Circuit breaker with rotor and stator

Abstract

The disclosure relates to a circuit breaker (200), comprising: a pair of rotationally movable contacts (130a, 130b) which are configured to contact a respective pair of bus terminals (110a, 110b) in a closed position of the circuit breaker (200); a rotor (220) being configured to rotate the movable contacts, the rotor comprising a set of magnets (221, 222) which are rotationally symmetrically arranged around a rotor axis of the rotor, wherein two magnets arranged next to each other are oppositely magnetized; and at least one stator (210) to which the rotor (220) is rotationally attached; the at least one stator (210) comprising a set of coils (211) which are rotationally symmetrically arranged around a stator axis of the at least one stator (210) that coincides with the rotor axis of the rotor (220). In the closed position of the circuit breaker (200) the magnets are arranged angularly offset with respect to the coils (211) in the set of coils (211) in order to apply a torque force (145) on the rotor upon activation of the circuit breaker by a current flowing through the coils (211) in the set of coils (211) thereby moving the pair of contacts (130a, 130b) in an open position of the circuit breaker.

Description

[0001] CIRCUIT BREAKER WITH ROTOR AND STATOR

[0002] TECHNICAL FIELD

[0003] The disclosure relates to the field of fast interruption of fault currents in alternating current (AC) and direct current (DC) systems by using circuit breakers. The disclosure relates to a circuit breaker, a circuit breaker with a rotor and one or more stators. The disclosure also relates to a high-speed circuit breaker.

[0004] BACKGROUND

[0005] Fast breakers are an emerging field. Normally such fast breakers are not needed since AC systems are dominant. However, due to the push of renewable energy technologies to reduce the emission of carbon dioxide gases, and increase efficiency, DC systems are becoming more and more important. Hence fast breakers are becoming very important. In many application scenarios, complete interruption speeds less than 1 ms are achieved by using solid-state breakers. However, solid-state breakers suffer from high conduction losses, they are expensive and less reliable and do not provide isolation. Since solid-state breakers are made of semiconductor materials, they do not conduct well resulting in high conduction losses. This often results in the need to use a cooling system such as water cooling which is very expensive and not very reliable. Lastly, semiconductors do not offer a physical isolation and always have leakage currents limiting their use independently.

[0006] SUMMARY

[0007] This disclosure provides a circuit breaker for interrupting fault currents without suffering from the above-described problems. For example, a reliable non-expensive circuit breaker with an interruption speed less than 1 ms that does not suffer from conduction losses.

[0008] The disclosure presents a novel high-speed motor to drive the contacts of a circuit breaker really fast, in less than 1 ms. Such ultra-fast circuit breaker can interrupt the circuit before any damage can happen to the circuit. In the event of a fault, the circuit breaker can open the electrical contacts very fast before the current has a chance to increase in magnitude and becomes harder to interrupt.

[0009] The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

[0010] In this disclosure, a new circuit breaker is introduced able to interrupt fault currents really fast, in less than 1 ms. The new circuit breaker is based on a new motor design, also referred to as axial flux motor hereinafter. This axial flux motor comprises a rotor and at least one stator. The design is described below with respect to Figures 1 to 7.

[0011] In order to describe the disclosure in detail, the following terms and notations will be used.

[0012] AC Alternating current

[0013] DC Direct current

[0014] PV Photovoltaic

[0015] LV Low voltage

[0016] S magnetic south pole

[0017] N magnetic north pole According to a first aspect, the disclosure relates to a circuit breaker, comprising: a pair of rotationally movable contacts which are configured to contact a respective pair of bus terminals in a closed position of the circuit breaker; a rotor being configured to rotate the movable contacts, the rotor comprising a set of magnets which are rotationally symmetrically arranged around a rotor axis of the rotor, wherein two magnets arranged next to each other are oppositely magnetized; and at least one stator to which the rotor is rotationally attached; the at least one stator comprising a set of coils which are rotationally symmetrically arranged around a stator axis of the at least one stator that coincides with the rotor axis of the rotor; wherein in the closed position of the circuit breaker the magnets of the set of magnets are arranged angularly offset with respect to the coils in the set of coils in order to apply a torque force on the rotor upon activation of the circuit breaker by a current flowing through the coils in the set of coils thereby moving the pair of contacts (130a, 130b) in an open position of the circuit breaker.

[0018] Such a circuit breaker allows for an ultra-fast interruption of fault currents without suffering from the problems of solid-state circuit breakers as described above. The circuit breaker is a reliable non-expensive device with an interruption speed less than 1 ms or even faster that does not suffer from conduction losses. The circuit breaker is able to interrupt the circuit before any damage can happen to the circuit. In the event of a fault, the circuit breaker is able to open the electrical contacts very fast before the current has a chance to increase in magnitude and becomes harder to interrupt.

