DE202015009737U1 - Drive unit with a control unit for safety monitoring - Google Patents

Abstract

mit einem Winkel (α) bestimmt wird,
- eine zeitliche Änderung des Winkels (α) bestimmt und als Drehzahl (n) herangezogen wird, und
- wobei eine sichere Funktion (SLS) mit der Drehzahl (n) als Eingabewert ausgeführt wird.

Drive unit (2) with an inverter (6), and / or with an electric motor (4), as well as with a safety monitoring control unit (24), which is operated according to the method (26), in which
- a river space pointer $\left(\overrightarrow{\Psi }\right)$

determined with an angle (α),
a temporal change of the angle (α) is determined and used as the speed (n), and
- where a safe function (SLS) with the speed (n) is performed as an input value.

Description

The invention relates to a drive unit with a control unit for security monitoring. The drive unit preferably comprises a converter and an electric motor.

Industrial plants usually have a large number of rotating electrical machines, by means of which, for example, tools or conveyor belts are driven. The electrical energy required for this purpose is provided by means of converters which are signal-technically coupled to a process controller. By means of the process control, a target speed is predetermined, to which the respective electrical machine is regulated by means of the associated converter. The inverter is electrically coupled to a utility network and includes a semiconductor switch connected in series between the utility network and the electrical machine. The control of the semiconductor switch is performed such that the speed of the electric machine corresponds to the predetermined by the process control target speed. The switched by means of the semiconductor switch electrical voltages are usually over 800 volts. The switched electrical currents have a current above 1 A or 10 A.

In order to exclude a violation of operating personnel of the electric machine or to reduce such consequences, so-called "emergency stop" switches are known. In an unauthorized or unwanted approach of a person to the electric machine, this switch is manually operated to substantially terminate an operation of the electric machine immediately. For this purpose, the switch is usually signal technology coupled with the process control. By means of the process control, a signal is transmitted to the control part upon actuation of the switch, and as a result the energization of the electric machine is prevented. For this purpose, the power semiconductor switch is usually placed in an electrically non-conductive state.

However, if the electric machine or else the tool driven by the electric machine is to be set or calibrated, such a safety function is not suitable, since in this way it is not possible to control the entire area traveled by the tool. Therefore, it is common practice to operate the electric machine at a limited speed at which injury to a person adjusting the tool or electrical machine is ruled out. For this purpose, the actual speed of the electric machine is usually detected by means of a so-called safe encoder, and in case of an unwanted exceeding of the limited speed, the inverter is de-energized. By means of the safe encoder in this case it is ensured that the actual speed of the electric machine is detected error-free, or at least with only a relatively small error even under adverse circumstances.

However, a secure donor is comparatively expensive. Such a safe encoder, in particular its monitoring electronics, also has a comparatively high energy requirement during operation. In addition, it is still possible, although unlikely, that the rotational speed of the electric machine is not correctly determined, or is not evaluated correctly by means of the monitoring electronics, which leads to a so-called frozen position information. In this case, exceeding the limited speed is not or at least not detected in time, so still injury to persons can take place.

Drury et al., Adaptive Sensorless Position Estimation of a Field-Weakened Permanent Magnet Machine at Extended Temperature Range, 5th IET International Conference on Power Electronics, Machines and Drives, 2010 , 1-4. IEEE shows an encoderless rotor position detection of an electric motor. The calculated rotor position and a torque request are supplied to a controller for determining a current setpoint that controls the electric motor.

DE 103 58 359 B4 describes a scalable safety module for controllers. To detect the operating situation of an electric motor driven by the drive controller, safe sensors are used.

The invention has for its object to provide a particularly suitable drive unit with a control unit for security monitoring, in which expediently increased security and preferably costs are reduced.

With regard to the drive unit, this object is achieved by the features of claim 1 according to the invention. Advantageous developments and refinements are the subject of the respective subclaims.

The drive unit has an inverter or an electric motor. Particularly preferably, the drive unit comprises both the converter and the electric motor which is operated by means of the converter. In particular, the converter has at least one semiconductor switch for controlling an energy flow to the electric motor. The drive unit further comprises a control unit which serves to monitor safety. Safety monitoring is a safe function and in particular safe limited speed ("safe Limited Speed ", SLS). In other words, the safe limited-speed safe function is executed by the control unit.

