tailieunhanh - High Performance Driver P2

Tham khảo tài liệu 'high performance driver p2', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | HIGH PERFORMANCE DRIVES 7 2. MATHEMATICAL MODELLING OF AN INDUCTION MACHINE AND THE SUPPLY . INTRODUCTION As far as the AC machines are concerned simple speed control systems are not capable of providing decoupled independent flux and torque control. All the so called scalar speed control methods constant volts hertz control slip frequency control voltage control etc. are able of controlling the steady-state behaviour of the machine only. All these methods rely on controlling the rms values of AC voltage and or current while instantaneous torque depends on instantaneous values of currents. Therefore torque developed by the machine exactly corresponds to the commanded torque in steady state only while the dynamic response is generally sluggish and slow. Transition from one steady-state to another is not controllable and follows internal dynamics of the machine. The idea of field orientation or vector control as it is called as well can be briefly stated as a control method that converts an AC machine into its DC machine equivalent from the control point of view and thus enables instantaneous decoupled control of flux and torque . Instantaneous decoupled flux and torque control is made possible by control of instantaneous current values rather than rms values. Extremely fast response that fully corresponds to the one obtainable from a DC machine is enabled by this method of speed control. However the control system capable of realising such a good quality speed control is due to AC nature of all the variables in the machine much more complicated. Due to significantly more complex structure of AC machines compared to DC machines application of field orientation as a practical speed control method has become possible only by microprocessors. Field oriented control is nowadays applied in variety of manners in conjunction with both induction and synchronous machines sinusoidal and trapezoidal permanent magnet synchronous machines wound rotor synchronous machines .