[0019] In an exemplary implementation of the circuit breaker, in the closed position of the circuit breaker the set of coils of the at least one stator is rotationally aligned edge-to-edge with the magnets of the rotor. This alignment guarantees a precise and fast movement of the rotor. Thus, a maximum amount of torque can be generated for fast acceleration of the rotor.

[0020] In an exemplary implementation of the circuit breaker, each coil of set of coils of the at least one stator comprises a plurality of windings which are wound in axial direction to generate an axial flux. By such configuration of the windings of the coils an axial flux motor can be formed as the basic component of the circuit breaker.

[0021] In an exemplary implementation of the circuit breaker, the at least one stator comprises a first stator and a second stator which are sandwiching the rotor. Such a dual stator can be easily designed and it guarantees fast acceleration of the rotor for a fast opening of the contacts.

[0022] In an exemplary implementation of the circuit breaker, in the closed position of the circuit breaker the set of coils of the first stator is aligned to the set of coils of the second stator. This configuration implements a symmetric design which is optimal for accelerating the rotor and moving the contacts in the open position.

[0023] In an exemplary implementation of the circuit breaker, the coils of the first stator which are aligned to respective coils of the second stator are wound in opposite direction in order to generate an axial flux in the first stator that is in opposite direction to an axial flux in the second stator. By such configuration a closed magnetic field can be generated which creates a circular flux and minimizes magnetic reluctance.

[0024] In an exemplary implementation of the circuit breaker, the windings of consecutive coils of each stator are wound in opposite direction. This feature also results in the generation of a closed magnetic field which creates a circular flux and minimizes magnetic reluctance.

[0025] In an exemplary implementation of the circuit breaker, a number of coils of a respective stator corresponds to a number of magnets of the rotor. This topology allows to generate maximum torque to the rotor. In an exemplary implementation of the circuit breaker, the set of coils of the at least one stator is electrically connected to a power source for simultaneously energizing all coils. By simultaneously energizing all coils, the magnetic fields in all coils can be simultaneously generated, thereby avoiding any imbalances.

[0026] In an exemplary implementation of the circuit breaker, the circuit breaker comprises: an electrical activation circuit configured to activate the circuit breaker by energizing the set of coils of the at least one stator based on a pulse width modulated pulse signal. The electrical activation circuit can be used for an efficient control and activation of the circuit breaker.

[0027] In an exemplary implementation of the circuit breaker, the electrical activation circuit comprises: a capacitor chargeable by a power source; and a controllable semiconductor device electrically connected between the capacitor and the set of coils of the at least one stator, the controllable semiconductor device being controllable by the pulse width modulated pulse signal. Such an electrical activation circuit is easy to design. By energizing the capacitor, high currents for driving the axial flux motor can be generated.

[0028] In an exemplary implementation of the circuit breaker, upon an activation of the circuit breaker the rotor is configured to rotationally move from the closed position of the circuit breaker in which the set of magnets are arranged angularly offset with the set of coils to an open position of the circuit breaker in which the set of magnets are axially aligned with the set of coils. By such configuration, the acceleration of the rotor is variable. When the set of magnets are arranged angularly offset with the set of coils, acceleration is at its maximum, while when the set of magnets are axially aligned with the set of coils, acceleration is at its minimum.

[0029] In an exemplary implementation of the circuit breaker, upon the activation of the circuit breaker the rotor is configured to move further from the open position into another position in which the set of magnets are arranged angularly offset with the set of coils which is different from the closed position. In the other position, a negative acceleration can be applied to the rotor to bring it back to the open position.

[0030] In an exemplary implementation of the circuit breaker, the circuit breaker comprises: a locking element configured to lock the rotor in the open position or in the other position. Such a locking element can safely lock the rotor in the open position guaranteeing a lasting interruption of the contacts without swinging back to the closed position.

[0031] In an exemplary implementation of the circuit breaker, the circuit breaker is configured to break an AC current flowing through the pair of bus terminals upon the activation of the circuit breaker before a next zero crossing of the AC current. This guarantees that the circuit breaker is faster than conventional AC circuit breakers which use the zero crossing points of the AC current for interrupting the fault current. Thus, the requirement of being faster than 1ms can be fulfilled while traditional AC breakers may require up to 10 ms (for a 50 Hz system).

