阅读说明：本技术 具有诊断能力的软启动器、诊断方法和电机装置 (Soft starter with diagnostic capability, diagnostic method and motor device ) 是由 D.赫兹 J.塞茨 于 2018-05-02 设计创作，主要内容包括：本发明涉及一种软启动器(10),其具有多个导电的相(12,14,16),其中,在每个相(12,14,16)中布置有半导体开关元件(21,23,25)和与之并联连接的机电开关(22,24,26),其中,在软启动器(10)中,在半导体开关元件(21,23,25)和机电开关(22,24,26)的面向负载的侧(46)上,多个相(12,14,16)连接在形成星形中性点的电路(40)中,其特征在于,形成星形中性点的电路(40)包括至少一个无源部件(43),并且被构造为用于在半导体开关元件(21,23,25)和/或机电开关(22,24,26)的有缺陷的状态下采集降低的电压降(38)。(The invention relates to a soft starter (10) having a plurality of electrically conductive phases (12, 14, 16), wherein in each phase (12, 14, 16) a semiconductor switching element (21, 23, 25) and an electromechanical switch (22, 24, 26) connected in parallel therewith are arranged, wherein in the soft starter (10) a plurality of phases (12, 14, 16) are connected in a circuit (40) forming a star point on the load-facing side (46) of the semiconductor switching elements (21, 23, 25) and the electromechanical switches (22, 24, 26), characterized in that the circuit (40) forming the star point comprises at least one passive component (43), and is designed to detect a reduced voltage drop (38) in the event of a defective state of the semiconductor switching element (21, 23, 25) and/or of the electromechanical switch (22, 24, 26).)

1. A soft starter (10) having a plurality of electrically conductive phases (12, 14, 16), wherein in each phase (12, 14, 16) a semiconductor switching element (21, 23, 25) and an electromechanical switch (22, 24, 26) connected in parallel therewith are arranged,

it is characterized in that the preparation method is characterized in that,

in a soft starter (10), a plurality of phases (12, 14, 16) are connected in a circuit (40) forming a star point on a load-facing side (46) of the semiconductor switching elements (21, 23, 25) and the electromechanical switches (22, 24, 26), the circuit (40) forming the star point comprising at least one passive component (43) and being designed to detect a voltage drop (38) in the event of a defective state of the semiconductor switching elements (21, 23, 25) and/or of the electromechanical switches (22, 24, 26).

2. The soft-starter (10) of claim 1, wherein the at least one passive component (43) is configured to have a resistance (44) of 10k Ω to 500k Ω.

3. The soft starter (10) according to claim 1 or 2, wherein the at least one passive component (43) is configured as a capacitor (47), in particular a capacitor having a capacitance of 4nF to 400 nF.

4. The soft-starter (10) according to any of claims 1 to 3, wherein the soft-starter (10) is provided with a control unit (50) configured as an internal control unit (52) and/or as a superior control unit (56).

5. The softstarter (10) according to any of claims 1 to 4, wherein a voltage measuring device (36) is arranged in each phase (12, 14, 16) for collecting voltage drops (38) occurring over the semiconductor switching elements (21, 23, 25) and the associated electromechanical switches (22, 24, 26).

6. An electromechanical device (80) having a SIL rating of 1, said electromechanical device comprising an electric motor (60) connected to a soft starter (10) coupled to a power supply device (11), wherein said soft starter (10) is configured according to any one of claims 1 to 5.

7. An electrical machine arrangement (80) with SIL rating 3, comprising an electric motor (60) connected with a switching device (68), in particular a contactor (65), with a soft starter (10) fronting on the switching device, the soft starter being coupled with a power supply device (11), wherein the soft starter (10) is configured according to any one of claims 1 to 5.

