Development of optical travel sensor for power circuit breaker

A travel sensor detects a motion of a mechanical part of a circuit breaker and checks its condition of the operation mechanism. We have developed a new optical travel sensor which measures a motion of a sealing rod with no contact. The design of the travel sensor and its fundamental inspections will be mentioned in this report. In our proposed sensor, the silhouette of the sealing rod is detected optically, and the motion of the rod is detected with no contact. Using optical fiber sheets, electric components such as the light source, the image sensor, and signal processing circuits are located remotely from the circuit breaker. As a result of this construction, the sensor is not affected by electro-magnetic noise. The travel sensor is constructed with two mirrors retro-reflecting illuminating light and prisms inverting the rod image. It is easy to adjust the mirrors according to the retro-reflecting construction. As the prisms compensate for the inverting effect of the lenses, intensity fluctuation of the rod image decreases. As a result of our fundamental inspections, we confirmed that the travel sensor had the detected range of 125 mm and the position resolution of 1 mm.