DE202016008166U1 - Device for current-controlled start-up of permanently excited electric motors - Google Patents

Abstract

A device for modulated voltage driving of a brushless motor with a voltage amplitude by means of a device for measuring the phase currents (i1, i2) of the brushless motor having a mean common motor current amplitude (isum, IA), characterized a. in that the device comprises means for estimating or calculating the magnitude (Iamp) of the average motor current amplitude (isum, IA) as the magnitude (Iamp) of the sum (| Iamp | = 3 | i1 | + 3 | i2 |) of at least two, the respective amounts (| i1 |, | i2 |) of the measured phase currents (i1, i2) respectively have proportional quantities (3 | i1 |, 3 | i2 |) and b. in that there is a device for controlling the average motor current amplitude (isum, IA) in the device, which, upon activation of the control, is based on the mean motor current amplitude (isum, IA) by the means for measuring the phase currents (i1, i2) and the amount (Iamp) the average motor current amplitude (isum, IA) and a current control loop (S, SG, PWM, LT, M, LT, SM, AM, AR), the voltage amplitude of the modulated voltage drive of the motor (M) so controls that the average motor current amplitude (isum, IA) reaches a predefinable target value (actual type).

Description

introduction

The current-controlled start-up of brushless permanent-magnet electric motors, hereinafter referred to as BLDC motors, poses the problem that at very low speeds the induction into the stator coils is very small. If the rotor position is to be determined, the voltages induced in the stator coils, referred to below as back-EMF or BEMF, are very small. Accordingly, the inevitable system noise of the engine control system leads to measurement and thus control errors.

• • der Versorgungsspannung,
• • der Drehzahl,
• • der Temperatur,
• • dem Innenwiderstand des Motors

When starting / starting PMSM and BLDC motors, a voltage is impressed into the motor. This causes a current flow in the motor. The amount of current flow depends on:

• The supply voltage,
• The speed,
• The temperature,
• • the internal resistance of the motor

These dependencies can lead to large fluctuations / scatters during the start. The actual goal of the starting process is to generate a torque that provides the rotor with an angular acceleration. To achieve this, a defined current amplitude would be desirable. The prior art often implements a finite polynomial that models the desired current command as a function of the supply voltage. Due to manufacturing variations in the production of the motors, it is necessary to determine the polynomial coefficients for each motor as part of the system production at the end of the tape, ie at the end of production, and store it in the system. The disadvantages of the polynomial approximation are obvious: First, the polynomial coefficients must be elaborately determined and calculated in the production and / or in the laboratory. On the other hand, the temperature dependence is not compensated by such a one-dimensional, namely by the supply voltage, dependent modeling. The consideration of the temperature as a further parameter in the form of a two-dimensional polynomial would lead to massively increased expenses in the calibration, which are only useful in exceptional cases. If this consideration of temperature does not occur, which is typically the case, then the current increases by a factor of up to two. The polynomial coefficients are therefore engine-specific and thus cause additional calibration costs in production.

Since a minimum torque is required to accelerate the motor during start / start, the lower limit of the starting current is always set to a required minimum value. In real operation, therefore, the current during startup is usually too high. This leads u. a. also to unwanted, z. T. high noise levels, especially in applications that target consumer markets are not desirable.

1 shows a section of a typical drive system for PMSM or BLDC motors from the prior art.

