Telwin Nordika 3250 Bedienungsanleitung Seite 7

supporting it, as close as possible to the join being made. For welding
machines supplied with a terminal, the cable is connected to the terminal
with the symbol .
AC/DC Versions:
Almost all coated electrodes are connected to the positive pole (+) of
the power source; as an exception to the negative pole (-) for acid coated
electrodes.
WELDING OPERATIONS WITH DIRECT CURRENT
Connecting the electrode-holder clamp welding cable
On the end take a special terminal that is used to close the uncovered
part of the electrode.
This cable is connected to the terminal with the symbol (+).
Connecting the welding current return cable
This is connected to the piece being welded or to the metal bench
supporting it, as close as possible to the join being made.
This cable is connected to the terminal with the symbol (-).
WELDING OPERATIONS WITH ALTERNATING CURRENT:
Electrode-holder clamp cable and earth cable to either of the related
terminals ( ~ / ~ ).
TAKE THE GREATEST CARE TO CONNECT THE WELDING CABLES
CORRECTLY e.g. ( - ) / ~ or (+) / ~ ).
Warnings:
- Turn the welding cable connectors right down into the quick
connections (if present), to ensure a perfect electrical contact;
otherwise the connectors themselves will overheat, resulting in their
rapid deterioration and loss of e ciency.
- The welding cables should be as short as possible.
- Do not use metal structures which are not part of the workpiece to
substitute the return cable of the welding current: this could jeopardise
safety and result in poor welding.
6. WELDING: DESCRIPTION OF THE PROCEDURE
AC Versions:
These welding machines consist of a single phase drooping-type
transformer and are suitable for welding in alternating current with
coated electrodes (E43R type).
AC/DC Versions:
These welding machines are power sources for mixed current (direct and
alternating), which can be selected using the welding terminals, and are
suitable for arc welding using electrodes with various types of coating
(rutile, acid, basic).
To switch on the welding machine operate the main switch (Fig. B (1)).
The intensity of the supplied welding current can be adjusted
continuously, by means of a manually operated magnetic shunt (Fig.
B (4)). The value for the current setting, (I
graduated scale (Fig.B (2)) on the top or front panel. The corresponding
arc voltage (U ) for the current shown is given according to the following
2
relationship: U = (20 + 0.04 I
2 2
THERMOSTATIC PROTECTION
This welder is automatically protected from thermic overheating
(thermostat automatic re-start). When the windings reach performance
temperature, the protections cut o the supply circuit, igniting the yellow
lamp on the front panel (Fig. B (3)). After a few minutes' cooling the
protection will reopen the supply line and turn o the yellow lamp. The
welder is ready for further use.
WELDING
AC Versions:
- Use electrodes suitable for working in alternating current. Choose
the outlet for connecting the clamp cable according to the type of
electrode: 50V for rutile or acid electrodes; 70V is preferable for basic
electrodes.
AC/DC Versions:
- Use the alternating current terminals for welding with rutile-coated
electrodes (the most widely used and easiest to use and obtain). When
basic coated electrodes or electrodes for stainless steel have to be used,
utilise the direct current terminals, connecting the electrode-holder
cable to the positive terminal (+); under exceptional circumstances the
negative terminal (-) is used with acid or rutile coated electrodes.
- It is most important that the user refers to the maker's instructions
indicated on the stick electrode packaging. This will indicate the correct
polarity of the stick electrode and the most suitable current.
) can be read in amps on the
2
) V (EN 60974).
- The welding current must be regulated according to the diameter of
the electrode in use and the type of the joint to be carried out: see
below the currents corresponding to various electrode diameters:
Ø Electrode (mm)
1.6
2
2.5
3.2
4
5
6
- The user must consider that, according to the electrode diameter,
higher current values must be used for at welding, whereas for vertical
or overhead welds lower current values are necessary.
- In addition to being determined by the selected current intensity, the
mechanical characteristics of the welded join are determined by the
other welding parameters i.e. arc length, working rate and position,
electrode diameter and quality (to store the electrodes correctly keep
them dry and protected by suitable packaging or containers).
Welding procedure
- Holding the mask IN FRONT OF THE FACE, strike the electrode tip on the
workpiece as if you were striking a match. This is the correct strike-up
method.
WARNING: do not hit the electrode on the workpiece, this could
damage the electrode and make strike-up di cult.
- As soon as arc is ignited, try to maintain a distance from the workpiece
equal to the diameter of the electrode in use. Keep this distance as
much constant as possible for the duration of the weld. Remember
that the angle of the electrode as it advances should be of 20-30 grades
(Fig. H).
- At the end of the weld bead, bring the end of the electrode backward,
in order to ll the weld crater, quickly lift the electrode from the weld
pool to extinguish the arc.
CHARACTERISTICS OF THE WELD BEAD
7. MAINTENANCE
WARNING! BEFORE
OPERATIONS MAKE SURE THE WELDING MACHINE IS SWITCHED OFF
AND DISCONNECTED FROM THE MAIN POWER SUPPLY.
EXTRAORDINARY MAINTENANCE
EXTRAORDINARY MAINTENANCE MUST ONLY BE CARRIED OUT BY
TECHNICIANS WHO ARE EXPERT OR QUALIFIED IN THE ELECTRIC-
MECHANICAL FIELD, AND IN FULL RESPECT OF THE IEC/EN 60974-4
TECHNICAL DIRECTIVE.
WARNING! BEFORE REMOVING THE WELDING MACHINE
PANELS AND WORKING INSIDE THE MACHINE MAKE SURE THE
WELDING MACHINE IS SWITCHED OFF AND DISCONNECTED FROM
THE MAIN POWER SUPPLY OUTLET.
If checks are made inside the welding machine while it is live, this
may cause serious electric shock due to direct contact with live parts
and/or injury due to direct contact with moving parts.
- Inspect the welding machine regularly, with a frequency depending
on use and the dustiness of the environment, and remove the dust
deposited on the transformer, using a jet of dry compressed air (max.
10 bar).
- At the same time make sure the electrical connections are tight and
check the wiring for damage to the insulation.
- At the end of these operations re-assemble the panels of the welding
machine and screw the fastening screws right down.
- Never, ever carry out welding operations while the welding machine is
open.
- If necessary use a very thin layer of grease, at a high temperature, to
lubricate the moving parts of the regulators (threaded shaft, sliding
surfaces, shunts etc.).
- After having carried out maintenance or repairs, restore the connections
- 7 -
Welding current (A)
min. max.
25 50
40 80
60 110
80 160
120 200
150 250
200 350
Fig. I
CARRYING OUT MAINTENANCE