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Exchange thyristors size H6
3ADW000488R0101 DCS880 Service manual e a
Install new thyristor
1. Ensure that the new thyristor is of the correct type (see
+ of this manual). Keep the semiconductor
and its surroundings clean.
Note:
Do not touch the polished surfaces of the thyristor.
2. Clean all parts with tissue paper moistened with solvent, which have had or will have contact with the
thyristor or each other (lower/upper heat sink). Do not clean the surfaces of grease too thoroughly, because
the aluminum surfaces will oxidize in a few seconds. Dry all surfaces.
3. Clean the polished surfaces of the semiconductor with a piece of tissue paper moistened with solvent. Dry
all surfaces. Spread a
thin
layer of conducting paste on both sides of the thyristor, if necessary use a rubber
spatula.
4. Connect the gate leads if possible.
5. Centre the thyristors by means of the spring pins.
Note:
Be sure that the thyristor is installed in the right direction. Do not pinch or cut the gate leads or any other
cable.
6. Turn the thyristor so that the gate leads point in the right direction.
7. Tighten the nuts of the mounting clamp by hand so that the clamp is in parallel with the contact surface of
the heat sinks.
Note:
The indicating spring is a very sensitive instrument and must be handled with care.
8. Tighten each nut in turn, half a turn at a time with the help of a ring spanner until the indicating spring clicks
into position “correct torque”. Do not tighten the screws any further.
Note:
The correct torque is indicated by means of the welded indicating spring.
9. Perform an OHM test to make sure the thyristor is ok.
10. Reconnect the DC-busbars, branch fuses and all other dismantled parts.
11. Perform an OHM test between U1, V1, W1 and C1, D1 to make sure the power part is ok.
