DE102017211219A1 - Method and device for operating an electric machine, in particular a steering assistance drive - Google Patents

Abstract

The invention relates to a method for operating an engine system (1) with an electric machine (3), in particular a steering assistance drive, a power driver circuit (2) for providing phase voltages (U, V, W) and a safety device (5) for separating phase strand supply lines (4), which connect the power driver circuit (2) with phase strands (31) of the electrical machine (3), wherein in the case of an error the following steps are carried out:
- Determining a speed of a rotor of the electric machine (3);
- Determining a direction of rotation of the electric machine (3) and the type of error of the error case;
- Determining a rotor position range (RB), in which a simultaneous separation of the phase strand leads (4) is allowed, depending on the speed, the particular type of error and the particular direction of rotation;
- interrupting the phase strand supply lines (4) depending on the determined rotor position range (RB) and of a current rotor position (φ _{motor, electric} ).

Description

Technical area

The invention relates to steering assistance drives, and in particular measures for carrying out a phase separation of such a steering assistance drive in the event of a fault.

Technical background

Steering assist drives that provide a steering assistance force for steering systems may be configured as electronically commutated multiphase electrical machines. These are usually controlled by a power driver circuit, which apply phase voltages to the electrical machine via phase strands in accordance with a steering assistance torque to be provided. If a short circuit fault occurs in the power driver circuit, this can lead to a high current flow through one or more phase strands, which causes a blockage or a considerable stiffness of the electrical machine.

Monitoring circuits are usually provided which check the proper functioning of the power driver circuits and accordingly provide an error signal in the event of a fault. In addition, disconnectors in the form of MOSFETs are provided in the phase-strand supply line between the power drive circuit and the respective phase strand of the electrical machine, which can separate the phase-strand supply lines by means of a corresponding control or can switch to high-resistance.

Diverse concepts are known from the prior art to make the shutdown of individual or all phase-strand supply lines. For example, from the publications DE 10 2012 208 632 A1 and US 2013 0320 895 A1 a sequential phase separation known. However, a sequential separation of the phase-strand supply lines increases the analysis effort, since several circuit states must be analyzed and evaluated.

There are also approaches known to open the circuit breaker simultaneously and thus to achieve a simultaneous separation of the phase strand leads.

From the publication DE 10 2010 033 440 B4 a method for safety shutdown of an electromechanical motor vehicle power steering is known, in which a fault signal is output to the disconnectors when an error occurs.

From the publication DE 10 2013 104 937 A1 a method for phase separation of a drive motor of a steering system is known. In this case, a voltage of a phase strand is measured and checks whether this voltage is not constant over a first period of time. A first time is determined at which this voltage changes from the conducting state of a body diode of a circuit breaker to the non-conducting state of the body diode, wherein a circuit breaker for phase separation of the phase line is driven after the first time point is detected.

From the publication US 8,884,559 B2 For example, an engine system is known that includes a driver circuit for driving multiple phases on the electric machine and a safety circuit that includes isolation switches for each of the phase strands. With the aid of a safety control unit, each of the disconnecting switches is actuated such that, when an error occurs, firstly the semiconductor switching elements of the driver circuit and after a predetermined period of time the disconnecting switches of the safety circuit are opened. This can be avoided that the circuit breaker of the safety circuit are destroyed by a peak voltage.

To avoid blocking the steering assist drive, so the phase currents can be interrupted by means of the disconnect switch. The circuit breakers are usually designed as a semiconductor switch, but which are dimensioned so that they can interrupt relatively low phase currents compared to the nominal current flow (rated current) in the electric machine. Especially at a high temperature of the circuit breaker this can interrupt only a very small phase current. After the usual in the event of failure deactivating the power drive circuit high currents can occur through the inductive load of the still rotating electric machine, which exceed the current carrying capacity of the circuit breaker. When the electrical machine is still rotating after an error has occurred, these vary Current flows through the rotor position, so that only during certain time windows, a simultaneous interruption of the current flows in the phase strands is possible.

