Mitsubishi Electric Develops World’s Fastest DC Circuit Breaker Technology for Railway Power-Supply Systems

Mitsubishi Electric has developed a high-speed direct-current (DC) circuit-interruption technology for railway power-supply systems that detects short-circuit faults instantly and isolates faulty circuits in just 13 milliseconds, which the company believes is a world’s first. The new technology developed by Mitsubishi Electric interrupts faulty current with unsurpassed speed by overcoming two key problems. First, a conventional DC circuit breaker detects a faulty current using an electromagnet that is driven by the faulty current itself and the weight of the moving core slows the time required for detection. The newly developed technology uses a lightweight core driven by a strong electromagnetic force, which is achieved with a new U-shaped conductor instead of a conventional I-shaped conductor. Consequently, Mitsubishi Electric’s DC circuit breaker takes less than 13 milliseconds from fault occurrence to contact separation.

Secondly, a conventional DC circuit breaker drives the arc generated between the contacts to the grid in order to shut off the high current. The new technology achieves faster current interruption by utilizing a new contact material and a new rib-shaped contact, which strengthens the electromagnetic force applied to the arc. he new breaker complies with Japanese Industrial Standards (JIS E 2501-2) for high interruption capacity (100 kA), high di/dt (10 kA/ms) and high cut-off current (55 kA). The new technology developed by Mitsubishi Electric is expected to enhance railway safety in terms of equipment protection and operational stability for power-supply systems, which supply railcars with power from off-board locations.

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