An amplitude / duty cycle is specified in the form of an amplitude / duty cycle signal (ATS) from outside the controller. From this and the correction signal (KS) explained in more detail below, the voltage form generation (SG) generates the voltage shaping signal (SF). The correction signal (KS) contains the frequency or angle information that comes as a result of a rotor position control (RLR). This voltage generation (SG) generates the time-dependent information about the output voltages to be generated on the connection lines (U, V, W) of the motor (M). This can z. B. in PMSM motors sinusoidal course (see 2 ) or block commutation with BLDC motors (see also 3 ) be. The output of the voltage waveform generator (SG) is passed to a PWM generator (PWM), which converts the information of the three mean phase reference voltages into usually PWM modulated signals, the control signals (STS) for the power unit (LT). The PWM generation (PWM) thus generates from the voltage shaping signal (SF) the control signals (STS) for the power unit (LT) which, by means of its drivers, typically several half-bridges, connect the motor (M) via typically three or two motor connection lines (U, V, W). The amplitude of the output voltages in PMSM motors and the duty cycle in block commutation in BLDC motors is given by the already mentioned amplitude / duty cycle signal (ATS) as an input signal of voltage waveform generation (SG). The power unit (LT) supplies a current measurement signal (SMW) from which a current measuring device (SM) generates synchronized current measurement signals (SSMW). In this case, a synchronizing device (SY) generates from signals of the PWM generation (PWM) the necessary synchronizing signals for the current measuring device (SM) and the rotor position detection (RD) which will be described below. This rotor position detection (RD), which either has separate position sensors or determines the rotor position from electrical variables which are measured back on the power unit (LT), determines the instantaneous rotor position in the form of a rotor position signal (α). The rotor position detection (RD) thus generates from rotor position signals (RLS) from the power unit (LT) and the synchronized current measurement signals (SSMW), the rotor position signal (α), which typically one Rotor position angle symbolizes, so is virtually a rotor position angle signal. This rotor position signal (α) is again the input variable for the rotor position control (RLR). The rotor position control (RLR). derives from the desired rotor position and the information about the actual rotor position in the form of the rotor position signal (α) from a frequency or angle signal in the form of said correction signal (KS) for the voltage waveform generation (SG). A rotor position control (RLR) thus generates from the rotor position signal (α) the said correction signal (KS).

Typically, such a system has the aforementioned current measuring device (SM) for measuring the instantaneous motor current in the motor phases. This is partly used as information for the rotor position detection (RD). At the same time, it is also partly used as information in higher-level sections of the system. Since the signals in the power section (LT) are PWM modulated signals, the synchronizing device (SY) is required to measure the motor current.

For the current measurement itself, two principles have prevailed in the prior art:
4 shows an exemplary summation current measurement from the prior art. The power unit (LT) consists of three exemplary half-bridges with two transistors each, so a total of six transistors (T1 to T6). A measuring resistor (R _sh ) enables the measurement of the total current of the power unit (LT). This total current and its information about the state of the motor (M) changes in time. Thus, depending on the state of the 6 transistors (T1 to T6), a specific phase current of the motor (M) can be measured. Instead of the measuring resistor (R _sh ), other components such as LEM sensors, Hall sensors or magnetoresistive current sensors, etc. may be used.

5 shows a variant for measuring 2 phase _currents with a first measuring resistor (R _sh1 ) and a second measuring resistor (R _sh2 ).

If sensors are used instead of the measuring resistors (R _sh , R _sh1 , R _sh2 ), the phase currents can also be measured directly in the motor phases and the current measurement is simplified considerably.

However, during engine startup there is often no position information that can be used for the rotor position control because the currents are either zero or too small for a low-error measurement. Therefore, at the start by means of the voltage waveform generation (SG), a forced field is generated independently of the value of the correction signal (KS) and impressed on the motor (M). As a result, in the starting phase in the prior art, he can not reach a low-current operating point. The motor current depends on how motor speed, voltage amplitude, motor internal resistance (M) and other parameters match. This typically leads to very high starting currents associated with said strong noise.

Examples of such methods and devices are known for example from DE 10 2009 037 913 A1 , of the DE 11 2008 002 464 T5 , of the DE 10 2009 000 927 A1 , of the DE 10 2008 018 0075 A1 and the DE 100 37 972 A1 known.

Object of the invention

It is the object of the invention to provide for a defined current amplitude during startup so as to avoid an increased current consumption and an undesirable noise development in contrast to the prior art. The current amplitude should be achieved regardless of the supply voltage, the speed, the temperature and the internal resistance of the motor. Furthermore, the current amplitude should be as easy as possible to parametrisierbar, so that the laboratory and / or manufacturing costs can be reduced in the parametrization and / or in production.

