Matsushita Electric Industrial Co., Ltd.

Masayuki Okubo

Masafumi Naruto

Yoshimichi Yasuhara

A welder has an electromagnetic switch for turning on and off the power to be supplied to the welder, a control circuit for controlling the turn on and off of this switch according to a starter signal that starts the welder and self-holding circuit for self-holding the switch. This self-holding circuit releases the switch from the self-holding when a voltage of the control circuit lowers to not more than a turn-on voltage of the switch. Therefore, when an applied voltage decreases too low to maintain the turn-on status, the switch is released from its self-holding. A voltage can thus never be applied again to the control circuit unless the starter signal is once turned off. As a result, a coil of the switch is completely free from being burnt out. Also current can be cut off when a temperature of the coil of the switch rises to not less than a given value. Therefore, if an abnormal temperature of the coil is sensed, the coil current is cut off. As a result, the coil of the switch is completely free from being burnt out.

Electromagnetic switch and welder using the same

An arc welding apparatus having output terminals of a constant current characteristic and a constant voltage characteristic is simply provided at low cost with a reactor appropriate for both the characteristics. A current control circuit 2 controls a secondary output current of a welding transformer 1 by means of a current control device, while a first reactor 3 and a second reactor 4 are constructed so that magnetic flux formed by a first winding 3a and magnetic flux formed by a second winding 4a, which are wound around an annular iron core 7, overlap each other. The other terminal of the first reactor 3 is connected to a constant current characteristic output terminal 8, while the other terminal of the second reactor 4 is connected to a welding base metal use output terminal 10. A constant voltage characteristic output terminal 9 and one terminal of the first reactor 3 are connected to the positive side of the current control circuit 2, while one terminal of the second reactor 4 is connected to the negative side of the current control circuit 2.

Arc welding apparatus for constant current and voltage characteristics

An arc welding apparatus is constructed of: a welding transformer 1, wherein a first tap T1 is provided at a point of half N/2 of the total number of turns N of the secondary winding of the transformer 1, the first tap T1 is connected to the electrification section 9 of a manual welding holder 8, a second tap T2 is provided at a point of N1 turns from the start Ts of the secondary winding, the second tap T2 is connected to a second thyristor 3, a first thyristor 2 and a third thyristor 4 are connected across both ends of the secondary winding, a third tap T3 is provided at a point of half N1/2 of N1 turns of the secondary winding and the third tap T3 is connected to a CO.sub.2 arc welding torch 10; a control circuit 6 for controlling these thyristors 2-4, a gate signal switchover circuit 5 for executing switchover between gate signals of the thyristors 2-4; and a reactor 7 for smoothing a welding current. The arc welding apparatus executes switchover between manual welding and CO.sub.2 welding by means of thyristors, thereby manufacturing the apparatus at low cost and achieving improved reliability.

Growing community of inventors

Takatsuki, Japan

Masayuki Okubo