Possible Electrical Failures; Necessary Routine Maintenance; Theoretical Outline Of Plasma Cutting; Plasma Cutting Process - Selco Genesis 60 Instruction Manual

8.2 Possible electrical failures

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 yel-
low LED L1 and red LED L3 on)
Fails to transfer from pilot arc to
cutting arc
Lack of power output
See also chapter 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.

9.0 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 brus-
hes.
* Check the electric connections and all the connec-
tion cables.
For the maintenance or replacement of torch
componente 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.
CAUSE
- Incorrect mains supply
- Break in the contacts of the
torch button (check the connec-
tion of the torch attachment 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 cir-
cuits
- Possible problems in control cir-
cuits
- Arc sensors faulty
- Protective devices triggered (see
chapter on
"Functions of controls")
- Possible problems in control cir-
cuits
10.0 THEORETICAL OUTLINE OF PLASMA
CUTTING
A gas assumes the plasma state when it is brought to an extremely high
temperature and ionizes wholly or partly, thus becoming electrically
conductive.
Although the plasma exists in every electric arc, by the term "plasma arc"
we refer specifically to a torch for welding or cutting that uses an elec-
tric arc, made to pass through the constricting 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

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.

11.0 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 condi-
tion 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, 9, 10, we can see that the thick-
ness to be cut is inversely proportional to the cutting speed, and
that both these values can be increased with an increase in current.
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