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 tripping mechanism including an electromagnetic coil is operable to move the switchable contact to an open position in response to a predetermined electrical condition when the fuse is engaged and when the switchable contact is in the closed position.

A power semiconductor circuit is provided for clamping the voltage across the circuit when a power semiconductor switch is opened (i.e., turned off). The circuit may include a first surge arrester and a first semiconductor switch coupled in parallel with the power semiconductor switch. The first semiconductor switch is coupled in series with the first surge arrester. A second surge arrester may be coupled to the gate of the first semiconductor switch to control current flow through the first semiconductor switch and the first surge arrester.

A method for estimating a property of an electrical switching device includes: detecting a movement of electrical contacts of the switching device beyond an opening threshold; measuring, for at least one phase of the electrical device, the electric current through this phase; evaluating, for at least one phase of the electrical device, the voltage of an electric arc between the electrical contacts that are associated with this phase; and calculating, for at least the phase of the electrical device, an energy value associated with the electric arc, by numerically integrating the product of the measured electric current and of the evaluated voltage, the integration being performed over a time interval starting from the detection of the movement of the electrical contacts.

A hybrid load protection apparatus (1) comprises a primary power supply path (1A) provided between an input terminal (2) and output terminals (2, 3) and a controllable mechanical switch (5A) connected in series with a primary coil (4A-1) coupled inductively to a secondary coil (4A-2) providing a voltage, U.sub.A, corresponding to a current rise speed of the electrical current flowing through the primary path (1A). The voltage, U.sub.A, is applied directly to a driver input (IN) of a first driver circuit (6A) to trigger automatically a switch-off of the mechanical switch (5A) within a first switch-off period (Δt1) to interrupt the primary power supply path (1A), A secondary power supply path (1B) is provided in parallel to the primary path (1A) and having a further coil (4B) connected in series with a semiconductor power switch (5B). wherein a second driver circuit (6B) associated with the secondary path (1B) detects an increasing electrical current, I, flowing through the secondary path (1B) caused by the interruption of the primary current path (1A) on the basis of a voltage drop (ΔU.sub.4) generated by the further coil (4B) and a non-linear voltage drop (ΔU.sub.5) along the semiconductor power switch (5B) applied as a sum voltage (U.sub.B) directly to a driver input (DESAT) at a high voltage side of the second analog driver circuit (6B) to trigger automatically a switch-off of the semiconductor power switch (5B) within a second switch-off period (Δt2) to interrupt the secondary power supply path (1B).

A method for estimating a property of an electrical switching device includes: detecting a movement of electrical contacts of the switching device beyond an opening threshold; measuring, for at least one phase of the electrical device, the electric current through this phase; evaluating, for at least one phase of the electrical device, the voltage of an electric arc between the electrical contacts that are associated with this phase; and calculating, for at least the phase of the electrical device, an energy value associated with the electric arc, by numerically integrating the product of the measured electric current and of the evaluated voltage, the integration being performed over a time interval starting from the detection of the movement of the electrical contacts.

A circuit-breaker includes an electronic trip unit, which initiates an interruption or reduction of the current flow in a low-voltage circuit when current or current-time limits are exceeded in the low-voltage circuit. The electronic trip unit includes at least two processors that independently check whether current or current-time limits are being exceeded. A test signal is fed to the circuit-breaker via a first communication interface, which is fed to one of the two processors during operation so that a test of the circuit-breaker is carried out during operation, while at the same time an active protection is provided with regard to the exceeding of current or current-time limits.

Disclosed is an air circuit breaker including a safety cover. According to embodiments disclosed herein, a setting unit of an overcurrent trip relay exposed to the outside through an opening is covered by the safety cover, and thus manipulation of the setting unit is not allowed before opening the safety cover. Accordingly, an accident due to malfunction or manipulation of the overcurrent trip relay by an unauthorized person may be prevented.

A smart circuit breaker includes a communication interface, separable contacts, a processing unit having a memory with a routine stored therein which, when executed by the processing unit causes the processing unit to: sense a power outage in an electrical grid, control a meter to open contacts to disconnect from the electrical grid, sense power restoration to the electrical grid, control contacts corresponding to a secondary power source to open, control the meter to close contacts to reconnect to the electrical grid, sense that a frequency of power from the electrical grid matches a frequency of power from the secondary power source, and control the contacts corresponding to the secondary power source to close.

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 tripping mechanism and control circuitry are provided to move the switchable contact to an open position in response to a predetermined electrical condition.

A solid-state circuit breaker (SSCB) with self-diagnostic, self-maintenance, and self-protection capabilities includes: a power semiconductor device; an air gap disconnect unit connected in series with the power semiconductor device; a sense and drive circuit that switches the power semiconductor device OFF upon detecting a short circuit or overload of unacceptably long duration; and a microcontroller unit (MCU) that triggers the air gap disconnect unit to form an air gap and galvanically isolate an attached load, after the sense and drive circuit switches the power semiconductor device OFF. The MCU is further configured to monitor the operability of the air gap disconnect unit, the power semiconductor device, and other critical components of the SSCB and, when applicable, take corrective actions to prevent the SSCB and the connected load from being damaged or destroyed and/or to protect persons and the environment from being exposed to hazardous electrical conditions.