The invention relates to an electrical device for transferring electric energy between the electrical device and an external electric circuit. The invention further relates to a computing device for use in cooperation with the electrical device. The invention further relates to a vehicle comprising the electrical device. The invention further relates to a method for detecting an arc fault using an electrical device. The invention further relates to a computer program having instructions to be executed by a computing device of an electrical device.

An electric circuit may suffer from arc faults. An arc fault is a high power discharge between two or more conductors. A common cause for such a discharge is damaged electrical wires in the electric circuit. If the insulating layers of two adjacent electrical wires are damaged, a voltage between the two electrical wires may cause an electrical discharge between the two electrical wires. Another common cause for an arc fault is a poor electrical connection in the electric circuit. The poor electrical connection may cause to repeatedly interrupt and reconnect the electric circuit. A voltage on the electrical connection may cause an arc at the poor electrical connection. The arc fault may cause a large amount of heat, causing further damage to the electrical wires and electrical connections. The arc fault may lead to fire.

If an arc fault occurs, this does not trip a fuse or an earth leakage circuit breaker. Despite that the arc fault generates a lot of heat, the electric current caused by the arc fault is typically not enough to exceed the threshold of the fuse. Also, the arc fault typically does not lead to any event that would trip the earth leakage circuit breaker.

To protect an electric circuit from arc faults, dedicated arc fault protection devices are available. A known arc fault protection device is disclosed in US6414829. The known arc fault protection device is arranged in the fuse box. The fuse box is connected to the power grid. Electric power is provided from the fuse box, via the arc fault protection device to a power outlet. If a device connected to the power outlet suffers an arc fault, the arc fault protection device interrupts the electric circuit.

Despite the safety features of arc fault protection devices, they are not very common in many countries. Also, if people want to use arc fault protection devices at home, in many cases they would need to replace the fuse box in their homes. Such a replacement is costly, and may not always be possible, e.g., in case of a rented house. It is an object of the invention to provide an electrical device that increases the safety of the electric circuit involved, especially the safety relating to arc faults, or to at least provide an alternative electrical device.

The object of the invention is achieved, in a first aspect of the invention, by an electrical device for exchanging electric energy with an external electric circuit. The electrical device comprises a coupling device, a sensor, and a control unit. The coupling device is adapted to connect the electrical device to the external electric circuit to form an AC circuit. The sensor is adapted to generate a signal representative of a current and/or a voltage of the AC circuit. The control unit is configured to receive the signal. The control unit is configured to operate the electrical device based on the signal. The control unit comprises a computing device adapted to detect an arc fault in the AC circuit based on the signal.

The control unit uses the sensor signal to operate the electrical device. Without the sensor, the electrical device would not work or would not work properly. The inventors have discovered that the same sensor that is used to operate the electrical device can have an additional function. The additional function is that the sensor is used to detect an arc fault in the external electric circuit.

If an arc fault occurs in the external electric circuit, the arc fault causes variation in the voltage and/or the electric current of the external electric circuit. There are many causes for variation in the voltage and/or the electric current in the external electric circuit. For example, switching high power appliances coupled to the external electric circuit on or off would cause variation. For example, a sudden increase or decrease of power supplied by a solar panel coupled to the external electric circuit would cause variation. However, despite all these variations, the variation caused by the arc fault has a typical frequency content or a typical variation over time. Because the electrical device is coupled to the external electric circuit, the arc fault occurring in the external electric circuit becomes visible in the AC circuit via the sensor. As a result, the arc fault becomes visible to the electrical device. The computing device is configured to identify the variation caused by the arc fault based on the signal from the sensor. This way the electrical device is able to detect the arc fault in the external electric circuit, improving the safety of the external electric circuit. The safety is improved without the need to adjust the fuse box of the external electric circuit. The safety is improved by simply coupling the electrical device to the external electric circuit. After the electrical device has detected the arc fault, the external electric circuit may need to be repaired to prevent the arc fault from occurring in the future. For example, damaged wiring of the external electric circuits is replaced, or an electrical connection is properly reconnected. So by using the signal from the sensor to operate the electrical device as well as to detect an arc fault, the electrical device increases the safety of the external electric circuit without the need for any dedicated arc detection system.

The electrical device may be any device that is able to transfer electric energy with the external electric circuit. The electrical device is adapted to receive electric energy from the external electric circuit, adapted to provide electric energy to the external electric circuit, or adapted to receive electric energy from the external electric circuit as well as to provide electric energy to the external electric circuit. The electrical device, for example, has a heating element to convert the electric energy from the external electric circuit to heat. The electrical device, for example, has an actuator to convert the electric energy from the external electric circuit to motion. For example, the electric energy is transferred from the external electric circuit to the electrical device when the actuator accelerates the motion, whereas the electric energy is transferred from the electrical device to the external electric circuit when the actuator decelerates the motion. The electrical device, for example, has a radiation source to convert the electric energy from the external electric circuit to radiation, such as visible light.

The external electric circuit is referred to as ‘external’ because the external electric circuit is an electric circuit that does not form part of the electrical device. The external electric circuit is an AC circuit. The external electric circuit has a phase wire, a neutral wire and an earth wire. An AC voltage is applied to the phase wire. When the AC circuit is closed, a current runs through the AC circuit. The current runs through the phase wire and the neutral wire. The earth wire is connected to an earthing point. The external electric circuit is, for example, the electric circuit of a house. The external electric circuit is, for example, the electric circuit of a public building or a factory or a server room. The external electric circuit is, for example, connected to the power grid. The external electric circuit has safety mechanisms such as a circuit breaker and an earth leakage circuit breaker. The circuit breaker interrupts the external electric circuit if a current through the circuit breaker exceeds a threshold. The earth leakage circuit breaker interrupts the external electric circuit if a leakage is detected, e.g., if a current is applied to the earth wire from the phase wire or from the neutral wire.

