Breaking capacity expert sheet

Breaking capacity

To guarantee the safety of users and installations, a plug socket-outlet must be able to:

Prevent accidental or unintentional removal of a plug from its socket
Resist accidental closure on fault current (blocked engine, damaged cable...)
Be connected and disconnected under normal load and in overload conditions (or in an emergency) or in the case of a machine with residual inductive current
Be short-circuit proof

Standard IEC/EN 60309-1 - Plug socket-outlets for industrial use

According to IEC/EN 60309-1, appliances without interlock must have sufficient breaking capacity. Compliance is checked by testing each appliance with a new complementary appliance.
Compliance with this standard is assessed by the same appliance passing the successive tests of sections 20 (breaking capacity), 21 (normal operation) and 22 (temperature rise). Any failure invalidates the entire set.

Standard IEC 60309-4 – Plug socket-outlets and couplers for industrial purposes – Part 4: Switch-controlled plugs, socket-outlets and couplers with or without interlock.

This standard applies to plug socket-outlets with a switching element, including those with a built-in circuit-breaking device. Section 20 of IEC/EN 60309-1 is applicable for compliance, with the following exception:

An electrical base or a mobile socket-outlet partnered with a switch without a locking device shall be tested with the switching device in the closed position.
A base or a mobile plug socket-outlet with an onboard switching device without an interlocking device must be tested twice:
- the first test with the switching device in the closed position (test of the base or mobile plug socket-outlet)
- a second time with the plug which operates the switching device still inserted in the base or mobile plug socket-outlet (switch test)

DECONTACTOR™ are covered by this standard.

Standard IEC 60947-3 – Part 3: Switches, disconnectors, switch-disconnectors and fuse-combination units.

Closing and breaking capacities: The rated closing and breaking capacities are given in relation to the rated voltage and current used and the category of use.