Abstract :
AS pointed out in a number of recent papers,1,2 a mercury-arc rectifier draws a distorted current from the a-c supply system, even though power to the system is supplied by a sine-wave source. The harmonics in the current wave react on the supply system to cause distortion in the voltage wave, the degree of distortion being a function of the rating of the rectifier, the number of phases in which power is supplied to the anodes, the impedance at harmonic frequencies of the supply system, and the rectifier load. It is well known that, in theory at least, reductions in the wave-shape distortion may be effected by increasing the number of rectifier phases and thus reducing the number of harmonic components present in the supply-circuit current.1,2 Up to 1937, however, because of practical difficulties, largely in the design of the complex transformer arrangement required, no attempts were made to produce rectifiers commercially having more than 12 phases.
