Connection To Mains Supply; Protection System; General Notes - Elettro CF MMA 770 Instruction Manual

2.2 CONNECTION TO MAINS SUPPLY

Before connecting the unit to the mains make sure that
mains voltage corresponds to the voltage of the welding
machine.
As regards the welding machines with two input voltages
(i.e. 230/400V or 240/415V etc.), voltage can be
changed by removing the switch knob (pos. 2 picture 2),
after unscrewing (pos. 1 picture 2) and by properly
setting the disc under the knob, after over - turning it
(pos. 3 picture 2).
The yellow-green lead is the protection wire, which is
connected to the casing of the machine and is to be
introduced into the ground pin of the plug. The system
shall be properly grounded and provided with suitable
leads and protections, according to the regulations in
force.
The required power ranges from 4,5 to 8 kW depending
on the intensity of the current used.

2.3 PROTECTION SYSTEM

The unit is equipped with an internal protection, which
assures a lasting proper operation.
A thermostat situated on the secondary winding of the
transformer opens the supply circuit in case of
overheating, assuring the protection of the transformer.
In this case, it is necessary to await some minutes to
have the reset of the thermostat.
OVER VOLTAGE CAN DAMAGE THE UNIT.
2.4 UNIT DESCRIPTION
2.4.1 Picture 3 description
1a) 70V electrode holder welding cable connection.
1b) 50V electrode holder welding cable connection.
2) Earth welding cable connection.
3) Hand – wheel for the current adjustment.
4) Input supply cable.
5) Switch.
6) Pilot light.
7) Thermostat pilot light.
2.4.2 Pictures 3a and 3b description
A) Main selector switch: turns the machine on or off.
The voltage change disk is located beneath the
knob.
B) Complete handle.
C) Setting indicator : indicates the welding current to
which the machine is set.
D) Welding current adjustment knob: turn this knob
clockwise to increase the current intensity, or
counter-clockwise to decrease.
E) Positive terminal 70V.
F) Negative terminal.
G) On light: indicates that the machine is working.
H) Positive terminal 50V.
I) Thermostat pilot light : indicates the thermostat
intervention.
L) Cable holder.
M) Input power cable.

2.5 GENERAL NOTES

Before using this welding machine, carefully read the
CEI 26/9 CENELEC HD 407 and HD 433 standards and
also check insulation of cables, electrode holder clamp,
sockets and plugs and that the section and length of
welding cables are compatible with current used.
2.6 COATED ELECTRODE WELDING
Use electrode holder clamps in compliance with the
−
safety standards and without projecting tightening
screws.
Make sure that switch is in 0 position or not inserted
−
in supply socket then connect welding cables.
Welding circuit should not be deliberately placed in
−
direct or indirect contact with protection wire if not in
piece to be weld.
If earthing is deliberately made on the workpiece by
−
means of protection wire, the connection must be as
direct as possible, with the wire having a section at
least equal to the welding return current wire and
connected to the piece being worked on, in the same
place as the return wire, using the return wire
terminal or a second earth terminal close by.
All possible precautions must be taken in order to
−
avoid stray currents.
When taking voltage from a three-phase line, be
−
very careful when connecting supply cable earth
wire to the socket earth pole.
Connect supply cable. When mounting a plug, make
−
sure that its capacity is adequate and that the yellow-
green wire of the supply cable is connected to the
earth plug pin.
The capacity of magnetothermic switch or fuses in
−
series with mains supply should be more than or
equal to current I absorbed by the unit.
1
Absorbed current I
−
1
technical specifications on unit i.e. power supply
voltage U available.
1
Any extensions should have adequate sections for
−
absorbed current I .
1
Turn machine on with switch 5 picture 3 (A picture
−
3a).
WARNING : ELECTRIC SHOCK CAN KILL !
Do not touch live electric parts.
−
Do not touch weld output terminals when unit is
−
energised.
Do not touch electrode holder and earth clamp at the
−
same time.
Regulate current based on the diameter of the
−
electrode, welding position and type of joint to be
carried out. When
remember to turn unit off, and to remove electrode
from electrode holder.
2.7 ADVICE ABOUT WELDING
A good preparation of the wedges to be welded is
fundamental to get the best welding; it is also necessary
to remove all impurities (grease, paint, rust) from the
edges.
In order to prevent the strains of the piece owing to
shrinkage, in particular with thin thickness, before
starting the real welding we recommend to tack the
pieces on several spots at a distance of 200 mm approx.
from one another.
In the butt weldings for thickness up to 3 mm, keep the
pieces in contact; from 3 to 5 mm keep a gap of 1 to 2
mm (picture 4). For thickness from 5 to 15 mm the V set-
up required (picture5); over 15 mm make use of X set-up
(picture 6).
Adjust the welding current according to the diameter of
the electrode and the thickness of the piece to be
welded. Carry out this adjustment by rotating the
handwheel located on the front of the welding machine:
rotate counterclockwise to decrease and clockwise to
increase.
Spark starting put the point of the electrode at 2 mm
approx., from the spot to weld, with an angle of about
45° as to the welding plane; put the faceplate on and, by
rubbing, put the point of the electrode in contact with the
piece to be welded; always keep the same inclination. As
soon as the spark starts, move the electrode away by 1
is determined by reading the
finished welding, always
8