1. Overheating of the Switch and Wire Contact Area

1.Loose Bolts or Failed Spring Washers:

Cause: Loose connection bolts or failed spring washers can increase contact resistance, leading to overheating.

Solution: Replace the failed spring washers promptly and tighten the connections.

2.Undersized Bolts:

Cause: Using undersized bolts can cause overheating at the connection points when the switch carries its rated current.

Solution: Select bolts based on appropriate current density. For copper bolts, the current density is 0.3 A/mm² for currents below 200A, and 0.1 A/mm² for currents below 600A. For iron bolts, M6, M8, M10, and M12 can be selected for currents of 50A, 100A, 150A, and 300A, respectively.

3.Galvanic Corrosion Between Different Metals:

Cause: Connecting different metals (such as aluminum wires and copper terminals) can lead to galvanic corrosion, increasing contact resistance and causing overheating.

Solution: Use copper-aluminum transition terminals and apply conductive paste at the connection points to prevent galvanic corrosion.

2. Overheating or Welding of Switch Contacts

1.Arc Damage to Blades and Contacts:

Cause: Arcing during operation can cause pitting or damage to the blades and contact points, leading to poor contact.

Solution: Grind the moving and static contact points to restore proper contact, but avoid excessive grinding.

2.Improper Pressure Adjustment of Spring in Iron-Cased Switches:

Cause: Incorrect spring pressure adjustment can cause poor contact between the switch contacts, leading to overheating or even welding.

Solution: Regularly check the elasticity of the spring and adjust the anti-loosening nuts or bolts as needed to ensure tight contact and proper switch operation.

3.Oxidation on Blade and Contact Surfaces:

Cause: The formation of an oxidation layer on the blade and contact surfaces can increase contact resistance.

Solution: Remove the oxidation layer from the blade and contact surfaces, and apply a thin layer of petroleum jelly to the contact areas to prevent further oxidation.

4.Insufficient Insertion Depth of Blade Contacts:

Cause: If the blade contacts do not insert deeply enough, it reduces the current-carrying capacity, leading to overheating or even welding of the contacts.

Solution: Adjust the lever operating mechanism so that the blade insertion depth meets the required specifications.

5.Operation with High-Load Equipment:

Cause: Operating large-capacity equipment under load can cause high current surges, resulting in arc flash between the moving and static contact points.

Solution: Strictly follow operating procedures, and avoid improper operation under load.

6.Overcrrent Due to Short Circuits:

Cause: During a short circuit, the high current may exceed the thermal stability of the switch, causing contact welding.

Solution: Eliminate the short circuit fault and replace the switch with one of a higher capacity. For lightly welded contacts, pry them apart and repair them for continued use. For severely welded contacts, replace them entirely.