The control unit is operated according to a procedure. In operation, a flow space pointer is first determined at an angle. In a further step, a temporal change of the angle is determined. The temporal change of the angle is used as speed and used as input value of the safe function. Preferably, the speed is compared with a limit. The limit is suitably a fixed speed limit. Preferably, a second safe function is performed depending on the comparison, in particular safe torque off. For example, the second safe function is performed when the speed is less than the limit. Preferably, however, the second safe function is performed if the speed is greater than the limit. In this way, the determination of the speed is relatively safe, so that the safe function is always performed and only if the actual speed of the electric motor meets the predetermined dependence on the limit.

The control unit comprises, for example, a number of electrical and / or electronic components which serve to carry out the method. In particular, the control unit has a programmable processor / microchip, by means of which the method is carried out. In this way it is possible to adapt the method to different requirements. Alternatively, the method is implemented by means of an application-specific integrated circuit (ASIC), which leads to reduced execution times.

The method thus serves to monitor the safety of the electric motor operated by means of the converter, wherein the electric motor is energized in particular by means of the converter. The electric motor is, for example, an asynchronous motor, but preferably a synchronous motor, such as a synchronous reluctance motor, or a permanent-magnet synchronous motor. The permanent-magnet synchronous motor comprises, for example, asymmetrical inductances, in particular the transverse inductance (L _d ) is smaller than the longitudinal inductance (L _q ). For example, the permanent-magnet synchronous motor has comparatively deep embedded / buried magnets, in which a reluctance torque is suitably additionally used during operation. Alternatively or in combination with this, the permanent-magnet synchronous motor is operated in the field weakening area. In a further alternative, the electric motor is a separately excited synchronous motor, which preferably has comparatively pronounced poles. In particular, the transverse inductance (L _d ) is greater than the longitudinal inductance (L _q )

For example, the electric motor is a brushless DC motor (BLDC), or more preferably a servomotor. Conveniently, the electric motor has two or three electrical phases, which are offset from each other by 120 ° in particular. The converter preferably has a semiconductor switch, for example four or six semiconductor switches, which are expediently interconnected in a bridge circuit. In other words, the inverter has a B4 or B6 circuit. Preferably, the inverter comprises an intermediate circuit which is guided against the bridge circuit. In particular, the converter comprises a rectifier side, which is coupled to a supply network having, for example, a three-phase current with a frequency of 50 Hz or 60 Hz.

The method provides that a flow space pointer is determined. The flow space pointer is a vector and thus has an angle with respect to a defined further vector or a straight line. The further vector or the straight line is in particular constant during the method. In a further step, a temporal change of the angle is determined. For this purpose, for example, the flow space pointer is first determined again, that is, the angle is determined again. On the basis of the two determined angles, the time change is determined by taking the time interval between these two times. In other words, the time for detecting each angle is detected, and the change of the angle when the angle is detected again is set in relation to the time period between these two times. In particular, the angle is determined substantially continuously, wherein the time period is preferably constant. In an alternative to this, the temporal change of the angle is derived from the temporal change of the flow space vector.

The temporal change of the angle is used as the speed. In other words, the change of the angle is used as the speed. The speed is used as the input value of a safe function. The speed is thus used as the input value of the safe function, where the safe function has a single input value or a number of input values. In other words, the safe function is performed with the speed as the input value. Under input value is understood in particular a parameter of the safe function, but also particularly preferably the variable of the safe function. By means of the safe function, the inverter and / or the Electric motor in a safe state transferred and / or left in a safe state, so that essentially no injury to persons or damage to an environment is expected this. In summary, the method provides that the safe function is performed, using as input value the speed which is determined by means of the temporal change of the angle, which has the Flußraumzeiger.

Due to the use of the flow space hand, a reliable execution of the safe function is ensured, with the speed determination used for this purpose being relatively stable. In other words, their determination leads on the one hand to no singularities and on the other to a comparatively small error. Also, no evaluation of measured values of a speed sensor is required for this purpose. The speed determination and thus the reliable execution of the safe function are also secured at a possible speed change of the electric motor, so acceleration or deceleration.

Suitably, the inverter and / or the electric motor is part of an industrial plant. In particular, the converter has a maximum power output and / or the electric motor has a maximum power consumption between 700 W and 500 kW. Conveniently, the power output / power consumption is greater than or equal to 1 kW, 5 kW, 10 kW, 50 kW, 100 kW or 200 kW. For example, the power output / power consumption is less than or equal to 400 kW, 250 kW, 100 kW, 50 kW, 15 kW or 2 kW.