[0032] In an exemplary implementation of the circuit breaker, the circuit breaker comprises: a pair of splitter plates which are rotationally symmetrically arranged towards the rotor axis, each splitter plate electrically connected to a respective bus terminal and configured to elongate a path of an arc created between the bus terminal and the respective contact upon activation of the circuit breaker.

[0033] By elongating the arc path, higher arc voltages can be generated which enable faster decay of the fault current. The equation that best describes this phenomenon is as follows: difault— - (Vsystem— Varc)dt. where ifauit represents the fault current, Vsystem the system voltage, Varc the arc voltage and L the inductance between the contacts. According to a second aspect, the disclosure relates to a method for handling a circuit breaker according to the first aspect described above, the method comprising: detecting a fault current between the busbars in the closed position of the circuit breaker; and activating the circuit breaker by a current flowing through the set of coils upon detection of the fault current.

[0034] Such method allows an ultra-fast interruption of fault currents, thereby protecting the circuit from damage. The advantages and effects describe above apply to the method accordingly.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Further embodiments of the disclosure will be described with respect to the following figures, in which:

[0037] Figure 1 shows a cross section of a circuit breaker arrangement 100 according to the disclosure;

[0038] Figure 2 shows a 3D representation of a circuit breaker 200 according to the disclosure that can be used in the circuit breaker arrangement 100 shown in Figure 1;

[0039] Figure 3 shows cross sections of an exemplary stator 210 and an exemplary rotor 220 that can be used in the circuit breaker 200 shown in Figure 2;

[0040] Figure 4 shows a cross section of two consecutive exemplary stators 210 and respective magnet polarizations that can be used in the circuit breaker 200 shown in Figure 2;

[0041] Figure 5 shows cross sections of the two consecutive stators 210 shown in Figure 4 in different states of the circuit breaker: acceleration (leftmost) 500a, cruise (middle) 500b and deceleration (rightmost) 500c;

[0042] Figure 6 shows a circuit diagram of an exemplary electric drive 600 that can be used for driving the circuit breaker 200 shown in Figure 2;

[0043] Figure 7 shows an exemplary pulse pattern 700a (top of Fig. 7) for controlling the IGBT 611 of the electric drive 600 shown in Figure 6 to create a nearly constant current profile 700b (bottom of Fig. 7) for feeding the coil 211 shown in Fig. 6; and

[0044] Figure 8 shows a schematic diagram illustrating a method 800 for handling a circuit breaker according to the disclosure.

[0045] DETAILED DESCRIPTION OF EMBODIMENTS

[0046] In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the disclosure is defined by the appended claims.

[0047] It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

[0048] In the following, AC systems and DC systems as used in this disclosure are described.

[0049] Traditionally, AC systems dominated over DC systems mainly due to the reliance of transformers to deliver power over long distances. Transformers rely on AC and hence all electric utilities and most electric appliances relied on AC as an input. Phones or computers are such examples where they rely on an AC input that gets converted to DC to operate the PC. Datacenters are other such examples.

[0050] Another reason for the justification of AC systems is due to breakers. It is much easier to interrupt an AC system than a DC system. It is very difficult to interrupt a DC system due to the absence of a current zero crossing. In AC systems, the current crosses zero three times in one period. Hence, every 10 ms (for 50 Hz systems), the breaker has a chance to interrupt the current. However, in DC systems, since the current is constant, it poses a big challenge. The current has to be forced and taken down to zero artificially. Besides, in DC systems, the system inductance is much lower than comparable AC systems. Hence, fault currents can rise very rapidly leading to high current magnitudes and further away from a zero-current crossing. This complicates the interruption process further and clearly shows the difficulty in interrupting a current that goes in the wrong direction.

[0051] In AC systems, the speed of the breaker is not so critical since the current will eventually go to zero regardless of the system and the breaker has a chance to interrupt fault currents every 10 ms. Consequently, AC breakers are not built for speed since it is expensive, complex, and unnecessary to do so.

[0052] However, for DC systems, speed plays a major role. The faster the breaker, the faster it can react and limit fault currents. The smaller the short circuit current, the easier it is to interrupt, and the smaller is the energy that needs to be absorbed by the breaker. This results in a smaller footprint and leads to cost reduction in breaker design.

[0053] Another major advantage is maintenance and lifetime. The faster the mechanical breaker is at interrupting a fault current at low current magnitudes, the less are the contacts ablated. This results in a prolonged lifetime and much less maintenance increasing reliability.

