A) Please read the procedure for replacing the IGBT's
carefully (fig. 4)
fig. 2B
fig. 2B
ohm
WARNING!
B) Please read the procedure for replacing the
secondary board diodes carefully (fig. 4)
N.B.
fig. 3
C) Please read the procedure for replacing the control
board (fig. 3)
WARNING!
WARNING!
A) Minimum load test:
fig. D;
The 2 IGBT's are attached to 2 different dissipators and
whenever a replacement is required, both IGBT's should be
replaced.
-
undo the screws attaching the dissipator to the board to
replace Q1.(
);
-
undo the screws attaching the dissipator to the board to
replace Q2 (
);
-
remove the 2 IGBT's Q1,Q2 and the 2 diodes D20, D14 by
unsoldering the rheofores and then clean the solder from
the printed circuit bump contacts;
-
remove the 2 dissipators from the board;
-
undo the screws locking the 2 IGBT's.
Before making the replacement make sure the components
piloting the IGBT's are not also damaged:
-
with the multimeter set in
mode make sure there is no
short circuit on the PCB between the 1 and 3 bump
contacts (between gate and emitter) corresponding to
each component;
-
alternatively, resistors R22 and R29 could have burst
and/or diodes D12, D15, D17 and D19 may be unable to
function at the correct Zener voltage (this should have
shown up in the preliminary tests);
-
clean any irregularity or dirt from the dissipators. If the
IGBT's have burst the dissipators may have been
irreversibly damaged: in this case they should be
replaced;
-
apply thermo-conductive grease following the general
instructions.- Insert the new IGBT's between the
dissipator and the spring, taking care not to damage the
component during assembly (the spring should be
inserted under pressure on the dissipator so as to lock the
component);
-
place the dissipators with the new IGBT's and primary
diodes D14 and D20 (
Make sure there is
insulation between the case of diode D20 and the
dissipator) in the PCB bump contacts, placing 4 spacers
between the dissipator and the PCB (2 for each dissipator)
and fasten them down with the screws (torque wrench
setting for screws 1 Nm ±20%);
-
solder the terminals taking care not to let the solder run
along them;
-
on the welding side cut away the protruding part of the
rheofores and check they are not shorted (between the
gate and emitter in particular).
The 3 SECONDARY DIODES (2 diodes for the Tecnica
Plasma 18) are attached to the same dissipator, and when a
replacement is required, all of them should be replaced:
-
undo the screws attaching the dissipator to the board, to
replace diodes D36, D37 and D38;
-
remove the 3 secondary diodes D36, D37 and D38,
unsoldering the rheofores and cleaning any solder from
the bump contacts on the board;
-
remove the dissipator from the board;
-
remove the spring locking the 3 diodes;
-
clean any irregularity or dirt from the dissipator. If the
diodes have burst the dissipator may have been
irreversibly damaged: in this case it should be replaced;
-
apply thermo-conductive grease following the general
instructions;
-
insert the new diodes between the dissipator and the
spring, taking care not to damage the component during
assembly (the screw should be inserted under pressure
on the dissipator so as to lock the component);
-
place the dissipator with the new components in the PCB
bump contacts and fasten them down with the screws
(torque wrench setting for screws 1 Nm ±20%);
-
solder the terminals taking care not to let the solder run
along them;
-
on the soldering side cut away the protruding part of the
rheofores and check they are not shorted (between
cathode and anode).
make sure resistor (R45) and capacitor (C43) on the
snubber have been soldered to the PCB correctly (
).
Whatever fault occurs in the control board, we strongly
recommend its replacement without attempts at repair.
To remove it, cut and then unsolder from the power board the
connector keeping it fixed perpendicular to the PCB, replace it
and re-solder the connector.
Tests should be carried out on the assembled machine before
closing it with the top cover. During tests with the machine in
operation never commute the selectors or activate the ohmic
load contactor.
Before proceeding to test the machine, we
should remind you that during these tests the power source is
powered and therefore the operator is exposed to the danger
of electric shock.
The tests given below are used to verify power source
operation under load.
A) Do not connect the compressed air supply to the power
source.
B) Connect the power source to the static load generator
using cables fitted with the appropriate dinse connectors
(code 802111).
C) Set up the dual trace oscilloscope, connecting probe CH1
x 100 to the collector of Q1 and the earth to the emitter of Q1,
probe CH2x10 to pin 9 of strip J8 (plasma control board) and
earth to connector J9.
D) Set up the multimeter in DC mode and connect the prods
to the OUT+ and OUT- bump contacts.
E) Connect the power supply cable to the 230Vac power
supply.
During tests the operator must avoid contact with
the metal parts of the torch because of the presence of
dangerous, high voltage.
-
set up the static load generator with the switch settings as
in the table in
-
on the front panel position the cutting current
potentiometer R42 to the minimum (turn the knob anti-
clockwise as far as it will go) and switch on the main
switch;
-
activate the static load generator, press the torch button
and make sure that:
-
the output current is +15Adc ±15%, and the output
voltage is +86Vdc ±5% for a time of 2 sec ±10%;
-
after 2 sec the output current changes to +7.5Adc
±15% and the output voltage is +83Vdc ±5%.
-
deactivate the resistive load and switch off the main
switch.
st
rd
1.1 Preparation for testing
1.2 Tests for the TECNICA PLASMA 31
TESTING THE MACHINE
- 14 -
TECNICA PLASMA 18 - 31
