System for blending dynamic and regenerative braking

Claim 1

In a motor system wherein an electric motor having an armature winding is coupled to a mechanical load for power transfer therebetween, and wherein there are first and second power conductors for conducting electric power between said motor and a power system, the combination for operating said motor in the braking mode comprising: A. said motor; B. first and second conductive elements; C. first, second and third circuits connected across each other and between said conductive elements, I. The first circuit including said armature winding, II. the second circuit including first switching means selectively operable to respective ON and OFF modes in response to ON and OFF signals, respectively, III. the third circuit including in series second switching means and impedance means for dissipating electric power generated by the motor in the braking mode, the second switching means being selectively operable in respective ON AND OFF modes; D. unidirectional current conduction means; E. said power cOnductors, one connected to one of said conductive elements through said unidirectional currentconduction means, the other connected to the other conductive element; said unidirectional current-conduction means being poled to pass regenerating current from said motor to said power system; F. adjustable first control means for providing respective ON and OFF signals to said first switching means for operating that switching means to respective ON and OFF modes in an adjustable ratio of ON time to OFF time; G. second control means responsive to a criterion of the power receptivity of said power conductors for controlling the second switching means to operate in the ON mode during the OFF time of the first switching means for an ON time that is a function of the degree of power receptivity, said second control means further comprising reference function generator means for initiating a reference function in response to each of said OFF signals and terminating the function in response to the next one of said ON signals, whereby the function is coextensive in time with the OFF periods of the first switching means, means for providing a reference signal representing a predetermined reference value, means for providing a signal that is a function of the voltage across said power conductors, means responsive to said reference signal and said signal that is a function of the voltage across said power conductors for providing an error signal indicative of the difference between said reference value and the voltage across said power conductors, and means responsive to a comparison between said reference function and said error signal for controlling the ON time of the second switching means.