| 摘要 |
<p>The invention relates to a control device for a lift installation without a speed sensor, having an induction motor (3) for driving a lift cab (5) which approaches a floor level indicated by a marking (8) from an initial marking (7) at a crawling speed, and having a VVVF invertor (2) which supplies the induction motor (3) with current. The VVVF invertor (2) measures the real current (Ia) supplied to the induction motor (3) when the lift cab (5) moves at a constant speed before reaching the initial marking (7). A slip compensation unit (13) determines from the measured real current an associated slip frequency and derives from this the rotor frequency preset for the crawling phase up to the next marking (8). A function specifying the crawling time (Tc) as a function of the measured real current is stored in a memory (11). A computer unit (12) calculates from the crawling time (Tc) a delay time (Td) by which the start of the braking process of the lift cab (5) is delayed for each movement and, taking into account the delay time (Td) thus calculated, determines a new virtual extrapolated crawling time (Tcv) after each movement. Finally, a profile generator (1) drives the VVVF invertor (2) with a voltage/frequency signal (f,u) as a function of the virtual, extrapolated crawling time (Tcv). <IMAGE></p> |
