Electric machine
阅读说明:本技术 电机 (Electric machine ) 是由 J.库尔菲斯 U.福尔默 于 2018-06-07 设计创作,主要内容包括:本发明涉及一种电机。所述电机具有至少两个分别拥有相同的相数的子电机,所述子电机分别构造用于彼此独立地产生用于使转子旋转运动的旋转磁场。所述电机优选对每个子电机来说具有功率输出级,其中所述功率输出级分别构造用于彼此独立地给所述子电机通电。所述电机也具有至少一个控制单元或者仅仅具有一个控制单元,所述控制单元与所述功率输出级相连接并且构造用于产生用于对所述功率输出级进行操控的PWM信号。按照本发明,所述控制单元构造用于:如此产生用于所述子电机的PWM信号,使得用于一个子电机的PWM脉冲分别在PWM周期的开始时刻开始;并且/或者如此产生用于另一个子电机的PWM脉冲,使得所述PWM脉冲分别在用于所述另一个子电机的PWM周期的结束时刻结束。(The present invention relates to an electric machine. The electric machine has at least two partial electric machines each having the same number of phases, which are each designed to generate a rotating magnetic field for rotating the rotor independently of one another. The electric machine preferably has a power output stage for each partial electric machine, wherein the power output stages are each designed to energize the partial electric machines independently of one another. The electric machine also has at least one control unit or only one control unit, which is connected to the power output stage and is designed to generate a PWM signal for actuating the power output stage. According to the invention, the control unit is designed to: generating PWM signals for the sub-motors such that PWM pulses for one sub-motor start at a start time of a PWM cycle, respectively; and/or the PWM pulse for the further partial motor is generated in such a way that it ends at the end of the PWM cycle for the further partial motor.)
1. An electric machine (1) having a stator (2) and a rotor (11), wherein the electric machine has at least two partial machines (3, 4) each having the same number of phases, wherein the partial machines each comprise a part of a stator coil (5, 6, 7, 8, 9, 10) of the stator (2) and are designed to generate a rotating magnetic field for rotationally moving the rotor independently of one another,
it is characterized in that the preparation method is characterized in that,
the electric machine (1) has a power output stage (13, 14) for each sub-electric machine (3, 4), and the electric machine (1) has at least one control unit (17) which is connected to the power output stage (13, 14) and which is designed to generate a PWM signal (53, 54) for controlling the power output stage (13, 14), and the control unit (17) is designed to generate the PWM signal (53, 54) for the sub-electric machine (3, 4) in such a way that a PWM pulse (61) for a sub-electric machine (3) starts at a starting time (63) of a PWM cycle (64).
2. The electric machine (1) according to claim 1,
it is characterized in that the preparation method is characterized in that,
the control unit (17) is designed to generate PWM pulses (65) for the other sub-motor (4) such that the PWM pulses (65) each end at an end time (67) of a PWM cycle (66) for the other sub-motor (4).
3. The electric machine (1) according to claim 1 or 2,
it is characterized in that the preparation method is characterized in that,
the control unit (17) is designed to generate PWM cycles (64, 66) of mutually different partial motors, phase-offset with respect to one another.
4. The electric machine (1) according to any of the preceding claims,
it is characterized in that the preparation method is characterized in that,
the electric machine (1) has at least one current sensor (15, 16) connected to the control unit (17) and designed to detect the phase currents of at least one or all phases of the partial electric machines (3, 4), wherein the control unit (17) is designed to detect the phase currents of at least one phase of the partial electric machines (3, 4) during a common pulse interval (36) of the PWM cycles of the partial electric machines (3, 4).
5. The electric machine (1) according to any of the preceding claims,
it is characterized in that the preparation method is characterized in that,
the control unit (17) is designed to lengthen or shorten the duty cycles for all phases of the partial motor by a predetermined time interval.
6. The machine (1) according to claim 5,
the control unit (17) is designed to lengthen or shorten the pulse duration (65, 65') of the high-side pulse and the low-side pulse alternately with one another.
