Electric drive having two-phase groups and operating patterns thereof

Abstract

An electric drive comprises at least one electric machine and a converter which has a multiplicity of half-bridges, wherein each half-bridge feeds a phase of the stator of the electric machine. Each half-bridge contains at least one high-side and low-side switch. In addition, the electric drive comprises an arrangement of phase groups, each having two phases per phase group and which are each connected to a star point on the first side and are coupled to the half-bridges on the second side. In a specific time period, at least one of the switches is kept in a constantly switched-on or switched-off state, while the other switches are operated in a pulse-width-modulated manner.

Description

[0001] ELECTRIC DRIVE WITH TWO-PHASE GROUPS AND THEIR

[0002] OPERATING SAMPLE

[0003] TECHNICAL AREA

[0004] The present invention relates to the technical field of electrical drive technology. In particular, the present disclosure relates to an electric drive with an improved inverter configuration that enables efficient torque control during the operation of an electric machine.

[0005] BACKGROUND

[0006] In the field of electrical drive technology, it is common practice to use electric machines in combination with frequency converters to enable efficient and precise control of motor functions such as motor power, torque, speed, or dynamics. Well-known solutions typically include frequency converters with a multitude of half-bridges, each consisting of high-side and low-side switches. These switches are often operated using pulse-width modulation (PWM), also referred to below as PWM control, PWM regulation, or PWM control, to control the voltage and current flowing through the electric machine and thus regulate the motor's torque and speed. However, whenever the singular "voltage and current flowing in the electric machine" is used here and in the following text, it also refers to multiple voltages or currents.For example, different phases of an electric machine also carry different phase voltages and phase currents, which are also part of the current and voltage flowing through the electric machine. Therefore, different phase currents and phase voltages are meant here and in the following. PWM enables fine-tuning of the motor function and contributes to improved energy efficiency. The terms PWM-active and PWM-inactive are also used below. PWM-active refers to a case in which one or more switches are actively PWM-controlled, meaning they are actively performing PWM. PWM-inactive refers to the opposite, i.e., a case in which one or more switches do not actively modulate a voltage but remain in either an on or off state.According to known technologies, the phases of electrical machines are often connected at a neutral point, whereas previously known, conventional configurations only provide a common neutral point for at least three phases. This is described, for example, in US2009128076A1. Such arrangements can lead to limitations in control flexibility and suboptimal efficiency conditions under certain operating conditions. Furthermore, while conventional PWM control is effective, it can lead to increased switching losses in some applications, especially when high switching frequencies are required to achieve the desired motor power. These switching losses can impair overall efficiency and lead to increased heat generation, which in turn can shorten component lifespan and increase the need for more sophisticated cooling.

[0007] With conventional solutions using a common neutral point, it was necessary to use at least three or more phases to generate a rotating field. When using pulse-width modulation (PWM) to generate a clean rotating field, the voltage of at least two or all of these three phases must be modulated. This means that a space vector can be kept constant and rotated cleanly. The basic idea behind such a space vector representation is that the so-called zero condition is fulfilled. This means that the neutral point of the load, if present, is not connected to the neutral conductor of the three-phase system. Therefore, the sum of the phase currents is always zero, and the third can be deduced from two quantities, which requires active PWM control of at least two of the three phases.The PWM control itself is achieved using space vector modulation, as described in US2009128076A1. PWM control can be supplemented with torque or speed control. Therefore, when using pulse width modulation to supply the phases of the electric machine, continuous active pulse width modulation of at least two individual half-bridges of the three phases was mandatory. Even with modern PWM technology, active control—i.e., switching the half-bridge switches on and off—is always associated with switching losses and the resulting additional heating. This loss-induced heating also increases the ohmic losses in all current-carrying parts, leading to further ohmic losses. Another disadvantage of known solutions with three-phase systems is the limitation of power scaling while maintaining constant power output per half-bridge.This is because the supply voltage is often predetermined by the design, and the performance of the half-bridge can only be influenced by the current (P=U*I). However, the power loss also increases quadratically with the current (P=R*I). 2 The current cannot be increased arbitrarily without compromising the economic viability or high efficiency of the electric machine. Therefore, at a constant supply voltage, the power output per half-bridge and phase is limited. To increase the power of a three-phase configuration nonetheless, it was known to use more than three phases. A 2x3-phase configuration seemed particularly logical. However, this can also be uneconomical if the power only needs to be increased slightly above the limit of a fully utilized 1x3-phase configuration. Configurations with a different number of phases than three per phase group were uncommon in the prior art.

[0008] Therefore, there remains a need for improvements in the efficiency and flexibility of electric machine control. In particular, there is a need to minimize switching losses while simultaneously ensuring precise control of the motor function. Furthermore, it is desirable to optimize the control of the individual phases of the electric machine to achieve higher efficiency and improved power density. The development of inverter configurations that enable more differentiated control of individual phases could lead to a significant increase in the performance and efficiency of electric drives.

[0009] Therefore, the present invention is based on the technical problem of providing an electric drive that at least partially overcomes the disadvantages of known solutions.

[0010] SUMMARY

[0011] An objective of the present invention is to provide an electric drive that has improved efficiency, performance and reliability, enables a simplified design and increases the flexibility in the control of the electric machines.

[0012] According to the present invention, this problem is solved by the features of claim 1. Further advantageous embodiments are described in the dependent claims and the description. The solution comprises an electric drive that can achieve improved efficiency and performance through a specific configuration and control of the components. The drive comprises at least one electric machine and an inverter having a plurality of half-bridges, each half-bridge feeding one phase of the stator of the electric machine. Each half-bridge includes at least one high-side and at least one low-side switch, but the respective number of switches can be arbitrarily high. In the case of multiple switches per high- and / or low-side, a parallel connection of switches is typically located on the high- and / or low-side.The switches in a parallel circuit are always operated identically and can be considered collectively as a single large switch. Therefore, in the following, "switch" refers to all high- and / or low-side switches of a single half-bridge, if multiple switches are used for this purpose. These switches are responsible for converting the electrical energy from direct current (DC) from a DC source, such as a battery, to alternating current (AC) for the phases of the electric machine's stator. An arrangement of phase groups in the stator of the electric machine, with two phases per phase group connected to a neutral point on the first side and coupled to the half-bridges on the second side, allows each phase group to have its own neutral point. This can contribute to improved current distribution and a reduction in interference between the phases.The inverter is configured to keep one or more switches in a constant on or off state for specific periods, while the other switches operate with pulse-width modulation. This control enables precise generation of the fundamental frequency over varying time periods, which in turn provides torque to the electric machine. This specific control of the switches allows the electric drive to achieve efficient, powerful, and accurate torque control, which can be particularly advantageous in applications with high demands on precision and energy efficiency, such as electric vehicles or industrial drives.

[0013] The present solution is based on the use of multiple pairs of phases forming phase groups. Each phase within a phase pair is fed by a half-bridge, and the phase group is connected in a star point configuration. Accordingly, there are two half-bridges per group of two phases, which use PWM control to generate the current for the stator phases. To generate a clean rotating field for driving the rotor of the electric machine, which requires more than just two stator phases, the stator of the present invention comprises a plurality of these phase pairs, i.e., phase groups. Operating with only exactly two phases per phase group means that, at any given time, only one of the two phases in the group requires active PWM control, without compromising the system's performance.While one phase actively modulates a phase current, the second phase can have continuously switched high-side or low-side switches, since the current from this phase flows directly into the actively controlled phase via the neutral point of the phase group. This is because the sum of the currents of the two phases is always zero, meaning that actively modulating the current in one phase simultaneously determines the current in the other. Active pulse-width modulation of only one of the two phases per phase group eliminates the switching losses associated with pulse-width modulation of the other phase, as the switches in that phase do not need to be clocked. If three or more phases were connected to a neutral point, however, at least two of the three phases would have to be continuously pulse-width modulated to generate a suitable phase current according to the space vector model or space vector modulation.Examples of suitable pulse width modulation frequencies include the ranges of several kilohertz, such as 5 to 10, 10 to 20 or 20 to 30 kilohertz, but also higher and lower frequencies.

[0014] The advantage of this solution is that the switching losses associated with PWM control for the phases in the stator can be reduced by up to approximately 75 percent compared to full PWM control, for example, because half or three-quarters of the phases do not need to be actively PWM-controlled. The resulting efficiency is therefore higher compared to the state of the art.

[0015] The present solution can also employ an intelligent, time-alternating switching of the actively pulse-width modulated (PWM) phases of the two phases per phase group. This means that the first of the two phases in a phase group can be actively PWM-modulated for an initial period, while the switches of the second phase's half-bridge remain continuously on or off during this time. After this initial period, the roles of the phases can be reversed, so that the second of the two phases can then be actively PWM-modulated, and the first phase cannot. It is possible for only one of the two half-bridges to operate in a PWM-inactive state, while the other half-bridge remains PWM-active for the majority of the time period. However, both phases, and thus both half-bridges, can also have a PWM-inactive phase.The roles of the PWM-active and PWM-inactive phases can thus be regularly exchanged within a phase, within a phase group, or both. This increases the flexibility of torque generation in the electric machine, while in all these cases, switching losses can still be reduced. In this way, the half-bridge of each phase can cool down repeatedly in the PWM-inactive operating states, thereby advantageously reducing the thermal heat generated by PWM control losses. This further improves the machine's thermal management, and local overheating can also be avoided through intelligent control.This also enables the management and efficient handling of dynamic load requirements of the electric machine, which can be particularly advantageous in electric vehicles where the instantaneous load can fluctuate rapidly. Furthermore, the reduced heat leads to lower ohmic losses, resulting in even higher efficiency. This is due to the reduced average losses per phase. Consequently, the electric machine can achieve a higher power level with reduced component costs, as the components themselves can also have lower maximum power requirements and therefore be less expensive. Thus, the present invention can ensure stable and efficient performance under various load conditions.

