Fuji Electric Co., Ltd.

Junzo Tanaka

Takahiro Kudo

Kimitada Ishikawa

Tomio Shimizu

Kazusue Itoga

Masahide Ishikawa

Kazuo Sakurai

An over-current protection device is constituted of a current detection unit for detecting a current from a power-supply source to a load having a magnetism detection element with a magnetic impedance (MI) effect, an AC-current supply device for supplying an AC current to the detection element, a bias-current supply device for supplying a bias current to a bias coil, a peak detection device for detecting a peak of impedance of the magnetism detection element as a variation of voltage, and a switch corresponding to a phase for selecting an output of the peak detection device. In the current detection unit, a holding device for holding a switch output and an amplifier are disposed in common for detecting the current in each phase, thereby expanding a current detectable range and reducing power consumption and cost.

Over-current protection device

A current sensor which constitutes an overload protection apparatus and senses a current supplied from a power source to a load is constituted by providing a magnetic sensor having the effect of magnetic impedance (MI), an AC supply means which impresses AC on this sensor, a bias current supply means which supplies a bias current to a bias coil, a peak sensing means which senses the peak or a change in impedance of the magnetic sensor as a change in voltage, and a switch which selects the output of the peak sensing means in accordance with each phase. A holding means which holds switch outputs one after another and an amplification means are provided in common to enable current sensing for each phase. Thus, a range of current sensing is enlarged to reduce power consumption and cost.

Overload current protection apparatus

Semiconductor switching elements (inverse-parallel connected thyristors) of each main circuit element unit are connected in parallel to a main contact of an electromagnetic contactor. An operation input voltage signal applied to an electromagnetic coil of the electromagnetic contactor is detected by an input-voltage detecting circuit of a control section. When the electromagnetic contactor is closed and opened, a one-shot-pulse generating unit outputs a one-shot pulse based on an output of the input-voltage detecting circuit and a signal indicating an opening/closing state of an auxiliary normally-closed contact of the electromagnetic contactor. The semiconductor switching elements are made on only for a short time by a firing circuit based on the one-shot pulse, to turn on and off a load current.

Hybrid switch using a one-shot firing pulse

A multiphase solid-state contactor for controlling a principal circuit, comprising a plurality of thyristors connected in anti-parallel relation, and an electronic control circuit connected to the thyristors including a firing control circuit, an input circuit and a surge absorbing circuit. The input circuit may include a rectifier and voltage detector for compensating for variations in the operating voltage of the principal circuit. Each of the firing control circuit, the input circuit and the surge absorbing circuit may comprise separate printed circuit boards which may be mounted in stacked relation in a casing for ease of handling and repair. Auxiliary terminals are also provided for outputting an auxiliary output signal from the device.

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Saitama, Japan

Junzo Tanaka