| 摘要 |
A method and apparatus for controlling an AC induction motor, having at least two phases. The motor is controlled by two input signals (S<u1>u, S<u2>u), which are connected to a resolver (1), the output signals of which are used to generate separate supply signals to the motor phases. When doing this a first and a second signal (B<u1>u, B<u2>u), representing the magnetic field in the motor, are fed back to the resolver (1) for modification of the input signals (S<u1>u, S<u2>u). A measuring and calculating unit (12) generates the signals which represent the magnetic field in the motor by reconstruction from measuring signals and has two signal channels for generation of the magnetic field signals above and below a predetermined frequency (w<u0>u), respectively. In a first signal channel a signal (E') which represents the magnetizing voltage is integrated and fed through a high pass filter (24), the integrator and the high pass filter being combined into a single block, while in the other signal channel a signal (I'<u0>u) which represents the stator current is fed through a low Pass filter (26). The signals from the high pass filter (24) and the low pass filter (26) are connected to a summer (25) and thence to a scaling unit (27), the output signal of which is used together with signals from other motor phases as one of said signals representing the magnetic field in the motor, eventually after coordinate transformation. The signal (E') which represents the magnetizing voltage is obtained either from a measuring winding (20) in the motor stator or by measuring the stator current (I<u0>u) and the supply voltage (V<u0>u) and by calculation according to the formula E =V<u0>u - R<uS>u x I<u0>u, where the constant R<uS>u represents the resistance in the stator winding. The signal (I'<u0>u) which represents the stator current is obtained either by measuring the stator current (I<u0>u) or by measuring the supply voltage (V<u0>u) and multiplying the measured voltage signal (V'<u0>u) by a constant 1/R<uS>u, where R<uS>u represents the resistance in the stator winding. |
