Contactors and IEC Classification

Selecting the right contactors and relays for use in motor control and other industrial circuits is extremely important.  It is important that the contactors are chosen keeping in mind the equipment which is to be connected to it and the current it needs to interrupt.

A contactor which is chosen for a heater circuit cannot be used in a motor circuit of the same current rating.
The International Electrotechnical Commission (IEC) has categorized contactors into the following categories.

IEC Categories Applications
Non-inductive or slightly inductive rows
AC2 Starting of slip-ring motor
AC3 Starting of squirrel-cage motors and switching off only
after the motor is up to speed. This contactor is designed
to make Locked Rotor  Current and  Break the Full Load Current.
AC3 Starting of squirrel-cage motors with inching and
plugging duty. Rapid Start/Stop. (Make and Break Locked Rotor
AC11 For use in Auxiliary (control) circuits