In addition, there may be a problem that the phase currents can not be measured upon the occurrence of a fault in the power driver circuit. Therefore, it is not known at the time of occurrence of a fault whether an immediate opening of the disconnect switch is possible without jeopardizing or destroying the disconnect switch.

It is therefore an object of the present invention to provide an improved method for operating a motor system with a safety circuit for disconnecting phase strand feed lines, that allows to switch disconnectors only at low switching currents, and moreover requires no phase string measurement.

Disclosure of the invention

This object is achieved by the method for operating an engine system with an electrically commutated electric machine according to claim 1 and by the shutdown device and the motor system according to the independent claims.

Further embodiments are specified in the dependent claims.

• - Bestimmen einer Drehzahl eines Rotors der elektrischen Maschine;
• - Bestimmen einer Drehrichtung der elektrischen Maschine und der Fehlerart des Fehlerfalls;
• - Ermitteln eines Rotorlagebereichs, in dem eine gleichzeitige Auftrennung der Phasenstrangzuleitungen zugelassen wird, abhängig von der Drehzahl, der bestimmten Fehlerart und der bestimmten Drehrichtung;
• - Unterbrechen der Phasenstrangzuleitungen abhängig von dem ermittelten Rotorlagebereich und von einer aktuellen Rotorlage.

According to a first aspect, a method for operating an engine system with an electric machine, a power driver circuit for providing phase voltages and a safety device with disconnectors for disconnecting phase strand leads that connect the power driver circuit with phase strands of the electric machine is provided, wherein in an error case following steps to be executed:

• - Determining a rotational speed of a rotor of the electric machine;
• Determining a direction of rotation of the electrical machine and the type of error of the error case;
• - Determining a rotor position range in which a simultaneous separation of the phase strand supply lines is allowed, depending on the speed, the particular type of error and the particular direction of rotation;
• - interrupting the phase strand supply lines depending on the determined rotor position range and of a current rotor position.

One idea of the above method is to simultaneously open the circuit breakers in the safety device in the event of a fault within a time window, i. while the amounts of all phase currents are less than a predetermined maximum amount for the phase currents. The maximum amount of phase currents corresponds to a phase current that can be safely interrupted by the circuit breaker used, without causing the switching operation to damage or malfunction of the circuit breaker.

The circuit breakers are usually formed by semiconductor devices, in particular as power MOSFETs, the design has an inverse diode between the drain and source terminal. If such a semiconductor device is switched to high impedance in a high current flow in an inductive load, there is a strong voltage increase between the drain and source terminal, which may exceed a breakdown voltage depending on the level of the switched current. When a voltage breakdown, the semiconductor device is destroyed in the rule.

When an error occurs in a power drive circuit during operation of the electric machine, the power drive circuit is turned off. Due to the continued inertia of the rotor of the electric machine due to the mass inertia or the action of external forces, phase currents arise in the phase strands due to induced voltages. If the induced voltages are greater in magnitude than the threshold voltages of the inverse diodes of the switching transistors in the power drive circuit and directed to bring the inverse diodes into the conductive state, phase currents flow through the phase strands of the electrical machine.

In the case of a short circuit in a switching transistor connected to a high supply potential of the power driver circuit, the inverse diodes of other switching transistors of the power driver circuit are temporarily brought into the conductive state. The height of the phase currents varies dependent on the rotor's electrical rotor position. In a rotor position range, the phase currents in the phase strands are simultaneously low, ie lower than the maximum switching current, so that at a rotor position within the rotor position range, the disconnectors can be switched off at the same time, without a breakdown voltage occurs in one of the circuit breaker. However, the rotor position range varies with engine speed, and the rotor position range in which simultaneous disconnection of the disconnect switches is permitted decreases with increasing engine speed.

