53
Exchange thyristors size H7
3ADW000488R0101 DCS880 Service manual e a
Install new thyristor
1. Ensure that the new thyristor is of the correct type (see Appendix 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. 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.
5. Turn the thyristor so that the gate leads point in the right direction. When changing BCTs make sure, that
gate A is in front (see Bidirectional-Controlled-Thyristors
).
6. Connect the gate leads if possible.
7. Insert first the top DC-busbar plate and then the bottom one.
Note:
The DC-busbar plates should line up with the adjacent heat sinks.
8. Reconnect the DC-busbars.
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