Electric motor with an electronic assembly

Abstract

Electric motor with an electronic assembly, wherein the electric motor has two or more coils, wherein the coils of the electric motor are arranged in a so-called star connection, wherein the star connection has a star point, wherein the star point of the star connection is designed to be contacted, wherein the electronic assembly has an electrical return, wherein the star point is connected to a phase line by means of the electrical return, so that the equivalent circuit has the form of a Wheatstone bridge.

Description

Prior ArtElectric motors are known. In particular, electronically commutated motors, so-called EC motors, are known.In the case of an EC motor, the drive has commutation electronics which supply the EC motor with current. As a result of the commutation, interference signals arise on the commutation electric ink, which inter alia act on the electric motor. This results in disturbing signals in the electric motor, such as disturbing voltages and / or disturbing currents, which have a disadvantageous effect on the operation of the electric motor.Solutions are also known which lead to a reduction of the interference signals. A reduction of the interference signals is guided in specialist circles under the term noise balancing. It is known here to provide the connection of the electronics to the motor via the motor phases. In this known variant, however, the required capacitances of the known circuit must be recharged with each change in the common mode voltage or in the common mode current, which leads to increased losses of the inverters.Object and Advantages of the InventionThe object of the present invention is to provide an electric motor with an electronic assembly in which the interference signals, such as interference voltages and / or interference currents, are reduced or reduced in a comparatively simple manner and the disadvantages known from the aforementioned prior art are reduced.This object is achieved by the independent claims.In the dependent claims, exemplary variants of the invention are mentioned.The invention is based on an electric motor having an electronic assembly, wherein the electric motor has two or more coils, wherein the coils of the electric motor are arranged in a so-called star connection.A star connection is the interconnection of any number of components to a common point, referred to as a star point. For example, the components are designed as at least two coils and the coils are interconnected at a common point, the star point. For example, the electric motor has three or more coils.The essential point of the invention can now be seen in the fact that the star point of the star circuit is designed to be contacted, wherein the electronic module has an electrical feedback, wherein the star point is connected to a phase line by means of the electrical feedback, such that the motor circuit diagram has the form of a Wheatstone bridge. This makes it comparatively simple to realize a reduction of the interference signals, such as interference voltages and / or interference currents.For example, the motor circuit diagram is the circuit diagram of the electric motor and the electronic assembly. For example, the motor circuit diagram is the electrical (motor) equivalent circuit diagram of the inverter with EMC filter and motor. For example, the equivalent circuit diagram of the electric motor, for example with integrated electronics of the electronics assembly, has the form of a Wheatstone bridge.For example, the star point has one or more impedance (Z add). It is conceivable that the impedance (Z add) is designed as a capacitance (C add). It is conceivable that the impedance is designed as an electrical feedback (C add). It is conceivable for the electrical return (C add) or the electrical return (C add) to connect the neutral point to a respective phase line or a neutral conductor. It is also conceivable that one of the electrical return lines (C add) is connected to one of the phase lines in each case. This realizes a simple realization of the Wheatstone bridge circuit.For example, the star point is electrically conductively connected to the electrical return or a part of the electrical return. For example, an electrical feedback connects the star point to a phase in an electrically conductive manner. For example, the star point is connected to a ground, e.g., the stator potential. It is conceivable that the star point is connected to ground via a capacitance, e.g. a capacitor. It is conceivable that the star point connects the ground to the electrical return (C add).It is further proposed that the electrical feedback is formed as a capacitance (C add), as a discrete component and / or as an impedance. As a result, a reduction of the interference signal is realized comparatively easily. This also realizes a comparatively compact and cost-favorable construction of the electric motor.For example, the electrical feedback has a capacitance (C add), e.g. a capacitor, a discrete component and / or an impedance.It is also proposed that two components be present, wherein one component has an impedance, wherein a first component of the two components has a first impedance (Z CM) wherein a second component of the two components has a second impedance (Z YCK) wherein the electrical feedback connects the neutral point to the first component, wherein the electric motor has a first parasitic capacitance (C parMOTCM1), a second parasitic capacitance (C parMOTCM2) and a motor impedance (Z MOT) wherein the first impedance (Z CM), the second impedance (Z YCK), the motor impedance (Z MOT) and the second parasitic capacitance (C parMOTCM2) are interconnected by means of the electrical feedback in such a way that a Wheatstone bridge is realized. This realizes a comparatively simple reduction of the interference signals.For example, the electrical feedback connects the star point to the first impedance (Z CM) in an electrically conductive manner. For example, the electric motor has two components. It is also conceivable that the electric motor has three, four or more components. For example, the electric motor has the two or more components. It is conceivable for the electronics module of the electric motor to have the two or more components.It is conceivable that the electrical return is formed as a cable, as a wire or as a conductor track. For example, the electrical feedback has a low impedance. For example, the impedance of the electrical feedback is small relative to the first impedance (Z CM), the second impedance (Z YCK) and the motor impedance (Z MOT).In an exemplary embodiment of the invention, the