Contactors and load ratings can be a bit of a minefield when trying to decide which contactor or relay is suitable for your specific application. Some manufacturers and service engineers refer to the resistive loading values known as AC-1, while others refer to the inductive loading values known as AC-3, these values differ depending on load type and voltage. Operating coil voltages and auxiliary contacts can also vary widely across any given range of contactors. Care should be taken to ensure you have the correct operating coil voltage, contact configuration and amperage rating.
AC-1 Versus AC-3 Electrical AMP Rating There are two main types of amperage ratings that are used for contactors.
AC-1 rating, which is always higher than the AC-3 rating and is used for resistive loads such as heating elements and simple loads where the current draw is either on or off and does not fluctuate or spike under normal operations.
AC-3 rating, this rating is used for inductive loads such as motors where the starting current and breaking current can surge or spike and be higher than normal 'running' current.
Why is this important? Knowing which rating you need is important when replacing a contactor. You may look at the side of a contactor and see a rating of 22 AMPS and think you simply need any 22 AMP contactor. While that may be the case, it would depend on whether that 22 amp rating refers to AC-1 or AC-3. For example, the Eaton DILM9-10-EA model of contactor is rated for 22 AMPS AC-1 but only 9 AMPS AC-3.
Any questions about the item please don’t hesitate to ask!