According to one or more embodiments, a current limiting device is provided. The current limiting device includes a transformer including: a primary winding configured to accept an input current, a core electromagnetically coupled to the primary winding, and a secondary winding electromagnetically coupled to the core. The secondary winding is configured to provide a current limiting energy source based on the input current where the current limiting energy source is limited to a predetermined maximum current based on at least one characteristic of the core.

According to an aspect of this disclosure, an intrinsically safe circuit includes a voltage source, a Zener diode, a transistor, a switching element, one or more resistors, and a current limiting stage. According to this aspect, the intrinsically safe circuit may be configured such that an over-voltage threshold is determined by a voltage across the Zener diode, a base-emitter voltage of the transistor, and a voltage across the one or more resistors.

An intrinsically safe (IS) multi-drop communication hub operable in a hazardous environment, including a power contact; a controller and a first signal input contact; a multiplexer communicatively connected to the controller; and a communication port communicatively connected to the controller to transmit the signal data provided by the multiplexer, wherein when the controller causes the multiplexer to supply power in a predetermined sequence to a first of the IS devices during a first time interval to generate a signal from the first of the IS devices and, after the first time interval, to a second of the IS devices during a second time interval, which does not overlap in time with the first time interval, to generate a signal from the second of the IS devices.

An electronic barrier device, includes an Isolating Barrier or a Zener Barrier, with a voltage limiter or voltage shunt such as at least one zener device for voltage limitation in a circuit during a fault condition. The barrier device includes a crowbar device arranged to latch across the at least one voltage shunt device to reduce power dissipation in the at least one voltage shunt device in the circuit fault condition. The crowbar device is arranged to latch responsive to a change in a current flowing in the barrier device.

A method and a device for supplying energy to a low-voltage load using an electronic power supply device. The method involves: a) setting the power supply device to be able to provide an output current to the low-voltage load up to a specified peak current value upon demand; b) monitoring the output current (I.sub.L) provided to the low-voltage load by the electronic power supply device to detect an increase of I.sub.L over a threshold (I.sub.N) which is lower than the peak current value, c) if an increase of I.sub.L to an increased output current value higher than I.sub.N is detected, detecting the increased I.sub.L value and ascertaining an output current pulse duration (t.sub.Pulse) based on the increased current value; d) providing I.sub.L at the level of the increased current value for the duration of the ascertained t.sub.Pulse; and e) providing the I.sub.L at the level of I.sub.N after t.sub.Pulse has expired.

A method of establishing current limits for each of a plurality of device couplers mounted on a trunk of an electrical circuit at distributed physical positions, in which each of said device couplers is capable of servicing one or more spurs connected thereto, and in which said trunk has a total trunk current and a known resistive component, comprising the steps of: a) establishing physical characteristics of the electrical circuit including i) an order in which said device couplers are mounted on said trunk along its length; ii) a load current each device coupler requires to service the one or more spurs connected thereto; and, iii) a voltage drop of each of said sections of trunk caused by the resistive component thereof, which is proportional to a physical length thereof and the combined load currents of each device coupler serviced by that section of trunk; b) calculating a current limit for each device coupler, which current limit is greater than said load current, according to a predetermined tolerance rationale; c) calculating an intermediate trunk current available to each device coupler by deducting from said total trunk current the current limits of each device coupler preceding that device coupler in said order, as well as a consequential reduction in current caused by said voltage drop of each of said sections of trunk preceding that device coupler; and, d) adjusting said current limits so none exceeds the intermediate trunk current available to the corresponding device coupler.

A device is provided for intrinsically safe redundant current supply of field devices with a common current-limiting resistor in the mesh of the field device and with redundant current supply units. A current sensor can be provided in the mesh of the field device, the output signal of which sensor is connected to a controllable voltage source in the redundant current supply units.

A guided wave radar level gauge comprising a housing providing explosion proof protection and having an intrinsically safe output, a transmission line probe connected to the IS output. The housing encloses radar level gauge circuitry which is incompatible with intrinsic safety requirements, a microwave unit connected to the IS output, an electrical barrier connected between the RLG circuitry and the microwave unit, the electrical barrier having a barrier ground potential which is independent from the grounded housing wall, and a set of blocking capacitors connected between the microwave unit and the IS output.

A power conditioning circuit includes at least one power storage device having electrodes coupled for receiving power from a DC power source. At least one active current limit (ACL) circuit coupled to the electrodes of the power storage device is for limiting a maximum power output from the power storage device under fault conditions. A DC-to-DC converter has its inputs coupled to the ACL circuit. At least one crowbar circuit has a first terminal and a second terminal and a shorting device coupled to an output of the DC-to-DC converter for providing output terminals for the power conditioning circuit.

Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.