[0016] For an electric drive, the integration of an electric motor is of central importance. The motor is the heart of the drive system and is powered by electrical energy to perform mechanical work. Electric motors can be of various types, such as DC, AC, synchronous, or asynchronous motors, depending on the application and specific requirements. A frequency converter is an essential component of the electric drive. Its function is to convert the electrical energy into a form suitable for the electric motor. For example, it can convert the voltage supplied by a DC source, such as a battery, into an AC voltage that powers the phases of the electric motor's stator. The frequency converter modulates the voltage supplied to the electric motor to enable precise control of its operation.Within the inverter are several half-bridges, which serve as building blocks for the conversion of electrical energy. Each half-bridge consists of an array of switches capable of controlling the current flow in precise patterns to generate the desired output voltage.

[0017] Each half-bridge within the inverter contains at least one high-side switch and at least one low-side switch. These switches play a crucial role in generating the output voltage by alternately enabling or interrupting the current flow through the phases of the electrical machine. These switches can be transistors. A high-side switch is the switch that connects the phase terminal of a phase to a positive supply potential. The low-side switch is the switch that connects the same phase terminal to a negative supply potential. The negative potential can also be a ground connection.

[0018] The inverter controls a multitude of phase groups, each consisting of two phases. These phases are connected on one side to a common star point, which serves as a neutral reference point for the phase voltages. On the other side, each phase is coupled to a corresponding half-bridge of the inverter.

[0019] The arrangement of the phases in phase groups, each with its own star point, enables differentiated control of the phase currents, which contributes to improved performance and efficiency of the electric drive.

[0020] The inverter is configured to operate one or more switches of the half-bridges of a phase group in a permanently on or off state for specific periods. This allows for different operating modes of the electric machine. Depending on the load requirements at different speeds or torques, the optimal operating mode can be selected from a variety of options.

[0021] Meanwhile, the remaining switches in the half-bridges of the same phase group can be operated in a pulse-width modulated (PWM) state. This operating state allows for fine control of the phase voltage supplied to the machine, enabling precise control of the motor function. Over the various time periods, a fundamental wave is generated by the coordinated control of the switches in the half-bridges. This fundamental wave serves to generate a continuous torque in the electric machine, which is necessary for powering vehicles, machinery, and other applications.

[0022] In the context of the present invention, the time periods of the plurality of time periods are freely definable time segments. These time periods serve as a reference period by means of which the operating state of the components of the electric drive can be defined with a certain temporal reference. They are therefore helpful in order to describe, for example, the simultaneous or sequential behavior of different components of the drive, such as different half-bridges or different switches of the half-bridges, even across multiple phases.

[0023] A pulse-width modulated (PWM) operating state is a condition during which a switch or half-bridge in this operating state actively modulates the voltage using pulse-width modulation. This involves repeatedly switching the half-bridge switches on and off, thereby providing a current with a specific frequency and voltage. The pulse-width modulation is clocked at a frequency many times higher than the fundamental frequency of the electrical machine to ensure maximum efficiency. The voltage is set based on the ratio of the on-time to the off-time of each PWM pulse.

[0024] A continuously on or off operating state is a state during which a switch or half-bridge in this operating state does not actively modulate the voltage using pulse-width modulation (PWM). This means that the switches of the half-bridge are not repeatedly switched on and off, but instead remain continuously in either the on or off state. These operating states last longer than a PWM clock cycle, so repeated switching on and off always occurs slower than the PWM clock cycle.

[0025] Pulse width modulation control can be implemented in all embodiments using either hardware or software, which may, but does not necessarily have to, be included in a control unit or controller of the inverter. For this purpose, the device can contain a computer-readable medium with program code, which, when executed by a processor, causes the device to execute the program code. The computer-readable medium can be any form of medium for storing digital data. The device can also include a computer capable of executing the program code.

[0026] According to one embodiment, the electric drive, which comprises an electric machine and an inverter, can be enhanced by additional features that enable improved control and efficiency. The inverter can include a plurality of half-bridges, each half-bridge having a plurality of switches, including at least one high-side switch and one low-side switch. The inverter can further be configured to control a plurality of phase groups, each phase group having two phases connected to its own neutral point on one side and coupled to a corresponding half-bridge on the other.This inverter configuration allows at least one high-side or at least one low-side switch of a half-bridge from at least one phase group to operate in a continuously on or off state for at least one of a multitude of time periods. This operating state can be alternated over the multitude of time periods with at least one of the remaining high-side or low-side switches of the two half-bridges of the at least one phase group. This alternation, in combination with the voltage modulation by the PWM-active switches, results in precise control of the generated torque of the electric machine. In the continuously on or off operating state, the one or more affected switches and their PWM control hardware can remain largely PWM-inactive, thus eliminating switching losses. This increases the efficiency of the electric drive.It is possible for only the switch(es) of one phase within a phase group to be in a continuously on or off operating state. However, multiple switches from different phases within the phase group can also be continuously PWM-active or PWM-inactive. This can increase the flexibility of torque delivery. Furthermore, by alternating the PWM-inactive switches, different switches can cool down at different times due to the absence of switching losses. This can reduce average ohmic losses, which can occur, for example, due to increased resistance of current-carrying components at elevated temperatures. On average, all the alternating components can operate cooler and therefore more efficiently.The pulse-width modulated control of the remaining switches generates a fundamental waveform necessary for providing torque to the electric machine. The specific communication mechanisms between the components involve the coordinated switching of the switches on and off to generate the desired waveform and thus the desired motor power. This control and communication can be implemented using either hardware or software, which may, but does not necessarily, be contained within a control unit or controller of the inverter. By alternating the operating states of the switches, more efficient and precise control of the motor power can be achieved.This more precise control itself can also lead to a reduction in losses, improve the efficiency of the drive and extend the service life of the components, as the thermal stress on the switches is reduced.

[0027] Furthermore, the improved control can lead to more precise torque control, which can be of particular importance in applications where high precision is essential, such as in robotics or electric vehicle drives.

[0028] According to a further embodiment, an electric drive is described which builds upon the preceding embodiments and has additional features relating to the configuration and control of the inverter. All these features can be freely combined. The inverter can be configured such that the high-side and low-side switches can change their operating state over a variety of time periods. This change in operating state makes it possible to vary the operating mode of the switches between a continuously on or off state and a pulse-width modulated state. Pulse-width modulation, a technique for controlling the power output to electrical devices, depends on the electrical angle of the electric machine.This means that the pulse control is related to the electrical angle within the electric machine, enabling more precise control of the generated torque. The ability to switch between constant and modulated operating states offers improved flexibility in controlling the electric machine. In particular, by continuously switching a switch on or off during specific operating phases, energy consumption can be optimized and the efficiency of the drive increased. At the same time, pulse-width modulated control allows for finer adjustment of the motor power and a reduction in electrical disturbances and losses.Controlling the operating states of each switch based on the electrical angle of the electric machine enables synchronization between the electrical control of the phases and the mechanical position of the rotor. This can lead to improved efficiency, performance, and thermal stress, as well as optimized operating behavior of the electric machine. Controlling the operating states based on the electrical angle in a frequency converter allows the efficiency and performance of the electric drive to be maximized by selecting the most suitable operating state of the switches according to the operating requirements, electrical angle position, and load condition of the electric machine. This enables the electric drive to be used in a wide variety of applications, each offering an optimal balance between energy efficiency, performance, and controllability.

[0029] According to a further embodiment, an electric drive is described which is characterized by a specific configuration and operating mode of the inverter that can improve the efficiency and performance of the drive. This embodiment can be freely combined with the other embodiments. The inverter can be configured to enable precise control of the switches over a multitude of time periods, which is helpful for generating a fundamental wave to provide torque in the electric machine. The switches of each half-bridge in at least one phase group, consisting of high-side and low-side switches, can be operated in a pulse-width modulated (PWM) state.This operating state allows for precise control of the voltage and current flowing through the electric machine by switching the switches on and off at a specific frequency, resulting in finer adjustment of the motor's power output. Some switches can also be operated in a continuously on state, meaning they can remain permanently switched on for a certain period. This reduces power loss and increases drive efficiency by minimizing switching losses, as the switches do not need to be repeatedly switched on and off, which can lead to losses.By keeping at least one high-side or low-side switch continuously on and at least one high-side or low-side switch continuously PWM-active, the remaining switches of the half-bridges can be operated either PWM-active or continuously on or off. Any combination of the switch operating states is therefore possible and can be alternated as desired. The operating time of the switches, both in pulse-width modulated and continuously on modes, can be controlled such that it averages out over time for each of the high-side and low-side switches of the two half-bridges of at least one phase group. This equalization of operating time helps to ensure a symmetrical load on the switches and maximize the service life of the components.Precise control and synchronization of operating times ensure uniform heat distribution across the switches and half-bridges, preventing local thermal overload, which is particularly important in high-power applications. This allows for the achievement of a performance specification with smaller and less expensive half-bridges than would be possible if all switches were PWM-active for more periods. The specific communication mechanisms between components that enable these operating states can include intelligent control electronics capable of processing signals in real time and controlling the switches according to the desired power output and efficiency. This control electronics can utilize feedback systems to monitor the actual performance of the electrical machine and adjust the switching operations of the half-bridges accordingly.Overall, this intelligent control leads to optimized operation of the electric drive, characterized by improved performance, higher efficiency and longer component lifespan.