The flow space vector is expediently determined by means of an electric motor current (stator current). In other words, the electric motor current is used to determine the Flußraumze. Consequently, the electrical current provided with the aid of the converter is determined, in particular detected, by means of which the electric motor is energized. This is expediently carried out by means of a sensor for measuring current, that is to say by means of direct measurement. Consequently, the motor current is measured. Preferably, the electrical current flow of a line is detected, by means of which the converter and the electric motor are electrically connected. For example, the current sensor includes a Hall sensor that is suitably positioned within a slot of a slotted ring of soft magnetic material. Here, the ring expediently surrounds the line, by means of which the electric motor is energized. In particular, a current space vector (space vector of the electric motor current, stator current vector) is determined. In other words, the electric motor current as a vector with a torque-forming component, namely I _q , and a flow-forming component, namely I _d determined, wherein the vector corresponds to the current space pointer. If the electric motor is a synchronous motor, this is preferred in this case with a flow-forming portion I _d operated, which is different from zero (0).

Alternatively or in combination, the flux space pointer is determined by means of an electric motor voltage. Consequently, the electric motor voltage is used to determine the Flußraumze. Preferably, a space vector of the electrical motor voltage is determined for this purpose. In other words, the electric motor voltage is determined vectorially. Thus, a d and a q component of the electrical motor voltage are determined. In particular, the electric motor voltage is measured, resulting in a relatively high safety. For this purpose, the electric motor suitably has a voltage sensor.

Alternatively, the electric motor voltage is determined based on an intermediate circuit voltage of the inverter, which leads to a reduced number of components, so that the electric motor can be created relatively inexpensively. The DC link voltage is in particular that electrical voltage which prevails between a rectifier side and an inverter side of the converter. Between the DC link and the electric motor, a semiconductor switch of the inverter side is connected. Depending on the switching state of the semiconductor switch, the electric motor is set in a rotational movement. For example, the semiconductor switch is switched by means of pulses (control signals) from an electrically conductive to an electrically non-conductive state. In particular, the inverter side is realized by means of a bridge circuit having the semiconductor switch, in particular a plurality of semiconductor switches, which is expediently locked when executing a safe function. The semiconductor switch expediently has a freewheeling diode. Suitably, the rectifier side has a number of diodes connected in a bridge circuit, the rectifier side being electrically connected between an electrical utility network and the intermediate circuit.

Advantageously, the state of the semiconductor switch is used to determine the electrical motor voltage, which is in particular part of the bridge circuit, if it is present. Preferably, a frequency of the control signals of the semiconductor switch is determined. For this purpose, the control signals of the semiconductor switch are advantageously filtered, or the time intervals between individual edges of the control signals are determined. The frequency may also be, for example, by time detection between zero crossings or a Fourier transform the phase values are determined. To determine the electric motor voltage thus the known switching states of the semiconductor switch are used, as well as the known DC link voltage. Consequently, a determination of the electric motor voltage without the aid of additional sensors is made possible, wherein the switching signals of the semiconductor switch are created in particular by means of an electronics of the inverter.

For example, a determination is made for determining the flow space vector, in particular electrical, stator resistance. This is determined, for example, during manufacture of the electric motor, for example by means of measurement or else by calculation based on the materials used. In particular, when determining the Flußraumze assumed that the stator resistance is constant. In other words, a constant stator resistance is used to calculate the flow space vector.

In an alternative to this, a temperature-dependent stator resistance is used to determine the flow space vector. In other words, the stator resistance, which is used to determine the Flußraumze, tracked as a function of temperature. In this way, the determination of the Flußraumzeer is relatively accurate, so that any error in the determination of the speed is relatively low, regardless of the current state or environmental parameters of the electric motor. Thus, both at a start of the electric motor and consequently a low temperature, as well as in the electric motor, which has a comparatively high temperature due to an increased load or an increased operating time, a reliable speed detection allows.

