Wednesday, April 9, 2014

Electrical Contactors AC1, AC2, AC3, AC4

Electrical Contactors Utilization Categories:-

Electrical Contactors are categorized according to the current making and breaking values for contactors.
This will depend on the following:

  1. The type of load to be controlled (Inductive load, Lighting load, Motor load, Resistive load, Capacitive load)
  2. The operating cycle conditions.
For any applications there are different contactors available depending upon load application which every electrical engineer you must know before designing any systems. 

You may have often seen the ratings described on contactor name plate depicting various parameters. One of most important to be considered are as described in this article. 

  • AC1 - These type of contactors are used for Non-inductive or slightly inductive loads they are used for Heaters which are resistive loads.
  • AC2 - These type of contactors are used in Starting of slip-ring motors
  • AC3 – They are particularly used for Starting of squirrel-cage motors and switching off only after the motor is up to speed.
  • AC4 - Starting of squirrel-cage motors with inching and plugging duty. Rapid Start/Stop.
  • AC11 - Auxiliary (control) circuits i.e. they don’t have power contacts.
  • AC-6a- Switching of Transformers.
  • AC-6b- Switching of Capacitor banks
Figure below shows the AC-3 contactor:-

AC-3 Contactor
You can see how name plate shows the AC-3 contactor applications at different Voltages.

Difference between AC1 and AC3 Contactors:-

There is most frequently asked question that what is difference between AC1 and AC3 contactor??
As clear from above it is very much clear that AC1 contactors are used for Non Inductive loads and are used for heaters , resistive loads.

But AC3 contactors are used for starting of Squirrel Cage Induction motors, They are also used for squirrel cage motors where breaking occurs while motor was running. There are so many examples of using of these contactors which are as below:-

Example of use: all squirrel cage motors, lifts, escalators, conveyors, bucket elevators, compressors, pumps, mixers, air conditioning units, etc.