The coupling device comprises, for example, a plug and a cable to connect to a socket of the external electric circuit. The coupling device has, for example, an indicator light indicating if the energy is being transferred between the external electric circuit and the electrical device.

The sensor is adapted to generate the signal representative of a current and/or a voltage of the AC circuit. For example, the sensor is arranged in a part of the electrical device through which an AC current flows. The AC current originates from the AC circuit. For example, the sensor is arranged in a part of the electrical device at which an AC voltage is applied. For example, the sensor is adapted to be coupled to a phase wire and/or a neutral wire of the AC circuit via the coupling device. For example, an AC current from the external electric circuit flows through the sensor in the electrical device. When an arc fault occurs in the external electric circuit, the AC current changes. Typically, an arc fault creates a variation of the AC current with a certain frequency content and/or with a certain variation over time. Because the current sensor is able to detect the AC current, the computing device is able to determine that an arc fault occurs in the external electric circuit. In an example, the sensor comprises a voltage sensor configured to generate the signal based on a voltage of the AC circuit. An AC voltage from the external electric circuit is applied to the sensor in the electrical device. When an arc fault occurs in the external electric circuit, the AC voltage changes. Typically, an arc fault creates a variation of the AC voltage with a certain frequency content and/or with a certain variation over time. Because the voltage sensor is able to detect the AC voltage, the computing device is able to determine that an arc fault occurs in the external electric circuit.

The control unit is configured to operate the electrical device based on the signal from the sensor. For example, the control unit is configured to operate the electrical device to have the electrical device perform a main function. In case the electrical device is a motor, the main function is to provide motion. In case the electrical device is a heater, the main function is to provide heat. In case the electrical device is a cooler, the main function is to absorb heat. Based on the signal from the sensor, the control unit starts or stops the main function, or sets the main function at a certain level. For example, depending the signal from the sensor, the control unit converts a certain amount of electric power to perform the main function.

The computing device is a device that is able to receive the signal from the sensor and to process the signal. After processing the signal, the computing device is able to detect whether an arc fault has occurred in the AC circuit. For example, the computing device comprises a microprocessor or a Field-Programmable Gate Array (FPGA). For example, the computing device comprises a digital signal processor. For example, the computing device is configured to compare the signal from the sensor with a reference signal. The reference signal is, for example, a signal that indicates an arc fault or a signal that indicates that there is no arc fault. The computing device detects the arc fault when the difference between the signal from the sensor and the reference signal exceeds a threshold. The computing device is, for example, implemented on the same microprocessor as the control unit. For example, the computing device is integrated with the control unit. In another example, the control unit comprises multiple units, one of which is the computing device.

In an embodiment, the control unit is configured to operate the electrical device by controlling a current through the coupling device based on the signal.

According to this embodiment, the control unit controls the value of the current through the coupling device based on the signal from the sensor. For example, in case the signal from the sensor indicates that the AC voltage at the coupling device is above a threshold or below a threshold, the control unit prevents the current from flowing through the coupling device. This way damage to the electrical device may be prevented. For example, in case the signal from the sensor indicates that the AC current through the coupling device exceeds a threshold, the control unit reduces the AC current through the coupling by increasing an electrical resistance in the AC circuit. This way, damage to the electrical device may be prevented. In an example, the control unit is configured to determine a phase of the AC voltage based on the signal from the sensor. The control unit controls the AC current through the coupling device by adjusting the phase of the AC current through the coupling. This way, the power factor of the electrical device is improved, which improves the efficiency of the electrical device.

In an embodiment, the electrical device comprises a tripping unit configured to trip a safety mechanism of the external electric circuit in response to the computing device detecting the arc fault.

According to the embodiment, the external electric circuit has a safety mechanism, such as a fuse or a circuit breaker or an earth leakage circuit breaker or a combination thereof. All or almost all electric circuits are provided with one or more of such safety mechanisms. Such electric circuits are typically required to have the safety mechanisms because of safety regulations. Such safety regulations require that circuit breakers and earth leakage circuit breakers are provided in electric circuits in housing and office buildings. An example of such a safety regulation is the Dutch NEN 1010 regulation. The electrical device makes use of the safety mechanism of the external electric circuit. When the computing device detects an arc fault in the external electric circuit, the tripping unit trips the safety mechanism. This leads to an interruption of the external electric circuit. Because of the interruption, the arc fault stops to exist. This way, damage caused by the arc fault is prevented or limited. In most electric circuits, the safety mechanism is arranged at an upstream location of the external electric circuit, for example in the fuse box at which a main power line is connected to various groups of electric circuits. The safety mechanisms are placed at the upstream location to ensure that if the safety mechanism is tripped, a large portion or all of the electric circuit is interrupted. By interrupting the large portion or all of the electric circuit, no voltage is applied to the electric circuit anymore, or at least to a large portion thereof. By interrupting the large portion or all of the electric circuit, no current flows through the electric circuit anymore, or at least not through a large portion there off. Because the tripping unit trips a safety mechanism when the computing device detects the arc fault, there is a very high chance that the part of the external electric circuit in which the arc fault occurs is interrupted. Due to the interruption, the arc fault no longer occurs. In case the electrical device would only disconnect from the external electric circuit when detecting an arc fault in the external electric circuit, there is a high chance that the arc fault maintains even if the electrical device is disconnected from the external electric circuit.

