Selco Genesis 90, Руководство по ремонту

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4.8.2 Possible electrical failures
See also chapter 4.4.1 for problems with alarm code.
If you have any doubts or problems, do not hesitate to con-
sult your nearest technical service centre.
4.9 NECESSARY ROUTINE MAINTENANCE
Prevent metal powder from accumulating near the aeration fins
and over them.
Disconnect the power supply before every opera-
tion!
Carry out the following periodic controls on the
power source:
* Clean the power source inside by means of low-
pressure compressed air and soft bristel brushes.
* Check the electric connections and all the connec-
tion cables.
For the maintenance or replacement of torch com-
ponente and/or earth cables:
* Disconnect the power supply before every operation.
* Check the temperature of the componente and make
sure that they are not overheated.
* Always use gloves in compliance with the safety stan-
dards.
* Use suitable spanners and tools.
* For torch maintenance, keep carefully to the directions
shown under instructions for use of the torch enclosed with
this manual.
Note: Failure to perform said maintenance will invalidate all
warranties and exempt the manufacturer from all liability.
4.10 THEORETICAL OUTLINE OF PLASMA CUTTING
A gas assumes the plasma state when it is brought to an extre-
mely high temperature and ionizes wholly or partly, thus beco-
ming electrically conductive.
Although the plasma exists in every electric arc, by the term
"plasma arc" we refer specifically to a torch for welding or cut-
ting that uses an electric arc, made to pass through the constric-
ting neck of a suitable nozzle, to heat a gas coming out of this,
so as to take it to the plasma state.
Fig. 5 Manual plasma cutting plant
4.10.1 Plasma cutting process
The cutting action is obtained when the plasma arc, made very
hot and highly concentrated by the design of the torch, transfers
onto the conductive piece to be cut, closing the electrical circuit
with the generator. The material is first melted at a high tempe-
rature of the arc, and then removed by the high exit velocity of
the ionized gas from the nozzle.
The arc can have two different states: that of the transferred arc,
when the current passes through the piece to be cut, that of the
pilot arc or non-transferred arc, when this is sustained between
the electrode and the nozzle.
4.11 CUTTING SPECIFICATIONS
In plasma cutting, the thickness of the material to be cut, the
speed of cutting and the current supplied by the generator have
values which are related to each other; these depend on the
type and quality of the material, type of torch as well as the type
and condition of the electrode and nozzle, distance between
nozzle and piece, pressure and impurity of the compressed air,
cut quality required, temperature of the piece to be cut, etc.
In the diagrams as in Fig. 6, 7, 8 we can see that the thickness
to be cut is inversely proportional to the cutting speed, and that
both these values can be increased with an increase in current.
12 Description of operation of the power sources
Fault
Apparatus fails to come on
(Yellow LED L1 off)
Pilot arc fails to ignite (with
yellow LED L1 on)
Pilot arc fails to ignite (with
yellow LED L1 and red LED
L3 on)
Fails to transfer from pilot arc
to cutting arc
Lack of power output
Cause
- Incorrect mains supply
- Break in the contacts of the
torch button (check the con-
nection of the torch attach-
ment is working after having
cut off the power supply)
- Torch parts subject to wear
out of action
- Air pressure too high
- Possible problems in control
circuits
- Possible problems in control
circuits
- Arc sensors faulty
- Protective devices triggered
(see chapter on
"Functions of controls")
- Possible problems in control
circuits