The computational effort for the determination of the current amplitude should be minimized compared to the mentioned prior art.

This object is achieved by a device according to claim 1 and a method according to claim 8.

Description of the invention

The description is first made on the basis of the figures.

The invention performs an extension over the prior art here. This extension is in 6 shown. An amplitude determination (AM) determines the current amplitude in the form of a current amplitude signal (I _A ) from the instantaneous values of the back-measured motor currents (SW) which are output by the current measurement (SM) as corresponding instantaneous value signals (SW) to the amplitude determination (AM). The amplitude control (AR) compares the determined amplitude, that is, the current amplitude signal (I _A ), with the desired value, which is shown in the image as a starting current (I _start ). The amplitude control (AR) generated from the deviation of the setpoint, so the starting current (I _start ), from the actual value, ie from the current amplitude signal (I _A ), the amplitude that serves as an input value for the generation of voltage during startup. This is the start amplitude signal (AS). During startup, this start amplitude signal (AS) for example, by a multiplexer and / or a switch (S) as an input signal (ES) of the voltage generation (SG) used.

After the start of the start, the input signal (ES) is switched by means of the switch (S) to the amplitude / duty cycle signal (ATS), which is typically output from a higher-level unit.

One way to determine the current amplitude for the current amplitude signal (I _A ) is a suitable vector addition. This is in 7 shown.

Both the summation current measurement and the two-phase measurement always provide the information about two instantaneous currents. These are in as the first phase current (i ₁ ) and second phase current (i ₂ ). So z. B. in the summation current measurement of the sum current (i _sum ) during the sequence of a PWM pattern typically in two successive steps, for example, only the second phase current (i ₂ ) and then the first phase current (i ₁ ) measured. The angle Φ between the second phase current (i ₂ ) and the first phase current (i ₁ ) is always ~ 120 °. The magnitude (i _amp ) of the sum current (i _sum = i ₂ -i ₁ ) is identical to the amplitude of the motor current. It can be determined by means of vector addition or cosine set and is:

Here, the phasor character of the quantities in this equation must be considered.

This sum (i _amp ) of the sum current (i _sum = i ₂ -i ₁ ) is calculated in the amplitude determination (AM) and compared in the amplitude control (AR) with the starting current (i _start ). It is the basis for determining the current amplitude signal (I _A ), which is preferably generated in proportion to this amount (i _amp ) of the sum current (i _sum = i ₂ -i ₁ ). In any case, however, the current amplitude signal (I _A ) preferably depends strictly monotonically on the magnitude (i _amp ) of the sum current (i _sum = i ₂ -i ₁ ).

As will be apparent to those skilled in the art, the calculation of the root requires a more sophisticated hardware implementation. A realization in analog circuit technology is at least difficult or possibly in a realization on analog logarithmic and exponentiation typically highly temperature-dependent and thus unsuitable for manufacturing. According to the invention, it has now been recognized that, in the start phase, substantial simplifications can be made in the case of tolerable errors contrary to expectation, which in particular make possible the realization in a very simple analog circuit technology. It was recognized that in a simplified embodiment, instead of the amplitude, the square of the amplitude can be calculated and parameterized as the starting value: i _amp ² = | i ₁ | ² + | i ₂ | ² - 2 | i ₁ || i ₂ | cos (Φ) = | i ₁ | ² + | i ₂ | ² + | i ₁ || i ₂ |

According to the invention, it was further recognized that, for example, an approximation which is already sufficient for many purposes can be achieved by a linearization of the total differential at the development point i _amp = 0 A: i _amp ≈ 3 | i ₁ | + 3 | i ₂ |

