초록 ▼

Speed control of an induction motor is effected in digital fashion through use of a computer but without complex processing, and with a computer that need not be large in scale. This is accomplished by processing at least a speed command signal, actual speed signal and torque signal in analog fashio

Speed control of an induction motor is effected in digital fashion through use of a computer but without complex processing, and with a computer that need not be large in scale. This is accomplished by processing at least a speed command signal, actual speed signal and torque signal in analog fashion, enabling simplification of an induction motor speed control digital processing section which performs all other control operations in a digital manner. In a speed control network having a closed loop, a frequency-to-voltage converter, adder-subtractor, proportional integrator, polarity determining circuit absolute value circuit and voltage-to-frequency converter are constructed of circuitry operable on the basis of analog values, with all other circuits being constructed of circuitry operable on the basis of digital values.

대표청구항 ▼

A system for controlling an induction motor by a microprocessor having a processing unit, a control program memory and a data memory, said system comprising: memory means for storing motor characteristics including a torque-current amplitude characteristic, a torque-phase characteristic, a rotationa

A system for controlling an induction motor by a microprocessor having a processing unit, a control program memory and a data memory, said system comprising: memory means for storing motor characteristics including a torque-current amplitude characteristic, a torque-phase characteristic, a rotational speed-slip characteristic and a rotational angle-sinusoidal value characteristic; means for deriving an analog value difference voltage between a voltage indicative of a speed command and a voltage indicative of the actual induction motor speed; voltage-to-frequency conversion means for converting the difference voltage into a digital pulse train Pe; means for obtaining torque information by reading, at fixed periods, Ne-number of pulses of the pulse train Pe, and for obtaining induction motor speed information by reading, at fixed periods, Nv-number of pulses of a pulse train having a frequency proportional to the induction motor speed; means for deriving a numerical value corresponding to the Nv-number of pulses on the basis of the rotational speed-slip characteristic stored in said memory means; first counter means, responsive to said numerical value corresponding to the Nv-number of pulses and to the pulse train Pe, for dividing said pulse train Pe by said numerical value corresponding to the Nv-number of pulses to produce a pulse train Ps indicative of induction motor slip; means for mixing the pulse train Ps with said pulse train having a frequency proportional to the induction motor speed; second counter means for counting the pulses in the mixed pulse trains to produce rotational angle information fu, iv, iw by executing a predetermined operation to control slip frequency, on the basis of said Ne-number of pulses, said rotational angle fu, iv, iw.