8. A diagnostic method (100) for identifying defective semiconductor switching elements (21, 23, 25) and/or defective electromechanical switches (22, 24, 26) in a soft starter (10) having a plurality of conductive phases (12, 14, 16), comprising the steps of:

a) outputting a control command (55) for switching off the semiconductor switching elements (21, 23, 25) and the electromechanical switches (22, 24, 26),

b) collecting the reduced voltage drop (38) in one of the electrically conductive phases (12, 14, 16) which is connected to at least one further electrically conductive phase (12, 14, 16) by a circuit (40) forming a star point, which is arranged in the soft starter (10) on the load-facing side (46) of the semiconductor switching elements (21, 23, 25) and the electromechanical switches (22, 24, 26);

c) when it is detected in step b) that there is a reduced voltage drop (38), a defect in one of the semiconductor switching elements (21, 23, 25) or in one of the electromechanical switches (22, 24, 26) is identified.

9. The diagnostic method (100) as claimed in claim 8, wherein a warning (49) is output in the event of a defect being identified and/or an operation for closing the semiconductor switching elements (21, 23, 25) and/or the electromechanical switches (22, 24, 26) is inhibited by means of the control unit (50).

10. The diagnostic method (100) according to claim 8 or 9, for its application in an electric machine arrangement (80) according to claim 7, further comprising a further step to be carried out before step b):

a1) an operating command (55) for opening the contacts of a switching device (68) is output, by means of which the conductive phases (12, 14, 16) are switched.

11. A computer program product (70) for receiving measurement data (33) of a measurement device (21, 23, 25) which is connected to a semiconductor switching element (21, 23, 25) and/or an electromechanical switch (22, 24, 26) of a soft starter (10) and for outputting operating instructions (55) to the semiconductor switching element (21, 23, 25) and/or the electromechanical switch (22, 24, 26) of the soft starter (10), wherein the computer program product (70) is configured for carrying out the diagnostic method (100) according to any one of claims 8 to 10.

Technical Field

The present invention relates to a soft starter with diagnostic capabilities and a diagnostic method for identifying defective components in a soft starter. The invention also relates to a computer program product by means of which the diagnostic method according to the invention is implemented in a soft starter. The invention also relates to an electric machine arrangement based on a soft starter according to the invention, a diagnostic method according to the invention or a computer program product according to the invention.

Background

A three-phase power output stage in which thyristor pairs and parallel switching contacts are arranged in the respective phase is known from EP2017868a1(Phoenix Contact GmbH & co.kg), on 21 st 1/2009. A voltage detector is connected between the phases, the voltage detector having a plurality of resistances for each phase. A plurality of resistors form a voltage divider and cooperate with current detectors in the respective phases. The voltage divider and the current detector are used here for fault detection in the power output stage.

From US2122107(l.j. meller et al), 6/28/1938, a plurality of reactances are known, which are configured inductively, capacitively or as ohmic resistors. The reactances are connected to each other and to the relay coil at the ends. The relay coil is in turn connected at the opposite end to the star point of the electric motor.

DE102014223856a1 (siemens ag), 5.25.2016, describes a circuit arrangement for controlling a three-phase electric motor, having one or more fuses and soft starters, which are arranged in the respective phase between the associated grid connection and the electric motor; the soft starter is arranged between the motor and the fuse. In this case, a monitoring device for monitoring whether a circuit arrangement has a fault and one or more controllable switching elements are provided, wherein the respective switching element is connected between one phase and the other phase or the circuit conductor, wherein the monitoring device is switched into conduction in order to force triggering of the fuse in the event of detection of a fault in at least one of the switching elements.

Furthermore, motor arrangements are known which comprise a soft starter and at least one downstream contactor. Such an electromechanical device requires at least one contactor placed after the soft starter in order to ensure SIL level 1. A safety switching device is additionally required. For SIL class 3, at least two contactors and safety switching devices are again required in the known motor arrangement. Such a motor arrangement can be based, for example, on the combination of the safety switching device 3SK1 and the soft starter 3RW4 from siemens.

In automation technology, there is a need for a device for operating an electric motor, which provides a high level of safety and which at the same time is simple, compact and inexpensive. In particular, it is desirable to provide an electric machine arrangement with a higher or at least constant safety with reduced hardware and installation effort.

