| 摘要 |
PROBLEM TO BE SOLVED: To obtain a star-delta starting apparatus, in which an rush current generated in a changeover operation is suppressed effectively by a method, wherein in a closed-circuit transition system, the value of a start resistance used to changeover star connection to delta connection is set rationally. SOLUTION: In this star-delta starting apparatus, a torque ratio when the resistance value of a starting resistance 2 inserted into every coil 1 of an induction motor is changedover to the transient delta connection of the induction motor, into which the starting resistance is inserted with reference to a torque that the induction motor should have in a delta connection state in which no starting resistance is inserted at a maximum torque developing speed in a transient delta connection state (c) under the condition in which the time shifted to the transient delta connection state (c) from a star connection state (a) is set optimally, at a value from 1/4 to 1/3 or at a value 1/3 or thereabouts. Thereby, while the value of an rush current generated at a point of time changed over to a delta connection from a star connection is being suppressed, the induction motor can be started smoothly and surely so as to have sufficient acceleration torque.
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