Such a calculation has the advantage that it can be implemented as a simple voltage or current divider in an analog controller. Such a sub-device can be understood as a device which makes an estimate of the mean motor current amplitude (I _sum , I _A ) and can be referred to as an "estimator". A device according to the invention is thus particularly distinguished from the prior art in that the device according to the invention comprises means for estimating or calculating the magnitude (I _amp ) of the average motor current amplitude (i _sum , I _A ) as the amount (I _amp ) of the sum (| I _amp | = 3 | i ₁ | + 3 | i ₂ |) of at least two quantities proportional to the respective amounts (| i ₁ |, | i ₂ |) of the measured phase currents (3 | i ₁ |, 3 | i ₂ |). According to the invention, the estimated motor current amplitude (I _amp ) thus determined is now used for the regulation, although this estimated motor current amplitude (I _amp ) has a definitely significant error. According to the invention, however, it has been recognized that in practice, this error is not pronounced in many applications and can therefore be permitted.

A device according to the invention thus has a device for regulating the average motor current amplitude (i _sum , I _A ) in the device, which is activated by means of the device for measuring the phase currents (i _sum , I _A ) when the control is activated on the basis of the average motor current amplitude ( i ₁ , i ₂ ) and for estimating the magnitude (I _amp ) of the average motor current amplitude (i _sum , I _A ) on the basis of the measured phase currents (i ₁ , i ₂ ) and of a current control loop (S, SG, PWM, LT, M , LT, SM, AM, AR) controls the voltage amplitude of the modulated voltage drive of the motor (M) such that the average motor current amplitude (i _sum , I _A ) reaches a predefinable target value (I _start ).

One possible procedure of starting the engine using the method presented here is in 8th shown.

The system is usually in the "off" state before engine start ( 1 ). In this state, the power unit (LT) is typically either turned off or the three motor phases (U, V, W) are shorted together by appropriate drive signals (STS).

By activating the start ( 2 ), the power unit (LT) by the PWM generation (PWM) is activated and also the current control via the amplitude determination (AM) and the amplitude control (AR) by setting the appropriate switch (S) is activated. This transition represents the state transition from the "Off" state ( 1 ) to the state "adjust current" ( 3 The thus initiated current control via this regulates the amplitude of the current amplitude signal (I _A ) at initially stopped motor to the externally predetermined starting current (I _start ). If this starting current (I _start ) is reached by the current amplitude signal (I _A ), the system carries out the state transition "target value reached" (FIG. 4 ) and changes from the "adjust current" state ( 3 ) in the state "align rotor" ( 5 ) above. In this state "align rotor" ( 5 ) the system remains active with current control via the existing current control loop (S, SG, PWM, LT, M, LT, SM, AM, AR) until a configurable fifth time (τ ₅ ) has expired or another condition has been reached. This fifth time (τ ₅ ) is typically chosen so that the connected motor (M), can align its rotor according to the applied field and its kinetic energy recorded in this alignment process, if necessary

should have degraded sufficiently or should already turn in a target direction. At the end of this fifth time (τ ₅ ), the system executes the state transition "alignment time expired" ( 6 ) and changes from the state "align rotor" ( 5 ) into the "speed ramp" state ( 7 ). In this state "speed ramp" ( 7 ), the motor (M) is supplied with electrical energy and accelerated. In this case, the voltages on the motor connection lines, for example, according to the signals after 2 or 3 modulated with fixed or increasing frequency. The current control over the existing control loop (S, SG, PWM, LT, M, LT, SM, AM, AR) is also active in this state, in contrast to the prior art. After a transient condition, typically represented by a number of revolutions and / or a total angle traveled and / or minimum rotational speed achieved during a start-up operation, the system executes the state transition "number of revolutions" (FIG. 8th ) and changes from the "Speed ramp" state ( 7 ) in the state "start completed" ( 9 ). Thus, the starting method according to the invention is completed. The current control is deactivated either by means of the switch (S) or, if necessary, is further used as an active current limit for the further running of the motor.

It should be noted that the expiration in represents only an exemplary use of the proposed method. Other processes are conceivable. The core of the method itself according to the invention consists in the suitable determination of current amplitudes and their regulation as stated above.

