Please read the procedure for replacing the IGBT's
carefully (fig. 3).
ohm
NOTE.
WARNING!
figure3
WARNING!
The 4 IGBT's are attached to 2 different dissipators and whenever
areplacement is required,both IGBT's should bereplaced.
- Unscrewthefour(4) nutsthat fix the dissipator onto thecard;
- unscrew the four (4) screws that fix the four (4) IGBT onto the
dissipator;
- unscrew the two (2) screws that fix the two diode bridges onto
thedissipator;
- remove the four (4) IGBT and the two (2) diode bridges by
unweldingthe reophores,then removetin from the p r i n t e d
plates;
- removedissipator from card.
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 R3, R4, R7, R8 could have burst and/or
diodes D11, D12, D15, D16 may be unable to function at the
correct Zener voltage (this should have shown up in the
preliminarytests);
- clean any irregularity or dirt from the dissipators. If the IGBT's
have burst the dissipators may have been irreversibly
damaged:inthis case theyshould be replaced;
- apply thermo-conductive 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
undertension near thecase).
- position the components on the dissipator with the fastening
screws, but donot tighten thescrewscompletely
- join the dissipator/component assembly to the printed board,
inserting all the rheofores in the bump contacts and the
threadedspacers on the4 attachment holes.
- attach the dissipators with the nuts and lock them once and for
allin the followingorder:
- the nuts fastening the dissipators to the printed circuit with a
torquewrench setting of2 Nm ±20%;
- the screws fastening the rectifiers to the dissipators with a
torquewrench setting of2 Nm ±20%;
- the screws fastening the IGBT's to the dissipators with a
torquewrench setting of1 Nm ±20%.
- solder the terminals taking care not to let the solder run along
them.
- on the component side cut away the protruding part of the
rheofores and check they are not shorted (especially the gate
andemitter).
The 4 IGBT's should belong to the same selection kit
suppliedbyTelwin.
- remove the 4 diodes by unsoldering the rheofores and also
removethe solder fromthe bumpcontacts on thePCB;
- clean any irregularities or dirt from the dissipators.If the diodes
haveburstthe dissipator maybe irreparablydamaged:in such a
caseit should bereplaced;
- apply thermoconductive paste following the general
instructions;
- place the dissipator with the new components on the bump
contacts of the PCB and fasten it down with the screws (torque
wrenchsetting 1 Nm20%);
- solder the terminals taking care not to let the solder run along
them;
- on the soldering side cut the protruding part of the rheofores
and make sure they have not shorted (between cathode and
anode).
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
underload.
A) Connect the machine to the static load generator (code
802110)using cablesfitted with the appropriatedinse connectors.
B) Set up the dual trace oscilloscope with the voltage probe
CH1x100 connected between the collector (probe) and the emitter
ofQ4 (earth) on the primary board ( ).
C) Pass the current probe of the Hall effect transducer along the
cable connecting the power transformer at faston CN10 with the
reference arrowpointing intoCN10.
D) Lastly, connect the Hall Probe and the current probe to the
oscilloscope.
E) Set up a multimeter in DC volt mode and connect the prods to
theOUT+ and OUT-dinse connections.
F) On the front panel set switch SW1 to SOFT (as low as it will
go).
the high frequency voltage will permanently damage
any instrument connected to the generator. Before proceeding
makevery sure that the fastons listed above are disconnected and
completelyisolated from oneanother.
st rd
TESTING THE MACHINE
1.1 Preparation for testing
7.2 Removing the hybrid board (fig. 3)
7.3 Removing the secondary board (fig. 4)
If the fault is in the hybrid board remove it from the primary board
asfollows:
with the primary board removed from the machine structure
unsolder the rheofores from the hybrid board on the soldering
side;
removethe solder fromthe bumpcontacts on thePCB;
removethe hybridboard from theprimaryboard;
for assemblyproceedin the reverseorder.
If the fault is in the hybrid board we strongly advise replacing it
withoutfurther intervention.
If the fault is in the secondary board, unless the dissipator has
been damaged by a destructiveexplosion of the diodes, the board
does not generally need to be removed and the diodes can be
replaced directly with the board mounted on the machine. In any
case, it should be specified that to remove it, it is necessary to
separatethe basefrom the machine structure as follows:
- with the machine disconnected from the main supply undo the 4
side screws (2 on the front and 2 on the back) that attach the
boardto the base;
- turn the machine upside down and undo the 2 screws fastening
thebase to thestructure;
- finallyremovethebase from thestructure.
Completeremovalofthe secondary boardfrom the structure:
- undo the 4 side screws fastening the board to the machine
structure;
- remove the 3 hexagonal-head screws that fasten the shunt and
connectthe powertransformer;
- disconnectthe wiringforthe thermostatic capsule.
for assemblyproceedin the reverseorder.
The 4 secondary DIODES are attached to the dissipator and
whenevera replacementis made,all 4 diodesshould be replaced:
make sure that resistor R1 and capacitor C1 of the snubber
aresoldered correctly ( ).
-
-
-
N.B.
N.B.
Take special note of the procedure for replacing the
secondary diodes:
N.B.
fig.3
-14-
TECHNOLOGY 150-170-200-186CE/GE
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