[0030] According to a further embodiment, an electric drive is described that can offer improved control and efficiency in generating the torque of the electric machine. This embodiment can be freely combined with the other embodiments; in particular, the electric drive can be configured as in the other embodiments. In this embodiment, the time intervals can be structured to form a period that can repeat cyclically. This period can have at least the length of one period of the fundamental frequency of the electric machine. This structuring enables both precise and repeatable control of the torque, which can be advantageous for applications where high precision in torque control is required.The cyclic repetition of the period ensures a smooth and predictable torque output from the electric machine, contributing to the stability of the drive's operation. Matching the period length to the electric machine's fundamental frequency allows for periodization of operating states based on the fundamental frequency, facilitating efficient and cool operation of the inverter at any given time, load point, or speed. This optimizes the electric drive's performance and maximizes energy transfer between the cooler inverter and the electric machine, potentially leading to improved overall drive performance.

[0031] According to a further embodiment, an electric drive can be provided which comprises a further development of the electric drive. This embodiment can be combined with the other embodiments. The inverter of this drive can be specially configured to enable improved control of the electric machine. During at least one period from a plurality of periods relevant to the operation of the drive, the at least one high-side switch in one of the two half-bridges of the at least one phase group can be operated in pulse-width modulated (PWM) mode. Simultaneously, the at least one low-side switch in the same half-bridge can also be operated in PWM mode.This type of modulation allows for fine-tuning of the voltage and current passing through the half-bridge, thus contributing to the generation of a precise fundamental frequency required for generating torque in the electric machine. During this at least one period, the at least one high-side switch of the other of the two half-bridges of the at least one phase group can operate in a state that is either continuously on or off. Likewise, the at least one low-side switch of the other half-bridge can operate in a corresponding continuously on or off state. This configuration allows one of the half-bridges to supply a continuous voltage during a period, while the other half-bridge is responsible for modulating the voltage.This approach can increase drive efficiency by reducing the switching losses typically associated with switching semiconductor components. By combining a continuous and a modulated operating state within a phase group, the inverter can optimize the drive's electrical characteristics, resulting in improved performance, higher energy efficiency, and reduced electromagnetic interference. This specific configuration of switching states within the half-bridges allows the inverter to operate the electric machine with precisely controlled voltage and current, which can be advantageous for applications requiring precise torque control. In particular, this limits switching losses to a single half-bridge whose switches are in the PWM-active operating state during the relevant period.For example, it is possible to configure this half-bridge to have lower switching losses than half-bridges in a different configuration. This can be achieved, for instance, by using switches with the lowest possible switching losses in this half-bridge. Simultaneously, the other half-bridge can be configured to have lower conduction losses. This can also be achieved, for instance, by using switches with the lowest possible conduction losses in this half-bridge. Thus, a combination of advantageous hardware configuration of the different half-bridges, along with advantageous and intelligent PWM control, is possible.This combination can lead to even greater reductions in losses, further improve the thermal management of the electric drive, prevent local thermal overloads, increase the power density of the drive, and enable more cost-effective manufacturing, since not all components need to be optimized for the lowest possible conduction and switching losses. This can also further improve the service life of the electric drive.

[0032] According to a further embodiment, the electric drive, comprising at least one electric machine and at least one inverter, can be enhanced by specific phase control mechanisms to further improve the system's functionality and efficiency. This embodiment, apart from the aforementioned embodiment in which the inverter alternates the operating states under different switches over a multitude of time periods such that the respective durations average out, can be freely combined with the other embodiments. The inverter, which includes a plurality of half-bridges, each with a plurality of switches, can be configured such that all high-side and low-side switches of the two half-bridges of at least one phase group can be controlled in a specific switching pattern over a plurality of time periods.This configuration enables precise control of the power supply to the electric machine by ensuring that the switches of all half-bridges in a phase group can be synchronized according to the desired switching pattern, which can contribute to improved torque generation performance. The high-side and low-side switches in one of the two half-bridges of at least one phase group can be operated in pulse-width modulated (PWM) mode. This means that these switches can be operated in a state that allows for fine voltage adjustment through rapid switching on and off. This mode is particularly useful for precise control of power transmission and can contribute to increased efficiency and reduced losses.The high-side and low-side switches in the other of the two half-bridges of at least one phase group can then be operated in either a continuously on or off state. This switching pattern allows one half-bridge to provide a constant voltage pass, while the other half-bridge is responsible for voltage modulation. This can increase system stability and reduce control complexity, as not all switches need to be constantly modulated. By combining these two operating states in the half-bridges of a phase group, the inverter can generate a fundamental frequency that provides torque to the electric machine over time.This configuration can lead to more efficient and reliable performance of the electric drive by combining the advantages of pulse-width modulation with the stability of a constant operating state, resulting in improved energy conversion and optimized operation of the electric machine. In particular, switching losses are limited to a single half-bridge whose switches are in the PWM-active operating state. For example, this half-bridge can be configured to have lower switching losses than half-bridges in a different configuration. This can be achieved, for instance, by using switches with the lowest possible switching losses in this half-bridge. Simultaneously, the other half-bridge can be configured to have lower conduction losses.This is possible, for example, by using switches in this half-bridge that exhibit the lowest possible conduction losses. Thus, a combination of advantageous hardware configuration of the various half-bridges, along with efficient and intelligent PWM control of the half-bridges, is possible. This combination can lead to even greater reductions in losses, further improve the thermal management of the electric drive, prevent local thermal overloads, increase the power density of the drive, and enable more cost-effective manufacturing, since not all components need to be optimized for the lowest possible conduction and switching losses. This can also further improve the service life of the electric drive.

[0033] According to a further embodiment, an electric drive can be provided that builds upon the features already described and exhibits specific mechanisms for communication between the components as well as functional advantages of the new features. This embodiment, except for the embodiment in which the high- and low-side switches of one half-bridge in a phase group are PWM-active and the high- and low-side switches of the other half-bridge are PWM-inactive, is freely combinable with the other embodiments. The electric drive can comprise an electric machine and a converter, which in turn contains a plurality of half-bridges, each half-bridge having at least one high-side switch and one low-side switch. The converter can be specifically configured to implement a particular operating pattern in at least one period from a plurality of periods.In one of the two half-bridges of a phase group, either the at least one high-side or the at least one low-side switch can be operated in pulse-width modulated (PWM) mode, while the at least one other switch can be kept in a continuously off state. This allows for precise control of the power supply for the respective phase. During the same period, in the other half-bridge of the phase group, either the at least one high-side or the at least one low-side switch can be kept in a continuously on state, while the other at least one switch remains continuously off. This configuration results in asymmetrical control of the half-bridges, which, depending on the operating conditions and the instantaneous load requirements of the electric drive, can enable improved efficiency in generating the fundamental wave.This specific operating pattern allows the inverter to control the electric machine in such a way as to optimize torque and minimize energy consumption. Pulse-width modulated control of one switch, in combination with the permanently on or off state of the other switch in the respective half-bridge, enables finer adjustment of electrical characteristics, such as the voltage and current supplied to the electric machine. This can lead to improved performance and efficiency of the drive. The targeted control of the switches in the half-bridges makes it possible to reduce losses that can normally occur during energy conversion, thus contributing to the overall optimization of the electric drive. Specifically, the switching losses of a phase group can be reduced by more than half, namely by approximately 75 percent.This configuration can also offer the advantage of improved electromagnetic compatibility by minimizing interference caused by switching operations. Overall, this design of the electric drive enables more precise and efficient drive control, which can lead to improved performance, lower operating costs, and a longer component lifespan.

[0034] According to a further embodiment, an electric drive is described that builds upon the preceding claims and in which the inverter can be configured in a specific way to further improve the functionality and efficiency of the system. This embodiment can be freely combined with the other embodiments. The inverter, which contains a plurality of half-bridges, can now be configured such that only the high-side switches that are in a continuously switched-on operating state for at least one period of operation need to be connected to and equipped with a galvanically isolated power supply. This galvanic isolation can ensure electrical isolation between the high-side switches and the rest of the electrical machine. This can have the advantage that expensive galvanic isolation does not need to be unnecessarily used for all switches.The galvanically isolated power supply circuit ensures that the high-side switches receive a stable and isolated supply voltage, which is advantageous for precise control and reliable operation. If the half-bridges of a phase group are operated such that only one half-bridge is in the PWM-active state and the other in the PWM-inactive state, then only the at least one high-side switch of the half-bridge and phase operating in the PWM-inactive half-bridge or phase of the phase group needs to be connected to the galvanically isolated power supply circuit. This can enable further cost reductions. The combination of these features allows for the provision of an electric drive with improved performance and reliability, particularly with regard to the control of the electric machine and the generation of the required torque.