Disclosure of Invention

The technical problem underlying the present invention is to provide a soft starter that improves upon the known solutions in the described point.

The technical problem addressed is solved by a soft starter for automation technology, which can be connected to a power supply device via a plurality of phases on the side facing the power grid. The softstarter has a semiconductor switching element in each phase, and the electromechanical switch is arranged in parallel with the semiconductor switching element. The semiconductor switching elements and the electromechanical switches in the phases are configured to allow or prevent current flow through the respective phases by coordinated operation. On the load-facing side of the semiconductor switching elements and the electromechanical switches, the softstarter may be connected to an electrical application, for example an electric motor. According to the invention, in the soft starter, a circuit forming a star point is formed between the phases on the side of the semiconductor switching element and the electromechanical switch facing the load, said circuit having lines connected in the star point. Alternatively, the lines may be connected as a delta circuit. The circuit forming the star point has at least one passive component, which is arranged in each case in the line of the star point circuit. Passive components are understood to be, for example, resistors or capacitors. In the event of a defect in the semiconductor switching element or the electromechanical switch in the first phase, a reduced voltage drop occurs in the semiconductor switching element of the first phase due to the circuit forming the star point. The reduced voltage drop due to the circuit forming the star point can be detected by a voltage measuring device which is arranged in parallel with the semiconductor switching element in the first phase. In the case of a defect, the voltage drop is reduced relative to the voltage drop in the defect-free state. The voltage measuring device in the first phase detects the voltage drop across the semiconductor switching element. From this voltage drop it can be identified that the semiconductor switching element and/or the electromechanical switch in the first phase in the softstarter is defective. The circuit forming the star point ensures a diagnostic function for defective semiconductor switching elements and/or defective electromechanical switches.

The diagnostic function thus achieved is based on a minimum number of components with the circuit forming the star point (which preferably has only passive components) and suitable voltage measuring means, and can thus be produced compactly and inexpensively. The diagnostic function can also be implemented when a connected electrical load, for example an electric motor, is disconnected. The circuit forming the star-shaped neutral point on the load-facing sides of the semiconductor switching elements and the electromechanical switches of the softstarter provides a high level of reliability and offers the softstarter the possibility of quickly identifying defects of its own. Thus, with the soft starter according to the invention it is already possible to achieve a SIL level 1 without additional components, such as contactors. In the case of the use of the soft starter according to the invention, the contactor can be dispensed with in the case of an electric motor arrangement without the safety of the entire electric motor arrangement being impaired.

In a preferred embodiment, at least one passive component in the star-shaped neutral circuit is configured to have a resistance of 10k Ω to 500k Ω. A resistance in this range of values limits the power loss in the circuit forming the star point to an acceptable level. At the same time, a resistance in this value range allows a sufficiently high voltage drop across the semiconductor switching element for reliable detection.

It is further preferred that in each phase, in particular in three phases, a resistor is arranged in each line of the circuit forming the star point. The resistors in the lines of the star point circuit particularly preferably have resistance values that are equally large. This ensures an even distribution of the voltage over the normally functioning semiconductor switching elements when defective semiconductor switching elements and/or defective electromechanical switches are identified. Furthermore, the resistors having the same resistance value in each phase ensure a stable continuous operation of the soft starter according to the invention and a uniform distribution of the generated power losses.

Furthermore, in the soft starter according to the present invention, the voltage measuring device may be connected to the control unit. The measurement data can be transmitted to the control unit via this connection. The control unit is designed to send operating commands to the semiconductor switching elements and/or the electromechanical switches, thus opening or closing the semiconductor switching elements and/or the electromechanical switches. Furthermore, the control unit has a memory and an operator, adapted to store and implement a computer program product with which the operation of the soft starter according to the invention can be implemented. By means of the control unit it can be checked that: whether the detected reduced voltage drop in the star point circuit is below an adjustable threshold value, a defect of the semiconductor switching element and/or the electromechanical switch can be verified. After the detection of such a defect, the control unit likewise allows corresponding measures to be actively undertaken, for example suppression of operating commands which preset the closing of the functionally normal semiconductor switching elements and/or electromechanical switches.

