Install New Thyristor - ABB DCS 500B Service Manual

Chapter 5 - Exchange of Thyristors for Size A5

Install new thyristor

VI A
5 - 4
1. Ensure that the new thyristor is of the correct type
dix A). Keep the 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 thyris-
tor, if necessary use a rubber spatula.
3. Connect the gate leads if possible.
4. Clean all parts with tissue paper moistened with solvent, witch
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 aluminium surfaces will oxidise in a
few seconds. Dry all surfaces.
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 direc-
tion.
Loose
condition
TORQUE INDICATING SPRING
Insulating plate
Correct torque
Figure 5-3 Aluminium spring with welded indicating spring
3ADW000093R0701_DCS500B/DCS600_Service manual_e_g
Heatsink
DCS 500 / DCS 600 Service Manual
(see Appen-