What is the difference between relay and contactor?
Technical Terms:
Relay – Widely used across various industries to refer to low and medium power components;
Contactor – More commonly used in high-power applications.
Unlike the hinged armature design commonly found in relays, the magnetic “motor” in a contactor typically operates through a plunger located at the center of the contactor coil.
In traditional fields, the distinction between relays and contactors has been well established – Relays were developed for use in various single-phase systems, such as automotive applications, motor control, industrial automation, and power load management; Contactors, on the other hand, were designed for three-phase networks, including motor starters, capacitor bank switching, and lighting systems.
As a committed player in the renewable energy sector, BSB Electric focuses on delivering high voltage DC contactors and relays tailored for industrial equipment in emerging renewable energy systems. Today, we will introduce contactors and relays specifically designed for use in high voltage applications.
👉 Learn what a high-voltage DC contactor is? Check out this article.
What are the applications of High Voltage (HV) relays and contactors?
High voltage relays and contactors are widely used in electric vehicles (EVs), EV charging infrastructure, energy storage systems, and various other power control applications. In hybrid and fully electric vehicles, high voltage (HV) relays and contactors are typically used in the following applications:
- Main Contactors:
Installed on the positive and negative lines of the traction battery, main contactors are responsible for connecting and disconnecting the high-voltage battery from the vehicle’s powertrain system. - Pre-charge Relays:
Used together with pre-charge resistors to protect the main contactors from inrush currents. They gradually charge the input capacitors of the power inverter to about 90–98% of the battery voltage before the main contactors close. - Charging Contactors:
Establish a connection between the on-board charger and the traction battery when the vehicle is plugged into a charging station. - Auxiliary Contactors:
Control additional high-voltage loads in the vehicle that are powered by the battery. A typical example is the electric cabin heater in fully electric vehicles, which replaces the waste-heat-based heating from internal combustion engines.
In addition to vehicle systems, HV contactors are also used in stationary applications such as DC fast charging stations, stationary battery storage systems, and uninterruptible power supplies (UPS).