In a power unit, an output current supplied from the power unit to a load device is constantly detected as a load current. When the detected load current exceeds a predetermined current value, output power supplied from the power unit to the load device is reduced or cut off. An output voltage supplied from the power unit to the load device is constantly detected. When the detected output voltage has continued to be lower than a predetermined voltage value over a predetermined time period, the output power is reduced or cut off.

There is disclosed a power regulating system for portable engine generator wherein overcurrent protection is provided by connecting the AC output of an AC generator driven by an engine to a rectifier for conversion to a DC current, supplying the DC current so obtained to an inverter to obtain an AC current of an arbitrary frequency, and providing for stopping of the driving signal to the inverter when an overcurrent state is detected in the inverter.

An automobile generator apparatus for producing commercial line power when driven by an automobile engine comprises a generator, an inverter unit, a controller for controlling the generator field and an accelerator actuator. The accelerator actuator is mounted opposite the accelerator pedal in such manner as to prevent erroneous operation thereof. The generator field is controlled while monitoring both the low-voltage side output and the high-voltage side output so as to prevent a large output current from flowing through the low-voltage side load. A circuit is further provided for preventing the occurrence of an overvoltage as a result of field control transistor malfunction. The switching elements constituting the output stage of the inverter unit are controlled to vary the duty ratio of the output waveform so as to stabilize the inverter output voltage and controlled to remove the center portion of the output waves so as to cope with the startup load. The inverter unit is also provided with an improved constant voltage circuit. There is further provided a synchronized operation control for combining the outputs of a plurality of automobile generator apparatuses. The generator is a single-shaft, dual-output type wherein the windings of the high-voltage side coils are disposed at the bottom of slots in the stator while the windings of the low-voltage side coils are disposed near the entrance of the slots.

A procedure and an apparatus for producing an a.c. voltage, in which procedure the a.c. voltage (u.sub.o) is produced via inversion from a d.c. voltage (U.sub.A). The d.c. voltage (U.sub.A) is produced by a generator (4). Moreover, the d.c. voltage (U.sub.A) is measured and stabilized. The frequency of the a.c. voltage is determined by means of an oscillator (9).