MECHATRONICS FOR ELEVATOR INSTALLERS AND TECHNICIANS MODERNIZING ELEVATORS WITH DC TECHNOLOGY WHILE LEAVING THE WINCHES IN PLACE?

摘要

DC units - both those fitted with gearing and, in particular, gearless DC units with their often incomparably comfortable ride - are still to be found in many older buildings. Many of them are due for modernization. The question, which arises here, concerns the extent to which existing equipment can be retained. If we look first at the drive technology, then we find old DC systems with Ward-Leonard converters and those - usually newer models -with a transformer and rectifier (and, in some cases, even with a thyristor DC-converter). Important to making these decisions is the condition and design of the drive unit. In the geared DC versions, one will leave the DC motor in place only if its armature voltage is at least 400VDC. The reason is that conversion to asynchronous technology is more economical even if the gearing is reused. Given the high efficiency of the DC unit, the nominal inverter current required, at 400VDC, corresponds roughly to that of a 400 volts, three-phase AC motor and, as regards the power output electronics, the price difference is negligible. If the armature voltage falls (to 200VDC, for instance), then the inverter will require, when compared with a new asynchronous motor, about twice as much power for the DC motor, and this will boost the price of the power output section accordingly. Consequently, the old DC motor will be removed in a geared system.