[0035] According to another embodiment, the electric drive can be further developed by specific configurations of the half-bridges in the phase groups to optimize the drive's efficiency and performance. This embodiment can be combined with the embodiment in which the high- and low-side switches of one half-bridge in one phase group are PWM-active, and the high- and low-side switches of the other half-bridge are PWM-inactive. This combination leads to a further increase in the converter's economy, performance, and efficiency. For example, a half-bridge within at least one phase group operating in pulse-width modulated mode can be configured to exhibit the lowest possible switching losses. This can be achieved by designing the switches of this half-bridge to cause minimal losses during the switching activity required for pulse-width modulation.Pulse-width modulation (PWM) is a method in which switches can be rapidly turned on and off to control the voltage and current flowing to the electric machine, thereby regulating the torque produced by the machine. Lower switching losses in this operating state can increase the efficiency of the inverter and reduce heat generation, which in turn can improve the reliability and lifespan of the system. The other half-bridge of the same phase group, in which at least one switch is either continuously on or off, can be configured to have lower conduction losses. Conduction losses occur when current flows through the switch while it is in the on state.Optimizing for lower conduction losses is particularly advantageous in operating conditions where the switches are not frequently engaged but remain in a single state for extended periods, which is typically the case during fundamental wave generation. By specifically adapting the half-bridges to either lower switching or conduction losses, depending on their function and operating condition, the overall efficiency of the inverter can be improved, leading to more efficient torque generation in the electric machine. This configuration allows the electric machine to operate with higher efficiency and lower losses, increasing the overall power output of the electric drive while simultaneously reducing the thermal stress on the components.This also reduces operating costs and extends the lifespan of the drive, which is advantageous in the application of electric drives.

[0036] According to another embodiment of the electric drive, the specific design of the switches in the half-bridges can be further refined. This embodiment can be freely combined with the other embodiments. The switches of at least two half-bridges can be implemented as transistors, enabling precise and fast switching, which is essential for the efficient control of the electric machine. Using transistors as switches offers the advantage of higher switching speeds and lower power losses compared to other switch types such as relays or thyristors, resulting in improved energy efficiency of the drive. Furthermore, the use of transistors allows for miniaturization of the half-bridges, contributing to a more compact design of the inverter, even when multiple transistors are used per high-side and low-side switch.Furthermore, the different substrate technologies and / or substrate materials of the transistors allow for optimization of their electrical properties. Different substrate technologies, such as silicon-, silicon carbide-, or gallium nitride-based transistors, can exhibit varying electrical characteristics like switching speeds, on-resistance, and thermal conductivity. This diversification makes it possible to use different transistors specifically tailored to the requirements of the respective half-bridges and / or switches and their associated phase groups, further increasing the efficiency and performance of the inverter.The use of different substrate materials can also help optimize the thermal stability and efficiency of the transistors, for example, by using materials with higher thermal conductivity or lower electrical resistance. These adjustments can lead to improved heat dissipation and a reduction in switching losses, which extends the service life of the electric drive and increases its reliability. Overall, these features help the electric drive respond more flexibly to different operating conditions and deliver optimized performance across a wider range of applications.

[0037] According to another embodiment, the electric drive can be designed such that switches of at least two half-bridges are implemented as transistors, and the transistors of one of the at least two half-bridges can have a gallium nitride substrate. This embodiment can be freely combined with the other embodiments. Gallium nitride, or GaN for short, is known for its electronic properties, such as a high breakdown field strength and high electron mobility, which make it possible to realize switches that can operate efficiently at high frequencies and voltages. This can lead to improved power density and efficiency of the inverter and thus of the entire electric drive. The use of GaN transistors can also reduce heat generation and extend the service life of the components, since GaN has better thermal conductivity than conventional materials such as silicon.Alternatively, the transistors of at least one half-bridge can have a silicon substrate, which is a more cost-effective solution and, due to mature silicon technology, can ensure high reliability and availability. Silicon transistors are widely available and offer good performance for a variety of applications, making them a viable option for many electric drives. The transistors can be driven to operate at least one of the high-side or low-side switches in a continuously on or off state for at least one period out of a variety of time periods, while the remaining switches operate in a pulse-width modulated state. This differentiated control makes it possible to generate a fundamental wave that provides torque in the electric machine.The choice of substrate material for the transistors can therefore have a direct impact on the efficiency, performance and cost of the entire electric drive and helps to meet the requirements of different applications and markets.

[0038] According to another embodiment of the electric drive, the stator of the electric machine can be designed to have a maximum of one conductor per slot. This embodiment can be freely combined with the other embodiments. This specific stator configuration can contribute to a number of technical advantages. By limiting the number of conductors to a maximum of one per slot, heat dissipation in the stator is improved, as a larger convection surface is available for air or liquid cooling, which can lead to increased efficiency and reliability of the electric machine. Furthermore, this arrangement allows for simpler stator manufacturing, as complex winding steps are not required, which can lead to a reduction in production costs and a simplification of assembly processes.Reducing the number of conductors to one per slot can also optimize the stator's magnetic properties. The concentrated winding configuration within the stator reduces stray fluxes, leading to improved electromagnetic performance. This is particularly advantageous in combination with the inverter, which ensures efficient voltage modulation. The precise control of the switches in the half-bridges, coupled with an optimized stator, contributes to improved fundamental wave quality. This fundamental wave is crucial for generating consistent torque in the electric machine. Furthermore, using one conductor per stator slot allows for a more compact drive design, as the winding heads can be made smaller. This can also save material and weight in the winding head area.The inverter can control the half-bridge switches in a way that allows for precise adjustment of the electrical currents to the requirements of the electric machine, while the simplified stator topology enables more efficient transmission and utilization of these currents. Overall, this embodiment results in an electric drive that is not only more efficient and cost-effective to manufacture, but also offers improved performance and reliability in operation.

[0039] According to a further embodiment, an electric drive is described which builds upon the features of a preceding claim and can extend it with additional functionalities. This embodiment can be freely combined with the other embodiments. The inverter of the electric drive can be configured to enable improved control and efficiency of the energy conversion. This can be achieved by a specific adaptation of the pulse-width modulation (PWM) clock. Pulse-width modulation is a method in which the voltage is supplied to the electric machine in the form of pulses of variable width to enable efficient motor control. The pulse-width modulation clock of at least one phase group can be shifted by one phase compared to the pulse-width modulation clock of at least one other phase group.The amount of the shift can be defined by a specific phase, also known as the interleaving angle. This time shift can lead to a phase shift of the PWM signals between the different phase groups. This phase shift optimizes the electrical and magnetic interaction between the phase groups, which can reduce interference and result in a more even distribution of the electrical load across the different phases. This can increase the system's efficiency, as the load on individual components can be reduced, thus decreasing heat generation in the inverter and the electric machine. Furthermore, this configuration can contribute to a reduction in harmonics in the electric drive's power grid, which can improve the drive's electromagnetic compatibility and extend the component lifespan.The specific communication mechanisms between the components can include the synchronization of the half-bridge switching operations and the precise control of the high-side and low-side switches to achieve the desired time shift of the pulse-width modulation. This configuration allows the fundamental wave to be generated over time, even in continuous or pulse-width modulated operating states of the switches, in such a way that optimized torque can be provided in the electric machine. This embodiment thus offers a way to improve the performance and efficiency of the electric drive, particularly in applications where precise motor control and high system efficiency are beneficial.

[0040] According to a further embodiment, an electric drive is described which builds upon the features of a preceding claim and can extend it with additional functionalities. This embodiment can be freely combined with the other embodiments. The inverter of the electric drive can be configured to offer improved energy efficiency and power density. This can be achieved by an implementation in which at least two phase groups share a DC link capacitor. The DC link capacitor can serve as an energy storage device that smooths the voltage spikes generated by the half-bridges and thus enables a more stable voltage supply for the phase groups.Sharing a DC link capacitor across multiple phase groups reduces the need for separate capacitors for each phase group, leading to a reduction in component count, cost, and footprint. By sharing a single DC link capacitor, phase groups can operate more efficiently because energy fed back into the capacitor can be used by other phase groups instead of being wasted. This can result in improved overall efficiency. This configuration can also help reduce electromagnetic interference. Therefore, this design offers significant advantages in terms of efficiency, cost, installation space, and electromagnetic compatibility, making the electric drive more attractive for a wide range of applications, especially where space and energy efficiency are critical.

[0041] BRIEF DESCRIPTION OF THE FIGURES

[0042] The present invention is explained in more detail with reference to the figures in which it is illustrated by way of example:

[0043] Figure 1 shows a schematic representation of a two-phase group 10 of an electric drive with two phases Ui, Vi, half-bridges 11, 12, high-side switch 13, low-side switch 14, electric machine 3, controller 4, connections to power terminals 5, 6 and a DC link capacitor 7. Figure 2 shows a schematic representation of an electric drive with four phases Ui, Vi, U2, V2, an electric machine 3, two phase groups 10, 20 with half-bridges 11, 12, 21, 22, high-side switches 13, 23 and low-side switches 14, 24, connections to power terminals 5, 6, a controller 4 and a DC link capacitor 7.