[0054] The circuit breaker arrangement and the circuit breaker presented in this disclosure provide a solution to the above-described problems. A circuit breaker is utilized, also referred herein as hybrid circuit breaker that comprises a novel custom-made motor with high power density to accelerate the contacts of the breaker very fast. The breaker is so fast that even AC systems seem as a DC system to the breaker since it is able to completely interrupt fault currents within 1 ms or even faster. It does not wait for a current zero but creates its own by generating an arc voltage that is high enough to counteract the system voltage and drive the fault current down to zero.

[0055] The following figures illustrate the circuit breaker and a method for handling the circuit breaker in detail.

[0056] Figure 1 shows a cross section of a circuit breaker arrangement 100 according to the disclosure.

[0057] The circuit breaker arrangement 100 comprises a circuit breaker 200 as described below with respect to Figure 2; and a pair of bus terminals 110a, 110b which are configured to contact a respective pair of rotationally movable contacts 130a, 130b of the circuit breaker 200 in a closed position of the circuit breaker 200. Upon activation of the circuit breaker 200 by a current flowing through the coils 211 as described below with respect to Figure 2 the pair of contacts 130a, 130b is moved in an open position of the circuit breaker 200 in which the pair of bus terminals 110a, 110b is interrupted thereby breaking a fault current.

[0058] Figure 1 also shows a pair of splitter plates 120a (only one splitter plate is shown in the cross section of Figure 1) which are rotationally symmetrically arranged towards the rotor axis of the rotor 220 of the circuit breaker 200 and described below with respect to Figure 2. Each splitter plate 120a is electrically connected to a respective bus terminal 110a, 110b and configured to elongate a path of an arc created between the bus terminal and the respective contact 130a, 130b upon activation of the circuit breaker 200.

[0059] Figure 2 shows a 3D representation of a circuit breaker 200 according to the disclosure that can be used in the circuit breaker arrangement 100 shown in Figure 1.

[0060] The circuit breaker 200 comprises: a pair of rotationally movable contacts 130a, 130b which are configured to contact a respective pair of bus terminals 110a, 110b in a closed position of the circuit breaker 200; a rotor 220 and at least one stator 210 as shown in Figure 2. In Figure 2, an exemplary number of two stators 210 is shown. It understands that the circuit breaker 200 can also be implemented with one stator 210 or with any other number of stators 210.

[0061] The rotor 220 is configured to rotate the movable contacts 130a, 130b. The rotor 220 comprises a set of magnets 221, 222 which are rotationally symmetrically arranged around a rotor axis of the rotor 220, wherein two magnets arranged next to each other are oppositely magnetized.

[0062] The rotor 220 is rotationally attached to the at least one stator 210. The at least one stator 210 comprises a set of coils 211 which are rotationally symmetrically arranged around a stator axis of the at least one stator 210 that coincides with the rotor axis of the rotor 220.

[0063] In the closed position of the circuit breaker 200 the magnets 221, 222 of the set of magnets 221, 222 of the rotor 220 are arranged angularly offset with respect to the coils 211 in the set of coils 211 of the stator 210 as shown in Figure 2 in order to apply a torque force 145 on the rotor 220 upon activation of the circuit breaker by a current flowing through the coils 211 in the set of coils 211, thereby moving the pair of contacts 130a, 130b in an open position of the circuit breaker 200.

[0064] In the closed position of the circuit breaker 200 the set of coils 211 of the at least one stator 210 can be rotationally aligned edge-to-edge with the magnets 221, 222 of the rotor 220.

[0065] Each coil of set of coils 211 of the at least one stator 210 may comprise a plurality of windings which are wound in axial direction to generate an axial flux 155. Hence, the motor formed by the rotor 220 and the at least one stator 210 is also called an axial flux motor.

[0066] The at least one stator 210 may comprise a first stator 210a and a second stator 210b which are sandwiching the rotor 220, as shown in Figure 2.

[0067] In the closed position of the circuit breaker 200 the set of coils 211 of the first stator 210a can be aligned to the set of coils 211 of the second stator 210b. The coils 211 of the first stator 210a which are aligned to respective coils of the second stator 210b can be wound in opposite direction in order to generate an axial flux 155 in the first stator 210a that is in opposite direction to an axial flux 155 in the second stator 210b.

[0068] The windings of consecutive coils 211 of each stator 210a, 210b can be wound in opposite direction.

[0069] A number of coils 211 of a respective stator 210a, 210b may correspond to a number of magnets 221, 222 of the rotor 220.

[0070] The set of coils 211 of the at least one stator 210 can be electrically connected to a power source for simultaneously energizing all coils 211.

