The present invention is intended to provide constant drive conditions of a relay switch. A relay drive circuit includes a current mirror circuit, a current suppression circuit 26, and a transistor Q3. The current mirror circuit includes a transistor Q1, a first resistor element R1, a transistor Q2, and a second resistor element R2. A relay coil 18 is provided on a current supply path extending from a collector terminal of the transistor Q1 to an earth conductor. The current suppression circuit 26 includes a capacitor C1 as a current suppression element configured to suppress, after conduction between an emitter terminal and a collector terminal of the transistor Q2 has been made, the current flowing through the current suppression element itself as compared to that in such conduction.

This disclosure describes systems, methods, and apparatus for determining a relay delay for a relay of a relay device used to switch AC power to and from a load. The relay delay can be pre-determined as a model or polynomial including variables for temperature and age, such that the switching instructions can be sent to the rely a relay delay before a zero crossing of the AC signal that the relay is switching, and where the relay delay accounts for temperature and age of the relay in real time or near real time.

A circuit and method for controlling a voltage applied to a coil to actuate electromechanical relays or contactors. The strength of a magnetic field operating the coil is a function of the product of the number of turns of the coil wire and the magnitude of current, in amperes, passing through the coil wire. An adjustable voltage regulator provides a regulated voltage as an output to a first terminal of a coil to energize the coil based on the temperature of the coil as sensed by a temperature sensing device located proximate the coil. The regulated voltage is controlled based on the sensed coil temperature to consistently provide a current of optimal magnitude to actuate the coil at the sensed temperature. A transient voltage suppression circuit may be used with the coil to suppress back electromotive force generated currents and voltages when the coil is de-energized.

A PCB motor controller comprises relays mounted on a PCB and interconnected to power traces in or on the PCB to receive incoming three-phase power and to output three-phase power to a motor. Control power traces in or on the PCB connect the relays to control circuitry, also mounted on the PCB. A power supply is mounted on the PCB and connected to the control circuitry to provide power for its operation and for switching of the relays. The relays are switched in accordance with a point-on-wave (POW) switching scheme, allowing for the use or relays and the PCB, which may not otherwise be suitable for motor control applications.

A controllable trip device includes a magnetic actuator, including a coupling member intended to be coupled to a switching mechanism of an electrical circuit breaker to cause the switching thereof and a coil configured to displace the coupling member towards a tripped position when it is supplied with a pulse of a current of intensity greater than a first predefined threshold for a duration greater than or equal to a predefined duration, a control device, configured to supply the coil, immediately on receipt of a control signal, with a series of pulses of duration equal to the predefined duration and of intensity greater than or equal to the first threshold and less than or equal to a second threshold equal at most to 120% of the first threshold.

The magnetic coil driving circuit of the magnetic contactor according to the present invention comprises a semiconductor switch configured to open or close a circuit for magnetizing or demagnetizing a magnetic coil; a pulse width modulation unit configured to output a pulse signal as a control signal for turning on or off the semiconductor switch; a control unit configured to output a control signal for changing a pulse width of the pulse signal to the pulse width modulation unit; and a temperature detection and protection unit configured to detect a temperature inside the magnetic contactor, output an output signal for turning off the semiconductor switch when the temperature exceeds an allowable temperature, and control the semiconductor switch by the pulse signal from the pulse width modulation unit when the temperature is within the allowable temperature.

The present invention relates to a method for monitoring the state of the earthing contacts of a contactor controlled by an exciter coil, said contactor being operated as part of an isolation unit for galvanically isolating a voltage source from an electric consumer device connected to the voltage source, wherein a first power loss (22), which is transferred via the earthing contacts, and a second power loss (23), which is transferred via the exciter coil, are detected, and the first power loss (22) and the second power loss (23) are fed as input variables to a thermal model (21) of the contactor, the thermal model (21) determines an earthing contact temperature (24) according to at least one of the input variables and provides said contactor temperature as an output variable, and the provided earthing contact temperature (24) is evaluated.

A PCB motor controller comprises relays mounted on a PCB and interconnected to power traces in or on the PCB to receive incoming three-phase power and to output three-phase power to a motor. Control power traces in or on the PCB connect the relays to control circuitry, also mounted on the PCB. A power supply is mounted on the PCB and connected to the control circuitry to provide power for its operation and for switching of the relays. The relays are switched in accordance with a point-on-wave (POW) switching scheme, allowing for the use or relays and the PCB, which may not otherwise be suitable for motor control applications.

A circuit and method for controlling a voltage applied to a coil to actuate electromechanical relays or contactors. The strength of a magnetic field operating the coil is a function of the product of the number of turns of the coil wire and the magnitude of current, in amperes, passing through the coil wire. An adjustable voltage regulator provides a regulated voltage as an output to a first terminal of a coil to energize the coil based on the temperature of the coil as sensed by a temperature sensing device located proximate the coil. The regulated voltage is controlled based on the sensed coil temperature to consistently provide a current of optimal magnitude to actuate the coil at the sensed temperature. A transient voltage suppression circuit may be used with the coil to suppress back electromotive force generated currents and voltages when the coil is de-energized.

The present invention relates to a relay protective device, a construction machine, a relay protection control method and apparatus, and a computer readable storage medium. The relay protective device includes: a power supply input contact; a relay protective module comprising a bistable relay and an output contact, wherein the bistable relay comprises a contact, a pull-in coil, and a release coil; an input terminal of the contact, an input terminal of the pull-in coil, and an input terminal of the release coil are connected to the power supply input contact; an output terminal of the contact is connected to the output contact; and a central control unit comprising a first port connected to the output contact, a second port connected to an output terminal of the pull-in coil, and a third port connected to an output terminal of the release coil; the central control unit is used for controlling the pull-in coil and the release coil to be alternately powered on so as to oscillate the contact when a voltage of the output contact is less than a first threshold and is not less than a second threshold, wherein the first threshold is less than a standard working voltage of the bistable relay, and the second threshold is the minimum allowable working voltage of the bistable relay.