Control device for induction motor
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United States of America Patent
Stats
-
Jul 27, 1993
Grant Date -
N/A
app pub date -
Mar 18, 1991
filing date -
Mar 16, 1990
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
In a slip frequency control system hitherto widely employed as a control system for an induction motor type electric rolling stock (in which a slip frequency is determined from a current deviation, an inverter frequency is calculated from the slip frequency and a motor rotation frequency, and the inverter frequency is multiplied by a predetermined correction factor to determine a modulation rate, thereby operating an inverter), a motor output torque decreases in a low speed region. It is difficult to make the correction for this decrease of torque by detecting the torque. In the present invention made considering that a torque curve and sin .phi. (.phi.: the internal impedance angle of a motor) obtained from the result of simulation resemble each other, the decrease of sin .phi. is regarded as being the decrease of torque and a voltage to frequency ratio is corrected so as to compensate for the decrease of sin .phi..
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