Safety device for an electrical apparatus powered by an AC mains power supply, the safety device comprising: an electric circuit having inputs for connecting to an active, neutral and earth conductors of the electrical apparatus which are in turn coupled to the AC mains power supply, the circuit being operable to: produce and apply a stepped down voltage and current to the earth conductor from the main supply; and electrically isolate the active and neutral conductors from the earth conductor in response to detecting that either: the active conductor is incorrectly wired to the neutral circuit of the AC mains power supply; the neutral conductor is incorrectly wired to the active circuit of the AC mains power supply; or the neutral conductor is switched; wherein one or more solid state relays are employed by the circuit for both producing the stepped down voltage and electrically isolating the conductors from earth.

The disclosure relates to a control device for a motor vehicle which comprises a first electrical terminal for receiving a first supply voltage of a first vehicle electrical system and a second electrical terminal for receiving a second supply voltage of a second vehicle electrical system, the second supply voltage being smaller than the first supply voltage, wherein an electrical ground terminal is provided for closing a common ground potential of the first and second vehicle electrical systems, and a switching device connected downstream of the first terminal is set up, depending on a voltage signal which is determined by a potential difference between the second terminal and the ground terminal, to block a current flow through the first terminal, wherein the switching device interrupts the current flow if the voltage signal indicates an interruption of an electrical connection between the ground terminal and the ground potential.

An apparatus for detecting an open neutral condition in a split phase power system is described. The apparatus includes two powered lines providing output electricity to an electrical distribution system and a shared neutral line providing a grounded neutral to the first and second powered lines. The apparatus is configured for detecting when an open neutral condition is present in the split phase power system by determining when a power current is present on one or both of the first and second powered lines while a return current is not present on the neutral line; and in response to detecting that the open neutral condition is present, causing an interrupter to interrupt the power supplied by the first and second powered lines or to generate a signal indicating an open condition.

A ground fault monitoring system for an electrical service panel is provided. The ground fault monitoring system includes a current transformer coupled to a primary bonding location of the electrical service panel. The ground fault monitoring system also includes a current monitoring device in communication with the current transformer to detect ground fault electrical current returning to the electrical service panel. The ground fault monitoring system also includes a ground fault output interface in communication with the current monitoring device to provide ground fault status of the electrical service panel.

A load drive circuit includes a power source terminal (PST), a power source and a load terminal connecting a load to the power source. A semiconductor switch connects the PST to the load terminal. A control circuit includes an output terminal for opening/closing the semiconductor switch. A freewheeling circuit includes a freewheeling diode and a protection switch blocks a current from the power source to the semiconductor switch when the power source is connected in a reverse manner. A first terminal connects the control circuit to a first fixed potential and a second terminal connects an anode of the freewheeling diode to a second fixed potential. A connection circuit includes a connection switch connecting the output terminal and the first terminal. The connection circuit connects the output terminal to the first terminal when a rise in a potential difference between the first terminal and the second terminal is detected.

A circuit for detecting a status of a ground connection in an electric motor includes a rectifier, a converter, a voltage conditioning circuit, a leakage circuit, and a comparator. The rectifier couples to an AC line within the motor and generates a first DC voltage. The converter steps-down the first DC voltage to a second DC voltage. The voltage conditioning circuit couples to the converter, leakage circuit, and comparator, and generates a reference DC voltage signal and a leakage voltage from the second DC voltage. The leakage circuit includes an impedance coupled to ground, and applies the leakage voltage to the impedance and generates a measurement signal representing a leakage current through the impedance to ground. The comparator couples to the leakage circuit and generates a logic signal, indicating a status of the ground connection, based on a voltage difference between the reference DC voltage signal and the measurement signal.

In one embodiment, an aircraft electronics system includes a hardware processor, a charge collection circuit to collect charge; a switching circuit controlled by the hardware processor to discharge the charge collected on the charge collection circuit through a bonding circuit formed from a chassis and a bonding surface; and a voltage measurement circuit to measure a voltage difference between measurement terminals across the chassis and the bonding surface.

In an embodiment, a missing utility ground detection circuit includes a pair of balanced resistors each connected to receive utility voltage from a different one of a pair of utility power lines, the balanced resistors being connected together at a summing node to be capable of summing the voltages from the pair of utility power lines. It includes an unbalance resistor connected to shunt voltage from one of the utility power lines. It has a summing amplifier with an input coupled to the summing node and to a reference voltage, and an input coupled to a second reference voltage. It has an averaging circuit connected at the output of the summing amplifier. A comparator is provided having an input connected to the averaging circuit an input connected to a threshold voltage.

A power supply control device that includes a switch control unit that is configured to switch on and off a first switch and a second switch and receive a supply of power from a battery, the first switch and the second switch being respectively provided in a plurality of power supply paths through which power is supplied from one end of a battery to one end of a first load and one end of a second load; an output terminal from which current that flows from the battery via the switch control unit is output; a diode whose anode is connected to the output terminal, and whose cathode is connected to one end of the second load; an opening detection circuit; and a voltage detection circuit.

The present disclosure discloses a grounding wire detection circuit, for monitoring whether an electrical device is grounded in real time, the grounding wire detection circuit including: a grounding detection circuit and a sampling control circuit, wherein the grounding detection circuit is electrically connected to a live wire, a neutral wire and a grounding wire of a single-phase three-wire type input, the live wire and the neutral wire are electrically connected to a main circuit of the electrical device; and the sampling control circuit is configured to isolate a current detected by the grounding detection circuit and convert the current into a sampling voltage. The real-time monitoring of whether or not a device is grounded may be achieved by detecting the sampling voltage, so as to alarm, cut off electrical device accordingly, which can improve safety of using the electrical device.