The control unit of the soft starter is preferably configured as an internal control unit, which is arranged within the soft starter, for example in the form of a microcontroller. Alternatively, the control unit can also be designed as a superordinate control unit. This may also be a safety switching device, a parameterization device, a programmable logic controller (SPS for short) or a cloud. Further alternatively, the functions of the control unit can also be divided into internal and higher-level control units, which cooperate for operating the soft starter according to the invention.

Further preferably, the softstarter according to the present invention may have a voltage measuring device in each phase. The voltage measuring devices are each arranged in at least one phase, so that the voltage drop across the respective semiconductor switching element and the associated electromechanical switch can be detected. In the case of a defective semiconductor switching element and/or a defective electromechanical switch, there is a reduced voltage drop across it as a result of the circuit forming the star point compared to a normally functioning blocked semiconductor switching element and the associated parallel-connected open electromechanical switch. In this way, even when the load-side terminal is open or a downstream switching device, for example a contactor, is open, the identification of a defective semiconductor switching element and/or a defective electromechanical switch can be achieved. This ensures differentiated verification of defects that have occurred and a higher SIL level is reached.

The technical problem posed is also solved by the electric machine arrangement according to the invention. The electric machine arrangement has a SIL rating of 1 and thus meets application specific safety requirements. The motor device comprises a motor, and the motor is directly connected with the soft starter. The soft starter is in turn connected to a power supply having a plurality of phases. The soft starter is here constructed according to one of the embodiments described above. The motor arrangement according to the invention has no additional contactors and provides a high level of safety. In particular to a safety integrity level of 1, abbreviated SIL 1. The motor arrangement according to the invention thus offers a correspondingly high level of safety with reduced component outlay compared to known solutions. The motor arrangement can thus be produced quickly, simply and inexpensively.

Also, the technical problem to be solved is solved by a further electric machine arrangement according to the present invention. The electric machine arrangement has a SIL rating of 3 and is therefore suitable for safety critical applications. The motor arrangement comprises an electric motor which is supplied with power via a plurality of phases. The motor device is therefore also coupled to the respective polyphase supply device. The contactor is arranged in front of the motor, and the soft starter is arranged in front of the contactor. The soft starter is connected with a multiphase power supply device. The electrical energy required for the operation of the electric motor therefore passes from the polyphase supply device through the softstarter and the contactors downstream of the softstarter to the electric motor. According to the invention, the soft starter is constructed according to one of the above-described embodiments. The motor arrangement according to the invention thus provides a SIL rating of 3 with only one contactor. This represents a reduction in hardware costs with respect to the known solution with two contactors. The motor arrangement according to the invention achieves a safety integrity level (SIL for short) 3 overall with a smaller number of components. The motor arrangement according to the invention can thus be produced quickly, simply and inexpensively.

The technical problem described is also solved by the diagnostic method according to the invention. The claimed diagnostic method is designed for a soft starter, which is connected to the power supply and the electric motor via a plurality of phases. In the soft starter, a semiconductor switching element and an electromechanical switch connected in parallel are mounted in each phase. The diagnostic method according to the invention serves to identify defective semiconductor switching elements and/or defective electromechanical switches. For this purpose, in a first step, an operating command is output by the control unit, by means of which the opening of the semiconductor switching element and the electromechanical switch is preset. Thus, in the normal, i.e. defect free, state of the soft starter, the current flow in all phases is interrupted. In a further step, the voltage drop across the semiconductor switching element and/or the electromechanical switch is detected. Here also collected are: whether the voltage drop is reduced relative to a defect-free state. This is achieved by means of voltage measuring devices, which are connected to the respective phases. In this case, a defective semiconductor switching element and/or a defective electromechanical switch can be identified in the respective phase when the reduced voltage detected by the voltage measuring device falls below an adjustable threshold value. The adjustable threshold value is stored, for example, in a control unit, by means of which the diagnostic method according to the invention is carried out. The threshold value may be fixedly preset, adjusted by the user of the soft starter and/or a superior control unit. In the case of a defective semiconductor switching element and/or a defective electromechanical switch, the voltage which can be detected there with the voltage measuring device is significantly reduced, wherein the adjustable threshold value is a measure of the sensitivity with which this reduction is detected relative to the normal state.