For example, the temperature of the stator is measured to determine the temperature-dependent stator resistance. In particular, the electric motor comprises a temperature sensor for this purpose. In this way, a comparatively precise determination of the temperature of the stator and thus also of the currently valid stator resistance is made possible. In an alternative to this, the temperature of the stator is calculated, for which purpose a model is suitably used. Appropriately, a temperature coefficient of a winding of the stator is used. For calculation, the electric motor current guided by the stator winding and the applied electrical voltage are expediently used, the temperature coefficient of the stator winding being taken into account. In particular, both the electric motor current (stator current) and the electrical motor voltage are measured for this purpose. Alternatively or in combination, a cooling loss is determined. In other words, it is determined how much energy due to cooling is dissipated into the environment of either the inverter and / or the electric motor. Based on this, the temperature of the stator is calculated. In a further alternative, the frequency of the actuation of a possible semiconductor switch of the inverter is determined and calculated on the basis of the switching losses, in particular taking into account the switched electrical voltage and the switched electric current, a switching loss. This is expediently deducted from any loss of cooling, since this leads only to a heating of the inverter and not to a heating of the electric motor.

In summary, the stator resistance is used as a parameter for determining the flow space vector. Preferably, the pole pair number of the electric motor is used for determining the flow space pointer. In particular, with the exception of the pole pair number and the stator resistance, no further parameter is used for determining the flow space vector, and consequently for determining the rotational speed.

ermittelt. Hierbei bezeichnet $\overrightarrow{u_1}$

den Raumzeiger der elektrischen Motorspannung, R₁ den Statorwiderstand, der entweder temperaturabhängig oder aber konstant gewählt ist, und ${\overrightarrow{i}}_1$

den Raumzeiger des elektrischen Motorstroms also den Stromraumzeiger. Bei der Integralrechnung werden entweder geeignete Grenzen gesetzt, oder aber anderweitig ein Wegdriften des Integrals verhindert. Der Statorflussraumzeiger ist vergleichsweise einfach zu ermitteln, sodass vergleichsweise geringe Rechenkapazitäten zur Ermittlung der Drehzahl erforderlich sind. Ferner sind etwaige Fehler aufgrund vergleichsweise komplexer mathematischer Umformungen vermieden.For example, an air gap flow pointer is used as the flow space vector. However, a stator flux space vector is particularly preferably used as the flow space vector, that is, the stator flux is determined and evaluated. For example, the Statorflussraumzeiger is based $$\overrightarrow{{\Psi }_1}={\displaystyle \int \left(\overrightarrow{u_1}-R_1\cdot {\overrightarrow{i}}_1\right)}dt$$

determined. Hereby designated $\overrightarrow{u_1}$

the room hand of electric motor voltage, R ₁ the stator resistance, which is selected either temperature-dependent or constant, and ${\overrightarrow{i}}_1$

the room pointer of the electric motor current so the current space pointer. Integral calculus either sets appropriate limits or otherwise prevents the integral from drifting away. The Statorflussraumzeiger is comparatively easy to determine, so that comparatively low computing capacity to determine the speed are required. Furthermore, any errors due to relatively complex mathematical transformations are avoided.

ermittelt. Hierbei bezeichnet $\overrightarrow{{\Psi }_1}$

den Statorflussraumzeiger, L₁ die Induktivität des Stators, und ${\overrightarrow{i}}_1$

den Stromraumzeiger, also den Raumzeiger des elektrischen Motorstroms.In an alternative to this, a rotor flux space vector is used as the flow space vector, which leads to a comparatively precise determination of the rotational speed, ie to a comparatively small error between the determined rotational speed and the actual rotational speed of the electric motor. Preferably, the Rotorflussraumzeiger is based on the formula $$\stackrel{}{{\Psi }_{}}$$$$\overrightarrow{{}_2}=\overrightarrow{{\Psi }_1}-L_1\cdot {\overrightarrow{i}}_1$$

determined. Hereby designated $\overrightarrow{{\Psi }_1}$

the stator flux-space pointer, L ₁ the inductance of the stator, and ${\overrightarrow{i}}_1$

the current space pointer, so the room pointer of the electric motor current.

For example, the safe function is Safe Direction (SDI). Consequently, the electric motor is prevented from operating in an undesired direction of rotation. Alternatively, the safe function is "SSM" (Safe Speed Monitor). Consequently, a safe output signal is generated as long as the speed of the electric motor remains below a certain specific value. Alternatively, the safe function is "SSR" (Safe Speed Range). As a result, the speed of the electric motor remains between predefined limits. Particularly preferred is the safe safe limited speed (SLS) function. Consequently, the rotational speed of the electric motor is monitored by means of the determination of the flow space vector, whereby expediently no measured values of a safe encoder are used. In particular, the speed is compared with a limit value in the safe function. Suitably, when the limit value is exceeded, the energization of the electric motor is reduced. Preferably, a second secure function is performed depending on the comparison. In other words, in the safe function, the speed is compared with the limit, and in response to this, the second safe function is performed. For example, the second safe function is performed when the speed is less than the limit. Alternatively, the second safe function is preferably carried out if the rotational speed is greater than the limit value.

