- On the board, removed from the machine, unscrew the 4 nuts
TESTING THE MACHINE
fastening the dissipators and the 8 screws fastening the IGBT’s and
diode bridges (figure 5).
The test should be carried out on the assembled machine before
- Disconnect the thermostat wiring from the connector JP1.
closing it with the top cover. During the tests with the machine in
- Before making the replacement check whether the components
operation never commute the selectors or activate the noninductive
piloting the IGBT's are also damaged:
load electromagnetic switch.
- with the multimeter on ohms make sure there is no short circuit
between the 1st and 3rd bump contacts of the printed circuit
Preparation for testing
(between gate and emitter) for each component.
A)
Using cables with suitable dinse sockets, connect the machine to the
- alternatively, the resistors R17, R19, R24, R45, R46, R47 could
static load generator
have burst and/or diodes D9, D14, D22 and D23 may be unable to
B)
Connect a voltage probe x100 between the collector (prod) and
function at the correct Zener voltage (this should have shown up in
emitter (earth) of Q5.
the preliminary tests).
C)
Pass the current probe of the Hall effect transducer along the cable
- Unsolder the components, clean the solder from the bump contacts
connecting the power transformer to the faston PIN2TRAFO (J2)
and separate the board components.
with the reference arrow entering J2.
- Clean any irregularity or dirt from the dissipators. If the IGBT's have
D)
Lastly, connect the Hall Probe and the voltage probe to the
burst the dissipators may have been irreversibly damaged: in this
oscilloscope.
case they should be replaced.
E)
Disconnect the jumper JP2 on the primary board.
- Apply thermoconductive grease following the general instructions.
- Prepare the components for replacement. For the IGBT's, bend the
rheofores at 90° (never bend and/or place the parts under tension
near the case).
- Position the components on the dissipator with the fastening screws,
but do not tighten the screws completely
G)
Disconnect the wiring connecting the control board (J3) and primary
- Join the dissipator/component assembly to the printed board,
board (J1) and replace it with the special test wiring as in
figure B
(as
inserting all the rheofores in the bump contacts and the threaded
before).
spacers on the 4 attachment holes.
H)
- Attach the dissipators with the nuts and lock them once and for all in
the following order:
I)
Connect the machine power supply cable to the 3-phase variac with
- the nuts fastening the dissipators to the printed circuit with a torque
variable output 0-500 Vac.
wrench setting of 2 Nm ±20%;
- the screws fastening the rectifiers to the dissipators with a torque
Recommended tests.
wrench setting of 2 Nm ±20%;
A)
No-load test:
- the screws fastening the IGBT's to the dissipators with a torque
- With the static load generator disconnected first switch on the HV
wrench setting of 1 Nm ±20%.
power supply and make sure that after a brief pause (green LED D8
- Solder the terminals taking care not to let the solder run along them.
and yellow LED D35 both lit up) the pre-charge relays K1 and K2
- On the component side cut away the protruding part of the rheofores
(figure 5)
commute and the fans start operating.
and check they are not shorted (especially the gate and emitter).
- Switch on the machine and the variac and bring the latter to 400 Vac.
- Check that the voltage and current wave forms displayed on the
NOTE.
The 6 IGBT's should belong to the same selection kit supplied by
oscilloscope resemble those in
figure F
.
Telwin.
B)
Removing the secondary board
(figure 6)
. Unless the dissipator is
damaged due to a destructive explosion of the diodes, in general it is
not necessary to remove the secondary board and the diodes can be
replaced directly on the board mounted on the machine. Anyway, if it
is necessary to remove it, undo the 4 screws attaching it to the
machine structure, remove the 3 hexagonal-head screws fastening
the shunt and connecting the power transformer then, lastly,
disconnect the thermostatic capsule wiring and make the
replacement.
Please read the procedure for replacing the secondary board
diodes carefully (figure 6):
- Turn the machine upside down, undo the screws fastening the
damaged components to the dissipator and unsolder the metal tab.
- Having removed the components, remove any dirt or irregularities
from the dissipator.
- Apply thermoconductive grease following the general instructions.
- Place the components on the dissipator coinciding with the soldering
areas and fasten them with the screws (torque wrench setting 1.4
Nm ±20%).
- Solder the tabs, taking care not to form short circuits with the solder.
NOTE.
Make sure that R1 and C1 (secondary snubber) are correctly
soldered to the printed circuit
- Switch off the machine, the variac and the HV power supply.
C)
Control board
- Disconnect the machine from the variac and the HV power supply.
If the fault is in the control board, we strongly advise its immediate
- Reset the jumper JP2 and the original wiring between the primary
replacement without further intervention.
(J1) and control (J3) boards.
B) Minimum load test:
- Set up the static load generator with the switch settings as in the
table in figure G, position the welding current potentiometer on the
F)
Connect the HV outlet of the HV power supply on the primary board
as follows (figure 5):
- (+) Positive (clamp) to the PIN of connector JP2 on the resistor
R75 side,
- (-) Negative (faston) to the negative faston of the diode bridge D19.
On the control board position the two potentiometers on minimum
(R72, R77) and position switch S1 on MMA.
Figure F
Amplitude tollerance:
÷10%
Frequency:
32,5Khz ÷ 10%
Current scale:
50mV=500mA
SUPERIOR 240 CE
15
