Low heat generation contributes to higher output of EV chargers G9KC 40A, 4-pole PCB Power Relay

With the acceleration of the spread of electric vehicles (EVs), demand is increasing for high-performance EV chargers that can use energy more effectively and without waste. This presentation introduces examples of solutions to equipment design challenges to realize these customer needs.

OMRON's relays: Low contact resistance & low heat generation => Value provided to EV chargers: (Suppresses temperature rise inside the housing and extends the life of equipment、Increases the output of equipment to reduce charging time、Makes equipment smaller and lighter、Saves labor by automating production) Compliant with EV charging related standard IEC6295

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AC EV Charger Trend

The trend in AC EV chargers include the need for higher output to reduce charging time, increased current, and three-phase compatibility. In addition, stationary AC EV chargers used in general households and commercial facilities require compact, slim, and lightweight equipment design in terms of installation, design, as well as improved productivity and cost reduction during assembly.

Trend towards higher output AC EV chargers

Single-phase: 3.6kW (230v/16A) => 7.4kW (230v/32A) Higher output (Globally common). 9.6-12kW (240v/40-50A) => 19kW (240v/80A) Higher output (Housing, commercial facilities, and offices in the U.S, etc.). Three-phase: 11kW (400v/16A) => 22kW (400v/32A) Higher output (Housing, commercial facilities, and offices in Europe, etc.).

Note: According to OMRON's research in March 2024

AC EV Charger Design Challenges

(1) Avoiding a decrease in charging capability (issues when using power relays)

One of the challenges in increasing the output of AC EV chargers is the rise in temperature inside the housing due to heat generation of components. When the internal temperature of the equipment rises, the charging current suppression circuit operates, resulting in longer charging time and lower efficiency. In particular, relays tend to have higher contact resistance than contactors, so large currents generate more heat.
EV chargers are generally installed outdoors, and their housings are basically almost completely sealed to prevent water from entering. In addition, as chargers become smaller and slimmer, their housings become smaller, making it even more likely for the internal temperature to rise.

Heat generation in relay => Current suppression circuit operation => Extension of charging time

(2) Cost reduction of equipment, downsizing and weight reduction (issues when using a contactor)

In some cases, contactors are used to interrupt high-capacity circuits such as EV chargers. However, contactors are generally cable-wired, so there are issues with assembly productivity, such as the amount of wiring work required and the need to check for screw tightening and incorrect wiring. Furthermore, contactors are large in size and are not effective in designing smaller, slimmer, and lighter equipment.

To solve this issue, it is necessary to select a relay with low contact resistance that will reduce heat generation.

OMRON Products: Value Provided by G9KC

EV chargers compatible with three-phase, which are capable of supplying a large amount of power with high efficiency, are beginning to spread in residential housing in Europe, as well as in housing complexes, commercial facilities, and business establishments around the world.
In addition, higher output (22 kW [400 VAC/32 A 3Φ], etc.) is making steady progress to reduce charging time.

Typical Configuration of 3-phase AC EV Charging Station

OMRON offers the compact 4-pole PCB power relay: G9KC that solves the issue with this three-phase EV chargers.

Value provided by power relay G9KC

(1) Longer equipment life through reduced thermal stress

The G9KC has low contact resistance (initial value: 6 mΩ or less), which suppresses heat generation. This helps suppress local temperature rise in the charger housing, reduce the deterioration rate and failure risk of surrounding components due to heat, and extend the service life of the equipment. It also increases flexibility in PCB design.

・Click here for details on test data and other information regarding low contact resistance

(2) Reduced charging time due to higher output of equipment

The G9KC generates low heat and suppresses the temperature rise inside the charger housing, which helps suppress charging current and avoid a reduction in charging capability due to overheating, contributing to the reduction of the design charging time.

(3) Contributing to smaller and slimmer chargers

By switching the contactor to the compact power relay G9KC, the equipment housing can be made smaller and slimmer. When the charger housing size (surface area) is smaller, the temperature rises more easily and the allowable heat generation becomes lower, so a low-heat-generating relay with low contact resistance is effective in making the charger smaller and slimmer.

(4) Contributing to automated production and labor saving of chargers

By switching from the contactor to the PCB-mountable power relay G9KC, production can be automated.
Reducing wiring man-hours and eliminating wiring mistakes can significantly improve productivity and reduce costs.

・Click here for temperature simulation data

G9KC specifications

Item Specification Remarks
Contact form 4PST-NO (4a)
4PST-NO (4a) + SPST-NC (1b)
Auxiliary contact: IEC 60947-4-1
Compliant with mirror contact structure
Contact rating 480 VAC, 40 A / 277 VAC, 32 A Main contact
Contact resistance 6 mΩ max. Main contact, Initial value (23°C)
Contact gap 3.6 mm min. Main contact,
Compliant with EV charger standards IEC61851-1 and others
Electrical durability 277 VAC, 32 A  50,000 times
480 VAC, 40 A  30,000 times
Main contact,
Switching frequency: 1 second ON - 9 seconds OFF
Dimensions W35 mm × L58 mm × H47 mm Average dimensions
Terminal shape PCB Terminals
Certified standards UL/C-UL, EN/IEC, CQC

・Refer to the latest G9KC datasheet for details.

Use for Other Applications

The power relay G9KC can be used for input/output switching of various devices as well as AC EV chargers.



Uninterruptible power supply

Energy storage

quick charger

* For applications for energy-related equipment, see Solutions for the Energy Market.

Related Contents

G9KC Power Relay Product Page

You can download data sheets, related contents, etc. for this product.

G9KC Power Relay White Paper

You can view detailed information about G9KC (market trends, applications, features and specifications, usage, performance data, etc.). Use this information for your design consideration.

Solutions for Energy Markets

Products for energy-related equipment such as EV charging facilities, PV inverters, and energy storage systems are introduced.

High-Capacity Relay Technical Support Page

Our technical professionals explain in detail about “What is difficult to understand” when using PCB power relays with high currents and large voltages, including counter electromotive voltage, holding voltage application circuits, effects of the magnetic field, and precautions when connecting in series or parallel.


FAQs for Engineers

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