说明：  This circuit uses the AC6 block of SimPowerSystems™ library. It models a permanent magnet (PM) synchronous motor drive with a braking chopper for a 3HP motor. The PM synchronous motor is fed by a PWM voltage source inverter, which is built using a Universal Bridge Block. The speed control loop uses a PI regulator to produce the flux and torque references for the vector control block. The vector control block computes the three reference motor line currents corresponding to the flux and torque references and then feeds the motor with these currents using a three-phase current regulator.