In an embodiment, the tripping unit is configured to trip the safety mechanism of the external electric circuit by creating a short circuit in the AC circuit.

According to the embodiment, the tripping unit causes a short circuit in the AC circuit if the computing device detects an arc fault in the external electrical circuit. For example, the tripping unit comprises a switch that is adapted to couple the phase wire of the AC circuit directly to the neutral wire of the AC circuit. When the computing device does not detect an arc fault, the switch does not couple the phase wire to the neutral wire of the AC circuit. When the computing device detects an arc fault, the switch is flipped to couple the phase wire to the neutral wire of the AC circuit. Due to the lack of sufficient electrical resistance, the flipping of the switch causes a large current via the switch from the phase wire to the neutral wire of the AC circuit. The large current trips a circuit breaker in the external electric circuit. For example, the electrical resistance of the switch is low enough to create a large current of at least 80 A. The tripping unit is, for example, adapted to set the switch only a small amount of time in the setting that couples the phase wire to the neutral wire of the AC circuit. The small amount of time is sufficient to trip the circuit breaker of the external electric circuit. However, in case the circuit breaker does not work, the small amount of time is small enough to prevent damage from the short circuit. For example, the tripping unit is adapted to couple the phase wire to the neutral wire of the AC circuit via the switch for less than 1 second, for example, less than 300 ms, or less than 90 ms or less than 20 ms.

In an embodiment, the coupling device is adapted to be coupled to a earth wire of the external electric circuit. The tripping unit is configured to trip the safety mechanism by providing a current and/or a voltage to the earth wire.

According to this embodiment, the coupling device is able to couple to a earth wire of the external electric circuit. During normal operation of the external electric circuit, no voltage and no current is provided to the earth wire. During normal operation, voltages and currents are provided to the phase wire and the neutral wire of the external electric circuit. When the computing device detects an arc fault in the external electric circuit, the tripping unit provides a current and/or a voltage to the earth wire. For example, the tripping unit has a switch that is adapted to couple the phase wire of the AC circuit to the earth wire of the AC circuit. When the computing device does not detect an arc fault, the switch does not couple the phase wire to the earth wire of the AC circuit. When the computing device detects an arc fault, the switch is flipped to couple the phase wire to the earth wire of the AC circuit. This causes a current to flow through the earth wire. Because of the current through the earth wire, a difference is caused between the current through the phase wire and the current through the neutral wire. The difference causes the earth leakage circuit breaker of the external electric circuit to trip. The tripping of the earth leakage circuit breaker interrupts the external electric circuit. In another example, the tripping unit has a switch that is adapted to couple the neutral wire of the AC circuit to the earth wire of the AC circuit. When the computing device detects an arc fault, the switch is flipped to couple the neutral wire to the earth wire of the AC circuit. This causes a current to flow through the earth wire. Because of the current through the earth wire, a difference is caused between the current through the phase wire and the current through the neutral wire. The difference causes the earth leakage circuit breaker of the external electric circuit to trip. The tripping of the earth leakage circuit breaker interrupts the external electric circuit.

In an embodiment, the computing device is configured to detect the arc fault based on a variation of the signal over time and/or a frequency content of the signal.

According to the embodiment, the computing device receives the signal from the sensor. The computing device is, for example, configured to analyze the signal. For example, the computing device is configured to perform signal processing, such as performing a Fourier analysis. The computing device is, for example, configured to filter the signal from the sensor to remove or reduce components of the signal caused by other sources than an arc fault. For example, the filter may reduce or remove the 50 Hz or 60 Hz of the mains frequency of the AC circuit. For example, the filter reduces or removes other frequencies from the signal that are known to be caused by other sources, such as switching the power of appliances on and off. For example, the filter increases the amplitudes of frequencies in the signal caused by an arc fault to more clearly determine when an arc fault occurs. In an AC circuit, an arc fault typically creates a repetitive arc. The repetitive arc starts when the amplitude of the AC voltage exceeds a threshold. The repetitive arc is maintained as long as the amplitude of the AC voltage exceeds the threshold and disappears when the amplitude of the AC voltage becomes lower than the threshold. As a consequence of the repetitive arc, a current and/or a voltage of the AC circuit changes repetitively. The computing device is, for example, configured to identify such repetitive change to determine the presence of an arc fault.

In an embodiment, the computing device is configured to generate a warning signal in response to detecting the arc fault.

According to the embodiment, the computing device detects the arc fault and generates a warning signal. For example, the warning signal is sent to another component arranged in the electrical device. The other component is for example a display. The display shows a warning indicating an arc fault has been detected. The other component is, for example, a communication device. The communication device is configured to send a text message, or any other type of message based on the warning signal. The communication device is configured to send the message to a mobile device, such as a smartphone or tablet of the owner of the electrical device. The communication device is configured to send the message to a display. The display is, for example, electrically coupled to the external electric circuit. The display is, for example, arranged in the building having the external electric circuit. The communication device sends the message, for example, via WiFi or Bluetooth or any other type of wireless data transfer. For example, the electrical device is provided with a communication port to receive a network cable, such as an UTP cable or ethernet cable. The computing device is adapted to send the warning signal via the network cable. For example, the network cable is integrated in the coupling device.

In an embodiment, the control unit comprises a power factor correction controller. The power factor correction controller is configured to adjust a phase difference between the voltage of the AC circuit and a current through the coupling device.