The invention thus relates to a device for modulated voltage driving of a brushless motor with a voltage amplitude by means of a device for measuring the phase currents having a mean common motor current amplitude. The device is characterized in that it comprises, for the first, means for estimating or calculating the average motor current amplitude from the measured phase currents. Secondly, in the device according to the invention there is a device for controlling the average motor current amplitude, which regulates the voltage amplitude when the control is activated by the means for measuring the phase currents so that the average motor current amplitude reaches a predefinable target value.

A further feature of the device according to the invention is additionally characterized in that, during the start during the initial acceleration of the rotor, the device controls the average motor current amplitude to a predetermined target value. In this case, the period of the initial acceleration of the rotor of the motor according to this invention is characterized in terms of time, that the motor was not energized by the device immediately before this period.

A third possible embodiment of the device according to the invention is additionally characterized in that, during the start during the initial acceleration of the rotor, the device regulates the mean motor current amplitude to a predetermined target value. The period of the initial acceleration of the rotor of the motor according to the invention in time is characterized in that the engine stopped immediately before this period or a speed less than a maximum standstill speed (<25% and / or <10% and / or <5 % and / or <2.5% and / or <1% and / or <0.5% of the maximum speed).

A fourth possible embodiment of the device according to the invention is additionally distinguished by the fact that during operation of the device there is a temporal section in which the device is in a state in which the rotor is set to an initial position by the device, and that at the same time This additionally inserted temporal section, the device Motor current amplitude also regulated to a predetermined value except for a control error.

A fifth possible embodiment of the device according to the invention is additionally characterized in that the additional temporal section in which the device is in a state in which the rotor is set up by the device to an initial position is inserted before the start of the rotor acceleration.

A fifth possible embodiment of the device according to the invention is additionally distinguished by the fact that the device inserts a time interval before the interval for aligning the rotor, in which the regulation for the motor current through the device can settle to the target value.

A fifth possible embodiment of the device according to the invention is additionally characterized in that the device before the interval for controlling the motor current and settling of the motor current to the target value inserted a time interval for braking the motor and at the same time in this additionally inserted temporal section, the motor current amplitude is also controlled by the device to a predetermined value up to a control error.

advantages

• 1. Der Startstrom hat den genau für den Start des Motors nötigen Wert. Die sonst übliche erhöhte Belastung oder gar Überlastung des elektrischen Systems während des Starts wird durch das Verfahren ausgeschlossen.
• 2. Der Motor erzeugt genau das für den Start nötige Drehmoment. Die sonst übliche erhöhte Geräuschbelastung während des Starts wird durch das Verfahren ausgeschlossen.
• 3. In der Parametrierung ist nun nur noch ein Wert, der Startstrom, einzustellen. Dies vereinfacht die Parametrierung der Applikation erheblich und macht das Verfahren zuverlässiger als andere Parametrierungen, bei denen aus einer Reihe abgeleiteter Größen praktisch eine Störgrößenaufschaltung einer Spannung durchgeführt wird
• 4. Da das Verfahren selbst in einer Regelung besteht, ist es deutlich robuster gegenüber Variationen von Motorparametern, die sich z. B. über Temperatur ändern. Das Verfahren führt somit stets zum korrekten Startstrom unabhängig von anderen Betriebsparametern.

The process has three major advantages over the prior art:

• 1. The starting current has the value necessary for the start of the engine. The usual increased load or overload of the electrical system during start is excluded by the method.
• 2. The engine generates exactly the torque required for the start. The usual increased noise pollution during start is excluded by the method.
• 3. Now only one value, the starting current, must be set in the parameterization. This considerably simplifies the parameterization of the application and makes the method more reliable than other parameterizations in which a voltage feedforward control is practically carried out from a series of derived variables
• 4. Since the method itself is in a closed loop, it is much more robust to variations in motor parameters, such as: B. change over temperature. The method thus always leads to the correct starting current independently of other operating parameters.