first component of the electric motor is designed such that the formula ((Z CM) / ( Z MOT))=(( Z YCK) / ( C parMOTCM2)) is satisfied. This realizes an ideal bridge balance and thus the ideal state of the electric motor. It is conceivable that the first component is selected such that the formula is fulfilled in a specific frequency range or in a plurality of specific frequency ranges of the electric motor.In reality, the formula (Z CM) / ( Z MOT))=(( Z YCK) / ( C parMOTCM2)) cannot be fulfilled due to component and assembly tolerances; accordingly, it is proposed that the impedances, for example the first component, be selected such that the formula is approximately fulfilled. For example, the impedance (Z CM), ( Z MOT) and / or (Z YCK) and / or the capacitance (C parMOTCM2) are selected such that the ratio (Z CM) / ( Z MOT) and (Z YCK) / ( C parMOTCM2) results in a small functional disturbance voltage. In the ideal state-in the limit state-the formula ((Z CM) / ( Z MOT))=(( Z YCK) / ( Cp arMOTCM2)) would be fulfilled.It is also conceivable that the impedances contained in the formula (Z CM) / ( Z MOT))=(( Z YCK) / ( C parMOTCM2)) are selected such that the formula is satisfied or approximately satisfied in a specific frequency range of the electric motor. As a result, the electric motor can be adapted to a specific application.It is likewise proposed that the electric motor is designed as a three-strand or three-phase electric motor. However, it is also conceivable for the electric motor to be present as a single-phase electric motor or as a direct current electric motor. For example, the electric motor is designed as an electronically commutated electric motor (EC motor). For example, the electric motor has two, three or more coils with an inductance. For example, each coil of an electric motor having three coils has a winding inductance (L u, L v or. L w).A configuration of the electric motor as proposed is suitable, for example, for electronically commutated electric motors. For example, the electronic assembly has the components required for commutation of the electric motor. In particular, the electronic assembly has all the components required for commutation of the electric motor. It is conceivable for the electronics module to be arranged integrally on the electric motor. However, it is also conceivable that the electric motor and the electronics module are present spaced apart from one another. For example, the electronic assembly has the electrical return.It is also proposed that the first component be designed as a filter inductor. For example, the first component has a plurality of filter chokes, wherein the plurality of filter chokes together form the first impedance (Z CM). As a result, the first impedance (Z CM) can be formed comparatively easily in the direction of satisfying the formula (Z CM) / ( Z MOT))=(( Z YCK) / ( C parMOTCM2)) in particular with regard to different frequencies of the electric motor, by means of which the values of the first impedance (Z CM), the second impedance (Z YCK), the motor impedance (Z MOT) and the second parasitic capacitance (C parMOTCM2) can change.It is also proposed that the first component consists of a discrete and / or a passive element. However, it is also conceivable for the first component to comprise a clocked semiconductor or to be present as a module of elements. It is conceivable for the first component to be designed to be matched to the desired frequency range of the electric motor. The first component is designed, for example, as a passive power factor correction filter (PFC), as an active power factor correction filter (PFC), as an inverse converter (buck-boost converter) or as a switched-mode power supply.It is also proposed that the electrical feedback is connected to the star point via two or more capacitors. For example, one capacitor electrode of each of the two or more capacitors is connected to the neutral point. For example, two or more of the capacitors form the capacitance (C add) of the electrical feedback. It is also conceivable for the capacitors to form the capacitance (C add) of the electrical feedback. For example, the electrical return comprises the capacitors via which the cable or the electrical line of the electrical return is connected to the neutral point. For example, the electrical return includes multiple cables or multiple electrical lines. It is conceivable that each cable is connected to the star point via a capacitor.For example, the capacitors are connected to one another via a virtual star point and the electrical feedback is electrically conductively connected to the capacitors at the virtual star point. It is conceivable that one capacitor electrode of each of the capacitors is electrically conductively connected to the virtual star point. It is conceivable that the electric motor has at least two capacitors in a 1-phase embodiment or in a DC embodiment. It is also conceivable that the electric motor has at least three capacitors in a 2-phase embodiment.For example, the electrical feedback is designed as a parasitic capacitance.It is further proposed that the electrical feedback is present as a capacitance (C add) and the capacitance (C add) is selected as a function of the configuration of the electric motor and / or the application of the electric motor. As a result, the electric motor can be adapted with regard to its design or its specific field of application. It is conceivable that the electrical feedback is selected depending on the field of application of the electric motor and thus depending on the configuration of the electric motor.An exemplary embodiment of the invention is a method for reducing interference signals of an electric motor according to one of the aforementioned variants, wherein the method is characterized by the following method steps:selecting the first impedance (Z CM) and the second impedance (Z YCK), so that formula ((Z CM) / ( Z MOT)( Z YCK) / ( C parMOTCM2)) is satisfied,selecting the capacitance (C add) depending on the configuration of the electric motor and / or depending on the application of the electric motor,arranging the first impedance (Z CM), the second impedance (Z YCK) and the capacitance (C add) to the electric motor.It is also conceivable for the method to have iteration loops, so that first the first impedance (Z CM), the second impedance (Z YCK) and the capacitance (C add) are selected and arranged at the electric motor. The interference signal is then determined and, depending on this, the first impedance (Z CM), the second impedance (Z YCK) and / or the capacitance (C add) is changed. For example, the iteration loop is carried