| 摘要 |
Speed of a motor, generator or alternator, more particularly the speed of an alternating current (AC) induction motor is determined. Problems associated with previous devices are overcome by providing a speed monitoring device that is readily retrofitted to an existing motor. A test signal is superimposed onto an input voltage, which voltage in use is applied to at least one winding of the stator of a motor (the test signal is at a frequency substantially equal to the rotor frequency). The test signal frequency is varied so that it varies from a minimum frequency to a maximum frequency. A current monitor monitors a resultant current, in the at least one stator winding. and deriving from the resultant current is a signal indicative of the rotor frequency. |
