Patent ID: 6634463
Filing Date: 2003-10-21
Classification: B66B

Abstract:
Method for controlling the drive of a conveyor device (10), especially in the form of an escalator or moving sidewalk, switching between load operation and no-load operation, having a drive motor (26) and a frequency changer (42) controllable at least with respect to frequency and phase position of its output voltage, in which: the drive motor (26) in load operation is fed with a line voltage with essentially constant line frequency and in no-load operation with the frequency changer output voltage; the phase difference between the phase position of the line voltage and the phase position of the frequency changer output voltage is determined; the phase position of the frequency changer output voltage is corrected according to the determined phase difference and therefore brought essentially into agreement with the phase position of the line voltage; switching is produced as soon as this agreement is reached; and wherein to determine the phase difference the time occurrence of comparable events on the voltage trend of the line voltage and frequency changer output voltage are recorded and the phase difference between the phase positions of the line frequency and the frequency changer output voltage is derived from the time difference of occurrence of these events.