The advanced technology of the WS-V series is based on a proven Mitsubishi Electric patent, and in consideration of the layout of the current leads provides excellent opening cycles of the main conductors. The new circuit breaking technology “Expanded ISTAC” upgrades current limiting performance for a higher breaking capacity. With higher breaking capacity, lower class models can be used, thus leading to cost reduction of switch panels and machines. Extending the conductor (reaction circuit for movable conductor) beneath the fixed conductor makes the movable conductor open faster than the conventional ISTAC mechanism. This significantly improves the current limiting performance and reduces the maximum peak current by 10 %.