According to the embodiment, the control unit comprises a power factor correction controller. The power factor is defined as the ratio between the real power absorbed or generated by the electrical device, and the apparent power flowing in the AC circuit. Ideally, the AC voltage and the AC current of the AC circuit are exactly in phase with each other. The electric power formed by the AC voltage and the AC current is completely used to transfer electric energy. In this case, the power factor is 1. When the power factor is 1 , the apparent power equals the real power. However, due to inductance or capacitance in the AC circuit, the AC voltage and the AC current may be out of phase with each other. Due to this phase difference, part of the apparent power is created as reactive power. Reactive power does not transfer energy from or to the electrical device, and causes increased currents and energy loss. The power factor correction controller is configured to reduce the phase difference by for example by providing a capacitor or an inductor to change the phase difference. The power factor correction controller is, for example, a passive power factor corrector, an active power factor corrector, or a dynamic power factor corrector.

In an embodiment, the electrical device comprises a power converter adapted to convert the electric energy between AC power and DC power.

According to the embodiment, the power converter is configured to convert electric energy from DC power to AC power, from AC power to DC power, or both from DC power to AC power and from AC power to DC power. This allows, for example, the AC power from the external electric circuit to be consumed by an DC application or to be stored on a battery. This allows, for example, energy from a solar panel that is generated as DC power to be supplied to the external electrical circuit. The control unit is, for example, configured to control the amount of electric energy to be converted between AC power and DC power based on the signal from the sensor. For example, the control unit limits the amount of AC power to prevent an excessively large DC current.

In an embodiment, the electric device comprises a low-pass filter for filtering the AC power as received from the external electric circuit. In particular, the low-pass filter can be arranged in the AC circuit as formed. In such an embodiment, the detection of the arc fault by the sensor can take place upstream of the low-pass filter (330). Within the meaning of the present invention, upstream refers to a direction from the electric device towards the external electric circuit.

In an embodiment, the electrical device comprises, as the power converter, a solar power inverter configured to receive electric energy from a solar panel as DC power and to transfer the electric energy to the external electric circuit as AC power. The control unit is configured to operate the solar power inverter by controlling it to convert the electric energy from the solar panel as DC power to electric energy as AC power.

According to the embodiment, the power converter converts the electric energy from the solar panel from DC power to AC power. The control unit is configured to control the operation of the solar power inverter, for example, by controlling the AC current of the AC power converted by the power converter. For example, the signal from the sensor indicates a sine shaped AC voltage of the external electric circuit. The control unit is configured to control the solar power inverter to convert the DC power from the solar panel to an AC power with a desired AC current. The AC current is in phase or substantially in phase with the sine shaped AC voltage to achieve an efficient transfer of the electric energy. For example, the signal from the sensor indicates an AC current provided by the solar power inverter to the external electric circuit. The control unit is configured to control the solar power inverter to provide the AC current at a desired value. At the desired value, the AC current is in phase with the AC voltage of the external electric circuit. For example, the control unit uses the signal from the sensor that indicates the AC current provided by solar power inverter in a feedback loop. In an example, the sensor comprises both a voltage sensor and a current sensor to provide a signal representative of the AC current and a signal representative of the AC voltage.

In an embodiment, the power converter is configured to be coupled to a battery to form a DC circuit to transfer the electric energy as DC power between the power converter and the battery. The power converter and the coupling device are connected to each other in the AC circuit to transfer the electric energy as AC power between the power converter and the external electric circuit.

According to the embodiment, the power converter is able to transfer electric energy between a battery and the external electric circuit. For example, electric energy from the external electric circuit is transferred to the battery via the power converter to charge the battery. For example, electric energy from the battery is transferred to the external electric circuit via the power converter to provide the electric energy to an appliance coupled to the external electric circuit. The control unit is, for example, configured to control the power converter based on the signal from the sensor. For example, the control unit controls the amount of AC current to the power converter to control an amount of DC power directed to the battery. For example, the control unit limits the amount of DC power to reduce a DC current through the battery or limits a DC voltage of the DC power in case the battery has a low state of charge. In another example, the signal from the sensor indicates that the AC voltage of the external electric circuit is below a threshold, for example in case of an issue with the external electric circuit. Based on the signal, the control unit controls the electrical device to provide electric energy from the battery to the external electric circuit. In this example, the electric device is an electric power supply in case of a power failure of the external electric circuit.

In an embodiment, the electrical device comprises the battery. The battery is adapted for storing the electrical energy.

According to the embodiment, the battery is part of the electrical device. For example, the battery is integrated in the electrical device. For example, the coupling device, the sensor, the control unit and/or the computing device are integrated in the battery.

In an embodiment, the control unit is configured to operate the electrical device based on the signal by transferring electric energy from the battery to the external electric circuit in response to the signal indicating a voltage of the external electric circuit deviates from a desired value.

In this embodiment, the signal from the sensor indicates that the AC voltage of the external electric circuit is, for example, below a threshold, for example in case of a power failure of the external electric circuit. Based on the signal, the control unit controls the electrical device to provide electric energy from the battery to the external electric circuit. In this example, the electric device is an electric power supply. In an example, the signal from the sensor indicates that the AC voltage of the external electric circuit is above a threshold, for example in case of connecting the electrical device to a wrong external electric circuit. The wrong external electric circuit may operate at a voltage that is too high compared to the voltage for which the electrical device is designed. To prevent damage to the electrical device, the control unit is configured to block any current from flowing through the coupling device, based on the signal from the sensor.

