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Exchange thyristors size H8
3ADW000488R0101 DCS880 Service manual e a
4-quadrant converter:
4. Remove all screws of the DC - busbars either above or below the fuses of the defective branches.
Note:
The connection is made with a screw socket, which may fall down, when all screws are removed.
5. Put a small piece of isolator (e.g. paper) between the DC-busbar and the heat sink to insulate the anti-
parallel thyristors from each other.
6. Find the defective thyristors by performing an OHM test (both polarities) over their heat sinks.
2-quadrant converter:
7. Find the defective thyristors by performing an OHM test (both polarities) over their heat sinks.
Note:
Because “Disc Type” semiconductors need a certain compression force to operate properly, a measurement
outside the clamped heat sinks might be wrong. To be sure which thyristor is broken change only one thyristor,
clamp the heat sinks again and repeat step three.
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