relationship equ10 this relationship assumes that the correction angle u03c6 can vary by u00b1 33 from the value associated with the average conduction angles of u03c0 2 and 5 8 u03c0 radians it should also be pointed out that the attenuation and notch filter networks 22 24 of fig2 a 2c typically exhibit some 34 frequency plane 34 negative phase shift in the frequency spectrum below the maximum response frequency accordingly the positive phase lead network 26 preferably includes phase correction for these networks such that the phase lead angle u03c6 represents the composite phase characteristic of networks 22 24 and 26 it should also be pointed out that such attenuation and notch filters 22 and 24 although preferable are not essential to practice the present invention referring to fig5 a functional block diagram is shown which depicts a signal processing network generally designated 40 suitable for use in coupling the signal processing networks 20 of fig2 a 2c to the conduction angle control means of fig1 more particularly first summation devices 42 44 46 receive the positive phase shifted signals i ja i jb i jc outputs of summation devices 42 44 46 are respectively directed to second summation devices 48 50 52 summation devices 48 50 52 each receive bias input signals through positive summing inputs and regulating loop signals which are related to the reactive current coefficients associated with lines 1 2 and 3 through negative summing inputs the outputs of summation devices 48 50 52 respectively.