The rotor position ranges, in which the simultaneous phase separation can be performed by the circuit breaker can be determined as a characteristic curve or characteristic map as a function of an engine speed. The determination of the characteristics can be done by simulation or test bench tests, with temperature influences, disturbances, z. B. scattering of the component properties, and noise in the measurement of the electrical rotor position can be taken into account by appropriate tolerances.

In particular, the above method provides, based on a classified error case (reference error) and on a particular direction of rotation of the electric machine, the rotor position range in which the simultaneous phase separation can be performed or not allowed to determine depending on a predetermined reference rotor position range. The reference rotor position range corresponds to a specific error case (reference error), such. B. a short circuit of a particular switching transistor in a positive direction of rotation of the electric machine. That is, if the reference error occurs in a positive rotating direction of the electric machine, the rotor posture region in which the simultaneous phase separation can be performed corresponds to the reference rotor posture region.

In the event of a short-circuit fault under conditions which do not correspond to the reference error, the rotor position range within which the simultaneous phase separation can be carried out is determined by a shift of the reference rotor position range. The shift is realized by the addition of a rotor position offset to the limits of the rotor position range. The determination of the respectively applicable Abschaltungsrotorlagebereichs done by assigning the rotor position offset to the respective error case and the direction of rotation and a subsequent adjustment of the reference rotor position range. In this way it is possible to easily determine the rotor position range in which a safe separation of the phase strands can be allowed for the safety circuit.

Furthermore, a reference rotor position range can be assigned to the specific speed, wherein the reference rotor position range indicates a rotor position range for rotor positions, in which for a specified error case and a fixed direction of rotation simultaneous separation of the phase strand leads is allowed, wherein the rotor position range in which a simultaneous Separation of the phase strand supply lines is allowed, depending on the reference rotor position range, the specific type of error and the particular direction of rotation is determined.

According to one embodiment, the rotor position range can be determined by applying limits of the reference rotor position range with a rotor position offset which is predefined as a function of the determined error case and the specific direction of rotation.

Furthermore, a short circuit fault in a switching transistor of the power driver circuit can be detected as an error case.

• - Bestimmen einer Drehzahl eines Rotors der elektrischen Maschine;
• - Bestimmen einer Drehrichtung der elektrischen Maschine und der Fehlerart des Fehlerfalls;
• - Ermitteln eines Rotorlagebereichs, in dem eine gleichzeitige Auftrennung der Phasenstrangzuleitungen zugelassen wird, abhängig von der Drehzahl, der bestimmten Fehlerart und der bestimmten Drehrichtung;
• - Ansteuern der Sicherheitseinrichtung, um die Phasenstrangzuleitungen abhängig von dem ermittelten Rotorlagebereich und von einer aktuellen Rotorlage zu unterbrechen.

According to a further aspect, a motor system is provided with an electrical machine, a power driver circuit for providing phase voltages and a safety device for disconnecting phase-strand leads which connect the power-drive circuit with phase strands of the electrical machine, wherein a control unit is designed to carry out the following steps in the event of a fault execute:

• - Determining a rotational speed of a rotor of the electric machine;
• Determining a direction of rotation of the electrical machine and the type of error of the error case;
• - Determining a rotor position range in which a simultaneous separation of the phase strand supply lines is allowed, depending on the speed, the particular type of error and the particular direction of rotation;
• - Controlling the safety device to interrupt the phase strand supply lines depending on the determined rotor position range and a current rotor position.

Furthermore, the safety device can each have a disconnecting switch for each of the phase-strand supply lines, wherein the disconnectors are formed with semiconductor switches, in particular with MOSFET transistors.

According to a further embodiment, a rotor position sensor may be configured to detect the current rotor position.

list of figures

• 1 eine schematische Darstellung eines Motorsystems mit einer Leistungstreiberschaltung, einer Sicherheitsschaltung und einer elektrischen Maschine;
• 2 ein Flussdiagramm zur Veranschaulichung eines Verfahrens zum Betreiben des Motorsystems der 1 bei Auftreten eines Kurzschlussfehlers in der Leistungstreiberschaltung; und
• 3a und 3b beispielhafte Verläufe von Phasenströmen über dem elektrischen Rotorwinkel im Falle eines Kurzschlussfehlers bei verschiedenen Motordrehzahlen.