The diagnostic method according to the invention provides a possibility for verifying exactly in which phase a defective component can be found.

The diagnostic method according to the invention is supported by hardware that can be simply manufactured, is stable and can be manufactured inexpensively, with the circuit forming the star point. Furthermore, the diagnostic method requires only a minimum of measurement data and can be implemented in a simple manner, for example in the form of a computer program product. The diagnostic method according to the invention requires only a low level of computational power and can also be implemented quickly on a control unit with a low level of computational effort. The rapid implementation of the diagnostic method enables: corresponding measures are taken quickly if necessary and thus further damage to the softstarter or the connected motor is avoided. The diagnostic method ensures that the soft starter itself has a SIL rating of 1. The motor arrangement with higher safety requirements can therefore be realized with less outlay on additional components.

In a further preferred embodiment of the invention, a warning is output in the diagnostic method when a defective semiconductor switching element and/or a defective electromechanical switch is identified. Alternatively or additionally, when a defective component is identified, corresponding measures can also be implemented by means of a control unit which is designed to transmit operating commands to the semiconductor switching element and the electromechanical switch. In this case, the control unit inhibits the operation of each of the semiconductor switching elements and/or the electromechanical switches for closing by means of suitable programming. This is done, for example, in such a way that the control unit suppresses corresponding operating commands, which are sent by the superordinate control unit or are caused by user inputs, for example. Thereby preventing further damage to the softstarter and/or the connected application, e.g. the motor. Additionally preventing the risk of harm to personnel. Thus further increasing the level of security achievable.

In a further preferred embodiment of the invention, the diagnostic method is used for applying in an electrical machine device: the motor arrangement comprises a polyphase electric motor forming a load, which is supplied with power by a polyphase power supply via a plurality of phases. A switching device, such as a contactor, is preceded by the motor and a soft starter is in turn preceded by the switching device. The soft starter is connected with a multiphase power supply device. The electrical energy required for the operation of the electric motor therefore passes from the polyphase supply device via the softstarter and the switching device downstream of the softstarter to the electric motor. In the soft starter, a semiconductor switching element and an electromechanical switch connected in parallel are mounted in each phase. In the soft starter, on the side of the semiconductor switching element and the electromechanical switch facing the load, the connections are made in a circuit forming a star point, wherein the circuit forming the star point comprises at least one passive component. In this case, the circuit forming the star point is used to detect the voltage drop by means of a diagnostic method in the event of a defective state of the semiconductor switching element and/or of the electromechanical switch. For this purpose, in a first step, an operating command is output by the control unit, by means of which the opening of the semiconductor switching element and the electromechanical switch is preset. Thus, the current flow in all phases is interrupted in the normal, defect-free state of the soft starter. In a further step, an operating command is output by the control unit, the disconnection of the contacts of the switching device is preset by the operating command, and the switching device is used to switch the conductive phases on and off. The switching device is thus brought into a state with open contacts in the phase conductors. In a further step, the voltage drop across the semiconductor switching element and/or the electromechanical switch of the soft starter is detected. It is also detected whether the voltage drop is reduced compared to a defect-free state. This is achieved by means of voltage measuring devices, which are connected to the respective phases. In this case, a defective semiconductor switching element and/or a defective electromechanical switch can be identified in the respective phase when the reduced voltage detected by the voltage measuring device falls below an adjustable threshold value. The adjustable threshold value is stored, for example, in a control unit, by means of which the diagnostic method is carried out. The threshold value may be fixedly preset, adjusted by the user of the soft starter and/or a superior control unit. In the case of a defective semiconductor switching element and/or a defective electromechanical switch, the voltage which can be detected there with the voltage measuring device is significantly reduced, wherein the adjustable threshold value is a measure of the sensitivity with which this reduction is detected relative to the normal state.

