PURPOSE: To prevent expansion of a trouble in a system by a method wherein the upper and lower limit values of a slip of a wound-rotor induction motor of which an impedance viewed from an end of connection with a transmission line is of a small value is set by a slip range setting unit, and the wound-rotor induction motor is cut off from the transmission line when the slip just before occurrence of the trouble of the transmission line is within the set range.
CONSTITUTION: A slip of a wound-rotor induction motor is followed and stored in a following storage device 18-3 of a slip detector 18 based on a system signal voltage from a voltage transformer 19 and an output signal of a rotational angle detector 17 connected directly to a rotating shaft. When a trouble occurs in a transmission line at the time when the induction motor 11 is operated in the range of the slip of which an impedance viewed from the power station side is of a small value, it is determined in a slip range detector 20-2 that a the slip SM just before the trouble which is stored in the following storage device 18-3 is located between the upper and lower limit values S1 and S2 set in a slip range setting unit 20-1. Then, the logical product with a signal (b) from an overvoltage control device 16 is taken in an AND gate 20-3 and a breaker 12 is operated to break, while an alternating-current exciter 15 is stopped.
| JPS6450742 | SQUIRREL-CAGE INDUCTION MOTOR |
ABE MITSUYUKI
KANEKO HIROKAZU
YANAGISAWA TADAHIRO
TAKEDA SHINOBU
TOSHIBA CORP
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