Embodiments are explained below with reference to the accompanying drawings. Show it:

• 1 a schematic representation of an engine system with a power driver circuit, a safety circuit and an electric machine;
• 2 a flowchart for illustrating a method for operating the engine system of 1 upon occurrence of a short circuit fault in the power driver circuit; and
• 3a and 3b exemplary waveforms of phase currents versus the electrical rotor angle in the case of a short circuit fault at different engine speeds.

Description of embodiments

1 shows a schematic representation of an engine system 1 with a power driver circuit 2 for providing phase currents for an electrical machine 3 , The electric machine 3 is designed as an electronically commutated electric machine, such as a synchronous motor or the like. The electric machine 3 has several phase strands 31 on, which are connected in the embodiment shown as a star connection. In alternative embodiments, the phase strands may also be interconnected in polygon circuit.

The power driver circuit 2 is above a number of phase-strand supply lines 4 with the phase strands 31 the electric machine 3 in electrical connection. The number of phase-strand supply lines 4 thus corresponds to the phase number of the electric machine 3 , In the phase-strand supply lines 4 is a safety device 5 provided that a controlled electrical interruption of the phase strand supply lines 4 can make if an error occurs in the power driver circuit 2 occured.

The power driver circuit 2 is via a filter circuit 6 with a supply voltage U _DC between a high supply potential V _H and a low supply potential V _L connected. In the illustrated embodiment, the power driver circuit 2 for the operation of a three-phase electric machine 3 educated. The power driver circuit 2 For example, as shown, in the form of a B6 bridge circuit with a series circuit of two switching transistors assigned in each case to the phase strands 21 , for example in the form of MOSFET transistors 22 are formed, be provided. The MOSFET transistors have design intrinsic inverse diodes 23 on, in a respect to the voltage direction resulting from the arrangement of the switching transistors 21 results in opposite voltage can be transmitted, ie at a negative voltage between the drain terminal and the source terminal of the switching transistors 21 , which exceeds a threshold voltage, a diode current flows from the source terminal to the drain terminal of the respective switching transistor 21 ,

One each between the two serially connected switching transistors 21 located node K1 . K2 . K3 is via a corresponding one of the phase-strand supply lines 4 with the respective phase string 31 the electric machine 3 connected to each through the power driver circuit 2 provided phase voltage U . V . W to be applied to the electrical machine.

The control of the electric machine 3 is done using a control unit 24 , which depends on an external target specification B according to a Kommutierungsschema the switching transistors 21 controls and thereby opens or closes to phase voltages U . V . W for the individual phase strands 31 to generate and so certain phase currents in the electric machine 3 memorize. The commutation can be based on a current (electric) rotor position φ _{motor, electrically} the electric machine 3 be determined by means of a sensor or sensorless by measuring phase currents.

The safety device 5 includes a security unit 51 and disconnect switch 52 , which may each be formed as a semiconductor switch in the form of a MOSFET transistor. The MOSFET transistors each have a body diode, via which a current flow greater than a predetermined threshold current is possible. The security unit 51 serves a short circuit fault in at least one of the switching transistors 21 the power driver circuit 2 to detect in a conventional manner. The security unit 51 Accordingly, it is capable of a short circuit fault in one of the switching transistors of the power driver circuit by methods known per se 2 to identify this, to identify the type of fault and upon detection of a fault, in particular a short circuit fault (ie the relevant MOSFET transistor is permanently conductive) the separation of the electric machine 3 by simultaneously switching off the disconnect switch 52 the safety device 5 make.

Due to the limited breakdown voltage of the circuit breaker 52 However, a shutdown may not be made at high phase currents. Because when switching a too high phase current can due to the inductive properties of the electric machine, a high field strength between the drain terminal and source terminal of the semiconductor device designed as a circuit breaker 52 caused, which can lead to damage or destruction.