The soft starter has a lower impedance than the rear-mounted switching device. Now, if the voltage drop over the semiconductor switching elements and/or the electromechanical switches of the soft starter is picked up without the circuit of the soft starter forming the star point, an undefined voltage value is obtained due to parasitic resistances etc. This undefined voltage value cannot be used to safely diagnose the soft starter. Thus, a diagnostic function for a defective semiconductor switching element and/or a defective electromechanical switch of the soft starter is ensured by the circuit forming the star-neutral. The diagnostic method is designed for a soft starter, which is connected to the power supply via a plurality of phases and to the electric motor via a switching device.

The technical problem to be solved is also solved by a computer program product according to the present invention. The computer program product is designed to receive measurement data generated and transmitted by the voltage measuring device. The voltage measuring device is connected to the semiconductor switching element and/or the electromechanical switch and is designed to detect a voltage drop across the semiconductor switching element and/or the electromechanical switch. The softstarter is here connected to a plurality of phases and has in each phase a semiconductor switching element and an electromechanical switch connected in parallel. The computer program product is also designed for transmitting operating instructions to the semiconductor switching element and/or the electromechanical switch. According to the invention, the input measurement data are processed by a computer program product and are introduced into the implementation of the diagnostic method. The diagnostic method carried out in this way is configured in accordance with at least one of the above-described embodiments of the diagnostic method.

The computer program product is designed for implementation in a control unit of a soft starter according to at least one of the embodiments described above. The computer program product may be embodied in its entirety, i.e. continuously, in an internal control unit of the soft starter, for example in a microcontroller or in a superordinate control unit. Alternatively, the computer program product can also be divided functionally and the individual steps or functions of the implemented diagnostic method can be assigned to the internal control unit and the superordinate control unit. The computer program product according to the invention may be constructed as software or firmware. Alternatively or additionally, the computer program product according to the invention can also be implemented in hardware, for example in an Application-Specific Integrated Circuit (ASIC for short), in a fixed-wired manner.

The computer program product according to the invention enables a simple adjustability of the diagnostic method to be carried out (HMI ═ Human Machine Interface) by means of a customary Human-Machine Interface (abbreviated HMI) installed thereon in a correspondingly designed soft starter and/or in a superordinate control unit. This also includes additional parameters which characterize the interaction of the method according to the invention with other functions of the automation system. This may be, for example, the selection of an alert to be output after the corresponding action has been taken. The implementation of the diagnostic method with the aid of a computer program product also makes it possible to retrofit existing automation systems.

Drawings

The invention is described subsequently in terms of various embodiments. The features of the individual embodiments can be combined with one another here. In the drawings:

fig. 1 shows an embodiment of a soft starter according to the present invention;

FIG. 2 shows a flow chart of an embodiment of a diagnostic method according to the invention;

fig. 3 shows an embodiment of the motor arrangement according to the invention;

fig. 4 shows an embodiment of a further motor arrangement according to the invention.

Detailed Description

Fig. 1 schematically shows an embodiment of a softstarter 10 according to the present invention. The softstarter 10 is connected to a power supply 11 and has three phases 12, 14, 16. Each phase 12, 14, 16 has a connection terminal 13, 15, 17 on the end facing the load. The term load-oriented herein relates to the respective side of the softstarter 10 to which an application not shown in detail, in particular the electric motor 60, may be connected, whereas the opposite side of the load-oriented, i.e. the grid-oriented side relates to the side of the softstarter 10 to which the power supply 11 is connected. The position of the side facing the load is shown by arrow 46 and the position of the side facing the grid is shown by arrow 45 in fig. 1.

In each phase 12, 14, 16, a semiconductor switching element 21, 23, 25 is arranged, which is designed to interrupt or enable a current flow through the respective phase 12, 14, 16 in each case in cooperation with an electromechanical switch 22, 24, 26. The semiconductor switching elements 21, 23, 25 and the electromechanical switches 22, 24, 26 are controlled by a control unit 50, which is designed to transmit operating commands 55 to the semiconductor switching elements 21, 23, 25 and the electromechanical switches 22, 24, 26. The control unit 50 is configured as an internal control unit 52 structurally integrated into the softstarter 10. The internal control unit 52 is designed as a microcontroller, which is designed to store and implement a computer program product 70.

