AUTOMOTIVE DESIGN
within a wallbox will generate heat simply through normal operation, and the higher their power, the more heat is generated. Improved charging speeds can be achieved by using higher charging currents, however this requires the use of higher rated electronic components, resulting in more heat generated inside the wallbox enclosure. It therefore requires careful design to manage and mitigate temperatures to ensure optimum performance and longevity, without compromising on the amount of space required to deliver it. Power relays are one of the prime
culprits for heat inside wallboxes. As such, any reduction in their operating temperature can make a signifi cant diff erence to the eff iciency and longevity of the wider system. Specifi cally, the contact resistance of the relay is often crucial to the amount of heat it generates. Even a one milliohm increase in contact resistance can equate to up to 18˚C or more in increased load terminal temperature rise. Omron’s G9KC PCB relay
approaches this problem by using a mechanically coupled double-break contact ensuring full compliance to the coming revision IEC 61851 Ed.4. The structure is the result of meticulous development optimised specifi cally for AC wallbox charging. An optimal copper content with a performance enhanced contact card (cradle) design signifi cantly improves energy eff iciency while reducing heat dissipation. As a result, with good overall charger design, operating temperatures in a typical 22kW 32A wallbox can be reduced by as much as 10˚C. This not only facilitates faster, more eff icient charging, but also unlocks new possibilities for wallbox designers to develop more compact and robust designs. The relay’s 4-pole structure means
that a single device can replace larger multi-pole contactors and three or four single-pole relays with a single G9KC, reducing the footprint required. It has an extremely low contact resistance, with a guaranteed initial contact resistance of less than 6 milliohms – roughly half that of any equivalent solution on the market. This signifi cantly reduces hotspots caused by fl owing current. As well
Steve Drumm is at Omron Electronic
Components Europe BV
The G9KC PCB Relay
as improving charging eff iciency and performance, the G9KC’s lower operating temperature reduces the likelihood of reaching current throttling thresholds, while also contributing to improved reliability and longevity of the relays themselves, as well as surrounding components. Crucially, as well as a low initial contact resistance, the relay retains a low contact resistance throughout its lifetime. This is particularly important given that wallboxes will typically have an operational lifetime of several years or more.
THE FUTURE OF WALLBOX DESIGN It is widely acknowledged that charging infrastructure must improve quickly to accommodate the rapidly
growing EV market. Wallboxes in general off er a low-cost and safe solution for EV range anxiety, which continues to be cited by motorists as a reason not to switch to electric. With new developments in relay technology, they can also be designed to be unobtrusive and fi t in with the aesthetics of where it is installed. As well as permitting faster
charging, the use of lower heat generating components can facilitate the inclusion of more functionality into wallbox designs, incorporating sensors to monitor charging speeds, and potentially even new developments in wireless charging. Even so, passively managing heat will continue to be an energy eff icient and competitive approach to one of the most critical design challenges.
Steve Drumm is at Omron Electronic Components Europe BV.
www.components.omron.com/eu-en
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