To operate the engine system 1 leads the security unit 51 a method as shown by the flowchart of 2 is explained in more detail.

In step S1 it is determined whether an error occurs in the form of a short circuit fault. If an error occurs (alternative: Yes), then the method with step S2 otherwise, it will go to step S1 jumps back.

In step S2 Now the nature of the fault is detected, and in particular it is determined which of the switching transistors 21 has a short circuit fault. A short circuit fault exists if the relevant switching transistor can not be opened, ie can not be switched to high impedance.

In step S3 Now the direction of rotation of the electric machine is detected. This can be done by suitable evaluation of a rotor position signal for the current rotor position φ _{motor, electrically} , the control unit 24 is provided or by the control unit 24 is detected. This can be done by the control unit 24 with the security unit 51 be in communication via a suitable communication link to communicate the rotor position signal or a rotational direction determined therefrom.

Next will be in step S4 an engine speed determined. This can, for example, also by a suitable communication with the control unit 24 take place, which can determine a speed based on the rotor position signal by temporal differentiation in a conventional manner.

Depending on the speed is now in step S5 in the security unit 51 determines a reference rotor position range RRB indicating, for the respective speed and a certain one of the short-circuit errors (reference error) and a certain direction of rotation (reference direction of rotation), a reference rotor position range RRB with a lower and upper rotor position limit φ _reference1 , φ _reference2 , in which in the case of the reference error and the particular direction of rotation, a safe separation of the electrical machine 3 is possible.

The size of the rotor position range RB with a lower and upper rotor position limit φ ₁ , φ ₂ is dependent on the speed, as can be seen for example from the exemplary courses of the phase currents for different engine speeds in the 3a and 3b can take. By providing a suitable characteristic map for the determination of the reference rotor position range RRB, an upper and lower limit of the reference rotor position range φ _reference1 , φ _reference2 can thus be determined depending on the engine speed.

${\phi }_2={\phi }_{Referenz2}+\frac{2\pi }{3}$

4 Zweig V unterer Transistor >= 0 φ_{Motor,elektrisch} ${\phi }_1={\phi }_{Referenz1}-\frac{\pi }{3},$

${\phi }_2={\phi }_{Referenz2}-\frac{\pi }{3}$

5 Zweig W oberer Transistor >= 0 φ_{Motor,elektrisch} ${\phi }_1={\phi }_{Referenz1}-\frac{2\pi }{3},$

${\phi }_2={\phi }_{Referenz2}-\frac{2\pi }{3}$

6 Zweig W unterer Transistor >= 0 φ_{Motor,elektrisch} φ_Grenzwert = φ_Referenz 1n Zweig U oberer Transistor < 0 - φ_{Motor,elektrisch} ${\phi }_1={\phi }_{Referenz1}+\frac{\pi }{3},$

${\phi }_2={\phi }_{Referenz2}+\frac{\pi }{3}$

2n Zweig U unterer Transistor < 0 - φ_{Motor,elektrisch} φ₁ = φ_Referenz1 - π, φ₂ = φ_Referenz2 - π 3n Zweig V oberer Transistor < 0 - φ_{Motor,elektrisch} ${\phi }_1={\phi }_{Referenz1}-\frac{2\pi }{3},$

${\phi }_2={\phi }_{Referenz2}-\frac{2\pi }{3}$

4n Zweig V unterer Transistor < 0 - φ_{Motor,elektrisch} ${\phi }_1={\phi }_{Referenz1}+\frac{\pi }{3},$

${\phi }_2={\phi }_{Referenz2}+\frac{\pi }{3}$

5n Zweig W oberer Transistor < 0 - φ_{Motor,elektrisch} ${\phi }_1={\phi }_{Referenz1}+\frac{2\pi }{3},$