[0071] The circuit breaker 200 may comprise: an electrical activation circuit 600, e.g. as shown in Figure 6, configured to activate the circuit breaker 200 by energizing the set of coils 211 of the at least one stator 210 based on a pulse width modulated pulse signal 700a, e.g. as shown in Figure 7.

[0072] The electrical activation circuit 600 may comprise: a capacitor 601 chargeable by a power source (see Figure 6); and a controllable semiconductor device 602 (see Figure 6) electrically connected between the capacitor 601 and the set of coils 211 of the at least one stator 210. The controllable semiconductor device 602 may be controlled by the pulse width modulated pulse signal 700a as shown in Figure 7, for example.

[0073] Upon an activation of the circuit breaker 200 the rotor 220 may be configured to rotationally move from the closed position of the circuit breaker 200 in which the set of magnets 221 , 222 is arranged angularly offset with the set of coils 211 to an open position of the circuit breaker 200 in which the set of magnets 221 , 222 is axially aligned with the set of coils 211.

[0074] Upon the activation of the circuit breaker 200 the rotor 220 may be configured to move further from the open position into another position in which the set of magnets 221 , 222 is arranged angularly offset with the set of coils 211 which is different from the closed position.

[0075] The circuit breaker 200 may comprise a locking element (not shown in Figure 2) configured to lock the rotor 220 in the open position or in the other position.

[0076] The circuit breaker 200 may be configured to break an AC current 135 (see Figure 1) flowing through the pair of bus terminals 110a, 110b upon the activation of the circuit breaker 200 before a next zero crossing of the AC current 135. Hence, it is not necessary to wait for the next zero crossing of the AC current, the circuit breaker 200 is able to break the AC current before the next zero crossing. The circuit breaker 200 can break both AC currents and DC currents.

[0077] The circuit breaker 200 may comprise a pair of splitter plates 120a (see Figure 1) which are rotationally symmetrically arranged towards the rotor axis. Each splitter plate 120a is electrically connected to a respective bus terminal 110a, 110b and configured to elongate a path of an arc created between the bus terminal and the respective contact 130a, 130b upon activation of the circuit breaker 200.

[0078] Further embodiments of the circuit breaker 200 are described in the following.

[0079] The breaker 200 consists of a pair of contacts 130a, 130b with rotational symmetry. In the closed position, the contacts conduct the nominal current. When a fault is detected, a trigger signal is sent to the breaker and the breaker opens the two contacts

[0080] The higher the build-up of the arc voltage, the faster is the decay of the fault current. Two contacts are used in this design to speed up the interruption process. Increasing the number of series connected contacts will increase the interruption speed further at the expense of adding resistance and more losses. This is a tradeoff.

[0081] To be able to open the contacts so rapidly, a novel and unique axial flux motor is utilized as illustrated in Figure 2. In comparison to radial motors, the flux lines flow parallel to the axis of rotation in axial flux motors. Unlike traditional axial flux motors, the number of magnets and poles in this design match with a 1-1 ratio. Normally such a topology does not work since it prevents rotation. Since axial flux motors are usually used as motors, such a design has never been implemented or documented in literature. However, in this case the motor is used in a circuit breaker application where a 360-degree operation is not necessary nor needed. In this case, 45 to 90 degrees are enough to actuate the contacts. Therefore, continuous operation is not needed.

[0082] Furthermore, to maximize the starting torque, all poles are simultaneously energized. This results in a very large torque. This large torque leads to high accelerations rapidly opening the contacts when encountering a fault. An impulsive torque is generated that thrusts the contacts to open rapidly to act as a fault current limiter and interrupter.

[0083] An axial flux motor consists of two stators (according to the stators 210 shown in Figure 2) and one centralized motor (according to the rotor 220 shown in Figure 2) sandwiched between the two stators. This topology has the lightest moment of inertia and does not rely on a back iron to close the magnetic path on the rotor. Another reason for avoiding a back iron is due to its mechanical density. It is very heavy and will add moment of inertia hindering the motor from reaching very high accelerations.

[0084] Each stator consists of a number of trapezoidal shaped coils with several turns. The coils may consist of circular copper wire or alternatively, rectangular wire, for example. Using rectangular wire increases the fill factor. More copper can be effectively used reducing the resistance of the coil while at the same time maintaining the number of turns.

[0085] Application scenarios of the circuit breaker 200 are datacenters, DC systems especially LVDC up to 1500 V, renewables such as PV, or electric vehicles and charging stations. The circuit breaker 100 is highly useful in DC systems or in any system where complete fault current interruption in less than 1 ms is mandatory.

[0086] Figure 3 shows cross sections of an exemplary stator 210 and an exemplary rotor 220 that can be used in the circuit breaker 200 shown in Figure 2.

