Install New Thyristor - ABB DCS800 Service Manual

58

Install new thyristor

1. Ensure that the new thyristor is of the correct type
semiconductor and its surroundings clean. If necessary clean them with a
piece of tissue paper moistened with solvent.
Note:
Do not touch the polished surfaces of the thyristor.
2. Clean the polished surfaces of the semiconductor with a piece of tissue paper
moistened with solvent. Dry all surfaces. Spread a thin layer of heat
conducting paste on both sides of the thyristor, if necessary use a rubber
spatula.
Prepare disk type thyristor
3. 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.
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 BCT's make sure, that gate A is in front (see fig.
page 53).
6. Connect the gate leads if possible.
7. Insert first the top DC-busbar plate and then the bottom one.
Exchange of Thyristors for Size D6
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3ADW000195R0501 DCS800 Service Manual e e
(see appendix A). Keep the
Gates of BCT on