Preferably, the speed and the limit are selected unsigned. In other words, only absolute values are used for comparison. In this way, the safety monitoring is independent of the direction of rotation of the electric motor, and also any, unintentional reversal of the direction of rotation of the electric motor is taken into account. Alternatively, the speed and the limit are selected with signs.

Safe operation stop ("SOS") is expediently carried out as the second safe function, that is to say a change in the position of the electric motor is prevented. Alternatively, the second safe function is Safe Brake Control (SBC), which means that an external brake or holding brake is safely triggered. Particularly preferably, a safe torque off is used as the second safe function ("safe torque off"; STO ). In this case, the energization of the electric motor is expediently interrupted, so that a possible rotor trickles. The electric motor is preferably not supplied with energy, by means of which a rotational movement can be obtained or generated. In particular, the second safe function corresponds to stop category 0 of EN 60204-1. In this case, expediently all pulses are deleted, by means of which any semiconductor switches of the inverter are controlled. In other words, the electric motor is torque-free after activation of the safe function. Conveniently, the electric motor is also protected against a possible restart. Alternatively, a secure stop is used as the second safe function. In particular, the second safe function is a safe stop 1 ("Safe Stop 1", SS1) or safe stop 2 ("Safe Stop 2", SS2). In other words, the electric motor is braked and stopped at a standstill or after a certain period torqueless or momentarily, so STO or SOS running. In summary, the second safe function corresponds to the stop category 1 or the stop category 2 EN 60204-1.

Preferably, the electric motor is free of a safe speed sensor. In other words, the electric motor does not have a safe speed sensor (rotary encoder), so it is safer without a rotor. In this way, the manufacturing cost of the drive unit are reduced, but due to the control unit nevertheless a comparatively high level of security is ensured. A safe speed sensor is understood in particular to be any speed and / or position encoder, by means of which a safety monitoring takes place, that is to say depending on the directly measured speed / position values an execution of a safe function takes place, and / or its measured values are repeatedly used to generate the rotational speed. / Position value are evaluated. For this purpose, the safe speed sensor includes evaluation, which is constructed multi-channel.

Suitably, the electric motor is a synchronous machine, which allows a comparatively precise determination of the position of the electric motor and facilitates its regulation. For example, the electric motor is a brushless DC motor (BLDC). Particularly preferably, the electric motor is a servo motor, which in particular has a speed sensor for the control. This speed sensor is e.g. no safe speed sensor, and only serves to control the speed. In other words, no reliable function is carried out depending on the measured values produced by means of this speed sensor. At least, however, this speed sensor preferably has only a one-channel evaluation, which reduces the cost of the drive unit, in particular the manufacturing cost of an evaluation of the speed sensor.

Preferably, the drive unit is part of an industrial plant. In particular, the converter has a maximum power output and / or the electric motor has a maximum power consumption between 700 W and 500 kW. Conveniently, the power output / power consumption is greater than or equal to 1 kW, 5 kW, 10 kW, 50 kW, 100 kW or 200 kW. For example, the power output / power consumption is less than or equal to 400 kW, 250 kW, 100 kW, 50 kW, 15 kW or 2 kW.

• 1 schematisch einen mittels eines Umrichters betriebenen Elektromotor,
• 2 einen Flussraumzeiger mit einem Winkel, und
• 3 ein Verfahren zur Sicherheitsüberwachung des mittels des Umrichters betriebenen Elektromotors.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

• 1 schematically an electric motor operated by an inverter,
• 2 a river space pointer with an angle, and
• 3 a method for safety monitoring of the electric motor operated by means of the converter.

Corresponding parts are provided in all figures with the same reference numerals.

In 1 is a drive unit 2 an industrial plant, with an electric motor 4 and a converter 6 shown, wherein the electric motor 4 by means of the inverter 6 is operated. The electric motor 4 is free from a safe speed sensor and three-phase configured. In other words, the inverter 6 using a B6 circuit with three bridge branches 8th realized, each of which in each case by means of a line 10 against one of the phases of a stator of the electric motor 4 is guided. Here is the line 10 between in each case two semiconductor switches connected in series to one another 12 each of the bridge branches 8th with the respective bridge branch 8th electrically contacted.