[0087] Two stators 210 and the rotor 220 form the novel motor as introduced in this disclosure.

[0088] The novel motor consists of a dual stator and a single rotor solution. The stator 210 is shown in Figure 3 in a top view perspective. In this example configuration, the stator 210 has four poles only, denoted by A, B, C, and D. This is not limited to four poles only but this serves only for illustration purposes. Ideally, more than 10 poles are needed. Two such stators 210 sandwich one rotor 220 in between as shown in Figure 2. The rotor 220 can have exactly the same shape as the stator 210. However, one major difference is that the rotor 220 is mounted with magnets 221, 222, whereas the stator 210 is mounted with coils 211 made of electrically conductive wire such as copper, for example. In this topology, to generate the maximum amount of torque and accelerate really fast, the number of magnets a, b, c, d and the number of stators match with a 1: 1 ratio. This means if 4 poles are used, then 4 magnets 221 are needed which is not typical in a normal motor since such design cannot rotate continuously.

[0089] The two stators 210 should be aligned perfectly and the rotor 220 should be skewed by an angle of 45 degrees in this exemplary case to generate maximum torque as shown in Figure 3. The poles of each stator 210 should have a winding across it consisting of several turns, for example of 40 turns. The rotor 220 should have four magnets 221 , 222 that should be altematingly placed in terms of magnetization direction as shown in Figures 3 and 4.

[0090] Figure 4 shows a cross section of two consecutive exemplary stators 210 and respective magnet polarizations that can be used in the circuit breaker 200 shown in Figure 2.

[0091] In Figure 4 only 4 poles are shown with their respective windings in a front view perspective. The different turns of the coils wrapped around each pole can be seen as circles. Circular wire can be used but are not optimal. It is preferable to use rectangular wire to increase the fill factor and bring down the electrical losses and hence the resistance of the coils.

[0092] Two sets of magnets 221, 222 are shown with their respective starting positions whereby they are aligned edge to edge with the poles. All coils in this case are connected in series but a series and parallel combination can also be implemented depending on the voltage and current capability of the motor drive. As can be noticed here, the magnets 221 , 222 are placed in alternating directions.

[0093] When the coils are energized, a magnetic field is created that is oriented upwards. This attracts the magnets 221, 222 such that they start moving inwards. A net force that is oriented in the x direction is created as long as the airgap between the magnets 221, 222 and the stators 210 is the same. Thus, it is crucial to make sure everything is symmetric. Otherwise the magnets 221, 222 will move in the y direction also, in the direction that has the smaller airgap and latch and cause high friction. This is not desired and should be avoided at all costs. Hence tolerances are very important.

[0094] Another crucial point is that the coils of consecutive poles are also wound in opposing directions with respect to each other. The 2 coils 211 on the left cause a magnetic field B oriented in the positive axial direction and the two coils 211 on the right produce a magnetic field oriented in the negative axial direction. This causes a closed magnetic field that is also aligned with the magnets 221, 222. In other words, both coils 211 and the magnet 221, 222 on the left cause a magnetic field B oriented upwards, and both coils 211 and magnet 221, 222 on the right cause a magnetic field oriented downwards. This creates a circular flux and minimizes magnetic reluctance.

[0095] Figure 5 shows cross sections of the two consecutive stators 210 shown in Figure 4 in different states of the circuit breaker: acceleration (leftmost) 500a, cruise (middle) 500b and deceleration (rightmost) 500c.

[0096] The acceleration 500a, cruise mode 500b, and deceleration 500c phases are shown in Figure 5. In the beginning, the magnets 221, 222 (see Figure 4) accelerate to the middle. Once the magnets 221, 222 reach the middle position, the motor cannot accelerate anymore and cruises at constant speed. Once the magnets 221 , 222 reach the other end, then the motor decelerates to ensure smooth landing. All the coils 211 (see Figure 4) in the one stator 210 are connected in series such that they all share the same current. Furthermore, the two stators 210 are also series connected to make sure the current is also identical in the stators 210 to avoid any imbalances. Other versions may include a combination of series and parallel connections depending on the desired opening velocities and drive voltage.

[0097] Figure 6 shows a circuit diagram of an exemplary electric drive 600 that can be used for driving the circuit breaker 200 shown in Figure 2.

[0098] The drive 600 used to drive the axial flux motor is shown in Figure 6. A power supply is used to charge the capacitor 601 to a voltage that can be anywhere from 48 volts up to voltages of 5 kV or beyond, for example. In this design, the capacitor bank 601 was charged to 1.5 kV. An insulated gate bipolar transistor (IGBT) 602 is used to create a constant current that is fed to the coil 211, denoted by Rioaa and Lioad - A diode is used to freewheel the current through the coil 211. The coil 211 is comprised of all coils in both stators 210 connected in series.

