Three=phase network phase monitor for lift operation - derives extra vectors from normal voltage vectors, which are mutually opposed and equal, to obtain relay control signal from sum

摘要

The method monitors the phase sequence in a three-phase network, for instance in lift operation. Between the normal voltage vectors (R,S,T) indicating the phases are added extra vectors (R',S') which are mutually opposed and equal vectors, and that the extra vectors (R',S') and the voltage vectors (R,S,T) are added up and on the basis of the sum thus obtained, necessary steps are taken. The extra vectors (R',S') are produced in that from the vector (S) of one phase is formed a component (S') lagging 60 degrees behind, and which is compensated by suitably lengthening the vector (R) of the phase preceding said phase. The phase (S) which is lagged by 60 degrees has been connected a delaying circuit (VP) in parallel with this phase's summing resistor (R2) and that the summing resistor incorporated in the phase leading the lagged phase by 120 degrees is smaller of value than the summing resistors (R2,R3) in the other phases (S,T).