High Voltage Relay & Contactor Selector Guide
For energy applications
In the High Voltage Relay & Contactor Selector Guide, we explore our extensive selection of high voltage Relays and Contactors from our many supplier partners as well as how and where to use them in your designs.
We focus on higher-power Energy applications such as:
EV Charging
On-Board Charging
Solar Inverters
Energy Storage Systems
We also address why they are needed from a regulatory and safety perspective.
More information
What is a relay?
A relay is an electronically operated switch that is remotely activated by an electromagnet which pulls a set of contacts to either make or break a circuit.
Electromechanical relays are typically used for:
- Electrical isolation
- Controlling power in manufacturing, energy and transportation applications
- switching smaller current values in a control circuit, such as in building automation technology and control panels.
A relay is necessary to safeguard the electrical system against excessive voltage or current, ensuring the safe functioning of any connected equipment.
Without a relay, the electrical system may be vulnerable to damage from overvoltage or overcurrent situations, potentially leading to equipment malfunction or failure.
What is a contactor?
A contactor is essentially a heavy-duty version of a relay, typically controlled by a circuit that has far less power than the switched circuit. While considered a special type of relay, the essential difference between a relay and a contactor is that a contactor is used for applications which require higher current carrying capacity.
Electrical contactors are typically fitted with a normally open (NO) contact, and they suppress the arc that is produced when interrupting heavy-duty motor currents. They can handle currents that exceed 5000 amperes and high power exceeding 100 kW.
Electrical contactors are typically needed for high-current load applications such as:
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A contactor is crucial in electrical systems for managing the power supply to equipment, facilitating efficient and safe operation.
Without a contactor, controlling the flow of electricity to devices becomes difficult, potentially leading to uncontrolled power distribution, equipment damage, or safety hazards such as electrical fires or shocks.
When to use a contactor vs a relay
Relay
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A rule of thumb (until recently) was that relays were suitable for applications with less than 10A of current and up to 250 VAC with 1-phase circuits, and contactors were suitable for applications with currents above 10A and up to 1000 VAC with 1 or 3 phase circuits.
However, with the rise in electrification applications such as Electric Vehicles and Electric Vehicle Charging as well as Battery Energy Storage Systems, we now see a trend where manufacturers are designing much higher power relays as an alternative to contactors but with the benefits of the relay, known as High Power Relays.
Advantages of high power relays vs contactors
- Lower Cost Higher Switching capacity
- Smaller in size High Short Circuit Current Rating
- PCB Mounted More auxillary contact options
- Fast Switching speed Heavy duty cycle use
- Lower Coil Power
There may be some overlap in the voltage ratings of high-power relays and contactors. However, it's important to note that their intended applications set them apart.
High-voltage relays are designed for high-voltage applications with a focus on voltage isolation and can be board-mounted for ease of production, whereas contactors are designed for high-current, high-voltage applications and are usually panel-mounted or rail-mounted in control panels or electrical enclosures due to their size and high-current capabilities.