In an embodiment, the electrical comprises an electric motor having an electric coil arranged to generate a magnetic field to drive the electric motor. The control unit is configured to operate the electric motor based on the signal by providing a current to the electric coil.

According to the embodiment, the control unit uses the signal from the sensor to operate the electric motor. For example, the control unit controls the current to the electric coil to perform commutation. For example, the control unit controls the current to the electric coil to achieve a desired speed of the electric motor or a desired torque. The electric motor is, for example, a rotary motor or a linear motor. For example, the electric motor is an inwheel motor of a vehicle. For example, the electric motor has a rotor and a stator. The electric coil is arranged on the stator. An array of magnets is arranged on the rotor. The electric coil and the array of magnets cooperate together to create an electromagnetic force to drive the electric motor, i.e. , to move the rotor relative to the stator. In an example, the control unit is configured to control a current generated by the electric coil in case the electric motor decelerates. In case the electric motor decelerates, the electric motor may function as an electric generator. The kinetic energy of the electric motor is converted into electric energy via the electric coil. The control unit controls the amount of current generated from the kinetic energy by the electric coil.

In a second aspect of the invention, there is provided a computing device for use in cooperation with an electrical device according to any one of the preceding embodiments. For example, the computing device has an interface to connect with the sensor arranged in the electrical device. For example, the interface comprises a wired connection, such as a connection via an ethernet cable or UTP cable. For example, the interface comprises a wireless connection, such as WiFi or Bluetooth. A single computing device is, for example, configured to cooperate with a plurality of electrical devices. For example, the computing device is able to obtain signals from a sensor of each of the plurality of electrical devices simultaneously or in succession. For example, each of the plurality of electrical devices is connected to a different group in the external electric circuit. Each group has its own safety mechanism. When the computing device detects an arc fault in one of the electrical device, the corresponding group is interrupted by the corresponding safety mechanism, whereas the other groups are not interrupted.

In a third aspect of the invention, there is provided a vehicle comprising the electrical device according to any one of the preceding embodiments. The electrical device comprises an electric propulsion system for propelling the vehicle. The control unit is configured to operate the electric propulsion system.

The vehicle is a vehicle that uses electric energy to drive a motor to propel the vehicle.

The vehicle is, for example, a land-based vehicle, a water-based vehicle or an air-based vehicle. The electric vehicle is, for example, a car or a bus or a truck or a train. The electric vehicle is, for example, a boat or a ship. The vehicle is, for example, an aircraft. The electric vehicle has at least one electric motor to propel the vehicle. For example, the vehicle has an electric propulsion system that comprises multiple electric motors. For example, each of the multiple electric motors is coupled to a corresponding wheel to drive the corresponding wheel. For example, the propulsion system comprises an inwheel motor. For example, the vehicle is continuously in contact with the external electric circuit to receive electric energy. The external electric circuit, for example, comprises an overhead contact wire, and/or a live rail, which is also known as a third rail or conductor rail. For example, the vehicle is intermittently in contact with the external electric circuit to receive electric energy, and stores the electric energy from the external electric circuit in a battery.

For example, the vehicle has, in addition to the battery, a fuel tank, a combustion engine and a generator. The combustion engine is configured to combust fuel from the fuel tank to drive the generator. The generator is configured to generate electric energy. The generator provides the electric energy to the battery, to the electric motor or both the battery and the electric motor. The vehicle is, for example, an electric bicycle. The electric bicycle has an electric motor to provide some of the power to propel the electric bicycle. The electric bicycle has pedals coupled to a wheel of the electric bicycle to provide further power to propel the electric bicycle.

For example, the vehicle comprises a solar panel. The solar panel provides electric energy to the electrical device. In case the electric vehicle does not need the electric energy from the solar panel, for example in case the battery is fully charged, the electric energy from the solar panel may be transferred to the external electrical circuit. To do this, the power converter converts the electrical energy from the battery from DC power to AC power. The electrical energy as AC power is then transferred to the external electrical circuit via the coupling device.

In an embodiment, the vehicle comprises a battery. The electrical device is configured to transfer electric energy between the electric propulsion system and the battery. Optionally the electrical device is configured to transfer electric energy between the electric propulsion system and the external electric circuit. Optionally the electrical device is configured to transfer electric energy between the external electric circuit and the battery. In this option, the electrical device comprises or is, for example, an onboard charger. The onboard charger is configured to provide electric energy from the external electric circuit to the battery and/or vice versa.

According to the embodiment, the electric energy from the battery is used by the electric propulsion system to propel the vehicle. In addition, the battery is, for example, used to provide electric energy to systems of the vehicle that are not used for propelling the vehicle. Examples of such systems that are not used for propelling the vehicle are a light system, or a thermal control system configured to control a temperature of the vehicle, or an emergency brake control system configured to control the brakes of the vehicle in an emergency, or various electric controllers, such as a cruise control system configured to control a speed of the electric vehicle. The electric energy provided by the battery is, for example, provided at different voltages to these systems.

The battery is configured to store electric energy. For example, the battery is a lithium Ion (Li-Ion) battery, a molten salt (Na-NiCh) battery, a nickel metal hybrid (Ni-MH) battery, or a lithium sulphur (Li-S) battery. The battery is for example a single battery or comprises a plurality of batteries. The plurality of batteries are, for example, electrically arranged in parallel, in series, or in a combination of in parallel and in series. The plurality of batteries have the same maximum voltage or different maximum voltages. For example, the vehicle has a low voltage battery and a high voltage battery. The low voltage battery has, for example, a maximum voltage of 5 V or 12 V or 48 V. The high voltage battery has, for example, a maximum voltage of 60 V or 300 V or 400 V. For example, the high voltage battery provides electric energy to the drive train of the electric vehicle, such as the electric motor. For example, the low voltage battery provides electric energy to auxiliary components of the electric vehicle, such as the HVAC-system, and a lighting system.

