Variable speed control apparatus for induction motor

摘要

A variable speed control for induction motors with a primary angular frequency operating circuit has a multiplier that multiplies the output of a first regulator by a variable responsive to magnetic flux intensity. This first regulator holds the M axis induced voltage at zero. The primary angular frequency operating circuit corrects the primary angular frequency command value based on the output of the multiplier. An adder adds the output of a second regulator circuit and the output of the primary angular frequency operating circuit. The second regulator regulates (by proportional or proportional-integral control) the deviation between the command value of the torque current, or the torque and an actual value, to zero. In another embodiment, the magnetic flux operating circuit calculates a first value and a second value. The first value is obtained by adding a result of multiplication of a reference frequency value by a magnetic flux command value and an absolute value of an induced voltage or a T axis induced voltage. The second value is the sum of the reference frequency value and an absolute value of the primary angular frequency command value. The magnetic flux operating circuit divides the first value by the second and obtains a calculated magnetic flux value by passing the result of the division through a low pass filter. The calculated magnetic flux value serves as an equivalent of the magnetic flux, which is a necessary input of the primary angular frequency operating circuit and the magnetic flux regulator.