The bridge branches 8th themselves are parallel to each other between a positive pole 14 and a negative pole 16 of the inverter 6 connected. Between the positive pole 14 and a negative pole 16 is a substantially constant DC link voltage U _Z in the amount of 1200V, which means a DC link capacitor 18 is ensured, which is parallel to the individual bridge branches 8th is switched.

berechnet. In Abhängigkeit einer externen Vorgabe werden mittels der Steuereinheit 20 die Halbleiterschalter 12 mit PWM-Signalen beaufschlagt und folglich von einem leitenden in einen nichtleitenden Zustand und umgekehrt versetzt. Infolgedessen wird ein Energiefluss von dem Umrichter 6 zu dem als permanenterregte Synchronmaschine ausgestalteten Elektromotor 4 gesteuert, und der Energiefluss mittels der Stromsensoren 22 überwacht. Anhand des jeweiligen erfassten elektrischer Stroms I oder des Statorstromzeigers ${\overrightarrow{i}}_1$

werden die PWM-Signale angepasst, sodass eine vergleichsweise genaue Regelung des Elektromotors 4 realisiert ist.The semiconductor switches 12 are IGBTs, which preferably have a freewheeling diode. Each of the semiconductor switches 12 is signal technology with a control unit 20 coupled, wherein the gate of the respective semiconductor switch 12 electrically with the control unit 20 is contacted. In 1 only two such signal lines are shown. With the control unit 20 are also three current sensors 22 signal-wise coupled, each of which one of the lines 10 assigned. By means of the current sensors 22 becomes an electrical current during operation I detected and by means of the control unit 22 a current space pointer ${\overrightarrow{i}}_1$

calculated. Depending on an external specification by means of the control unit 20 the semiconductor switches 12 subjected to PWM signals and thus offset from a conducting to a non-conducting state and vice versa. As a result, an energy flow from the inverter 6 to the designed as a permanent magnet synchronous machine electric motor 4 controlled, and the flow of energy by means of the current sensors 22 supervised. Based on the respective detected electrical current I or the stator current indicator ${\overrightarrow{i}}_1$

the PWM signals are adjusted, so that a comparatively accurate control of the electric motor 4 is realized.

The control unit 20 further comprises a control unit 24 , by means of which a safety monitoring takes place. For this purpose, an in 3 illustrated method 26 executed. In a first step 28 becomes a safe function SLS started, which is safe limited speed. The first step 28 is executed as soon as a maintenance work on the electric motor 4 should take place at a complete standstill of the electric motor 4 can not be done in a satisfactory manner. For example, a means of the electric motor 4 driven tool can not be configured correctly, if not the complete range of motion can be traversed.

und ein Spannungsraumzeigers ${\overrightarrow{u}}_1$

ermittelt. Zur Ermittlung des Statorstromzeiger ${\overrightarrow{i}}_1$

wird der mittels der Leitungen 10 geführte elektrische Strom I herangezogen, der mittels der Stromsensoren 22 gemessen wird. Zur Ermittlung des Spannungsraumzeigers $\overrightarrow{u_1}$

wird zunächst eine elektrische Motorspannung U berechnet, die zwischen dem elektrischen Potential jeder der Leitungen 10 und einem konstanten Hilfspotential anliegt, beispielsweise Masse. Hierfür wird die Zwischenkreisspannung U_Z sowie die Schaltzustände der einzelnen Halbleiterschalter 12 herangezogen, die mittels mit der Steuereinheit 20 generierter Pulse angesteuert werden. Da die Information der Schaltzustände der Halbleiterschalter 12 bereits vorhanden ist, und die Zwischenkreisspannung U_Z mittels des Zwischenkreiskondensators 18 im Wesentlichen konstant ist, ist somit auch die jeweilige elektrische Motorspannung U berechenbar.In a second step 30 is by means of the control unit 20 the stator current indicator ${\overrightarrow{i}}_1$

and a voltage space pointer ${\overrightarrow{u}}_1$

determined. To determine the stator current indicator ${\overrightarrow{i}}_1$

becomes the by means of the wires 10 guided electric current I used, by means of the current sensors 22 is measured. To determine the voltage space vector $\overrightarrow{u_1}$

First, an electric motor voltage U calculated between the electrical potential of each of the lines 10 and a constant auxiliary potential, for example ground. This is the DC link voltage U _Z as well as the switching states of the individual semiconductor switches 12 used, which means with the control unit 20 generated pulses are controlled. Since the information of the switching states of the semiconductor switches 12 already exists, and the DC link voltage U _Z by means of the intermediate circuit capacitor 18 is substantially constant, so is the respective electrical motor voltage U predictable.