7. The electric machine (1) according to any of the preceding claims,
it is characterized in that the preparation method is characterized in that,
the control unit (17) is designed to generate a current detection interval (40), to detect a current during the current detection interval (40), and to generate the current detection interval (40) during the duration of a common pulse interval of the partial motors.
8. Method for controlling an electric machine (1) having at least two partial electric machines (3, 4), wherein the partial electric machines each have the same number of stator coils (5, 6, 7, 8, 9, 10), wherein for controlling the stator coils (5, 6, 7, 8, 9, 10) a pulse pattern (33, 34) of pulse width modulation is generated which comprises a plurality of PWM pulses (61), wherein the PWM pulses (61, 65) for one partial electric machine (3, 4) each start at a starting point (63) of a PWM cycle (64) and the PWM pulses (65) for the other partial electric machine (4) each end at an ending point (67) of the PWM cycle (66) for the other partial electric machine.
9. The method of claim 8, wherein the first and second light sources are selected from the group consisting of,
wherein the current flowing through at least one of the stator coils (5, 6, 7, 8, 9, 10) is detected within a current detection interval (40) during a common pulse interval for the pulses of the sub-motor.
10. The method according to any one of the preceding claims, wherein the PWM periods (65, 66) of the sub-motor (3) and the further sub-motor (4), respectively, are phase-shifted with respect to each other.
Technical Field
The invention relates to an electric machine, in particular an electric motor and/or generator. The motor has a stator and a rotor. The motor has at least two partial motors each having the same number of phases. The partial motors preferably each have a part of the stator coils of the stator and are each designed to generate a rotating magnetic field for the rotary movement of the rotor independently of one another. The electric machine preferably has a power output stage for each partial electric machine, wherein the power output stages are each designed to energize the partial electric machines independently of one another. The electric machine also has at least one or only one control unit, which is connected to the power output stage and is designed to generate a PWM signal (PWM = pulse width modulation) for controlling the power output stage. The partial motors preferably have at least one, at least two, at least three or only one stator coil for each phase.
Background
DE 102005043576 a1 discloses a method for operating an electric machine having at least two electrically separate stator windings, wherein a first stator winding is fed via a first sub-converter and a second stator winding is fed via a second sub-converter. The subconverters are controlled by means of signals which are excited by staggered ground pulses.
Disclosure of Invention
According to the invention, the control unit is configured to: generating the PWM signals for the sub-motors such that the PWM pulses for one sub-motor start at the start of the PWM period, respectively; and/or the PWM pulse for the other partial motor is generated in such a way that the PWM pulse ends at the end of the PWM cycle for the other partial motor in each case. With a control unit of this type, the PWM pulses for one of the partial motors can each be generated, in particular, at the left level, beginning together with the start of the PWM period, whereas the PWM pulses for the other partial motor can each be generated, in particular, at the right level, ending together with the end of the PWM period.
In this way, a time interval without switching pulses is advantageously formed, in which the phase currents on the stator coils switched from the power output stage to the partial motor are not switched on or off. That is, it has been recognized that switching stator coil currents on or off can cause EMC interference, which can affect or make impossible current sensing of the stator coil currents.
In a further variant, the control unit is designed to generate the PWM signals for the partial motors in such a way that the PWM pulses for one partial motor each start or end at the start of the PWM cycle and the PWM pulses for the other partial motor are generated in a centered manner. In this case, a time window for current detection can advantageously be generated for the modulation range without switching pulses.
In a further preferred variant, the control unit is designed to generate the PWM signals for the partial motors in such a way that the PWM pulses for at least two or all partial motors respectively start or end at the start of the PWM period. The time intervals for the current detection over a large modulation range of the electric machine can thus advantageously be formed by the PWM control of the power output stage thus formed.
In a preferred embodiment, the control unit has a pulse width modulator which is designed to vary the duty cycle for at least one or more PWM periods and thus to vary the modulation of the electric machine, in particular of the partial electric machine. The PWM modulator is preferably configured to: the pulse width modulated pulses for the partial motors are generated jointly beginning, in particular flush to the left, or jointly ending, in particular aligned to the right, with respect to the PWM periods.
