| 摘要 |
A drive having a double-supplied rotating-field machine (DM) makes it possible, by means of a variable-frequency, machine-commutated converter as the three-phase power source (DQR) for one of the two machine windings (WRO), for the rotation speed to be regulated from rest up to the maximum rotation speed with comparatively little complexity. In order to ensure an adequate commutation voltage, the operation is carried out in a known manner with the stator field and rotor field rotating in the same direction and the rotating-field frequency (fRO) increasing from equality with the other rotating-field frequency (fST) at rest to the maximum rotation speed. Feedback to the mains via a converter cascade in this case allows good efficiency, with a considerable portion of the power actually circulating via the converter, and with stringent frequency requirements on the machine-side converter at high rotation speeds. In order to solve the problem, while maintaining the essential advantages of a machine-commutated converter, the circuit arrangement makes it possible to break the overall rotation speed down into a lower range with rotating fields in the same direction and an upper region with rotating fields in opposite directions, the transition being achieved by changing the rotation direction of one of the two rotating fields by means of a rotation-direction reversing device (DUR) while keeping the direction of shaft rotation the same. In the case of the transition into the upper range, the variable frequency is reduced so that the maximum value remains low. <IMAGE> |