LIST OF REFERENCE NUMBERS

α

Rotor position signal

1

State "off"

2

State transition start

3

State "adjust power"

4

State transition "target value reached"

5

State "align rotor"

6

State transition "alignment time expired"

7

State "speed ramp"

8th

State transition "number of revolutions"

9

State "Start completed" ( 9 )

α

Rotor position signal

AT THE

amplitude determination

AR

amplitude control

AS

Start amplitude signal

AST

Amplitude / duty cycle signal

IT

Input signal of voltage generation (SG)

i ₁

first phase current

i ₂

second phase current

I _A

Current amplitude signal

i _amp

Amount of the total current (i _sum )

i _sum

total current

I _start

Starting current (external default value)

KS

correction signal

LT

power unit

M

engine

PWM

PWM generation

Φ

Angle between the first phase current (i1) and the second phase current (i2)

RD

Rotor position detection

RLR

Rotor position control

RLS

Rotor position signals

R _sh

measuring resistor

R _sh1

first measuring resistor

R _sh2

second measuring resistor

S

Switch, multiplexer or the like for switching the input signal of voltage generation (SG)

SdT

State of the art

SF

Voltage waveform signal

SG

Voltage waveform generation

SM

Current measuring device

SMW

Current measured value signal of the power unit (LT)

SSMW

synchronized current measurement signal of the current measuring device (SM)

STS

Control signal for the power unit (LT)

SW

Instantaneous values of the re-measured motor currents / instantaneous value signals

SY

synchronizing

t

Time

T1

first half-bridge transistor

T2

second half-bridge transistor

T3

third half-bridge transistor

T4

fourth half-bridge transistor

T5

fifth half-bridge transistor

T6

sixth half-bridge transistor

τ ₅

fifth time or alignment time (This is the time that the system aligns with rotor at startup ( 5 ) lingers.)

U

first motor connection cable

V

second motor connection cable

VDD

positive supply voltage

VSS

negative supply voltage

W

third motor connection cable

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009037913 A1 [0012]
• DE 112008002464 T5 [0012]
• DE 102009000927 A1 [0012]
• DE 1020080180075 A1 [0012]
• DE 10037972 A1 [0012]

Claims (8)

