Self-excited speed operated control switch - has permanent magnet generator with threshold circuit and display unit for speed exceeding critical speed

摘要

The switch is operated by the speed of a shaft rotation above and below a critical value. It has a multi-pole sub-divided permanent magnet, a.c. generator (11) connected to the driving shaft (19). It generates an initial a.c. signal with an amplitude corresponding to the shaft speed. A threshold circuit (12) has a data input connected to the above a.c. generator and generates an operating signal when the initial a.c. signal indicates a speed exceeding a critical value. A local current source (20) is supplied by the a.c. generator, and generated a d.c. voltage constant over a wide frequency speed range. It is the only energy supply for the threshold circuit. A display device (13, 18) is activated by the operating signal, and displays the shaft over-speed.