Abstract: Separate three-phase windings are connected to individual rectifiers arranged for series-parallel switching to improve the current-voltage output characteristic. The common exciter winding is fed through a voltage regulator. The switching of the rectifiers is controllable in response to alternator frequency, output current, temperature or efficiency and may be provided with a manual override switch.

Abstract: A direct current ramp potential signal which is produced in synchronism with each half cycle of the alternator output voltage and increases in magnitude within a predetermined range during each half cycle is compared with a direct current reference potential signal inversely proportional to alternator connected load. Circuitry is provided for effecting the electrical energization of the alternator field winding in response to an electrical signal produced when the potential level of the ramp potential signal has reached a value equal to that of the reference potential signal. Provision is also made for effecting the deenergization of the alternator field winding with sustained overvoltage conditions and for ramping the output voltage down linearly with conditions of output potential frequencies less than the desired frequency.

Abstract: The disclosed voltage generating system includes certain known components, such as an induction machine driven as a generator, the output connections of which are coupled to the normal load connections of a switching system, which can be a bridge-type inverter. The system switching frequency f.sub.1 is regulated by firing pulses from a logic circuit in turn controlled by an oscillator. By controlling operation of the inverter switches with respect to the synchronous frequency (mechanical rotational speed) of the machine, a d-c voltage is provided on the normal inverter bus conductors.In the disclosed system the conventional inverter switches (such as SCR's) are replaced by true two-way power switches, capable of passing current in either direction. In addition the firing signals provided by the usual logic circuit and applied to these power switches are modified so that the switching occurs as a function not only of the first oscillator frequency f.sub.

Abstract: Two cascaded induction machines provide asynchronous power transmission between two independent generating networks. The shafts of the two induction machines are mechanically connected for concurrent rotation and the rotor windings of the two machines are electrically connected in a reverse phase sequence. The cascaded induction machines are geared to a relatively low power variable speed drive which accurately controls the position and rotation of the shafts. A control system supplies low frequency excitation current for the variable speed drive and is capable of continuous operation through zero frequency to reverse the direction of rotation. The control system determines the level of power flow within the induction machines and is unresponsive to the difference in frequency of generation of the two generating networks so that the power flow is controlled even under transient load conditions.