A device for modulated voltage driving of a brushless motor with a voltage amplitude by means of a device for measuring the phase currents (i ₁ , i ₂ ) of the brushless motor having a mean common motor current amplitude (i _sum , I _A ), characterized a. in that the device comprises means for estimating or calculating the magnitude (I _amp ) of the average motor current amplitude (i _sum , I _A ) as the magnitude (I _amp ) of the sum (| I _amp | = 3 | i ₁ | + 3 | i ₂ | ) of at least two magnitudes (3 | i ₁ |, 3 | i ₂ |) proportional to the respective amounts (| i ₁ |, | i ₂ |) of the measured phase currents (i ₁ , i ₂ ) and b. in that there is a device for regulating the average motor current amplitude (i _sum , I _A ) in the device, which, when the control is activated on the basis of the mean motor current amplitude (i _sum , I _A ), is determined by means for measuring the phase currents (i ₁ , i ₂ ) and the magnitude (I _amp ) of the average motor current amplitude (i _sum , I _A ) and of a current control circuit (S, SG, PWM, LT, M, LT, SM, AM, AR) the voltage amplitude of the modulated voltage drive of the motor ( M) so that the average motor current amplitude (i _sum , I _A ) reaches a predefinable target value (I _start ). Device for modulated voltage control of a brushless motor according to claim 1, characterized in that a. in that the device is arranged to carry out a voltage or current addition in order to estimate or calculate the magnitude (I _amp ) of the average motor current amplitude (i _sum , I _A ). Device for modulated voltage control of a brushless motor according to claim 1, characterized in that a. in that the device is designed to regulate the average motor current amplitude (i _sum , I _A ) to a predetermined target value (I _start ) during startup during the initial acceleration of the rotor, with an acceleration not equal to 0 m / s ² , by i. Specifying a starting current value (I _start ) and ii. Generating a start amplitude signal (AS) by comparing the predetermined starting current value (I _start ) with the value of a start amplitude signal (I _A and iii) generating a voltage shaping signal (SF) by means of a voltage shape generation (SG) from the start amplitude signal (AS) and a correction signal (KS ) and iv. generating the control signals (STS) for a power unit (LT) by means of PWM generation (PWM) depending on the voltage shaping signal (SF) and v. Generating the drive signals (U, V, W) for the brushless motor (M) by means of the power unit (LT) in response to the control signals (STS) for the power unit (LT) and vi. Driving the brushless motor (M) with these drive signals (U, V, W) and vii. Measuring at least two phase currents (i ₁ , i ₂ ) of the motor; viii. Generating at least one rotor position signal (RLS) and ix. Determining a momentary value (SW) of the phase currents (i ₁ , i ₂ ) which have been measured back from at least the measured current value signal (SMW) of the power unit (LT) in the form of an instantaneous value signal and x. Generating a current measurement signal (SMW) of the power unit (LT) in the form of the current amplitude signal (I _A ) by estimating or calculating the magnitude (I _amp ) of the motor current amplitude (i _sum , I _A ) by forming the sum (| I _amp | = 3 | i ₁ | + 3 | i ₂ |) of the multiplied by a constant factor amounts (| I _amp | = 3 | i ₁ | + 3 | i ₂ |) of the at least two measured phase currents (i ₁ , i ₂ ) to form a Current amplitude signal (I _A ), which depends on the estimated magnitude (I _amp ) of the motor current amplitude (i _sum , I _A ) and represents the current measurement signal (SMW) and xi. Determining the rotor position in the form of a rotor position signal (α) as a function of the measured current value signal (SMW) of the power unit (LT) and / or the rotor position signal (RLS) and xii. Generation of a correction signal (KS) as a function of the rotor position signal (α), b. wherein the beginning of the period of the initial acceleration of the rotor in terms of this claim is characterized in terms of time that the device is not energized the motor immediately before this period and c. the end of this period being characterized by the fact that the characteristic a of this claim no longer exists after it existed during the period. Device for modulated voltage control of a brushless motor according to claim 1, characterized in that a. in that the device is suitable for regulating the average motor current amplitude (i _sum , I _A ) to a predetermined target value (I _start ) during startup during the initial acceleration of the rotor, for acceleration not equal to 0 m / s ² , namely by i , Specifying a starting current value (I _start ) and ii. Generating a start amplitude signal (AS) by comparing the predetermined starting current value (I _start ) with the value of a start amplitude signal (I _A and iii) generating a voltage shaping signal (SF) by means of a voltage shape generation (SG) from the start amplitude signal (AS) and a correction signal (KS ) and iv) generating the control signals (STS) for a power unit (LT) by means of PWM generation (PWM) as a function of the voltage shaping signal (SF) and v. generating the drive signals (U, V, W) for the brushless motor ( M) by means of the power unit (LT) as a function of the control signals (STS) for the power unit (LT) and vi. Driving the brushless motor (M) with