The control unit preferably has a processing unit which is formed by a microprocessor, microcontroller or FPGA (FPGA = Field-programmable-Gate Array). The control unit preferably has at least one driver for the power output stage, which is connected on the output side to a control terminal of the power output stage and is designed to generate a control signal for switching on or off a semiconductor switch of the power output stage as a function of the PWM signal and to transmit it to the power output stage.
In a preferred embodiment, the electric machine has at least one current sensor connected to the control unit, wherein the current sensor is designed to detect the phase currents of at least one or all phases of the partial electric machine. The control unit is designed to detect a phase current of at least one phase of the partial motor during a common pulse interval of the PWM periods of the partial motor. Compared to a centered actuation of the partial electric motors, it is advantageous if the aforementioned left-hand flush actuation of the partial electric motors and the right-hand flush actuation of a different one of the partial electric motors are performed with a time window, in particular a time interval during a PWM cycle, which is formed within a relatively large modulation range, during which no switching operation of the power output stage by a PWM pulse, in particular by the start or end of a PWM pulse, takes place.
In a preferred embodiment, the control unit is designed to generate PWM periods for the different partial motors relative to one another with a phase offset. The phase offset, also referred to as the phase difference, between the actuation of the partial motor and the actuation of the further partial motor is preferably between 30% and 70% of the PWM cycle duration, more preferably between 34% and 66% of the PWM cycle duration, and particularly preferably 50% of the PWM cycle duration.
With a control unit thus configured, the load of an intermediate circuit, in particular commonly used by the submotors, is reduced for at least a part of the modulation range of the submotors, wherein the intermediate circuit comprises an intermediate circuit capacitor. By actuating the partial electric machines in a time-staggered manner, voltage fluctuations in the vehicle electrical system due to ripple currents in the intermediate circuit can be advantageously reduced. Furthermore, it is advantageous to form the time window for the current measurement without switching pulses over a wide modulation range by means of phase shifting, in particular in conjunction with the actuation of the left and right level motors which differ from one another. The current measurement for the phase current can thus be electromagnetically free from interference by the switching pulses for switching the semiconductor switches of the power output stage. Since the current measurement is carried out in the time intervals, which are also referred to as time windows, in which no switching process is carried out at the power output stage, the current measurement resistor can advantageously be designed particularly small and therefore with particularly low losses. The measuring voltage, which represents the detected current and drops at the current measuring resistor, can therefore be made very small and can be amplified, for example by means of a measuring amplifier, for evaluation by the control unit and can thus be enlarged.
In a preferred embodiment, the control unit is designed to lengthen or shorten the duty cycles for all phases of the partial motor by a predetermined time interval. In this way, a voltage offset can be added or subtracted to the actuation of the submotors, which voltage offset has no influence on the actuation of the submotors electrically. However, the voltage offset advantageously causes the following results, namely: the time window for the current detection without switching pulses is also made correspondingly large for large modulation values.
In a preferred embodiment, the control unit is designed to lengthen or shorten the pulse duration of the high-side pulse and the low-side pulse alternately with one another. In this way, the thermal load of the power output stage can be reduced when voltage offsets occur.
The power output stage preferably comprises at least one semiconductor switch-half bridge for each phase. The semiconductor switch-half bridge comprises a low-side semiconductor switch and a high-side semiconductor switch connected in series with each other. The high-side and low-side semiconductor switches of the power output stage, in particular of the semiconductor switch half-bridge of the power output stage, can thus advantageously be subjected alternately to a thermal load.
In a preferred embodiment, the control unit is designed to generate a current detection interval and to detect the current during the current detection interval. The control unit is furthermore preferably designed to generate a current detection interval during the duration of the common pulse interval for the actuation of the partial motors.