[0099] Activating the same electric drive can be used to do a close or open operation. This clearly shows the potential of such a simple and robust design. An open or close operation will depend on the location of the rotor 220 and to which pole it is aligned to.

[0100] Figure 7 shows an exemplary pulse pattern 700a (top of Fig. 7) for controlling the IGBT 611 of the electric drive 600 shown in Figure 6 to create a nearly constant current profile 700b (bottom of Fig. 7) for feeding the coil 211 shown in Fig. 6.

[0101] By giving a defined pulse width modulated pulse 700a as shown in Figure 7 top, a constant current profile 700b canbe achieved as can be seen in Figure 7 bottom. In this example, a constant current of 500 A is generated. However, much higher currents can also be used as high as 5 kA for example.

[0102] The drive is not limited to an active semiconductor device like an IGBT (shown in Figure 6) that can be actively turned on or off. Another variation of the drive can be implemented by using thyristors since they are cost effective and can conduct larger currents. One drawback is that they cannot be turned off. This results in a complete discharge of the capacitor but will still generate high thrust forces.

[0103] The circuit breaker 200 and the circuit breaker arrangement 100 as described above canbe applied in both AC and DC systems. While in AC systems, the current crosses zero every 10 ms, every time it crosses zero, the circuit breaker has the potential to interrupt the fault current. The circuit breaker 200 described in this disclosure can interrupt the fault current even before the next zero crossing.

[0104] However new more efficient systems require DC and not AC. DC has numerous benefits and also low inductance and no current zero crossing. Due to the raw speed of the breaker described in this disclosure, it can interrupt both DC or AC currents extremely fast. Since it is so fast, it can act as a fault current limiter also protecting all equipment downstream. Moreover, since it is able to interrupt fault currents so fast, it does not have to be rated to absorb the full short circuit current and hence is able to interrupt the current while it is still small. This means the damage inflicted on the breaker is limited leading to more reliability and longer lifetimes without maintenance. This phenomenon can be compared to a snowball. It is much easier to stop a snowball at the top of the mountain before it starts to grow in size. On the other hand, stopping a snowball at the bottom of a mountain is very difficult since it will roll all the way increasing in both size and speed. Thus, the energy required to stop the snowball at the top of a mountain is much less than that at the bottom of a mountain. The circuit breaker described in this disclosure is a novel ultra-fast circuit breaker that can interrupt fault currents in less than 1 ms and even faster. The circuit breaker 200 represents a device for limiting and interrupting fault currents really fast with no conduction losses. The device can be deployed in datacenters, PV, battery systems, electric vehicles, or DC microgrids, for example.

[0105] The circuit breaker described in this disclosure allows to create an arc voltage that is higher than the system voltage forcing a current zero crossing. The breaker is able to interrupt both AC or DC systems extremely fast, in less than 1 ms and even faster. It will force a current zero crossing.

[0106] The circuit breaker according to an embodiment described in this disclosure comprises a unique axial flux motor to drive a dual contact system. An axial flux motor has never been used previously as a motor to drive a circuit breaker. Furthermore, the developed axial flux motor is new and has never been done before. It has been designed to generate maximum torque for a short time and it cannot rotate a full 360 degrees. It can only turn up to 90 degrees, for example. The motor itself is able to provide the latching forces needed to maintain the breaker in closed or open position. By such motor extra springs can be avoided.

[0107] Figure 8 shows a schematic diagram illustrating a method 800 for handling a circuit breaker according to the disclosure.

[0108] The circuit breaker may correspond to the circuit breaker 200 as described above with respect to Figures 1 to 7.

[0109] The method 800 comprises detecting 801 a fault current between the busbars 110a, 110b (see Figure 1) in the closed position of the circuit breaker 200 (shown in Figures 1 and 2).

[0110] The method 800 comprises activating 802 the circuit breaker 200 by a current flowing through the set of coils 211 (see Figure 2) upon detection of the fault current.

[0111] Such method allows an ultra-fast interruption of the fault current, thereby protecting the circuit from damage.

[0112] While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

[0113] Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein. Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence. Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the disclosure beyond those described herein. While the disclosure has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the disclosure. It is therefore to be understood that within the scope of the appended claims and their equivalents, the disclosure may be practiced otherwise than as specifically described herein.

