Self-excitation for an alternator of the low-carbon steel rotor type

Claim 1

A charging system for amplifying AC output voltages induced in at least one stator winding of an alternator by residual magnetism in the alternator rotor and energizing a field winding of the alternator at low alternator rotational speeds to self-energize the charging system by means of the residual magnetism, said charging system comprising: an alternator having at least one stator winding wound on a core, the alternator further having a field winding wound on a low carbon steel core and in operative proximity to said stator winding to provide an electromagnetic field for said stator winding; electronic voltage regulator means having at least one input terminal coupled to said stator winding of the alternator, the electronic voltage regulator means comprising an operational amplifier having one of its input terminals coupled to the input terminal of the electronic voltage regulator means, the operational amplifier providing an amplified output AC signal at its output terminal, peak detector means coupled to the output terminal of the operational amplifier to peak detect the magnitude of the amplified AC output signal, and circuit means coupled to the peak detector means and responsive to the output of the peak detector means to develop the output signal of the electronic voltage regulator means, whereby the electronic voltage regulator means is responsive to small AC output voltages induced into the stator winding by residual magnetism during low alternator speeds, such as during start-up, to develop an output signal at an output of the electronic voltage regulator means of sufficient magnitude to fully excite the alternator field winding even when said small AC output voltages are of lower magnitude than that required to forward a silicon semiconductor junction; and coupling means to couple the output signal of the electronic voltage regulator means to said field winding of the alternator.