out until the equation ((Z CM) / ( Z MOT))=(( Z YCK) / ( C parMOTCM2)) is satisfied or approximately satisfied at least for the desired frequency range or the desired frequency ranges of the electric motor.DESCRIPTION OF THE FIGURESSeveral exemplary embodiments are explained in more detail with reference to the following drawings, giving further details and advantages: FIG. 1 shows a schematic illustration of an electric motor with an electronic assembly, FIG. 2 is an equivalent circuit diagram of a known three-strand electric motor operated in a star connection, FIG. 3 the equivalent circuit diagram according to FIG. 2 is converted into an equivalent circuit diagram which is valid for common mode variables, FIG. 4 shows an equivalent circuit diagram of an electric motor with an electronic system with common mode choke that is valid for common mode variables, and FIG. 5 shows the equivalent circuit diagram according to FIG. 4, wherein the equivalent circuit diagram has been extended by a capacitance (C add) wherein the equivalent circuit diagram has the form of a Wheatstone bridge.FIG. 1 shows a schematic illustration of an electric motor 32 which has an electronics assembly 33. The electric motor further comprises a first coil 34 and a second coil 35. The first and the second coil 34, 35 are electrically conductively connected to one another at a star point 36.FIG. 2 shows an equivalent circuit diagram 1 of a known three-stroke electric motor. The electric motor has three coils 2, 3, 4, each of which has a winding inductance (L U, L V, L W). The three coils of the electric motor 2, 3, 4 are electrically conductively connected to one another at a star point 5. One of the three coils 2, 3, 4 is connected at one end 6, 7, 8 to a phase line U, V, W and at the other end 13 the coils 2, 3, 4 are connected via the neutral point 5 to a ground or the protective conductor. Furthermore, the known electric motor has a first parasitic capacitance 12 (C parMOTCM1) and second parasitic capacitances 9, 10, 11 (1 / 3 C parMOTCM2).In FIG. 3, the equivalent circuit diagram according to FIG. 2 is converted into an equivalent circuit diagram 14 valid for common mode variables (common mode (CM)). In the equivalent circuit diagram 14, the winding inductances (L U, L V, L W) are combined or transformed to form an inductance 15 (LMOTCM), and the second parasitic capacitances 9, 10, 11 (1 / 3 C parMOTCM2) are combined or transformed to form a parasitic capacitance 16 (C parMOTCM2). At point 17, the coils of the electric motor are contacted with the phases (U, V, W) of the three-phase current.FIG. 4 shows the common mode equivalent circuit 18 of an EC motor. In the common mode equivalent circuit 18 a common mode interference voltage 19 (U CMWR), which results from the use of an inverter which is present for the operation of the electric motor, is illustrated. Furthermore, a capacitance 20 (C YZK). results for the total capacitance of all capacitors located in the DC voltage intermediate circuit. For example, all capacitors and / or parasitic capacitances present in the DC intermediate circuit are connected to ground for this purpose. Moreover, a common mode impedance 21 (Z CM) is shown, which is formed by one or more filter chokes of the electric motor. The filter choke is used to suppress or reduce the negative influence of the common mode interference voltage 19 at a point 26. The filter inductor has the properties relevant for the common mode interference voltage, resistance EPR CM, capacitance EPC CM and inductance L CM. Also shown are the first parasitic capacitance 22 (C parMOTCM1) and the second parasitic capacitances 23 (C parMOTCM2) of the electric motor. The neutral point at which the two or more coils of the electric motor are connected to one another is shown at point 24. Further, the impedance 25 of the motor (Z MOT) is shown. The impedance 25 of the motor has the properties of resistance EPR LMOTCM, capacitance EPC LMOTCM and inductance L LMOTCM which are relevant for the common mode interference voltage 19. The common mode interference voltage 19 (U CMWR) can be measured indirectly at the point 26. The measuring instrument has an impedance 31 (Z LISN) in this case. For example, the capacitance 20 (C YZK) and common mode impedance 21 (Z CM) are part of the electronics module.In order to be able to reduce a negative influence of the common mode interference voltage 19 (U CMWR) in a comparatively simple manner, it is proposed according to the invention to connect the star point 24 to the phase line 30 or to a neutral conductor at the point 28 by means of an electrical feedback 27. In FIG. 4, the electrical feedback 27 is shown in dashed lines in order to represent the difference between the known prior art and the change according to the invention in the circuit.For example, the electrical feedback 27 has an additional capacitance 29 (C add).In FIG. 5, the circuit with the electrical feedback 27 is shown in the form of a Wheatstone bridge. In conventional Wheatstone bridges, provision is made for the common mode interference voltage 19 to be tapped. According to the invention, on the other hand, the object is to minimize the influence of the common mode interference voltage 19. For this purpose, the interference voltage 30 (U Stör), which is influenced by the common mode interference voltage 19, is measured at the phase line against a ground by the measuring instrument at the point 26.By means of the circuit configuration according to FIG. 5, it is now possible, by suitable selection of the parameters capacitance 20 (C YZK), common mode impedance 21 (Z CM) and / or electrical feedback 27 or additional capacitance 29 (C add) to reduce the common mode interference voltage 19 in the direction of the value zero. In particular, it is thereby possible to reduce the interference voltage 30 (U Stör) for an operating frequency or for an operating frequency range of the electric motor in the direction of the value zero or to zero. The influence of the common mode interference voltage 19 is thus reducedList of reference characters1 Equivalent circuit diagram 2 Coil 3 Coil 4 Coil 5 Neutral point 6 End 7 End 8 End 9 Parasitic capacitance 10 Parasitic capacitance 11 Parasitic capacitance 12 Parasitic capacitance 13 End 14 Equivalent circuit diagram 15 Inductance 16 Capacitance 17 Point 18 Common mode equivalent circuit diagram 19 Common mode interference voltage 20 Capacitance 21 Common mode impedance 22 Capacitance 23 Capacitance 24 Point 25 Impedance 26 Point 27 Feedback 28 Point 29 Capacitance 30 Interference voltage 31 Impedance 32 Electric motor 33 Electronics assembly 34 Coil 35 Coil 36 Neutral point