In a third step 32 which occurs substantially simultaneously with the second operation becomes a stator resistance R ₁ calculated for what first a temperature T the stator of the electric motor 4 is determined. The temperature T is either measured directly by means of a temperature sensor, or calculated by means of a mathematical model, for what initially the power loss of the electric motor 4 detected and this is used as that energy by means of which the electric motor 4 is heated. Taking into account a cooling of the electric motor 4 due to an ambient air or a special cooling circuit is thus the temperature T of the electric motor 4 determinable. By means of this temperature, taking into account the temperature coefficients of the material, by means of which the phases of the electric motor 4 are realized whose stator resistance R ₁ determined.

mit einem Winkel α ermittelt. Hierbei wird der Winkel gegenüber einem drehfesten Koordinatensystem 36 bestimmt. Der Flussraumzeiger $\overrightarrow{\Psi }$

ist der Statorflussraumzeiger $\overrightarrow{{\Psi }_1}$

oder der Rotorflussraumzeiger $\overrightarrow{{\Psi }_2}$

wobei die Flussraumzeiger $\overrightarrow{\Psi }$

gemäß $$\overrightarrow{{\Psi }_1}={\displaystyle \int \left(\overrightarrow{u_1}-R_1\cdot {\overrightarrow{i}}_1\right)dt}$$

bzw. $$\overrightarrow{{\Psi }_2}=\overrightarrow{{\Psi }_2}-L_1\cdot {\overrightarrow{i}}_1$$

ermittelt werden. L1 entspricht der Induktivität des Elektromotors 4. Hieran anschließend wird der zweite, dritte und vierte Arbeitsschritt 30, 32, 34 wiederholt, sodass der Winkel α zweimal bestimmt worden ist. Anschließend wird ein fünfter Arbeitsschritt 38 ausgeführt, bei dem die zeitliche Änderung des Winkels α bestimmt wird, also dα/dt berechnen wird. Hierfür wird die Zeitspanne zwischen den Zeitpunkten herangezogen, zu denen der zweite und dritte Arbeitsschritt 30, 32 ausgeführt wird. Die zeitliche Änderung des Winkels α wird als Drehzahl n des Elektromotors 4 herangezogen, die somit einen Eingabewert der sicheren Funktion SLS darstellt. In einem sechsten Arbeitsschritt 40 wird die Drehzahl n mit einem Grenzwert 42 verglichen. Es wird ermittelt, ob die Drehzahl n größer als der Grenzwert 42 ist. Sofern dies nicht der Fall ist, wird erneut der zweite und dritte Arbeitsschritt 30, 32 ausgeführt sowie die Drehzahl n erneut ermittel als auch der sechste Arbeitsschritt 40 ausgeführt.In a fourth step 34 becomes an in 2 shown river space pointer $\overrightarrow{\Psi }$

with an angle α determined. Here, the angle with respect to a non-rotatable coordinate system 36 certainly. The river space pointer $\overrightarrow{\Psi }$

is the stator flux-space pointer $\overrightarrow{{\Psi }_1}$

or the rotor flux space pointer $\stackrel{}{{\Psi }_{}}$$\overrightarrow{{}_2}$

the river space pointer $\overrightarrow{\Psi }$

according to $$\overrightarrow{{\Psi }_1}={\displaystyle \int \left(\overrightarrow{u_1}-R_1\cdot {\overrightarrow{i}}_1\right)dt}$$

respectively. $$\overrightarrow{{\mathrm{<figure-callout\; id="2"\; label="\Psi "\; filenames="DE202015009737U1\_0033.png"\; state="\{\{state\}\}">\Psi </figure-callout>}}_2}=\overrightarrow{{\mathrm{<figure-callout\; id="2"\; label="\Psi "\; filenames="DE202015009737U1\_0033.png"\; state="\{\{state\}\}">\Psi </figure-callout>}}_2}-L_1\cdot {\overrightarrow{i}}_1$$

be determined. L1 corresponds to the inductance of the electric motor 4 , This is followed by the second, third and fourth steps 30 . 32 . 34 repeated, so the angle α has been determined twice. Subsequently, a fifth step 38 executed, in which the temporal change of the angle α is determined, so dα / dt will calculate. For this purpose, the time interval between the times is used, to which the second and third step 30 . 32 is performed. The temporal change of the angle α is called the speed n of the electric motor 4 which is thus an input value of the safe function SLS represents. In a sixth step 40 is the speed n with a limit 42 compared. It is determined if the speed n greater than the limit 42 is. If this is not the case, the second and third work steps again 30 . 32 executed as well as the speed n redetermined as well as the sixth step 40 executed.

