have 2-3 days of snow each year, not 2-3 friggin months

On another note, I said I'd post a picture when the Nissan is running, and guess what happened yesterday?

[Bluechip]

Trion

Does this make better sense?

http://no.farnell.com/

Appears they do Nowegian anyway ..

Now why didn't I see this first time ?    Should have got the dog to do it ... more reliable.

Dave BC

[Trion]

Thanks, I'll look into that when the founds are back to normal again.

Speaking of founds, I figured it was about time to make some poor mans T-slot studs. I found a suiting piece of steel from the shelf, and put it in the saw


Cut of two even pieces of flat steel, aswell as to pieces of M14 threaded bar


Drilled holes into the plates


And dug out my tig welder, to try welding some steel


And on the other side


After a bit of snow-hardening


And ready for use


So now the vise is finally fastened to the table


But only by two bolts, as none of the other fixation points fit the slots. I also had to have the vise hanging over the table like that, to be able to clamp something in it and not have the table wound out all the way on the Y-axis.

[DMIOM]

.....So now the vise is finally fastened to the table ......
But only by two bolts, as none of the other fixation points fit the slots. I also had to have the vise hanging over the table like that, to be able to clamp something in it and not have the table wound out all the way on the Y-axis....

IF you want the vice more central in Y, you may find you can slide the head back a little on its ram? (and equally out again for wider workpieces)  - at least I think that's a slide I can see hiding under the bride's veil 

Dave

[Darren]

That's a big vice 

[Davo J]

Hi,
I have been following this thread from the beginning, keep up the good work.
With the vise you could put some hold downs at the head of the vice, in the first T slot closest to the column, it would help with the weight of the overhang on the other end.
Davo