The Shop > Tools
The Sajo mill is here
andyf:
:scratch: I wonder if the main relay which fires up everything on the machine is supposed to be wired up like a no-volt switch, holding itself on until current to its coil is interrupted by pressing the push-to break emergency stop which should be in series with the coil, but someone has managed to wire it up so that the emergency stop is acting as a push-to-make, in parallel with the coil. Then, virtually all the current which was going through the coil would be short-circuited direct from live (hot) to neutral (cold), which would not only de-energise the coil and open up the relay contacts, but also blow the supply fuse.
With the machine disconnected from the supply, a continuity tester could be used to establish whether the switch was in push-to-make or push-to-break mode, and whether pushing the switch was establishing a connection to neutral (or to earth).
Andy
John Hill:
I agree with Dave that the 'ground fuse' may be an earth leakage detector.
Now we do not know if that location has earthed neutral or not (we have earthed neutral in NZ) and it may be that some component is connected to phase and ground instead of phase and neutral but it is difficult to imagine why the fault only occurs at switch off.
It is a long guess but if the emergency stop switch is double pole it may be that someone thought it a good idea to ground the motor leads, or even the relay coil, during an emergency stop in which case the inductance of the motor or the relay coil may have enough back emf to trip an earth leakage breaker.
Bluechip:
The machine appears to be supplied from a 3Ph + Earth, two of the phases are picked off to supply T101 on photo 2 to give a 220v source.
This goes through the various switches to energise the contactor coils.
One side of the 220v secondary is connected to frame earth it seems.
On pic. 2 there is a 'PB 1' connected to the 220v tapping, in series with the overloads on the various contactors, which then enables 220v to go to the control switchgear and then to the various machine functions.
I cannot see, from this diag. where any ELCB, Trip, whatever, is connected. But then, I am not too good on Swedish or the somewhat non-standard symbols.
It would seem likely that PB1 is the EStop. Not certain though.
What is a 'BOMMOTOR' ?
'MATTNINGSMOTOR' ?
Tried to translate, got 'BAR MOTOR' ... handy for the legless ...
Which fuse(s) blow?
The input fuses appear to be 50A. If they're letting go, I shall maintain a discreet distance. :zap:
Dave BC
John Hill:
--- Quote from: Bluechip on February 23, 2010, 06:32:09 PM ---
The machine appears to be supplied from a 3Ph + Earth, two of the phases are picked off to supply T101 on photo 2 to give a 220v source.
This goes through the various switches to energise the contactor coils.
One side of the 220v secondary is connected to frame earth it seems.
--- End quote ---
Yes, I see that too but that is a transformer isolated DC circuit so its hard to imagine how that can cause an earth current. :scratch:
--- Quote ---On pic. 2 there is a 'PB 1' connected to the 220v tapping, in series with the overloads on the various contactors, which then enables 220v to go to the control switchgear and then to the various machine functions.
I cannot see, from this diag. where any ELCB, Trip, whatever, is connected. But then, I am not too good on Swedish or the somewhat non-standard symbols.
--- End quote ---
As the whole shop goes dark I assume the ELCB is in the main shop fuse box?
John
Trion:
I must say, I'm amazed! :nrocks:
To clear up some misunderstandings, what I call a ground fuse is in the electrical box of the building, supposed to prevent people from dying when touching a live wire and something that can lead to ground. The ground fuse is activated by only a few milli ampere. DIMON is absolutely correct :clap:
--- Quote from: DMIOM on February 23, 2010, 04:09:06 PM ---The reference to ground "fuse" may be what we poor non-Nynorsk/Bokmål speakers would refer to as a "Ground Fault Interrupter" or "Earth Leakage Trip" / "Earth Leakage Circuit Breaker".
--- End quote ---
The zero phase of the three phase is not ground on 400v systems, but I'm not sure how the 220v is. Ofcourse, this system is 220v..
BOMMOTOR - boom motor, the motor mounted in the boom driving the vertical head
MATNINGSMOTOR - feed motor
You seem to have looked more into this, than what I have done myself. I'm sitting at school now, and the teacher is talking about convergent solutions of cfd analysis. I think I ought to pay a bit of attention, will chime in on the electrical issue later today. :smart:
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