Omron Electronic Components Europe has put the G9KJ relay into production, a compact PCB-mount device rated to 1500 VDC and aimed squarely at pre-charge circuits in battery energy storage systems and high-voltage EV fast chargers. It is a small component with a pointed job, and its arrival reflects how seriously the industry now takes a switching function that was, not long ago, treated as an afterthought.

The physics of the problem are unforgiving. When a high-voltage DC system powers up, the uncharged capacitors on the DC link draw an inrush current that can be orders of magnitude higher than steady-state operation. Without a pre-charge path, that surge hammers the main contactor, stresses the DC-link capacitors and risks triggering protection trips before the system has done any useful work. The standard remedy is to route initial current through a resistance-limited bypass, closing the main contactor only once the capacitor bank has charged to near bus voltage. The relay that controls that bypass path takes all the punishment so the main contactor does not have to.

The G9KJ is built for precisely that role. It is rated to make at 1500 VDC and handle 25 A of inrush, but is intentionally taken out of circuit before any high-voltage break event occurs, with a break rating of 40 VDC reflecting that design intent. The 5 A continuous carry rating covers the charging window between make and dropout. Contact resistance is specified at 100 milliohms maximum and coil consumption sits at 530 mW, both consistent with a component that designers will want to integrate into dense, thermally constrained boards rather than bolt onto a chassis rail.

At 37.2 mm long by 17.0 mm wide by 25.5 mm high in its SPST-NO configuration, the G9KJ is considerably smaller than the screw-terminal contactors it replaces in this function, which matters increasingly as 800 V to 1500 V architectures push into grid storage and fast-charge infrastructure where board real estate and assembly time both carry a cost.

Omron positions the G9KJ as a purpose-built alternative to general-purpose high-voltage parts that are often over-rated and over-priced for a pre-charge role. The relay is available now.

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