In a fourth aspect of the invention, there is provided a method for detecting an arc fault using an electrical device, the method comprises the steps of:

- connecting the electrical device to an external electric circuit to form an AC circuit;

- generating a signal based on a current and/or a voltage of the AC circuit;

- operating the electrical device based on the signal,

- detecting an arc fault in the AC circuit based on the signal.

In an embodiment, the method comprises the step of:

- controlling a current between the electrical device and the external electric circuit based on the signal.

In an embodiment, the method comprises the step of:

- tripping a safety mechanism of the external electric circuit when detecting the arc fault. In an embodiment, the method comprises the step of:

- short-circuiting the AC circuit and/or tripping an earth leakage circuit breaker.

In an embodiment, the method comprises the step of:

- controlling a power factor of the electrical device based on the signal.

In a fifth aspect of the invention, there is provided a computer program having instructions which when executed by a computing device of an electrical device coupled to an external electric circuit to form an AC circuit, cause the electrical device to perform the steps of:

- generating a signal based on a current and/or a voltage of the AC circuit;

- operating the electrical device based on the signal;

- detecting an arc fault in the AC circuit based on the signal.

In an embodiment, the computer program causes the electrical device to perform the step of: - triggering a safety mechanism of the external electric circuit when detecting the arc fault.

In an embodiment, the computer program causes the electrical device to perform the step of detecting the arc fault in the AC circuit based on the signal to comprise the steps of:

- detecting a variation of the signal over time and/or

- detecting a frequency content of the signal.

In an embodiment, the computer program causes the electrical device to perform the step of:

- generating a warning signal when detecting the arc fault.

The invention will be described in more detail below under reference to the figures. In the figures, embodiments of the invention are shown. The figures show in:

Fig. 1 : an electrical device according to a first embodiment of the invention.

Fig. 2: an electrical device according to a second embodiment of the invention.

Fig. 3: an electrical device according to a third embodiment of the invention.

Fig. 4: a variation over time of a signal as detected with the computing device according to any of the previous embodiments of the invention.

Fig. 5: a frequency content of a signal as detected with the computing device according to any of the previous embodiments of the invention.

Fig. 6: a method according to a fourth embodiment of the invention.

Fig. 1 depicts an electrical device 100 for transferring electric energy between the electrical device 100 and an external electric circuit 110. The electrical device 100 comprises a coupling device 130, a voltage sensor 132, a current sensor 134, a control unit 136, and a computing device 138. The coupling device 130 is adapted to connect the electrical device 100 via a socket 114 to the external electric circuit 110 to form an AC circuit 140. The voltage sensor 132 is adapted to generate a voltage signal 162 representative of a voltage of the AC circuit 140. The current sensor 134 is adapted to generate a current signal 164 representative of a current through the AC circuit 140. In an embodiment, only one of the current sensor 134 and the voltage sensor 132 is present.

The electrical device 100 comprises a power converter 192, in particular a solar power inverter 192 configured to receive electric energy from a solar panel 190 as DC power and to transfer the electric energy to the external electric circuit 110 as AC power. The solar power inverter 192 can be considered an example of a power converter adapted to convert the electric energy between AC power and DC power. The AC circuit 140 has a phase wire 142, a neutral wire 144 and an earth wire 146. In the AC circuit 140, an AC voltage is applied to the phase wire 142. The AC circuit 140 transfers the AC power.

The solar panel 190 is connected to the electrical device 100 via a DC circuit. The DC circuit 150 has a positive DC wire 152 and a negative DC wire 154. The DC circuit 150 transfers the DC power.

The control unit 136 is configured to operate the power converter, i.e. the solar power inverter 192 by controlling the power converter to convert the electric energy from the solar panel 190 as DC power to electric energy as AC power. Alternatively or in addition, the power converter 192 can be configured to receive an AC power from an external circuit such as the external electric circuit 100 and convert the AC power to a DC power which can then be stored in a battery (not shown).

Optionally, the electric device 100 comprises a low-pass filter 194 configured to filter an AC power signal, e.g. an AC power as received from the external electric circuit 100. In the arrangement as shown, the low-pass filter 194 is arranged upstream of the power converter 192 and downstream of the voltage sensor 132 and the current sensor 134. In the embodiment as shown, the low-pass filter 194 is thus arranged in the AC circuit 140.

The control unit 136 is connected to the voltage sensor 132 to receive the voltage signal 162, and is connected to the current sensor 134 to receive the current signal. The control unit 136 is configured to operate the electrical device 100 based on the current signal 164 and the voltage signal 162. The control unit 136 is configured to operate the electrical device 100 by controlling a current through the coupling device 130 based on the current signal 164 and the voltage signal 162 by providing the current through the coupling device 130 in phase with the AC voltage of the AC circuit 140.

The computing device 138 is adapted to detect an arc fault 120 in the AC circuit 140 based on the current signal 164 and/or the voltage signal 162. As shown in Fig. 1, the current sensor 134 provides the current signal 164 to both the control unit 136 and the computing device 138. The voltage sensor 132 provides the voltage signal 162 to both the control unit 136 and the computing device 138.

