VECTOR CONTROL AND CONTROL DEVICE OF THREE-PHASE AC INDUCTION MOTOR

摘要

PURPOSE:To perform a vector control in low speed processing by means of a low-speed processor, by removing higher harmonic components in detecting the primary current. CONSTITUTION:The value of each phase of the primary current is detected as iu, iv, and iw by current detectors 3U, 3V, and 3W. These three-phase AC primary currents are converted into two-phase AC currents ialpha and ibeta by a three- phase/two-phase converter 4. The two-phase AC current ialpha and ibeta of a stator coordination system are time-integrated by an integrator 23 and converted into Ialpha and Ibeta. The integral values Ialpha and Ibeta are then converted into an exciting current component Id and a torque current component Iq of a rotating magnetic coordination system by an exciting current and torque current component detector 5. By obtaining the current in this way, higher harmonic components are removed. On this account, a high speed A/D converter is dispensed with and a vector control in low speed processing is made possible in a PWM carrier wave cycle or the sample cycles of its integer multiples by means of a low-speed processor.