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spuddevans:

--- Quote from: Bluechip on February 23, 2010, 06:32:09 PM ---One side of the 220v secondary is connected to frame earth it seems.

--- End quote ---

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:

--- Quote from: Bernd on February 24, 2010, 10:08:36 AM ---Andy,

I think you might be right.

Bernd

--- End quote ---

If I am, that'll be a first  :ddb: :ddb:

Andy

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

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 :D


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

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