A field coil is divided into the plural number, and each of these field coils is connected in parallel in relation to a battery at the time of engine starting, and in series during the generation of the electric current after engine starting, so that sufficient field electromotive force can be maintained in the event of a battery voltage drop during engine starting, and also a necessary, sufficient field electromotive force can be produced with little current at the time of voltage recovery during generator operation. Consequently, the amount of copper to be used for the field coils and a winding space can be decreased; therefore the present invention is effective to provide a light-weight, small and unexpensive engine starting and charging device.

A method and apparatus for controlling variations of the torque developed by the crankshaft of an internal combustion engine. An ac polyphase rotating electric machine is directly connected to the crankshaft so that the ac polyphase rotating electrical machine is used as a generator when the torque of the crankshaft is increased and used as a motor when the torque is decreased. Thus, rectifiers are provided by inverters and their power supply includes a high voltage power supply capable of generating a voltage higher than a battery voltage.

A vehicular generator motor performing generator operation and motor operation is disclosed. The generator motor comprises an AC-DC converter means and a switching means. The converter means is composed of a plurality of MOSFETs and connected between each armature coil and a vehicular storage battery. Alternating current produced across the coils is converted into a direct current for charging the battery by the AC-DC converter means in generator operation mode. In motor operation mode, the DC output from the battery is converted into an alternating current for setting up a rotating magnetic field by the converter means, and the battery output is fed to the armature coils. The mode of operation of the MOSFETs is switched between these two modes by the switching means. The rotating field produces a certain phase difference with the magnetic field developed by the rotating magnetic poles. The MOSFETs are made of SiC having a smaller resistivity than that of Si. This ensures a high withstand voltage necessary during power generation. Loss caused by large current flowing in the motor operation mode is reduced. Good driving torque can be obtained.

The system is directed to preserve the starter/alternator in an IC engine installation from potential overload and failure in response to electrical load increases. The system controller monitors starter/alternator output and phase current and regulates output voltage when monitored currents reach predetermined thresholds. Output voltage is stepped down incrementally to check output currents at threshold non-failure creating levels. When current demand, i.e., load, decreases, output voltage is stepped up incrementally to return to an original set point for voltage.

The rotor of a generator is provided with permanent magnets to ensure start-up of electricity generation without externally supplied field current after a vehicle engine starts. When the generation is detected, the external field current is supplied from a battery so that the battery is charged by the generator, thereby to prevent battery discharge in a low speed range.