Claims

CLAIMS1. A circuit breaker (200), comprising: a pair of rotationally movable contacts (130a, 130b) which are configured to contact a respective pair of bus terminals (110a, 110b) in a closed position of the circuit breaker (200); a rotor (220) being configured to rotate the movable contacts (130a, 130b), the rotor (220) comprising a set of magnets (221 , 222) which are rotationally symmetrically arranged around a rotor axis of the rotor (220), wherein two magnets arranged next to each other are oppositely magnetized; and at least one stator (210) to which the rotor (220) is rotationally attached; the at least one stator (210) comprising a set of coils (211) which are rotationally symmetrically arranged around a stator axis of the at least one stator (210) that coincides with the rotor axis of the rotor (220); wherein in the closed position of the circuit breaker (200) the magnets (221 , 222) of the set of magnets (221, 222) are arranged angularly offset with respect to the coils (211) in the set of coils (211) in order to apply a torque force (145) on the rotor (220) upon activation of the circuit breaker by a current flowing through the coils (211) in the set of coils (211) thereby moving the pair of contacts (130a, 130b) in an open position of the circuit breaker (200).

2. The circuit breaker (200) of claim 1, wherein in the closed position of the circuit breaker (200) the set of coils (211) of the at least one stator (210) is rotationally aligned edge-to-edge with the magnets (221, 222) of the rotor (220).

3. The circuit breaker (200) of claim 1 or 2, wherein each coil of set of coils (211) of the at least one stator (210) comprises a plurality of windings which are wound in axial direction to generate an axial flux (155).

4. The circuit breaker (200) of claim 3, wherein the at least one stator (210) comprises a first stator (210a) and a second stator (210b) which are sandwiching the rotor (220).

5. The circuit breaker (200) of claim 4, wherein in the closed position of the circuit breaker (200) the set of coils (211) of the first stator (210a) is aligned to the set of coils (211) of the second stator (210b).

6. The circuit breaker (200) of claim 5, wherein the coils (211) of the first stator (210a) which are aligned to respective coils of the second stator (210b) are wound in opposite direction in order to generate an axial flux (155) in the first stator (210a) that is in opposite direction to an axial flux (155) in the second stator (210b).

7. The circuit breaker (200) of any of claims 3 to 6, wherein the windings of consecutive coils (211) of each stator (210a, 210b) are wound in opposite direction.

8. The circuit breaker (200) of any of claims 3 to 7, wherein a number of coils (211) of a respective stator (210a, 210b) corresponds to a number of magnets (221, 222) of the rotor (220).

9. The circuit breaker (200) of any of the preceding claims, wherein the set of coils (211) of the at least one stator (210) is electrically connected to a power source for simultaneously energizing all coils (211).

10. The circuit breaker (200) of any of the preceding claims, comprising: an electrical activation circuit (600) configured to activate the circuit breaker (200) by energizing the set of coils (211) of the at least one stator (210) based on a pulse width modulated pulse signal (700a).

11. The circuit breaker (200) of claim 10, wherein the electrical activation circuit (600) comprises: a capacitor (601) chargeable by a power source; and a controllable semiconductor device (602) electrically connected between the capacitor (601) and the set of coils (211) of the at least one stator (210), the controllable semiconductor device (602) being controllable by the pulse width modulated pulse signal (700a).

12. The circuit breaker (200) of any of the preceding claims, wherein upon an activation of the circuit breaker (200) the rotor (220) is configured to rotationally move from the closed position of the circuit breaker (200) in which the set of magnets (221 , 222) are arranged angularly offset with the set of coils (211) to an open position of the circuit breaker (200) in which the set of magnets (221, 222) are axially aligned with the set of coils (211).

13. The circuit breaker (200) of claim 12, wherein upon the activation of the circuit breaker (200) the rotor (220) is configured to move further from the open position into another position in which the set of magnets (221 , 222) are arranged angularly offset with the set of coils (211) which is different from the closed position.

14. The circuit breaker (200) of claim 12 or 13, comprising: a locking element configured to lock the rotor (220) in the open position or in the other position.

15. The circuit breaker (200) of any of the preceding claims, configured to break an AC current (135) flowing through the pair of bus terminals (110a, 110b) upon the activation of the circuit breaker (200) before a next zero crossing of the AC current (135).

6. The circuit breaker (200) of any of the preceding claims, comprising: a pair of splitter plates (120a) which are rotationally symmetrically arranged towards the rotor axis, each splitter plate (120a) electrically connected to a respective bus terminal (110a, 110b) and configured to elongate a path of an arc created between the bus terminal and the respective contact (130a, 130b) upon activation of the circuit breaker (200).

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