Abstract: A safety apparatus for an elevator system is disclosed in which upon detection an instantaneous power service interruption, an emergency brake is applied to the car and continues to be applied for longer than the time required for the particular car to stop.

Abstract: In a speed feedback control system wherein a speed command signal and a speed feedback signal are compared and wherein the deviation between these signals is entered into a speed control unit, the speed signal is differentiated to apply speed damping in order to suppress the oscillations of the control system. In this case, while the speed command and the actual speed make a great difference transiently, the speed command is approximate to the sum between the speed feedback signal and the damping signal even transiently. Therefore, the speed command signal is compared with the sum between the speed feedback signal and the damping signal, and the fault of the speed control system is detected upon the fact that the deviation has exceeded a predetermined value.

Abstract: A thyristor fault-detecting apparatus comprises a thyristor bridge with A.C. terminals connected to a three-phase A.C. power supply and having six thyristor arms, and an inductive load connected to D.C. terminals of the bridge. Each of the A.C. paths has a saturable reactor with an output winding so set as to be excited by the line current within the range from .pi./3 to 2.pi./3 (rad). Output voltages of the reactors are rectified and added, so that a fault in the thyristor is detected by the disappearance of the added output.

Abstract: In order to control a DC motor, a main circuit is constructed in such a manner that a unidirectional thyristor converter is connected to the armature of the motor, while a bilateral thyristor converter is connected to the field system of the motor. Provided is a speed controller which is impressed with a speed command signal and a speed feedback signal so that the speed controller produces an error signal representing the difference between the speed command signal and the speed feedback signal and the error signal is applied to a function generator which in turn produces a field current command signal and an armature current command signal. The field current command signal assumes a value proportional to the error signal when the error signal is less than a predetermined value. The armature current command signal is kept constant when the error signal is below a predetermined value, while it increases, when the error signal exceeds the predetermined value, in proportion to the amount of the excess.