When the computing device 138 detects the arc fault 120 in the AC circuit 140, the computing device 138 sends a signal to the tripping unit 180. The tripping unit 180 is configured to trip a safety mechanism of the external electric circuit 110 in response to the computing device 138 detecting the arc fault 120. The tripping unit 180 is configured to trip the safety mechanism of the external electric circuit 110 by creating a short circuit in the AC circuit 140 by closing switch 184. By closing switch 184, the phase wire 142 becomes directly coupled to the neutral wire 144 of the AC circuit 140. This causes a short circuit in the AC circuit 140 that trips a fuse or a circuit breaker in the fuse box 112. By tripping the fuse or the circuit breaker, the AC circuit 140 is interrupted, preventing further damage due to the arc fault 120. In addition, or alternatively, the tripping unit 180 is configured to trip the safety mechanism of the external electric circuit 110 by providing a current and/or a voltage to the earth wire 146 by closing switch 182. By closing switch 182, the phase wire 142 becomes directly coupled to the earth wire 146 of the AC circuit 140. This causes the earth leakage circuit breaker in the fuse box 112 to trip. By tripping the earth leakage circuit breaker, the AC circuit 140 is interrupted, preventing further damage due to the arc fault 120.

Fig. 2 depicts an electrical device 100 according to a second embodiment of the invention. The second embodiment may have the same features as the first embodiment, except for the following.

The electrical device 100 comprises an electric motor 290. The electric motor 290 has three electric coils 292 arranged on the stator, and a magnet 294 arranged on the rotor. The rotor is rotatable relative to the stator. The electric coils 292 are arranged to generate a magnetic field to drive the electric motor 290, i.e., to rotate the rotor relative to the stator. The electric coils 292 generate the magnetic field in response to a current flowing through the electric coils 292.

The control unit 136 is configured to operate the electric motor 290 based on the signal 162 and/or the signal 164 by providing a current to the electric coil 292. The control unit 136 comprises a power factor correction controller. The power factor correction controller is configured to adjust a phase difference between the voltage of the AC circuit 140 and a current through the coupling device 130. Further, the control unit 136 directs currents the electric coils 292 to commutate the electric coils 292.

Fig. 3 depicts an electrical device 100 according to a third embodiment of the invention. The third embodiment may have the same features as the first embodiment, except for the following.

In the third embodiment, the electrical device 100 is an onboard charger 370 in an electric vehicle 300. The electric vehicle 300 comprises an electric circuitry 102. The electric circuitry 102 comprises a battery 304 and the onboard charger 370. The battery 304 is configured to store electric energy. The electric vehicle 300 has four wheels and four electric motors 331-334 to propel the vehicle. Each of the electric motors 331-334 is coupled to one of the four wheels. Each of the electric motors 331-334 drives one of the four wheels. The battery 304 is connected to the electric motors 331-334 and provides electric energy to the electric motors 331-334 to drive the electric vehicle 300. The four electric motors 331-334 form at least part of an electric propulsion system. The onboard charger 370 comprises the coupling device 130. The coupling device 130 is configured to electrically couple the onboard charger 370 to the external electric circuit 110 110. The external electric circuit 110 comprises a charging station 324, and the fuse box 112. The external electric circuit 110 forms part of the AC circuit 140. Electric energy is provided from the fuse box 122 to the charging station 324, and via the charging station 324 to the coupling device 130.

The onboard charger 370 and the battery 304 are arranged to form a DC circuit 150 to transfer the electric energy as DC power between the onboard charger 370 and the battery 304. The DC power through the DC circuit 150 has a DC voltage and a DC current. The charging station 324 comprises a plug, whereas the coupling device 130 comprises a socket, or vice versa.

The fuse box 122, the charging station 324, the coupling device 130 and the onboard charger 370 form the AC circuit 140 when coupled together. The AC power through the AC circuit 140 has an AC voltage and an AC current. The onboard charger 370 is configured to transfer the electric energy as AC power between the onboard charger 370 and the external electric circuit 110.

A part of the onboard charger 370 forms part of the DC circuit 150, whereas another part of the onboard charger 370 forms part of the AC circuit 140. The onboard charger 370 comprises a power converter configured to convert the electric energy between the DC power and the AC power.

In case the electric vehicle 300 is coupled to the external electric circuit 110, and the onboard charger 370 charges the battery 304 with electric energy from the external electric circuit 110, an AC current flows through the phase wire 142 and the neutral wire 144. The onboard charger 370 converts the AC power created by the AC voltage and the AC current in the AC circuit 140. The onboard charger 370 converts the AC power to DC power. The energy at the AC power is at a first voltage. The onboard charger 370 is configured to convert the energy at the AC power at the first voltage to energy at the DC power at a second voltage. The second voltage is a voltage that is suitable to charge the battery 304. The second voltage is a DC voltage. When the onboard charger 370 converts the AC power to the DC power, a DC current flows through the DC circuit 150.

In case the electric vehicle 300 is coupled to the external electric circuit 110, the battery 304 may be used to provide electric energy to the external electric circuit 110. In this case, a DC current flows through the DC circuit 150 at a DC voltage. The onboard charger 370 converts the DC power created by the DC voltage and the DC current in the DC circuit 150. The onboard charger 370 converts the DC power to AC power. The onboard charger 370 is configured to convert the energy at the DC power at the DC voltage to energy at the AC power at an AC voltage. The AC voltage is a voltage that is suitable for use in the external electric circuit 110. When the onboard charger 370 converts the DC power to the AC power, an AC current flows through the AC circuit 140. The AC power is created by the AC voltage and the AC current.