On the load-facing side of the semiconductor switching elements 21, 23, 25 and the electromechanical switches 22, 24, 26, a circuit 40 is arranged which forms a star point and which connects the phases 12, 14, 16 in an artificial star point 42. In each line 41, passive components 43 are arranged, which are each designed as a resistor 44. The semiconductor switching element 21 and the electromechanical switch 22 in the first phase 12 are associated with a voltage measuring device 36 which is adapted to pick up a voltage drop 38 over the semiconductor switching element 21 and the electromechanical switch 22. For this purpose, the voltage measuring device 36 is connected to a control unit 50. The voltage measuring device 36 generates measurement data 33 via its measurement channel 32, which are further transmitted to the control unit 50. The measurement data 33 are used as input for a computer program product 70, which is implemented in the control unit 50. In case of a defect in the semiconductor switching element 21 and/or the electronic switch 22 in the first phase 12, which may be caused, for example, by a short circuit or contact soldering, a reduced voltage drop 38 is formed across the semiconductor switching element 21 and the electromechanical switch 22 in the first phase 12.

In case of a defect in the semiconductor switching element 21 and/or the electromechanical switch 22 in the first phase 12, the voltage drop 38 over the semiconductor switching element 21 and/or the electromechanical switch 22 in the first phase 12 is significantly reduced. In this case, when the threshold value 53, not shown in detail, stored in the control unit 50 is undershot, this is verified as the presence of the previously identified defect in the first phase 12. Thus, in a soft starter with a voltage measuring device 36 in each of the plurality of phases 12, 14, 16, it can be verified in which phase 12, 14, 16 a defective semiconductor switching element 21 and/or a defective electromechanical switch 22 is present. Furthermore, when a defect is identified by means of the computer program product 70 in the control unit 50, a corresponding measure can be taken. The countermeasures relate inter alia to the suppression of operating commands 55, which preset the closure of the semiconductor switching elements 21, 23, 25 and/or the electromechanical switches 22, 24, 26.

Fig. 2 schematically shows a flow chart of an embodiment of a diagnostic method 100 according to the present invention for identifying defective semiconductor switching elements 21, 23, 25 and/or electromechanical switches 22, 24, 26 in a soft starter 10, which is not shown in detail. The diagnostic method 100 comprises a first method step 110, in which an operating command 55 for switching off the semiconductor switching elements 21, 23, 25 and the electromechanical switches 22, 24, 26 is output by the control unit 50. Thereby, the current flow is interrupted in the phase with the normally functioning semiconductor switching elements 21, 23, 25 and the normally functioning electromechanical switches 22, 24, 26.

In a second method step 120, the voltage drop 38 across the semiconductor switching element 21 and the electromechanical switch 22 in the first phase 12 is detected. The circuit 40 forming the star point is here mounted on the load-facing side of the semiconductor switching elements 21, 23, 25 and the electromechanical switches 22, 24, 26. In case a defective semiconductor switching element 21, 23, 25 and/or a defective electromechanical switch 22, 24, 26 is present in the first phase 12, a current connection 35 is present in this first phase. The current connection 35 leads here via a circuit 40 forming a star point to a voltage drop 38 across the semiconductor switching element 21 and the electromechanical switch 22 in the first phase 12. Depending on the result of collecting the voltage drop 38, the flow of the diagnostic method 100 branches. This is illustrated in fig. 2 by the bifurcation 125. When the voltage drop 38 is detected in the second method step 120, it is recognized from this that the semiconductor switching element 21 and the electromechanical switch 22 in the first phase 12 are functioning properly. This represents the end state 200 of the diagnostic method 100. When no voltage drop 38 is detected, the third method step 130 is followed. In a third method step 130, an alarm is output and the user or the superordinate control unit is informed of this. In particular, in a third step 130, a countermeasure is taken which prevents the soft starter 10 from being switched on again.