The invention also relates to a controller for an electric machine. The control unit comprises the already described control unit, which is connected on the output side to the power output stage. The power output stage is designed for connection to a partial motor which is formed by a part of the stator coils of the stator and for this purpose has output connections for connection to the stator.
The invention also relates to a method for controlling an electric machine. The motor has at least two sub-motors. The sub-motors each have the same number of stator coils of the stator of the motor. In the method, for actuating the stator coils, a pulse-width-modulated pulse pattern is generated which comprises a plurality of PWM pulses, wherein the PWM pulses for one of the partial motors each start at a starting time of a PWM period and the PWM pulses for the other partial motor each end at an end time of a PWM period for the other partial motor.
The time window for detecting the current without switching pulses can thus advantageously be made large for the electric machine.
Preferably, in the method, the current flowing through at least one of the stator coils is detected within a current detection interval during a common pulse interval for the pulses of the submotors. The current measurement window formed by the time intervals formed without the switching process of the power output stage can advantageously be larger than the current measurement window during the centered PWM control.
Preferably, in the method, the PWM periods of the sub-motor and the further sub-motor are phase-shifted with respect to each other, respectively. The phase offset is preferably between 37% and 66% of the period duration, more preferably half of the PWM period duration. Thus, the intermediate circuit off-load can advantageously be formed preferably in conjunction with the left-flush or right-flush PWM generation described above.
Preferably, the PWM periods of all the partial motors each have the same period duration. The actuation of the partial motors can thereby be carried out in time synchronism with one another.
Drawings
The invention will now be described below with the aid of figures and other embodiments. Further advantageous embodiments result from the features described in the figures and in the dependent claims.
Fig. 1 shows an exemplary embodiment for an electric machine having an inverter, wherein the inverter has a control unit which is designed to generate PWM pulses for a partial electric machine in such a way that the semiconductor switches of the inverter can be switched on in common at a common starting time or switched off at a common end time;
fig. 2 shows a diagram with PWM patterns that have been generated by the control unit shown in fig. 1.
Detailed Description
Fig. 1 schematically shows an embodiment for an electric machine 1. The electric machine 1 has a
The motor 1 also has a control unit 17. The control unit 17 is connected on the output side via a connecting line 27 to the
The control unit 17 is in this exemplary embodiment designed to actuate the
The control unit 17 has a
The
The control unit 17 is designed to detect the current signals generated by the
The control unit 17 is designed to jointly start a PWM pulse for the
The control unit 17 is configured in such an embodiment for: the modulation degree as a function of the PWM control changes, in particular lengthens or shortens, the control pulse duration of the control pulses for the submotors at least for the duration of the current detection or for at least one or more cycle times, and in this way the voltage offset is generated by means of the PWM pattern for the submotors. The time interval for measuring the current in the modulation range can thereby be additionally enlarged.
The control unit 17, for this purpose the
Fig. 2 shows a diagram in which the PWM control signals generated by the
The PWM signals each comprise PWM pulses that follow one another in time,
The
Furthermore, the
For the modulation degree of the
The diagram 50 also shows a
The phase offset 68 advantageously relieves the load on the
Fig. 3 shows a graph 80. The diagram 80 has an abscissa 81 which represents the degree of modulation of the electric machine 1 shown in fig. 1. The ordinate 82 of the diagram 80 represents the average ripple current in the intermediate circuit, which in turn represents the current fluctuations in the intermediate circuit. Curve 83 represents the ripple current as a function of the degree of modulation of an electric machine having two sub-machines, which are each operated centrally and without phase offset. Curve 84 represents the ripple current as a function of the degree of modulation of an electric machine having two sub-machines, wherein-as shown in fig. 2-one sub-machine is operated flush to the left and the other sub-machine is operated flush to the right, and wherein the PWM signals of the sub-machines have a phase offset with respect to one another of 50% of the PWM cycle duration. It can be seen that the ripple current in the intermediate circuit can be halved as a result of the switching processes of the partial motors that are separated from one another by the actuation according to curve 84, compared to the centered actuation according to curve 83, which is carried out without phase offset.