these control signals (U, V, W) and vii. Measuring at least two phase currents ( i ₁ , i ₂ ) of the motor, viii Generating at least one rotor position signal (RLS) and ix Determining a momentary value (SW) of the phase currents (i ₁ , i ₂ ) which have been measured back from at least the current measured value signal (S MW) of the power unit (LT) in the form of an instantaneous value signal and x. Generating a current measurement signal (SMW) of the power unit (LT) in the form of the current amplitude signal (I _A ) by estimating or calculating the magnitude (I _amp ) of the motor current amplitude (i _sum , I _A ) by forming the sum (| I _amp | = 3 | i ₁ | + 3 | i ₂ |) of the multiplied by a constant factor amounts (| I _amp | = 3 | i ₁ | + 3 | i ₂ |) of the at least two measured phase currents (i ₁ , i ₂ ) to form a Current amplitude signal (I _A ), which depends on the estimated magnitude (I _amp ) of the motor current amplitude (i _sum , I _A ) and represents the current measurement signal (SMW) and xi. Determining the rotor position in the form of a rotor position signal (α) as a function of the measured current value signal (SMW) of the power unit (LT) and / or the rotor position signal (RLS) and xii. Generation of a correction signal (KS) as a function of the rotor position signal (α), b. wherein the beginning of the period of initial acceleration of the rotor in terms of this claim is characterized by the fact that the engine is stationary immediately before this period or has a speed less than a maximum standstill speed (<5% of the maximum speed), c. the end of this period being characterized by the fact that the characteristic a of this claim no longer exists after it existed during the period. Device for modulated voltage control of a brushless motor according to claim 1, characterized in that a. in that the device is adapted to insert a time portion during engine start-up in which the device sets up the rotor to an initial position, and b. that the device is designed to simultaneously control the motor current amplitude to a predefinable value (I _start ) in this additionally inserted temporal section, namely by i. Specifying a starting current value (I _start ) and ii. Generating a start amplitude signal (AS) by comparing the predetermined starting current value (I _start ) with the value of a start amplitude signal (I _A and iii) generating a voltage shaping signal (SF) by means of a voltage shape generation (SG) from the start amplitude signal (AS) and a correction signal (KS ) and iv) generating the control signals (STS) for a power unit (LT) by means of PWM generation (PWM) as a function of the voltage shaping signal (SF) and v. generating the drive signals (U, V, W) for the brushless motor ( M) by means of the power unit (LT) in response to the control signals (STS) for the power unit (LT) and vi. Driving the brushless motor (M) with these control signals (U, V, W) and vii. Measuring at least two phase currents ( i ₁ , i ₂ ) of the motor, viii Generating at least one rotor position signal (RLS) and ix Determining a momentary value (SW) of the phase currents (i ₁ , i ₂ ) which have been measured back from at least the current measured value signal (S MW) of the power unit (LT) in the form of an instantaneous value signal and x. Generating a current measurement signal (SMW) of the power unit (LT) in the form of the current amplitude signal (I _A ) by estimating or calculating the magnitude (I _amp ) of the motor current amplitude (i _sum , I _A ) by forming the sum (| I _amp | = 3 | i ₁ | + 3 | i ₂ |) of the multiplied by a constant factor amounts (| I _amp | = 3 | i ₁ | + 3 | i ₂ |) of the at least two measured phase currents (i ₁ , i ₂ ) to form a Current amplitude signal (I _A ), which depends on the estimated magnitude (I _amp ) of the motor current amplitude (i _sum , I _A ) and represents the current measurement signal (SMW) and xi. Determining the rotor position in the form of a rotor position signal (α) as a function of the measured current value signal (SMW) of the power unit (LT) and / or the rotor position signal (RLS) and xii. Generation of a correction signal (KS) as a function of the rotor position signal (α), Device for modulated voltage control of a brushless motor according to claim 1, characterized in that a. in that the device inserts the additional time segment before the start of rotor acceleration. Device for modulated voltage control of a brushless motor according to claim 5 or 6, characterized in that a. in that before the rotor alignment interval the device inserts a time interval in which the motor current (i _sum , I _A ) controlled by the device reaches the target value (I _start ) except for a deviation less than 25% and / or less than 10% and / or less than 5% and / or less than 2% and / or less than 1%. Device for modulated voltage control of a brushless motor according to claim 7, characterized in that a. in that before the interval for controlling the motor current and for settling the motor current (i _sum , I _A ) to the target value (I _start ), the device inserts a time interval for decelerating the motor and b. that at the same time in this additionally inserted temporal section, the device also controls the motor current amplitude (i _sum , I _A ) to a predefinable value (I _start ) except for a control error.

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