The external electric circuit 110 may suffer from the arc fault 120. Because the onboard charger 370 forms part of the AC circuit 140, and because the onboard charger 370 comprises the voltage sensor 132 and/or current sensor 134 134, the computing device 138 is able to detect the arc fault 120.

Fig. 4 depicts a variation of time of a signal as measured with electrical device 100 according to any of the previous embodiments of the invention. Fig. 4 depicts a graph with time on the x-axis and a value representing a voltage on the y-axis. The graph represents the signal 164 provided by the voltage sensor 132 measuring the AC voltage of the AC circuit 140. The values of the voltage has been represented as a normalized value between -1 and + 1. Depending on the voltage of the AC circuit 140, the voltage may range from -110 V to +110 V, from -220 V to +220 V or any other range. The time on the x-axis has been indicated to increase when moving from left to right along the graph. The time values depend on the mains frequency of the AC voltage, for example 50 Hz or 60 Hz or any other suitable frequency.

The graphs shows a time period 400 at which no arc fault occurs. In the time period 400, the voltage sensor 132 measures a voltage that changes over time in a sine shape. Some small variations on the sine shape may occur. In the time period 410, an arc fault 120 occurs. As is clear from the graph, the sine shape changes and includes disturbances 411. These disturbances 411 are typical for an arc fault 120. By detecting the disturbances 411 with the voltage sensor 132, the computing device 138 is able to detect the arc fault 120.

Fig. 5 depicts a frequency content of the signal 162 as measured with the electrical device 100 according to any one of the previous embodiments. Fig. 5 depicts a graph with frequencies on the x-axis and a magnitude of those frequencies on the y-axis. The graph represents the frequency content of the signal provided by the voltage sensor 132 measuring the AC voltage of the AC circuit 140. A similar graph is for example made based on the signal from the current sensor 134. The values of the frequencies and the magnitudes are left out of the figure, because these depend on various factors, such as the mains frequency of the AC circuit 140, the amplitude of the AC voltage and the amplitude of the AC current.

Line 500 shows the frequency content of the signal when no arc fault occurs. The frequency content is mostly concentrated around the mains frequency 510 of the AC circuit 140. The mains frequency 510 is for example 50 Hz or 60 Hz. Ideally, the frequency content around mains frequency 510 is a narrow spike. However, due to various disturbances in the AC circuit 140, there is a frequency band around the mains frequency 510 caused by the disturbances. In case there is no arc fault, frequencies other than the mains frequency 510 are present in the frequency content of the signal. As shown in line 500, the magnitudes of those other frequencies are much lower than the magnitude of the mains frequency 510.

Line 502 shows the frequency content of the signal when the arc fault 120 occurs. Due to the arc fault 120, the amplitudes of frequencies other than the mains frequency 510 increase in the signal. As a result, the magnitude of the main frequency 510 reduces, whereas the magnitudes of frequencies other than frequency 510 increase. This makes that the signal has a lower magnitude for the mains frequency 510 when the arc fault 120 occurs compared to when the arc fault 120 does not occur. The signal has a higher magnitude for a frequency other than the mains frequency 510 when the arc fault 120 occurs compared to when the arc fault 120 does not occur. Based on the change in the frequency content, the onboard charger 106 is able to detect that the arc fault 120 occurs. For example, the computing device 138 detects the arc fault 120 when the change of the frequency content exceeds a threshold.

Fig. 6 depicts a method for detecting an arc fault 120 using an electrical device 100 having a sensor, according to a fourth embodiment of the invention. The method comprises the following steps. Connecting the electrical device 100 to an external electric circuit 110 to form an AC circuit 140. Generating with the sensor a signal based on a current and/or a voltage of the AC circuit 140. Operating the electrical device 100 based on the signal. Detecting an arc fault 120 in the AC circuit 140 based on the signal.

Optionally, the method comprises the step of controlling a current between the electrical device 100 and the external electric circuit 110 based on the signal.

Optionally, the method comprises the step of tripping a safety mechanism of the external electric circuit 110 when detecting the arc fault 120.

Optionally, the method comprises the step of short-circuiting the AC circuit 140 and/or tripping an earth leakage circuit breaker.

Optionally, the method comprises the step of controlling a power factor of the electrical device 100 based on the signal.

In an embodiment, there is provided a computer program having instructions which when executed by the computing device 138 of the electrical device 100 coupled to the external electric circuit 110 to form an AC circuit 140, the electrical device 100 comprising the sensor 132 or 134, cause the electrical device 100 to perform the following steps. Generating a signal with the sensor based on a current and/or a voltage of the AC circuit 140. Operating the electrical device 100 based on the signal. Detecting an arc fault 120 in the AC circuit 140 based on the signal. Optionally, the computer program causes the electrical device 100 to perform the step of triggering a safety mechanism of the external electric circuit 110 when detecting the arc fault 120.

Optionally, the computer program causes the step of detecting the arc fault 120 in the AC circuit 140 based on the signal to comprise the steps of detecting a variation of the signal over time and/or detecting a frequency content of the signal.

Optionally, the computer program causes the electrical device 100 to perform the step of generating a warning signal when detecting the arc fault 120. As required, this document describes detailed embodiments of the present invention.

The various terms used in the description should not be interpreted as restrictive but rather as a comprehensive explanation of the invention.

The word "a" used herein means one or more than one, unless specified otherwise. The phrase "a plurality of" means two or more than two. The words "comprising" and "having" do not exclude the presence of more elements.