[0044] Figure 3 shows a timing diagram of the switching states for high-side and low-side switches of two half-bridges of a phase group in an electric drive, with the switching states occurring over different time intervals Tzi, Tz2, Tz n are shown.

[0045] Figure 4 shows a timing diagram of the switching states for high-side and low-side switches of two half-bridges of a phase group in an electric drive, with the switching states occurring over different time intervals Tzi, Tz2, Tz n are shown.

[0046] Figure 5 shows a timing diagram of the switching states for high-side and low-side switches of two half-bridges of a phase group in an electric drive, with the switching states occurring over different time intervals Tzi, Tz2, Tz n are shown.

[0047] Figure 6 shows a timing diagram of the switching states for high-side and low-side switches of two half-bridges of a phase group in an electric drive, with the switching states occurring over different time intervals Tzi, Tz2, Tz n are shown.

[0048] Figure 7 shows a schematic representation of a two-phase electrical circuit, where the switches are implemented as transistors and an electrical machine is connected.

[0049] Figure 8 shows a diagram representing the voltage profile over time in relation to the electrical angle.

[0050] Figure 9 shows a timing diagram of the switching states for high-side and low-side switches of two half-bridges of a phase group in an electric drive, with the switching states shown over different time intervals Tzi, Tz2, Tz3, Tz4.

[0051] Figure 10 shows a timing diagram of the switching states for the high-side and low-side switches of two half-bridges of a phase group in an electric drive, showing the switching states over different time intervals T1, Tz2, Tz3, Tz4. Figure 11 shows a timing diagram of the switching states for the high-side and low-side switches of two half-bridges of a phase group in an electric drive, showing the switching states over different time intervals T1, Tz2, Tz3, Tz4 and over a time period TP.

[0052] Figure 12 shows a timing diagram of the switching states for high-side and low-side switches of two half-bridges of a phase group in an electric drive, with the switching states shown over different time intervals Tzi, Tz2, Tz3, Tz4 and over a time period TP.

[0053] Figure 13 shows a timing diagram of the switching states for high-side and low-side switches of two half-bridges of a phase group in an electric drive, showing the switching states over different time periods Tzi, Tz2, Tz3, Tz4 and over a time period TP.

[0054] Figure 14 shows a schematic representation of a stator of an electrical machine in two views, a top view and a perspective view.

[0055] Figure 15 shows a diagram with two superimposed PWM carrier signals and their temporal relationship to each other.

[0056] DETAILED DESCRIPTION

[0057] Figure 1 illustrates an embodiment of an electric drive comprising a phase group 10 with two phases Ui, V xand includes a controller 4. The phase group is shown schematically and includes an electrical machine 3 connected to the half-bridges 11 and 12. Each half-bridge 11 and 12 consists of an arrangement of switches, which can be transistors, for example, but other switches such as thyristors or relays are also possible. The switches are arranged in a half-bridge configuration, with each half-bridge comprising at least one high-side switch 13 and at least one low-side switch 14. In Figure 1, the high-side and low-side switches of the second phase 12 are not labeled with their own reference numerals. The switches of the two half-bridges can also differ from each other. The difference can lie in both the number and the type of switches. Thus, different types of transistors as well as other switches can be used.This allows the switches of each half-bridge to be adapted to their specific application and operating purpose. Each of these switches can also comprise one or more switches. For example, a high-side switch 13 can consist of one or more transistors.

[0058] The half-bridges are connected at terminal 5 to a positive voltage potential and at terminal 6 to a reference potential, e.g., a ground connection. Since the switches shown at the top in Figure 1 are each connected to the positive voltage potential terminal 5, these switches are the high-side switches of half-bridges 11 and 12. The low-side switches, on the other hand, are connected at terminal 6 to the reference potential, e.g., ground. By alternately switching the high-side and low-side switches on and off, it is possible to provide a suitable voltage at their outputs to phases Ui and Vi of the stator of the electric machine 3. This provides the output voltages of half-bridges 11 and 12 for phases Ui and V. xA fundamental wave can be generated from the stator, which serves to provide torque in the electric machine 3. The terminals 5 and 6 themselves can, for example, be connected to two voltage terminals of a source not shown in Figure 1, such as a battery or another voltage source.

[0059] Terminals 5 and 6 can be arranged within an intermediate circuit of the electric drive, which may also include an intermediate circuit capacitor 7. This intermediate circuit provides the power supply for the half-bridges 11 and 12 and enables the control of the switches of these half-bridges 11 and 12 to operate the electric machine.

[0060] Controller 4 is connected to half-bridges 11 and 12 via control signal lines and controls the switching states of high-side switches 13 and low-side switches 14. Controller 4 is configured to operate the switches in a continuously on or off state, or in a pulse-width modulated (PWM) state. The PWM control allows the generation of a fundamental waveform, which is used to provide torque to the electric machine 3. Controller 4 can be a separate control device or a component of another part of the electric drive. Controller 4 can be implemented in either hardware or software. For example, Controller 4 can be a computer or part of a computer that includes a processor capable of executing program code stored on a computer-readable data medium.This allows the controller 4 to selectively control the switches of the half-bridges 11 and 12 and, for example, change their operating state.

[0061] Figure 1 shows that phase group 10 can have its own star point. For this purpose, a first side of each phase Ui and V x , in Figure 1 towards the electric machine 3, connected to a common point, while the second side of each phase Ui and V x coupled to one of the half-bridges 11 and 12. This enables differentiated control of phases Ui and V. x and thus precise control of the torque generated in the electric machine 3.

[0062] The arrangement of the half-bridges 11 and 12 and the control by the controller 4 can be designed such that a fundamental wave is generated over a multitude of time periods. This can be achieved by appropriately controlling the switches of the half-bridges 11 and 12, whereby at least one of the switches is operated in a continuously on or off state, while the remaining switches are operated using pulse-width modulation.

[0063] Figure 1 does not explicitly show the galvanic isolation of the power supply circuit for the high-side switches 13, which can be operated in a continuously switched-on state. Likewise, no specific substrate technologies or substrate materials for the switches, if they are transistors, are shown. However, these can be selected differently and adapted to the respective application of each half-bridge in order to achieve an optimal configuration of the half-bridges 11 and 12, which can reduce both switching and conduction losses of the switches. Although Figure 1 only shows one phase group 10 with two half-bridges 11 and 12 for the two phases Ui and Vi, the electric drive can have any number of such or other phase groups. The half-bridges 11 and 12 can be used to implement part of a converter for the electric drive.The converter can, however, include additional half-bridges and phase groups. By using a plurality of at least two phase groups, each with two phases, it is possible to generate a clean rotating field even though fewer than three phases are used at a star point and in a phase group. Overall, Figure i presents a schematic representation of part of an electric drive designed for controlling and operating an electric machine 3. Figure 1 shows components of the electric drive and their connections, which are helpful for understanding the operation and integration of the electric drive components in technical applications.

[0064] Figure 2 illustrates a schematic representation of an exemplary electric drive. The electric drive comprises an electric machine 3 connected to a converter consisting of two phase groups 10 and 20. Each phase group 10 and

[0065] 20 is marked by dashed lines and includes two half-bridges each: 11, 12,

[0066] 21 and 22, each equipped with a multitude of switches. Within each half-bridge 11, 12, 21, and 22, there is at least one high-side switch 13, 23 and one low-side switch 14, 24. The respective half-bridges 11, 12, 21, and 22 provide the currents that drive the phases Ui, V x , U2 and V2 of the stator of the electric machine 3 are supplied. Thus, unlike Figure 1, Figure 2 illustrates two phase groups, each with two half-bridges 11, 12 and 21, 22 respectively, corresponding to phases Ui, V xas well as U2, V2. The individual half-bridges 11, 12 and 21, 22 can each correspond to those described above in connection with Figure 1, which is why reference is made to this description for the details of phase groups 10 and 20.

[0067] The controller 4 of the embodiment shown in Figure 2 can also correspond to the controller 4 as described in connection with Figure 1. Thus, the controller 4 can also control the operating state of the switches in the half-bridges of several phase groups simultaneously. This enables synchronization of the currents in the different phases Ui, Vi, U2, and V2. The phase groups and their respective phases can also be operated with a phase shift relative to each other in order to provide a fundamental wave and thus a torque in the electric machine 3.

[0068] The configuration of the inverter with its controller 4 allows the operating state of the switches to change between continuously on or off and pulse-width modulated operation over time periods, based on the electrical angle of the electric machine. This enables efficient adjustment of the torque and speed of the electric machine. The switches within the half-bridges can be transistors, with the substrate technology and / or substrate materials of these transistors varying. For example, the substrate can be gallium nitride (GaN) or silicon (Si), depending on the requirements for power efficiency and thermal resistance. This applies to both the exemplary configuration of the electric drive shown in Figure 2 and Figure 1.

[0069] It should be noted that Figure 2 is simplified and therefore shown without controller lines, meaning that the control signal connections between the controller 4 and the switches of the half-bridges 11, 12, 21, and 22 are not shown. This emphasizes the focus on the topology of the inverter and the electric machine 3 in this representation. As mentioned earlier, the controller 4 can be implemented in any way, either as a standalone component or integrated into another part of the electric drive, either as a hardware component or as a software component.

