Several sets of magnetic sensors are provided in a magneto motor to sense rotary pole variation of the rotor magnet. One set of magnetic sensors lets the stator portion and the rotor portion generate armature reaction of stronger magnetic flux density, and another set of magnetic sensors corresponds to rotary pole variation of the permanent magnet of the rotor portion in advance to let the motor generate weak magnetic control phenomenon so that the stator portion and the rotor portion generate armature reaction of weaker magnetic flux density. The torsion coefficient K.sub.T will decrease to increase the rotation speed of the rotor portion. A motor can be designed to have a larger K.sub.T. When the motor needs to operate at higher rotation speeds, a magnetic detection selection circuit will output a detection output signal letting the motor generate a lower K.sub.T to increase the rotation speed of the magneto motor.

In a power generating system having an AC power generator, a quantity which is related to the state of power generation of the power generator and varies according to the supply of a leading phase current to the power generator, is detected. When the passage of the leading phase current through each armature winding is determined as necessary based on the detected status quantity, the leading phase current is supplied to each armature winding (an increase in the amount of supply of the leading phase current is included). If passage is determined as unnecessary, then the supply of the leading phase current to each armature winding is stopped (a decrease in the leading phase current is included). If so, then a change (improvement) in the state of power generation such as an increase in output or the like due to the above supply can be achieved by supplying the leading phase current thereto when its change is required. When the above change is unnecessary, the supply of the leading phase current thereto can be stopped to suppress a defective condition incident to the supply of the leading phase current thereto, particularly, the rate of change in output current, i.e., an increase in ripple. Owing to the above construction, the supply of the leading phase current to the power generator can be achieved by a simple circuit configuration and the state of power generation can be improved.

Devices and methods for controlling a generator with an associated voltage converter that functions as a step-up converter are disclosed, in which the control of the generator is done as a function of its rpm and/or as a function of the rpm-dependent possible output voltage of the generator. Three different ranges are defined, in each of which different control actions are performed: at low rpm, a power control at the maximum allowable exciter current; at higher rpm levels, a voltage control by influencing the exciter current; and at an overvoltage at higher rpm and a sudden load reduction, a third control strategy, which reduces the overvoltage and the exciter current.

An output control device of a generation device including: a rectifier circuit that rectifies an output of an AC generator and applies the output across a battery; an inverter circuit provided between the battery and the generator; inverter control means for controlling the inverter circuit to convert a voltage across the battery into an AC control voltage and apply the voltage to an armature winding of the generator; and phase detection means for detecting a phase of a phase current flowing through the armature winding of the generator as a maximum output current phase, wherein the inverter control means is comprised to control a phase of the AC control voltage so as not to be delayed with respect to the maximum output current phase, and thus prevent a reduction in the output of the generator caused by an excessive delay of the phase of the AC control voltage.

An output controlling apparatus for a vehicle generator includes MOSFETs for full-wave rectification of a voltage output by the generator, a MOSFET for turning the flow of a field current on and off and a voltage controller for controlling the MOSFETs to sustain the voltage of a battery at a fixed value. In this configuration, the thermal resistance between the MOSFETs is set at a value smaller than the thermal resistance between the voltage controller and the MOSFETs. In addition, the MOSFETs are fixed on a common good heat conductive substrate to reduce the thermal resistance between the MOSFETs. In this way, the accuracy of the voltage controller is prevented from deteriorating and, at the same time, the maximum temperature of the MOSFETs can be reduced.