Fig. 3 schematically shows the structure of an embodiment of the motor arrangement 80 according to the invention, which is connected to the multiphase power supply 11. The motor arrangement 80 comprises an electric motor 60 which is supplied with power via the first, second and third phases 12, 14, 16. A softstarter 10 is connected between the power supply 11 and the motor 60, the softstarter having connection terminals 13, 15, 17 to which the motor 60 is connected. The softstarter 10 has a circuit 40, not shown in detail, forming a star-neutral point, as shown for example in fig. 1. The softstarter 10 has a control unit 50, which is configured as an internal control unit 52. The control unit 50 has a memory and an operator and is configured to store a computer program product 70. The computer program product 70 is implemented by the control unit 50 and ensures that the diagnostic function is implemented for the softstarter 10 in accordance with the diagnostic method 100 according to the present invention. The softstarter 10 is furthermore configured with a run switch 64 for operatively operating the motor 60. The operating switch 64 is coupled to the control unit 50 for this purpose. Also, the safety-oriented switch 66 is connected to the soft starter 10, and the motor 60 can be quickly and reliably brought into a safe state by the soft starter. For this purpose, the safety-oriented switch 66 is designed as an emergency stop. The motor arrangement 80 according to fig. 3 has a SIL level 1 by means of a diagnostic function in the soft starter 10. No additional contactors need be installed. Thus, a better safety level is achieved with the motor arrangement 80 according to fig. 3 with a reduced hardware expenditure.

Fig. 4 schematically shows the structure of an embodiment of a further motor device 80, which further motor device 80 is connected to the polyphase supply device 11. The motor arrangement 80 also comprises an electric motor 60. The motor 60 is powered by the three phases 12, 14, 16. As shown for example in fig. 1, the soft starter 10 is connected to a power supply 11. A switching device 68 configured as a contactor 65 is in turn placed after the softstarter 10. The softstarter 10 is connected to a run switch 64 by which the motor 60 is adapted to be operatively operated. Furthermore, the softstarter 10 is coupled with a safety switching device 67, which is coupled not only with the softstarter 10, but also with a switching device 68, respectively, via a communication connection 63. The safety switching device 68 is configured for acquiring the state of the softstarter 10 by communication with the control unit 50 of the softstarter 10 and sending instructions to the control unit 50 of the softstarter 10 in the sense of the upper level control unit 56. The safety switching device 68 is likewise coupled to the switching device 68, so that the state of the switching device 68 can be detected. For this purpose, the contactor 65 has signal contacts which are not shown in detail. The safety switching device 67 is also configured to send instructions to the switching device 68. Furthermore, a safety switch device 68 is connected to the safety-oriented switch 66, which safety-oriented switch 66 is designed as an emergency stop. The safety state of the electric motor 60 is quickly brought about by the safety-oriented switch 66 when required, for example in an emergency.

The soft starter 10 has an electrical circuit 40 forming a star point, by means of which, in conjunction with a control unit 50 designed as an internal control unit 52, a diagnostic method 100 can be carried out, with which defective components, in particular defective semiconductor switching elements 21, 23, 25 and defective electromechanical switches 22, 24, 26, in the soft starter 10 can be automatically verified as shown in fig. 1. This is achieved by means of the diagnostic method 100, which is implemented by means of a computer program product 70, which is stored in the control unit 40 in an implementable manner.

By the combination of the soft starter 10 according to the invention and the switching device 68, i.e. the contactor 65, a SIL rating of 3 is achieved in the motor arrangement 80 according to fig. 4. The softstarter 10 and the switching device 68 are here diversified with respect to each other. The motor arrangement 80 as a whole reaches a Safety Integrity Level (SIL) 3. In contrast to this, the solutions known from the prior art require at least two switching devices, in particular contactors. The motor arrangement according to the invention thus offers a high level of safety with a lower hardware expenditure. The structure of the motor arrangement according to the invention is thereby simplified, accelerated and designed more cost-effectively.