[0070] Figure 2 illustrates an electric drive configured for efficient control of the torque and speed of an electric machine by enabling precise control over the operating states of the switches in the inverter's half-bridges. As illustrated, the electric drive can include not only the two phases Ui, Vi of half-bridges 11, 12 of a first phase group 10 shown in Figure 1, but also two further phases U2, V2 of half-bridges 21, 22 of a second phase group 20. Furthermore, the electric drive can include any number of additional phase groups, up to a total of n phase groups.

[0071] Figure 3 illustrates a timing diagram representing the operating states of various switches in two half-bridges, for example, half-bridges 11 and 12 of Figure 1 or half-bridges 11, 12, 21, and 22 of Figure 2, from a converter over a series of time periods Tzi, Tz2, ..., Tzn. These time periods can be arbitrarily short or long, and can therefore be of equal or different lengths. This duration can be determined by controlling the converter and / or the controller 4 of the electric drive. The lower limit of the duration represents one cycle or period of the PWM clock, as this defines the maximum modulation speed. This allows the electric drive to respond flexibly to dynamically changing load conditions, which is advantageous, for example, in the application of an electric drive in the field of electromobility.The vertical axis of the diagram represents three possible operating states, where "i" indicates an on state (High) and "o" indicates an off state (Low). The horizontal axis represents time.

[0072] The first line of the diagram, labeled "HB 1 High", shows the operating state of the high-side switch of a first half-bridge. It can be seen that this switch can be operated in a pulse-width modulated state over the various time periods.

[0073] The second line, "HB i Low", represents the operating state of a low-side switch of the first half-bridge. This switch can remain in the off state continuously during the first period Tzi before transitioning to the pulse-width modulated operating state during the second period Tz2.

[0074] The third and fourth lines of the diagram in Figure 3, labeled "HB 2 High" and "HB 2 Low," show the operating states of the high-side and low-side switches of a second half-bridge. It can be observed that the high-side switch remains in a continuously pulse-width modulated (PWM) operating state, while the low-side switch is also in a continuously PWM operating state. Thus, the second half-bridge can be operated in a different operating mode than the first half-bridge.

[0075] Thus, according to the switching pattern of a phase group shown in Figure 3, the "Off" state can be operated at least once and the "PWM" state three times within a given period, and the "PWM" state four times within a later period. These states can vary over the multitude of different time periods Tz. nThis allows the inverter of the electric drive to be used flexibly to generate a torque corresponding to the instantaneous requirements of the electric machine 3. For example, if the time period Tzi is selected at a favorable point in time with respect to the electrical angle of the electric machine, the drive can provide the same torque as if all switches were operated in PWM mode, even though one switch is switched off during this period. Consequently, no switching losses occur for this switch. Thus, Figure 3 illustrates that the switches of the half-bridges can be operated in various combinations of continuously off operating state and pulse-width modulated operating state.

[0076] The timing of the switching states in the half-bridges is helpful for generating the correct voltage and current profiles required to control the electric machine 3. By selectively controlling the high-side and low-side switches, the inverter can operate the electric machine efficiently and precisely, resulting in improved performance and efficiency of the electric drive.

[0077] The operating pattern of the inverter and the operating states of the switches shown in Figure 3 are exemplary of the features described in the claims. The specific arrangement and timing of the switch states are designed to optimize the performance of the electric drive while simultaneously minimizing losses, which can be further supported by selecting suitable substrate technologies and materials for the transistors. Specifically, switching losses can be minimized during the exemplary period Tzi in Figure 3 because one of the low-side switches of the exemplary phase group does not need to be actively PWM-controlled. Instead, it can remain in a continuous off operating state. Eliminating the active PWM operation of a switch during a given period results in the advantage of lower switching losses.

[0078] The aspects explained in connection with Figure 3 also apply to the subsequent circuit diagram illustrations.

[0079] Figure 4, similar to Figure 3, illustrates a schematic representation of the control of switches in half-bridges of a converter, which can be used in an electric drive. The diagram shows a timing diagram depicting the switching states of high-side and low-side switches in two half-bridges over a variety of time intervals Ti, Tz2, ..., Tz. n The time axis t is mapped. The vertical axis represents, as in Figure 3, the switching state of the respective switches.

[0080] During the period Tzi, the high-side switch of the first half-bridge can be operated in a continuously on state, while the low-side switch of this half-bridge is continuously off. This means that the high-side switch is continuously conducting, while the low-side switch is continuously not conducting. During the same period Tzi, both the high-side and low-side switches in the second half-bridge are in a continuously pulse-width modulated (PWM) state. Consequently, during this period Tzi, the first half-bridge can be operated in a completely PWM-inactive state. Therefore, no switching losses occur in this half-bridge that would otherwise result from pulse-width modulation.

[0081] In the following period Tz2, the switches of the first half-bridge HB i change their operating state, so that the high-side and low-side switches are now in a pulse-width modulated (PWM) operating state. In the second half-bridge HB 2, the high-side and low-side switches remain continuously PWM-modulated. If, for example, the period Tzi is selected at a favorable time with respect to the electrical angle of the electric machine, the drive can deliver the same torque as if all switches were operating in PWM mode, even though two switches are continuously switching on and off during this period. Consequently, no switching losses occur for these switches.

[0082] Thus, Figure 4 shows that the switches of the half-bridges of a phase group over the multitude of time periods Tz nThe switches can continuously change their operating state between being on or off and pulse-width modulated. This enables flexible control of the electric machine to ensure optimized torque and efficient power delivery. Eliminating the need for active PWM operation of two switches simultaneously results in reduced switching losses while maintaining the full performance of the drive.

[0083] These switching states can be set by the inverter's control logic. Precise control of the switches is advantageous for the efficiency and performance of the entire electric drive.

[0084] Figure 5 illustrates another timing diagram, similar to those in Figures 3 and 4. The high-side switch of the first half-bridge can be continuously switched on during a first period and continuously pulse-width modulated during the following periods. The low-side switch of the first half-bridge can be continuously switched off during the first period and continuously pulse-width modulated during the following periods. The high-side switch of the second half-bridge can be continuously pulse-width modulated during a first period and the subsequent periods Tzn. In the second period in between, it can be continuously switched off. The low-side switch of the second half-bridge can be continuously switched off during a first period T. ziIt is operated in a continuously pulse-width modulated operating state and, in the subsequent period, in a continuously switched-on operating state. In the following periods Tz n It can be operated in pulse-width modulated mode.

[0085] Thus, Figure 5 illustrates that in the first period Tzi, the first half-bridge can be operated in a PWM-inactive state, while the second half-bridge operates in a PWM-active state. These operating states are then exchanged between the two half-bridges in the following period Tz2, making it possible to swap the roles of the half-bridges over several periods. This allows different switches of the half-bridges to be operated in an alternating pattern of PWM-active and PWM-inactive states, so that the half-bridges experience no switching losses when they are PWM-inactive. Unlike what is shown in Figure 5, this alternation can be carried out in the following periods Tz. n Furthermore, this process can be repeated and continued as often as desired. This allows the average ohmic losses to be reduced over time, because the half-bridges can cool down repeatedly and thus decrease their ohmic resistance.

[0086] Figure 6 illustrates another timing diagram depicting the operating states of the high-side and low-side switches of two half-bridges in a phase group. This representation is comparable to that of Figures 3, 4, and 5, so the details explained therein are not repeated. Unlike Figures 3, 4, and 5, the switching pattern in Figure 6 uses a passive freewheel, so that in the first period, only one switch of the two half-bridges is PWM-active. Furthermore, in the first period, only one other switch of the PWM-inactive half-bridge is switched on. All other switches are in the off operating state. If the period Tzi is selected at a favorable time with respect to the electrical angle of the electric machine, the drive can provide the same torque as if all switches were PWM-active, even though three switches are switched on or off during this period.Consequently, these switches incur no switching losses. By eliminating the active PWM operation of three switches within a given period, the advantage of reduced switching losses is achieved.

[0087] Figure 7 illustrates a schematic representation of an electric drive with a converter. The arrangement shown depicts a phase group consisting of two phases, i.e., two half-bridges, in which the switches are implemented as transistors.

[0088] Figure 7 shows two half-bridges, each consisting of a high-side switch and a low-side switch. However, more than one transistor can be implemented as each switch. Each half-bridge is connected to a supply voltage at its positive terminal, which is applied to the high-side switches. The low-side switches, on the other hand, are each connected to a ground terminal. The transistors can be controlled at their gates by a gate voltage, i.e., switched on or off.

[0089] Both phases of each half-bridge in Figure 7 are connected on one side to a common star point, which here is represented by the connection of the switches to the electric motor. On a second side, the phases are coupled to the respective half-bridges.

[0090] The transistors in the half-bridges can be configured to operate in either a continuously on or off state, or in a pulse-width modulated state, for at least one of a multitude of time periods. This enables the generation of a fundamental waveform over the multitude of time periods to provide torque in the electric machine.

[0091] The configuration is designed such that the high-side and low-side switches can alternate their operating state between being continuously on or off and pulse-width modulated based on the electrical angle of the electric machine. This applies to all embodiments of the present invention and can contribute to optimizing the efficiency and performance of the electric drive. It should be noted that Figure 7 is only a schematic representation and does not show all details of the actual implementation. The exact configuration of the switches, the type of transistors, the substrate materials used, and other specific features may vary depending on the application and design requirements.

