Power harmonics surveying of a modern elevator system

All modern power electronics-based elevator drives, such as direct current thyristor Leonard (DCTL), alternating current variable voltage (ACVV) and AC variable voltage variable frequency (ACVVVF), draw nonsinusoidal currents. These harmonic currents generate harmonic voltages on the power distribution system, which may affect the operation of other electrical appliances. Harmonic currents can be analysed by a Map 1000 FFT analyser. However, the magnitudes of harmonic currents vary greatly with the motion patterns of the elevator cars. It is important to correlate the harmonic currents generated with the traffic patterns within the elevator system. This paper describes the development of a computerised monitoring system which consists of 98 digital input ports and 8 analogue input ports for an elevator bank of 4 cars as an implementation example. The status of motion, the position of car, the status of car door and the loading within the car can be recorded and saved on a hard disk. The traffic patterns can be summarised into three modes, i.e. full-load up (equivalent to no load down), full-load down (equivalent to no load up) and half-load up (equivalent to half load down). The results serve as guidelines to aid the electrical design so as to solve the problem of harmonics pollution by modern elevator systems.