Abstract: In a current-fed static controlled synchronous motor drive which includes a ramp logic for establishing the desired firing retardation for the naturally commutated thyristors, an optical encoder provides a position signal and a velocity signal, while the ramp counting the velocity pulses is automatically aligned with the position signal by means of a phase detector causing either to add pulses from a local oscillator or to inhibit velocity pulses so as to compensate for a phase error in either direction. Alignment is also provided within 60.degree. initially by presetting the ramp counting in relation to a digital representation of sine 60.degree. time intervals over a fundamental cycle.

Abstract: A phase detector circuit is connected to a sine wave reference during a time interval of one-half cycle of the sine wave to be compared. Phase detection is provided by integrating the inputted sine wave reference during such time interval, and immediately following such accumulation of information, the latter is transferred to a holding circuit. The phase detector is applied to a phase locked loop in which the time intervals are established digitally to control FET devices for the sampling and holding functions.

Abstract: A firing pulse generator for sequential firing of thyristors digitally synthesizes time dependent references associated in succession with the respective thyristors with a hard pulse, and predetermined critical counts on a time dependent reference are identified representing the first and second end-stops defining the permissible fire-angle range. A substitute for the hard pulse is generated when the hard pulse is advanced, and when it is retarded in relation to predetermined limits, e.g. the end-stops. The time dependent reference is generated over a range sufficient to cover the permissible fire-angle range defined by the end-stops. Blocking of an illegal hard pulse is effected independently from the generation of a hard pulse. Pulse suppression is performed independently from the generation of a hard pulse, or of a substitute pulse.

Abstract: A digital firing pulse generator for thyristor rectifiers in a power converter system uses a time dependent waveform to trigger a one-shot multivibrator for generating a hard pulse of minimum duration and includes a free running oscillator generating a train of picket fence pulses applied to the thyristor rectifier after the hard pulse in order to insure extended conduction. A pulse suppressor actuated upon an emergency prevents the initiation of a hard pulse but does not shorten the duration of any initiated hard pulse, and suppresses the picket fence pulses. Provision for end stops on the picket fence pulses exist and the generation of a separate hard pulse is digitally controlled when a hard pulse is missing after the selection of a rectifier next to be fired.