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Research & Development High-capacity power relays for electronic control and switching circuit

| Author/ Editor: Panagiotis Venardos * / Erika Granath

Thanks to recent advances in the printed circuit board and relay technology, it’s not possible to run high currents and switches directly on the printed circuit board in many applications.

Increasing electrification and the associated changes in markets such as power generation, energy storage, and electromobility call for new solutions for energy management systems.
Increasing electrification and the associated changes in markets such as power generation, energy storage, and electromobility call for new solutions for energy management systems.
(Source: Public Domain / Pexels)

People are paying more and more attention to ecological and sustainable power generation. As a result, wind power, solar power, wave power, and other renewable types of energy are all hot topics in 2019. The proportion of electric vehicles on Europe's roads is growing at an ever-increasing rate. According to ACEA (European Automobile Manufacturers Association) statistics [1], the number of electric vehicles sold in the second quarter of 2019 rose by 35.6 percent compared to the same period last year.

Increasing electrification and the associated changes in markets such as power generation, energy storage, and electromobility call for new solutions for energy management systems. Previously, high loads were predominantly switched by contractors that were permanently wired in switch cabinets.

Thanks to new developments in printed circuit board technology (e.g. new multilayer boards or high-performance connectors) and sophisticated relay technology, it’s now possible to conduct and switch high currents directly on printed circuit boards.

However, this doesn’t mean that contractors and relays can be used interchangeably in a plug-and-play process. They’re fundamentally different switching elements. That said, they do have a lot in common. For example, both are remote-controlled electrical switches.

Electromechanical relays can be used to implement more compact and energy-efficient solutions in many areas. The total volume in cm³ has more than halved the last 20 years, while the power density has risen from around 0.8 to 1.1 KVA / cm³ since 2010. Today, it’s easier than ever to handle high loads with smaller and smaller relays.

High-capacity power relays for modern printed circuit board technology

When modern PCB technology is combined with the Panasonic Industry’s new HE series electromechanical relays high loads can be switched directly on the PCB. This means contractors in the control cabinet aren’t necessary in most cases.

The HE series is designed for loads up to 120 A (HE-N) and 1000 V DC (HE-V) at ambient temperatures up to 85°C. This makes the PCB relays suitable for high-performance applications such as solar inverters, car charging stations, or battery storage systems. The relay is no longer responsible for controlling a secondary contactor, instead, it becomes the central element since further contractors usually aren’t required.

Compared to contactors, the high-performance PCB relays are significantly more compact. The HE-S version, for example, integrates two NO contacts in an extremely small housing measuring 30 mm x 36 mm x 40 mm.

Image 1: The power relay HE-S' structure. With 3.2 milimeters between the opened contacts, this relay exceeds the legal requirements.
Image 1: The power relay HE-S' structure. With 3.2 milimeters between the opened contacts, this relay exceeds the legal requirements.
(Bild: Panasonic)

Besides, the HE relays are mounted directly on the printed circuit board, eliminating the need for a screwed or wired solution in the control cabinet. This not only saves space, but it also eliminates the need for manual assembly. This simplified installation ultimately improves quality because wiring errors are avoided, and costs are saved.

Reduced power dissipation leads to fewer overheated relays

In addition to the component size, the reduced energy consumption and therewith the minimal self-heating is a central feature of the relays in the HE series. Extremely low power dissipation at the contact point is achieved by lower contact resistance between 1 and 3 mΩ. This means that there’s no significant heating of the contacts; at 35 A and contact resistance of 2 mΩ, the power dissipation is 2.45 W.

If the control is carried out using a reduced holding voltage, a very low coil power loss of 170 mW (at 30 percent of the nominal coil voltage, 100 percent for at least 100 milliseconds in the switch-on process) can be achieved. This lower energy consumption is significantly lower than that of standard contactors. A further advantage is that, due to the reduced heating, cooling by, for example, additional fans aren’t required in most cases.

Possible use-cases for PCB high-performance‘s relays

Image 2: Power relays such as the HE-V can be used to separate positive and negative lines on the DC side in motor controllers.
Image 2: Power relays such as the HE-V can be used to separate positive and negative lines on the DC side in motor controllers.
(Bild: Panasonic)

HE series high-performance relays are suitable for many energy management applications. Where high currents must be conducted and switched safely, reliably and cost-effectively, making the HR relays a good investment. This is particularly true for HR relays for (solar) inverters, automotive charging solutions, and battery storage systems.

As modern solar inverters and battery storage systems become more and more compact power classes from 60 to 100 kW are no longer unusual. Today, the demands for high-performance switching electronics are increasing, also the market’s request for charging stations for electric vehicles is increasing.

As the charging times are going down, the European’s interest in e-mobility is going up. The relay structure of the HE-S allows the optional implementation of a 1FormB monitoring contact which detects the welding of the main contacts. This feedback contact complies with the EN60947-4-1 standard for safety circuits and the EN61851-1 standard, making the HE-S relay suitable for car charging solutions.

Energy Management focuses on renewable energy systems and energy efficiency

Image 3: Due to its low contact resistance, the HE-Y5 is well suited for use in solar inverters.
Image 3: Due to its low contact resistance, the HE-Y5 is well suited for use in solar inverters.
(Bild: Panasonic)

There’s a lot of development potential for energy management in all fields: electromobility, wind power plants, photovoltaic systems in private households, etcetera. The changing tides of the industry mean great potential for the companies active in it. In the ever-changing landscape of electronics, manufacturers always must be on their toes, looking for new ways to be more energy-efficient.

Conclusion

Power relays that can carry and switch high currents directly on the printed circuit board are revolutionizing the power electronics industry.

In short, replacing contactors with power relays soldered directly to the PCB saves space, energy, and money, without having to compromise quality, safety, or performance.

This article was first published in German by Elektronik Praxis.

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