${\phi }_2={\phi }_{Referenz2}+\frac{2\pi }{3}$

6n Zweig W unterer Transistor < 0 - φ_{Motor,elektrisch} ${\phi }_1={\phi }_{Referenz1}-\frac{\pi }{3},$

${\phi }_2={\phi }_{Referenz2}-\frac{\pi }{3}$

It may now be in step S6 depending on the type of error of the error occurred and the direction of rotation of the electric machine by a simple assignment table for the determination of the rotor position range RB with φ ₁ , φ ₂ are calculated from the reference rotor position range RRB. The calculation is made according to the following assignment: error number Defective transistor in bridge circuit (short-circuit fault) Direction of rotation of the motor Rotor position for interrogating the limits of the Rotorlagebereic hs Conversion formula for the upper and lower limits of the rotor position range calculated from the reference rotor position range [wheel] 1 Branch U upper transistor > = 0 φ _{engine, electric} φ ₁ = φ _reference1 , φ ₂ = φ _reference2 2 Branch U lower transistor > = 0 φ _{engine, electric} φ ₁ = φ _{reference 1} - π, φ ₂ = φ _{reference 2} - π 3 Branch V upper transistor > = 0 φ _{engine, electric} ${\phi }_1={\phi }_{Referen\mathrm{<figure-callout\; id="1"\; label="z"\; filenames="DE102017211219A1\_0018.png,DE102017211219A1\_0020.png"\; state="\{\{state\}\}">z</figure-callout>}1}+\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referen\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">z</figure-callout>}2}+\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

4 Branch V lower transistor > = 0 φ _{engine, electric} ${\phi }_1={\phi }_{Referenz1}-\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referenz2}-\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

5 Branch W upper transistor > = 0 φ _{engine, electric} ${\phi }_1={\phi }_{Referenz1}-\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referenz2}-\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

6 Branch W lower transistor > = 0 φ _{engine, electric} φ _{limit value} = φ _reference 1n Branch U upper transistor <0 - φ _{engine, electric} ${\phi }_1={\phi }_{Referen\mathrm{<figure-callout\; id="1"\; label="z"\; filenames="DE102017211219A1\_0018.png,DE102017211219A1\_0020.png"\; state="\{\{state\}\}">z</figure-callout>}1}+\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referen\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">z</figure-callout>}2}+\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

2n Branch U lower transistor <0 - φ _{engine, electric} φ ₁ = φ _{reference 1} - π, φ ₂ = φ _{reference 2} - π 3n Branch V upper transistor <0 - φ _{engine, electric} ${\phi }_1={\phi }_{Referenz1}-\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referenz2}-\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

4n Branch V lower transistor <0 - φ _{engine, electric} ${\phi }_1={\phi }_{Referen\mathrm{<figure-callout\; id="1"\; label="z"\; filenames="DE102017211219A1\_0018.png,DE102017211219A1\_0020.png"\; state="\{\{state\}\}">z</figure-callout>}1}+\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referen\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">z</figure-callout>}2}+\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

5n Branch W upper transistor <0 - φ _{engine, electric} ${\phi }_1={\phi }_{Referen\mathrm{<figure-callout\; id="1"\; label="z"\; filenames="DE102017211219A1\_0018.png,DE102017211219A1\_0020.png"\; state="\{\{state\}\}">z</figure-callout>}1}+\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referen\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">z</figure-callout>}2}+\frac{2\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

6n Branch W lower transistor <0 - φ _{engine, electric} ${\phi }_1={\phi }_{Referenz1}-\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}.$

${\mathrm{<figure-callout\; id="2"\; label="\phi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_2={\phi }_{Referenz2}-\frac{\mathrm{<figure-callout\; id="3"\; label="\pi "\; filenames="DE102017211219A1\_0018.png"\; state="\{\{state\}\}">\pi </figure-callout>}}{3}$

Thus, the rotor position range, which indicates the range of rotor positions between φ ₁ and φ ₂ , within which a separation of the phase strands can be made, can be determined in a simple manner.

