Contactor selection in battery system

How to select a contactor?

Contactor selection is an iterative process that includes consideration of system specifications as well as failure scenarios. Most of the contactor manufacturers share necessary information in datasheets. Thus, a wise approach would be making a comparison table to cover basic specifications like thermal and mechanical initially.

What is a battery contactor?

In a battery the contactors are a switch that can be operated by the control system. They are essentially a relay. These contactors are designed to be able to break (switch off) the circuit under full load (maximum current and at maximum system voltage). There are two main types of contactors: Normally Open (NO) and Normally Closed (NC).

What is a pre-charge contactor & a series current limiting resistor?

The pre-charge contactor with a series current-limiting resistor is in parallel with the main positive contactor and used to charge the initially discharged DC link capacitor before closing the main contactors to avoid the high inrush current which might damage the battery, power contactors, and DC link capacitor.

What are the elements of a contactor?

A contactor has the following elements in its structure: an actuator coil, moving core, return spring, moving contact, at least two fixed contacts, and an arc chamber. The structure of a contactor is below: When we actuate the contactor coil, the moving core starts to move towards the fixed contacts.

How do contactors work?

The contactor manufacturers make the arc chamber (or arc chute) with a dielectric medium such as low pressure hydrogen or nitrogen gas . Thermal and mechanical conditions are some of the constraints for contactor selection. Like fuses, contactors work together with other system elements to protect the electrical system.

What is the difference between a contactor and a relay?

For simplicity, we can consider the term relay for low and medium power device while the term contactor for high power device. For coil structure perspective, the magnetic “motor” is typically realized with a plunger in the center of the coil body for contactors, as opposed to a hinged armature design, which is normally used for relays.