[0092] In summary, Figure 7 presents an example of a section of the electric drive where the half-bridge configuration and the control of the switches for generating torque in an electric machine can be optimized. The arrangement shown is representative of a multitude of possible configurations, which in practice may vary depending on specific requirements and design parameters.

[0093] Figure 8 illustrates a representation of the voltage curve over time, representing the operating state of an electric drive system. The vertical axis of the diagram denotes the voltage UM, while the horizontal axis represents the time profile t and the electrical angle of the electric machine 3. The curve in Figure 8 shows the voltage profile as a function of the electrical angle and time. The time periods T1, T2, T3, and T4 illustrate a possible voltage profile that can be generated according to Figures 9 to 13 with the operating patterns in their respective time periods T1, T2, T3, and T4. The time periods T1 and T2 in Figure 8 do not correspond to the respective time periods in Figures 3 to 6.

[0094] Figure 8 shows four different time periods T1, Tz2, Tz3, and Tz4, which together define a switching period. This switching period can correspond to the period of the fundamental frequency generated by the pulse-width modulation of the switches in a converter. The switching states of the high-side and low-side switches of a half-bridge within a phase group of the converter can influence the voltage waveform through this switching period.

[0095] Within the example switching period shown, it can be seen that the voltage UM describes a sinusoidal wave that starts at 0, reaches its maximum value, and then returns to 0. The sinusoidal wave represents the fundamental wave generated by the PWM of the switches. The vertical dashed lines represent the transitions between the individual time periods and mark the points at which the operating state of the half-bridge switches can change. However, this only illustrates the simplest form of timing the time periods. Any number of additional time periods can occur within a switching period to optimize the operation of the electrical machine.

[0096] Figure 8 illustrates that the inverter switches are configured to change their operating state over different time periods. This can be a continuously on or off state, or a pulse-width modulated operating state, which can also be adapted to the electrical angle of the electric machine. The switches can alternate between these states to generate the desired fundamental frequency required to provide the torque to the electric machine.

[0097] Figure 9 illustrates another timing diagram, depicting the operating states of the high-side and low-side switches of two half-bridges in a phase group. This representation is comparable to those in Figures 3, 4, 5, and 6, so the details explained therein are not repeated. Unlike those figures, Figure 9, like Figure 8, shows four time intervals T1, TZ2, TZ3, and Tz4, which together can define a switching period. As in Figure 8, however, additional time intervals of arbitrary length can occur within a switching period, which is not shown in Figure 9.

[0098] During the time intervals Tzi and Tz2, it can be seen that the high-side and low-side switches of the first half-bridge are continuously in the pulse-width modulated (PWM) operating state. Simultaneously, the high-side switch of the second half-bridge is continuously off, and the low-side switch is continuously on. As illustrated in Figure 8, the voltage of the fundamental wave is always in the positive part, which extends from 0 to Pi.

[0099] In the subsequent time intervals Tz3 and Tz4, the operating state of the switches between the half-bridges alternates. The switches of the second half-bridge are now in the pulse-width modulated (PWM) operating state, while the high-side switch of the first half-bridge is continuously off and the low-side switch is continuously on. As illustrated in Figure 8, the voltage of the fundamental frequency is always in the negative part, extending from π to 2π. The alternating operating states of the half-bridges of this one phase group can thus be controlled as a function of the fundamental frequency of the electric machine. This correlates with control based on the electrical angle of the electric machine.

[0100] The diagram in Figure 9 illustrates an operating mode in which the high-side and low-side switches of the half-bridges alternate their operating state between being continuously on or off and pulse-width modulated (PWM) over the various time intervals, depending on the electrical angle of the electric machine. This operating mode represents an active freewheeling operation in the PWM-operated half-bridge, meaning that the switches do not need to be actively switched during certain phases of the operating cycle, which can help reduce switching losses. This is called active freewheeling because the current driven by the inductance of the electric machine in the PWM-operated half-bridge is always conducted by either the active high-side or the low-side.

[0101] Figure 10 illustrates a timing diagram depicting the operating states of the high-side and low-side switches of two half-bridges. This representation is comparable to that of Figure 9, therefore the details explained therein are not repeated.

[0102] As in Figure 9, in Figure 10, one half-bridge is operated in the PWM-active state. During time periods Tzi and Tz2, this is the first half-bridge; during the subsequent time periods Tz3 and Tz4, it is the second half-bridge. Unlike in Figure 9, however, in each PWM-active half-bridge, only one high-side or low-side switch is operated with pulse-width modulation. This operating mode can be described as passive freewheeling because the current driven by the inductance of the electrical machine is also partially routed through the freewheeling diodes when the one PWM-active switch is switched off within a PWM cycle. This further minimizes switching losses, as only one of the four switches is actively pulse-width modulated at any given time.

[0103] Figure 11 illustrates another timing diagram, depicting the operating states of the high-side and low-side switches of two half-bridges in a phase group. This representation is comparable to that of Figure 9, therefore the details explained there are not repeated. Unlike Figure 9, this figure also illustrates a time period Tp. Furthermore, unlike Figure 9, the role of the PWM-active half-bridge is reversed once within a half-cycle of the fundamental frequency of the electrical machine.

[0104] Within the depicted time period TP, the operating states of the switches are arranged in a sequence that can repeat cyclically. The individual time periods do not have to be of equal length, as previously described. The high-side and low-side switches of each half-bridge alternate between a continuously on or off state and a pulse-width modulated (PWM) operating state. More precisely, each switch changes its operating state in each of the four time periods. However, this occurs in such a way that, similar to the switching pattern in Figure 9, an active freewheeling phase is implemented. This means that in each time period, one half-bridge is operated with both its respective high-side and low-side switches in PWM mode, while the two switches of the other half-bridge are operated once on and once off. This operating pattern thus achieves, on the one hand, an alternation of the PWM-active and PWM-inactive half-bridges, and on the other hand, a PWM-inactive half-bridge.The phase transitions from one period to the next. Furthermore, the roles of the high-side and low-side switches of the PWM-inactive phase or half-bridge also change superimposed. Thus, each switch is only in an on and off operating state once in each of the four subsequent periods. This can serve to distribute the load symmetrically across each switch and half-bridge within the phase group and minimize both the average switching losses and the average conduction losses over time. The symmetrical utilization of all switches minimizes the average temperature of the switches over time, thereby minimizing their ohmic resistance and resulting in lower ohmic losses. The operating pattern in Figure 11 is the simplest operating pattern that achieves a symmetrical load distribution across all switches for a short time period T. pThis allows for certain operating patterns. However, as mentioned, any other operating pattern is possible. In particular, the PWM-active half-bridge can switch several times per half-cycle of the fundamental frequency of the electric machine to keep temperature spikes in the switches and half-bridge as small as possible.

[0105] Furthermore, the operating time of the switches in their respective operating states can be configured over the time period Tp in such a way that the average operating time for each switch becomes more consistent, which can lead to further optimization of switch losses and the efficiency of the inverter. The inverter configuration makes it possible to control and adjust the operating states of the switches over a wide range of time periods to achieve the desired performance and functionality of the electric machine.

[0106] Figure 12 illustrates another timing diagram, showing the operating states of the high-side and low-side switches of two half-bridges in a phase group. This representation is similar to that of Figure 11, so the details explained there will not be repeated.

[0107] In contrast to Figure 11, Figure 12 illustrates a switching pattern that is not based on the active freewheeling shown in Figure 9, but rather on the passive freewheeling similar to Figure 10. Thus, unlike in Figure 11, only one switch in each PWM-active half-bridge or phase is ever in the PWM-active operating state. Consequently, only one of the four switches is PWM-active at any given time. This allows for even greater reductions in switching losses. Accordingly, unlike in Figure 11, the switches of the half-bridges do not change their operating state from one time period to the next, but can maintain the same switching state within two time periods. This makes it possible to set a longer period during which the switching state of a switch does not change at all. This allows for the response to and compensation of short-term overloads.This switching pattern, like that of Figure 11, also leads, on average over time, to a symmetrical utilization of all switches with a short time period T. p .

[0108] Figure 13 illustrates another timing diagram, showing the operating states of the high-side and low-side switches of two half-bridges in a phase group. This representation is similar to that of Figures 11 and 12, so the details explained there are not repeated.

[0109] As shown in Figure 13, one half-bridge can be operated continuously with PWM active across all four time periods. Meanwhile, either the high-side or low-side switch of the other half-bridge can be operated in a continuously on or off state. This allows for a further reduction in losses, as the continuously PWM-inactive half-bridge can be optimized for low conduction losses and the PWM-active Hall bridge for low switching losses. This advantage can be achieved, for example, by using suitable substrate technologies and / or substrate materials such as GaN and Si. Additionally or alternatively, only the high-side switches of the PWM-inactive half-bridge can have galvanically isolated power supplies. This embodiment can therefore also result in further cost savings in the manufacture of the device.

[0110] Figure 14 illustrates a stator of an electric machine, which can be part of an electric drive. The stator is shown in two views. On the left is a top view, and on the right is a perspective view. In the top view, the stator can be seen as a circle with a multitude of evenly spaced slots oriented radially inward. Each slot is designed to receive a conductor in the form of a rod, which is part of the stator windings. The perspective view shows the stator in a three-dimensional representation, with the slots and the conductors contained therein visible in perspective. The connection of the individual conductors to form a winding and the winding heads required for this are not shown. The winding heads, not shown, contain the star points of each two-phase group 10, 20.

