Abstract: A magnetic circuit includes a stationary iron core, a permanent magnet, and an armature, in a circular pattern. A contact mechanism spring separates the armature from the stationary iron core to open the magnetic circuit to switch a contact mechanism to a reset position. A coil on the magnetic circuit generates a magnetic flux in a direction same as that of the permanent magnet when an overload is detected and in an opposite direction when a predetermined time is elapsed after detecting the overload. A reset bar switches a movable stopper between an engaging position and a non-engaging position with the contact mechanism against a biasing force of the contact mechanism spring.

Abstract: A magnetic circuit includes a stationary iron core, a permanent magnet, and an armature, in a circular pattern. A contact mechanism spring separates the armature from the stationary iron core to open the magnetic circuit to switch a contact mechanism to a reset position. A coil on the magnetic circuit generates a magnetic flux in a direction same as that of the permanent magnet when an overload is detected and in an opposite direction when a predetermined time is elapsed after detecting the overload. A reset bar switches a movable stopper between an engaging position and a non-engaging position with the contact mechanism against a biasing force of the contact mechanism spring.

Abstract: A current detector includes a Hall-effect device 18 for detecting a magnetic field generated by a current flowing across a conducting portion; a magnetic core 19 having a first end face for concentrating a magnetic flux and a second end face having a smaller area than the first end face, only the second end face being disposed at a position in close proximity to or in abutment against a magnetic field detecting surface of the Hall-effect device; and a signal processing circuit 26 for processing an output signal from the Hall-effect sensor 18 into a signal representing the current flowing across the conducting portion.

Abstract: An electromagnet coil 2 wound on a fixed iron core 6 is energized by d.c. current supplied from a full-wave rectifier 1 to attract a movable armature 7. A transistor 10 is connected in series with the coil, a bias resistor 8 is connected across the coil to the base of the transistor, and a capacitor is connected between the base and collector of the transistor. The capacitor absorbs inductive energy stored in the coil 2 when the a.c. supply circuit is opened to thereby reduce the armature release time.

Abstract: A current transformer and current sensing relay are used to determine the maximum conduction time of the main interrupter in a power circuit. The operating time of the current sensing relay is less than that of the main interrupter but greater than that of a plurality of branch interrupters.

Abstract: A power breaker apparatus comprises a permanent fuse and resistors connected in parallel to the permanent fuse through a connecting conductor and is connected between a power source and a load to break a current supply to the load when a fault current is passed. At least external surfaces of the parallel resistors near the connecting parts of the connecting conductor are coated by an insulating coat.

Abstract: A current limiting apparatus comprises a current limiter and cooling fins formed on each current terminal of the current limiter, and additional cooling fins fitted on a cylindrical tube of the current limiter near a heat generating source.