| 摘要 |
PURPOSE:To obtain the convenient and economical rotational frequency detecting means of high precision and high reliability which is excellent in maintainingability, by setting a magnetic field detector for detecting leakage flux generated on the shaft section of a squirrel-cage rotor, and by taking out slip frequency. CONSTITUTION:It is noted that leakage flux generated on a motor shaft section by the secondary current of a squirrel-cage induction motor 20 is corresponded with slip frequency, and a magnetic field detector 21 for detecting leakage flux generated on the shaft section of a rotor is set, and the slip frequency is taken out. The magnetic field detector 21 should be set at the end section or the peripheral section of the shaft section. Besides, the detecting signal of the magnetic field detector 21 may be inputted to a frequency counter 24 and an FV converter 25 via a filter 23 for cutting high frequency component except the slip frequency after the detecting signal is passed through a magnetic flux/ voltage converter 22. |
