| 摘要 |
A method and an arrangement for control of an alternating- current induction motor with at least two phases is described. The motor is controlled depending on two control signals S1, S2, which are sent to a vector rotation arrangement 1, whose output signals are used to generate separate drive signals for the motor's phases, wherein a first and a second signal B1, B2, representing the motor's magnetic field, are fed back to the vector rotation arrangement 1 in order to modify the control signals S1, S2. A calculation arrangement 12 calculates a signal Is' corresponding to the inductive current Is through the corresponding stator phase winding 2, determining the magnetic field of the motor, in at least two motor phases, using the formula Is' = E/sL, where E is the magnetisation potential, s is the Laplace operator and L is the inductance of the stator phase winding. The signals Is' calculated for each phase are scaled and utilised as signals representative of the motor's magnetic field. A signal E' representative of the magnetisation potential E can be obtained from a separate measurement winding 20 in the motor's stator. Without having any measurement arrangement on the motor, a signal E' representing the magnetisation potential can be computed from the formula E' = V - RsIo, where V is the power supply voltage, Rs is the resistance of the stator, Io is the power supply current. For low frequencies, an additional signal Is' is computed by approximation, representing the current of the stator phase winding. Both signals computed to represent the current of the stator phase winding go through a high- pass filter and a low-pass filter, respectively, and are then added, so that a signal Is' corresponding to the current of the stator phase winding is available for all frequencies. <IMAGE> |
