A method of operating an automatic transfer switch to switch an electrical load from one power source to another power source includes measuring one or more characteristics of a switching circuit in the automatic transfer switch. A value of one or more timing variables is determined based on the measured characteristics of the switching circuit. The switching circuit is operated to close relays in the automatic transfer switch. The timing of closing of the relays is based on the value of the timing variables.

The invention discloses a short circuit current hierarchical control tripping parameter circuit breaker. According to the invention, resistance of an alloy magnetic resistance body is changed through circuit current, and contract control can be carried out on short-circuit current. The control range of the circuit breaker can achieve that no magnetic resistance will be generated when current is no more than 8 times of rated operational current, and current limiting may be realized by the magnetic resistance when current is 8 times more than rated value. In this way, hierarchical control on short-circuit current of different levels of circuits can be carried out, and short-circuit current can be limited in a predetermined range, thereby restricting the short-circuit current in a predetermined range, solving a problem of power supply flickering, and avoiding large-area power failure accidents caused by override trip existing in an electrical control switch.

A low-profile electrical contactor is provided comprising at least one electrical contact switch, an actuation means and a current determining device. The or each electrical contact switch has first and second electrical terminals, an electrically-conductive busbar in electrical communication with the first electrical terminal, the busbar having two end faces between which a current can flow in a flow direction and at least two flat sides in parallel with the flow direction, at least one fixed electrical contact which is attached to the busbar, an electrically-conductive moveable arm in electrical communication with the second electrical terminal, and at least one moveable electrical contact which is attached to the electrically-conductive moveable arm to form an electrical contact set with the fixed electrical contact. The actuation means can actuate the electrically-conductive moveable arm of the or each electrical contact switch between open and closed conditions. The current determining device has a first field-modifying element formed of a magnetic material located at or adjacent to the first end face of the busbar, a second field-modifying element formed of a magnetic material and located at or adjacent to the second end face of the busbar, at least one sensing coil at or adjacent to the busbar and the first and second field-modifying elements, and having a coil axis between planes of the first and second flat sides. An electromagnetic field induced by the current flowing in the busbar is modified by the first and second field-modifying elements to extend more or substantially more in parallel with the coil axis of the sensing coil.

A voltage and/or current sensing device for low-, medium- or high voltage switching devices is disclosed as a constructively enhanced measuring device with high performance for use in switching devices. The sensing device can include a first voltage sensing part, a second voltage sensing part and a current sensing part all arranged in a same common single housing separated, from the switching device, in a way that an output wire from the first voltage sensing part, for sensing voltage at an upper terminal of the switching device, is located close to the current sensing part, the output wire being applied with an insulating cover, and mechanically fixed to the current sensor part, and/or the output wire being implemented in an isolation body, and only located near to the current sensing part.

A circuit breaker includes at least one coil for measuring electric current of an electrical conductor of an electrical circuit, connected to a control unit which compares the measured current or its equivalent with a first current limit value. Upon the first current limit value being exceeded, the control unit initiates an interruption of the electrical circuit. The two terminals of the coil are connected via a series circuit which has a first switch opened in its basic state, a voltage source and a voltage indicator. The control unit is designed such that, when a second current limit value is undercut and a first period of time is exceeded, the first switch is closed for a second period of time, the voltage indicator compares the voltage present with a first voltage value and, when the latter is exceeded, delivers information on the absence of faults of the coil.

The invention discloses a short circuit current hierarchical control tripping parameter circuit breaker. According to the invention, resistance of an alloy magnetic resistance body is changed through circuit current, and contract control can be carried out on short-circuit current. The control range of the circuit breaker can achieve that no magnetic resistance will be generated when current is no more than 8 times of rated operational current, and current limiting may be realized by the magnetic resistance when current is 8 times more than rated value. In this way, hierarchical control on short-circuit current of different levels of circuits can be carried out, and short-circuit current can be limited in a predetermined range, thereby restricting the short-circuit current in a predetermined range, solving a problem of power supply flickering, and avoiding large-area power failure accidents caused by override trip existing in an electrical control switch.

A method of operating an automatic transfer switch to switch an electrical load from one power source to another power source includes measuring one or more characteristics of a switching circuit in the automatic transfer switch. A value of one or more timing variables is determined based on the measured characteristics of the switching circuit. The switching circuit is operated to close relays in the automatic transfer switch. The timing of closing of the relays is based on the value of the timing variables.

A protective circuit breaker includes a switch housing; connection pieces; a switching contact arranged in the switch housing and connected to the connection pieces; a converter housing including a first passage opening and inserted into a recess in the switch housing and through which the second connection piece runs; a converter coil being arranged around the passage opening/the second connection piece; a plate-like converter cover including a second passage opening through which the second connection piece extends. In order to permit a simple voltage tap, in an embodiment the converter cover has arranged on it: a first contact bearing against the second connection piece at the converter cover, a second contact electrically connected to the first connection piece, and a third contact connected to the first or a second electronics system. An electrical connection is included, via which the third contact is selectively connectable to the first or second contact.

A fusible switch disconnect device includes a housing adapted to receive at least one fuse therein, and a switchable contact for connecting the fuse to circuitry. A current detecting element, a tripping mechanism, and control circuitry are provided to move the switchable contact to an open position in response to predetermined electrical current conditions in the device.

A circuit breaker device for a low-voltage circuit has a mechanical isolating contact unit connected in series with an electronic disconnection unit. The mechanical isolating contact unit is switched by opening contacts to prevent current flow or closing the contacts for current flow in the low-voltage circuit. The electronic disconnection circuit is switched by semiconductor-based switching elements into a high-resistance state of the switching elements or into a low-resistance state of the switching elements for current flow in the low-voltage circuit. When the amount of an instantaneous current value of the low-voltage circuit exceeds at least one current threshold value, prevention of the current flow of the low-voltage circuit is initiated. The at least one current threshold value is adjusted according to the magnitude of the voltage of the circuit breaker device.