If the speed n greater than the limit 42 is, becomes a seventh step 44 executed, in which a second secure function STO is executed, namely safe torque off. Consequently, all the pulses for driving the semiconductor switches 12 cleared and thus placed in an electrically non-conductive state. Consequently, the electric motor is spinning 4 torqueless, causing injury to people in the vicinity of the electric motor 4 is excluded. In an eighth step 46 becomes the electric motor 4 protected against any restart and the procedure 26 completed. In particular, the activation of the second secure function STO by means of a display unit of the control unit 20 signaled.

The invention is not limited to the embodiment described above. Rather, other variants of the invention can be derived therefrom by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the exemplary embodiment can also be combined with each other in other ways, without departing from the subject matter of the invention.

LIST OF REFERENCE NUMBERS

2

drive unit

4

electric motor

6

inverter

8th

bridge branch

10

management

12

Semiconductor switches

14

positive pole

16

negative pole

18

Link capacitor

20

control unit

22

current sensor

24

control unit

26

method

28

first step

30

second step

32

third step

34

fourth step

36

coordinate system

38

fifth step

40

sixth step

42

limit

44

seventh step

46

eighth step

α

angle

I

electrical current

Current space vector

n

rotation speed

R ₁

stator

SLS

safe limited speed

STO

second safe function

T

temperature

Voltage space vector

U

motor voltage

U _Z

Intermediate circuit voltage

Flux space vector

Statorflussraumzeiger

Rotor flux space vector

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 10358359 B4 [0007]

Cited non-patent literature

• Drury et al., Adaptive Sensorless Position Estimation of a field-weakened permanent magnet machine at extended temperature range, 5th IET International Conference on Power Electronics, Machines and Drives, 2010 [0006]

Claims (10)

Drive unit (2) with a converter (6), and / or with an electric motor (4), and with a safety monitoring control unit (24), which is operated according to the method (26), in which - a flow-space pointer $\left(\overrightarrow{\Psi }\right)$

is determined with an angle (α), - a temporal change of the angle (α) is determined and used as a speed (n), and - wherein a safe function (SLS) with the speed (n) is performed as an input value. Drive unit (2) after Claim 1 , characterized in that the Flußraumzeiger $\left(\overrightarrow{\Psi }\right)$

is determined by means of an electric motor voltage (U). Drive unit (2) after Claim 2 , characterized in that the electrical motor voltage (U) is measured or determined by means of an intermediate circuit voltage (U _Z ), in particular by using a state of a semiconductor switch (12) of the inverter (6). Drive unit (2) according to one of Claims 1 to 3 , characterized in that for determining the flow space pointer $\left(\overrightarrow{\Psi }\right)$

a temperature-dependent stator resistance (R ₁ ) is used. Drive unit (2) after Claim 4 , characterized in that the temperature (T) of the stator is measured or calculated, for which in particular a power loss is determined. Drive unit (2) according to one of Claims 1 to 5 , characterized in that as Flussraumzeiger $\left(\overrightarrow{\Psi }\right)$

a stator flux pointer $\left(\overrightarrow{{\Psi }_1}\right)$

or a rotor flux space pointer $\left(\overrightarrow{{\Psi }_2}\right)$

is used. Drive unit (2) according to one of Claims 1 to 6 , characterized in that in the safe function (SLS), the rotational speed (n) is compared with a limit value (42), wherein in particular a second safe function (STO) is carried out as a function of the comparison. Drive unit (2) according to one of Claims 1 to 7 , characterized in that the electric motor (4) is free of a safe speed sensor. Drive unit (2) according to one of Claims 1 to 8th , characterized in that the electric motor (4) is a synchronous machine. Use of a speed (n) based on a temporal change of an angle (α) of a Flußraumzeiger $\left(\overrightarrow{\Psi }\right)$

is determined with an angle (α) and corresponds to this, as input value of a safe function (SLS) in a method (26) for safety monitoring of an electric motor (4) operated by means of an inverter (6).

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