Claims

Electric motor (32) having an electronics assembly (33), wherein the electric motor (32) has two or more coils (2-4), wherein the coils (2-4) of the electric motor (32) are arranged in a so-called star connection, wherein the star point (13, 24, 36) of the star connection is designed to be contacted, wherein the electronics assembly (33) has an electrical feedback (27), wherein the star point (13, 24, 36) is connected to a phase line by means of the electrical feedback (27), such that the motor circuit diagram has the form of a Wheatstone bridge.Electric motor (32) according to one of the preceding claims, characterized in that the electrical feedback (27) is designed as a capacitance (C add) (29), as a discrete component or as an impedance.Electric motor (32) according to one of the preceding claims, characterized in that two components are present, wherein a first component (21) has a first impedance (Z CM) wherein a second component (20) has a second impedance (Z YCK) wherein the electrical feedback (27) connects the neutral point (13, 24) to the first component (21), wherein the electric motor has a first parasitic capacitance (C parMOTCM1)(22), a second parasitic capacitance (C parMOTCM2) (23) and a motor impedance (Z MOT) (25) wherein the first impedance (Z CM), the second impedance (Z YCK), the motor impedance (Z MOT) and the second parasitic capacitance (C parMOTCM2) are interconnected by means of the electrical feedback (27) in such a way that a Wheatstone bridge is realized.Electric motor (32) according to one of the preceding claims, characterized in that the first structural element (21) is designed in such a way that the formula ((Z CM) / ( Z MOT))=(( Z YCK) / ( C parMOTCM2)) is fulfilled.Electric motor (32) according to one of the preceding claims, characterized in that the electric motor (32) is designed as a three-strand electric motor.Electric motor (32) according to one of the preceding claims, characterized in that the first component (21) is designed as a filter throttle.Electric motor (32) according to one of the preceding claims, characterized in that the first component (21) consists of discrete and / or passive elementsElectric motor (32) according to one of the preceding claims, characterized in that the electrical feedback (27) is connected to the star point (13, 24) via two or more capacitors.Electric motor (32) according to one of the preceding claims, characterized in that the electrical feedback (27) is present as a capacitor (C add) and the capacitor (C add) is selected as a function of the configuration of the electric motor and / or the application of the electric motor.Method for reducing interference signals of an electric motor (32) according to one of the preceding claims, characterized by the following method steps: - selection of the first impedance (Z CM) and the second impedance (Z YCK), such that the formula ((Z CM) / ( Z MOT)=((ZYCK) / ( C parMOTCM2)) is fulfilled, - arrangement of the first impedance (Z CM) and the second impedance (Z YCK) to the electric motor.

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