| 摘要 |
PURPOSE:To diagnose the fracture state of a rotor conductor by deriving the power ratio of the power source frequency component and beat frequency component in a current which flows through a stator winding. CONSTITUTION:The primary current of the stator winding of an induction motor 25 flows through a current transformer 1 and a current-voltage converting circuit 2 to input a voltage proportional to the primary current to a frequency analyzing circuit 4, which detect frequency characteristics, thereby reading frequency components in the input waveform from the extremal value of the characteristic curve. Further, a detection coil is arranged in the gap between a stator and a rotor, an induced voltage due to leak magnetic flux of a revolving magnetic field produced with the secondary current of the rotor conductor is detected by a leak magnetic flux detecting circuit 7, and an LPF8 remove the power source frequency component in the induced voltage to extract only a slide frequency component. Then, a beat frequency derived from a frequency detecting circuit 9 and the frequency component contained in the current of the stator winding which is calculated by the circuit 4 are passed through a frequency discriminating circuit 6 and a power ratio arithmetic circuit 10 calculates the power ratio of the power source frequency component and the frequency component obtained by the circuit 6 to diagnose the fracture state of the rotor conductor.
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