Tachometric alternator for servo control system - utilises hall magnetic sensor to permit detection of speed sign

摘要

The speed sensor is for a servo control system and comprises a tachometric generator in the form of an alternator. Magnetic field sensors allow an electronic circuit to determine the sign of the speed and the rotational speed. This overcomes contact problems in DC tachogenerators. A two phase alternator (1) includes a Hall effect magnetic sensor (G1) which is located on a radius which is parallel to a winding (B1) and is in the machine gap. The sensor is excited by a current (ig) to produce a voltage output for a sign comparator circuit (20) as the alternator rotates. This circuit controls a sign inverter (21) connected to the output of a circuit (13, 14, 15, 16) which produces a bidirectional tachometric signal from the two windings (B1, B2).