Battery charging system with a permanent magnet alternator and means for minimizing noise

Claim 1

A battery charging system comprising a pair of supply lines between which in use the battery is connected, a permanent magnet alternator supplying power to the supply lines through a rectifying and regulating circuit which incorporates thyristors conduction of which determines whether an output is fed to the supply lines, a voltage regulator which is controlled by an input signal derived from the supply lines and has one state in which it supplies gate current to each thyristor and a second state in which no gate current is supplied to the thyristors, said voltage regulator inherently affecting stator flux modulation of said permanent magnet alternator whereby a noise frequency band results, and a control circuit means connected across the supply lines and providing to the regulator a second input signal which when the regulator changes state overcomes the first signal initially so that the regulator reacts to changes in the first input signal only after a delay, said control circuit means suppressing said noise frequency.