Disc (press-pack) mounting of SCRs In disc mounting of an SCR, how is the device clamped to the heat sinks?

Introduction / Context:
High-power SCRs often use press-pack (disc) packages, which rely on axial compression to ensure low thermal resistance and reliable electrical contact, especially in series/parallel stacks.

Given Data / Assumptions:

• Disc-type SCR with metallized contact faces.
• Dedicated clamping hardware is used to apply uniform pressure.
• Cooling is achieved through heat sinks on both sides.

Concept / Approach:
Press-pack mounting sandwiches the SCR between two heat sinks. The pressure ensures intimate contact, minimizing contact resistance and thermal impedance. This approach is robust under thermal cycling and is commonly used in traction, HVDC valves, and industrial drives.

Step-by-Step Solution:
Prepare two flat, clean heat sink faces.Insert the SCR between them, aligning terminals as specified.Apply and calibrate the specified clamping force.Achieve low thermal and electrical resistance paths through both sides.

Verification / Alternative check:
Manufacturer application notes specify required clamping forces and flatness tolerances for press-pack packages.

Why Other Options Are Wrong:

• Single-sided clamping is inadequate for disc types.
• “Low rating; no clamping” is false; ratings are typically high and clamping is essential.
• Adhesive attachment is not used for power SCRs.

Common Pitfalls:

• Incorrect clamping force causing damage or poor conduction.
• Dirty or warped surfaces raising thermal resistance.

Final Answer:
SCR is clamped between two disc-shaped heat sinks (press-pack)