In step S7 becomes the separation of the phase-strand supply lines 4 made as soon as the current rotor position is within the rotor position range. For this purpose, the current rotor position φ _{motor, electrically} detected and queried, whether this is in the previously determined rotor position range RB. If the rotor position φ _{motor, electrically} in this area, the phase strand leads 4 through the safety device 5 simultaneously separated.

LIST OF REFERENCE NUMBERS

1

engine system

2

Power driver circuit

21

switching transistors

22

MOSFET transistor

23

Inverse diode

24

control unit

3

electric machine

31

phase strands

4

Phase conductor leads

5

safety device

51

security unit

52

disconnectors

6

filter

V _H

high supply potential

V _L

low supply potential

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 102012208632 A1 [0004]
• US 20130320895 A1 [0004]
• DE 102010033440 B4 [0006]
• DE 102013104937 A1 [0007]
• US 8884559 B2 [0008]

Claims (9)

Method for operating an engine system (1) with an electric machine (3), in particular a steering assistance drive, a power driver circuit (2) for providing phase voltages (U, V, W) and a safety device (5) for disconnecting phase strand supply lines (4), connecting the power driver circuit (2) to phase strings (31) of the electrical machine (3), the following steps being carried out in the event of an error: - determining a rotational speed of a rotor of the electric machine (3); - Determining a direction of rotation of the electric machine (3) and the type of error of the error case; - Determining a rotor position range (RB), in which a simultaneous separation of the phase strand leads (4) is allowed, depending on the speed, the particular type of error and the particular direction of rotation; - interrupting the phase strand supply lines (4) depending on the determined rotor position range (RB) and of a current rotor position (φ _{motor, electric} ). Method according to Claim 1 wherein a reference rotor position range (RRB) is assigned to the determined speed, wherein the reference rotor position range (RRB) indicates a rotor position range for rotor positions in which a simultaneous separation of the phase strand leads (4) is permitted for a defined error case and a fixed direction of rotation in which the rotor position range (RB), in which a simultaneous separation of the phase-strand feed lines is permitted, is determined depending on the reference rotor position range (RRB), the specific type of fault and the determined direction of rotation. Method according to Claim 1 or 2 wherein the rotor position range (RB) is determined by applying limits of the reference rotor position range (RRB) with a rotor position offset which is predetermined depending on the determined error case and the determined direction of rotation. Method according to Claim 3 wherein the rotor position offset is a multiple of $\frac{\pi }{P}$

corresponds, wherein P corresponds to the number of phase strands of the electric machine (3). Method according to one of Claims 1 to 4 in which, as a fault, a short circuit fault in a switching transistor (21) of the power driver circuit (2) is detected. Motor system (1) with an electric machine (3), a power driver circuit (2) for providing phase voltages (U, V, W) and a safety device (5) for separating phase strand supply lines (4), the power driver circuit (2) with phase strands (U, V, W) of the electric machine (3) connect, wherein a control unit (24) is designed to carry out the following steps in the event of an error: - determining a rotational speed of a rotor of the electric machine (3); - Determining a direction of rotation of the electric machine (3) and the type of error of the error case; - Determining a rotor position range (RB), in which a simultaneous separation of the phase strand leads (4) is allowed, depending on the speed, the particular type of error and the particular direction of rotation; - Controlling the safety device (5) to interrupt the phase strand supply lines depending on the determined rotor position range (RB) and of a current rotor position (φ _{motor, electric} ). Motor system (1) after Claim 6 wherein the safety device (5) in each case has a disconnecting switch for each of the phase-strand supply lines (4), wherein the disconnecting switches (52) are formed with semiconductor switches, in particular with MOSFET transistors. Motor system (1) after Claim 6 or 7 , wherein a rotor position sensor is designed to detect the current rotor position (φ _{engine, electric} ). Use of the engine system (1) according to one of Claims 6 to 8th in a steering assist drive in a steering system of a motor vehicle.

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