Belleville Washers Used in Solar Disconnect Switches

Belleville washers are used in disconnect boxes for utility-scale solar projects operating at 400–600 A and 1500–2000 V.

Belleville washers are installed on the aluminum lug connections at the input and output terminals of the disconnect switch. Their main function is to maintain a stable clamping force between the electrical contact surfaces.

In high-current electrical connections, maintaining stable contact pressure is critical for long-term reliability.

 

During operation, the connection is affected by:

• Aluminum material creep
• Thermal cycling
• Thermal expansion and contraction
• Mechanical vibration

These factors can gradually reduce the bolt preload and contact pressure.

A reduction in contact force may increase electrical resistance, causing additional heat generation and potential connection failure.

 

Function of Belleville Washers

Belleville washer acts as an elastic preload element.

During installation, Belleville washer is compressed and generates a spring force. During service, it compensates for dimensional changes caused by temperature variation, material relaxation, and vibration.

This helps to:

• Maintain constant clamping force
• Reduce loss of bolt preload
• Keep stable electrical contact resistance
• Improve long-term connection reliability