[0111] The stator slots are configured to accommodate a maximum of one conductor per slot, enabling high phase current carrying capacity and thus improved performance, especially at low phase voltages. This also simplifies the winding design and reduces manufacturing costs. This configuration can help minimize the ohmic losses of the stator conductors and improve the thermal performance of the electric machine. The slot and conductor arrangement is symmetrical, ensuring a uniform distribution of magnetic flux and optimized electromagnetic performance. However, an asymmetrical arrangement is also possible.

[0112] The conductors in the slots are arranged to carry electric currents that generate a magnetic field which interacts with a rotor of the electric machine to produce torque. The specific arrangement and dimensioning of the slots and conductors can contribute to generating the desired magnetic properties and to the efficiency of the electric drive. The stator in Figure 14 can be used in conjunction with a converter. The converter is configured to supply the stator conductors with electric currents that are modulated over a variety of time periods by different operating states of the individual half-bridge switches to generate a fundamental waveform that provides the required torque in the electric machine, as described previously.

[0113] Figure 14 shows an exemplary stator designed for use in an electric drive with a specially configured inverter. The depicted arrangement and construction of the stator are aimed at achieving high performance and efficiency in conjunction with the described inverter. The details of the stator winding, the number of slots, and the precise arrangement of the bars within the slots can be selected depending on the purpose and requirements of the electric drive. However, the stator winding always forms phase groups of two phases each and has at least two such groups.

[0114] Figure 15 illustrates a diagram representing two pulse-width modulation (PWM) carrier signals that can be used to control an electric drive. The two PWM carrier signals are shown in a temporal relationship to each other, characterized by the time intervals TPWM and Tint.

[0115] The first carrier signal is represented as a sequence of triangular waves that repeat periodically along the horizontal axis, which represents time. The second carrier signal is also represented as a sequence of triangular waves and is shifted in time relative to the first carrier signal, PWM-Carrier 1, by an interval named Tint.

[0116] The TPWM time intervals represent the period of the PWM carrier signals, which can define the modulation frequency. Each period can be referred to as a PWM clock cycle. The modulation of the carrier signals is typically used to generate the gate drive signals for the switches in power electronics, such as the half-bridges of a converter. The switches could be transistors based on various substrate technologies or materials, such as gallium nitride (GaN) or silicon (Si). The PWM carrier signals in Figure 15 can be used by a converter to control the high-side and low-side switches over a variety of time periods such that the pulse-width modulation clock of at least one phase group is shifted by one phase relative to the pulse-width modulation clock of at least another phase group, for example, to improve the electromagnetic compatibility (EMC) of the system.This shift leads to a phase shift between the two carrier signals, which can be used in the control of electric drives, for example to reduce electromagnetic interference or to optimize power efficiency.

[0117] Using at least two PWM carrier signals to control at least two phase groups that are time-shifted can also make the operation of a DC link capacitor shared by at least two phase groups particularly efficient. This also reduces costs, since only one DC link capacitor is needed for multiple phase groups, and this capacitor can be smaller than would be the case if only one PWM carrier signal were used for the at least two phase groups.

[0118] REFERENCE MARK LIST

[0119] Phases U 1? V 15 U2, V2

[0120] Electric machine 3

[0121] Controller 4

[0122] Power connection terminal 1 5

[0123] Power connection terminal 2 6

[0124] Intermediate circuit capacitor 7

[0125] Phase group 1 10

[0126] Half-bridge 1 11

[0127] Half-bridge 2 12

[0128] High-Side Switch 1 13

[0129] Low-Side Switch 1 14

[0130] Phase group 2 20

[0131] Half bridge 3 21

[0132] Half bridge 4 22

[0133] High-side switch 2 23 Low-side switch 2 24

[0134] Time t

[0135] Period 1 Tzi

[0136] Period 2 Tz2

[0137] Period 3 Tz3

[0138] Period 4 Tz4

[0139] period n Tz n

[0140] Interval time tint

[0141] PWM period TPWM

[0142] Time period TP

[0143] Maximum voltage UM

Claims

Claims 1 to 15 1. Electric drive, including: -at least one electric machine (3); and -at least one inverter, which includes at least one inverter: -a plurality of half-bridges (11, 12, 21, 22), wherein each of the plurality of half-bridges (11, 12, 21, 22) comprises a plurality of switches (13, 14, 23, 24), wherein each half-bridge (11, 12, 21, 22) comprises at least one high-side switch (13, 23) and at least one low-side switch (14, 24); -a plurality of phase groups (10, 20) with two phases per phase group, wherein both phases of each individual phase group (10, 20) are connected to a star point on a first side and are coupled on a second side to one of the plurality of half-bridges (11, 12, 21, 22) of the converter, so that each phase group (10, 20) has its own star point;- wherein the inverter is configured such that, for at least one period of a plurality of time periods, at least one of the high-side or low-side switches (13, 23, 14, 24) of the two half-bridges (11, 12, 21, 22) of at least one phase group is operated in a continuously on or off operating state, while the remaining high-side and low-side switches (13, 23, 14, 24) of the two half-bridges of the at least one phase group are continuously operated in a pulse-width modulated operating state in order to generate a fundamental wave over the plurality of time periods by means of which a torque is provided in the at least one electric machine (3).

2. Electric drive according to claim 1, wherein the converter is further configured such that the at least one high-side or low-side switch of the two half-bridges of at least one phase group, which is operated in the continuously on or off operating state during the at least one period, alternates this operating state over the plurality of periods with at least one of the other high-side or low-side switches of the two half-bridges of the at least one phase group.

3. Electric drive according to one of the preceding claims, wherein the inverter is further configured to determine the operating state of at least one of the high-side or low-side switch of at least one phase group alternates over the plurality of time periods based on the electrical angle of the electrical machine (3).

4. Electric drive according to one of the preceding claims, wherein the converter is further configured such that, over the multitude of time periods, each of the high-side and low-side switches of the two half-bridges of at least one phase group is operated in the pulse-width modulated and the continuously on and off operating state for such a long time that the operating time in these three operating states for each of the high-side and low-side switches of the two half-bridges of at least one phase group becomes equal to each other on average over time.

5. Electric drive according to one of the preceding claims, wherein the plurality of time periods form a period which is repeated cyclically and which has at least the length of a period of the fundamental frequency of the electric machine (3).

6. Electric drive according to one of the preceding claims, wherein the converter is further configured such that in at least one period of the plurality of periods in one of the two half-bridges of the at least one phase group the at least one high-side and the at least one low-side switch are in a pulse-width modulated operating state; and that in this at least one period the at least one high-side and the at least one low-side switch of the other of the two half-bridges of the at least one phase group is each either in a continuously switched-on or switched-off operating state.

7. Electric drive according to one of claims 1 to 3 or 5 to 6, wherein the converter is further configured such that all high-side and low-side switches of the two half-bridges of at least one phase group are controlled over the plurality of time periods such that the high-side and low-side switches in one of the two half-bridges of the at least one phase group are in the pulse-width modulated operating state and that the high-side and low-side switches in the other of the two half-bridges of the at least one phase group are in the continuously either on or off operating state.

8. Electric drive according to one of claims 1 to 5, wherein the inverter is further configured such that in at least one period of the plurality of periods in one of the two half-bridges of the at least one phase group either the at least one high-side or the at least one low-side switch is in the pulse-width modulated operating state and the other of these at least one high-side or low-side switch is in a continuously off operating state; and that in this at least one period either the at least one high-side or the at least one low-side switch of the other of the two half-bridges is in a continuously on operating state and the other of these at least one high-side or low-side switch is in a continuously off operating state.

9. Electric drive according to one of the preceding claims, wherein the inverter is further configured such that only the high-side switches which are in a continuously switched-on operating state for at least one period of the plurality of periods are connected to a galvanically isolated power supply circuit.

10. Electric drive according to claim 7, wherein the half-bridge of the at least one phase group in which all high-side and low-side switches are in the pulse-width modulated operating state is configured such that it has lower switching losses than the other of the two half-bridges of the at least one phase group; and the other half-bridge of the same phase group in which all high-side or low-side switches are either in the continuously on or off operating state is configured such that it has lower conduction losses than the half-bridge of the at least one phase group in which all high-side and low-side switches are in the pulse-width modulated operating state.

11. Electric drive according to one of the preceding claims, wherein the switches of at least two half-bridge transistors are and wherein the substrate technology and / or the substrate materials of these transistors differ.

12. Electric drive according to one of the preceding claims, wherein the switches of at least two half-bridges are transistors and wherein at least the transistors of one of the at least two half-bridges must have a gallium nitride substrate, GaN, or a silicon substrate, Si.

13. Electric drive according to one of the preceding claims, wherein a stator of the electric machine (3) has a maximum of one conductor per slot.

14. Electric drive according to one of the preceding claims, wherein the converter is further configured such that the pulse width modulation clock of at least one phase group is shifted in time by one phase relative to the pulse width modulation clock of at least one further phase group.

15. Electric drive according to one of the preceding claims, wherein the converter is further configured such that at least two phase groups (10, 20) share a DC link capacitor (7).

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