Abstract: A d-c arc welding apparatus including an engine-driven welder converting the a-c power generated by an engine-driven alternator into d-c power for use as the drive power of the welder, a battery-driven welder using a battery as the drive power of the welder, and a changeover switch for selecting between a high-power mode in which the above-mentioned welding d-c outputs are connected in parallel and fed to the welding apparatus, and a low-power mode in which either of the above-mentioned welding d-c outputs is supplied independently to the welding apparatus.

Abstract: An engine-driven power generating system comprising a bridge circuit section in which a low-frequency switching elements driven alternately by low-frequency drive signals, and high-frequency switching elements driven by high-frequency drive signals during the ON period of the low-frequency switching elements are connected in a bridge network, and an inverter circuit section having a drive signal supply circuit for supplying low-frequency and high-frequency drive signals are each supplied to the low-frequency and high-frequency switching elements that form a pair; the a-c voltage generated by an engine-driven a-c generator is converted into d-c voltage that is in turn converted into a predetermined level of low-frequency a-c voltage; characterized in that an emergency relay circuit device for protecting the engine-driven power generating system against abnormal operating condition.

Abstract: A brushless generator having a rotor for generating a magnetic field, a stator having magnetic poles facing the rotor a main generating winding; and a voltage is induced as the magnetic field generated in the rotor intersects the main generating winding, in which slots are provided at the locations of the stator magnetic poles facing the rotor, exciting windings are wound on the slots to generate in the exciting windings voltages having different phases with respect to that of the voltage generated in the main generating winding, and brushes are eliminated by using the voltages generated in the exciting windings.