Method for operating a motor starter

Abstract

The invention relates to a method for operating a motor starter (50) which has a load current path (9) for conducting a load current, said method having the following steps: - receiving an input signal (101) at an interface (3) of the motor starter (50); - evaluating the received input signal (101) for the presence of an STO signal; - if an STO signal is present, causing an interruption in the load current path (9) on at least two independent command paths (P1, P2), as a result of which - on a first command path (P1) an interruption in the load current path (9) is triggered at a first point in time (t1) which has a defined relation to a current zero crossing of the load current in the load current path (9), and - on a second command path (P2) an interruption in the load current path (9) is triggered at a second point in time (t2) which is at a predefined period of time (Δt) after a detection point in time (t0) at which the presence of the STO signal was detected, wherein the predefined period of time (Δt) is selected such that it is longer than the period of time between the detection point in time (t0) and the first point in time (t1).

Description

[0001] 202408802

[0002] 1

[0003] Description

[0004] Method for operating a motor starter

[0005] Technical field

[0006] The present invention relates to a method for operating a motor starter and to a motor starter.

[0007] Technical background

[0008] In a well-known motor starter, the Siemens AG ET200SP motor starter, a STO command (STO = Safe Torque Off) is sent as a DC voltage signal to a safe digital input (STO+ (24 V), STO- (GND)) ("safety function STO hardwired"). When a logic zero (= STO) is present, the ET200SP motor starter cuts off the power supply to a downstream electric motor, preventing it from generating torque or force. Conversely, a logic one (= no STO) actively enables the power supply to the electric motor. See section "6.8.2 Behavior during safety-related shutdown" on page 90 of the device manual "SIMATIC / ET 200SP / Motor starter ET 200SP (3RK1308-...)", edition 10 / 2021, publication no.

[0009] A5E34821005001A / RS-AD / 004, Publisher Siemens AG, Smart Infrastructure, Electrical Products, PO Box 10 09 53, 90009 Regensburg, Germany.

[0010] The STO (Safety Tolerance Off) function of the ET200SP motor starter complies with Safety Integrity Level (SIL3). SIL3 requires redundancy in the evaluation and transmission of the STO signal to the switching elements. This redundancy results in a hardware fault tolerance of 1, meaning that the minimum number of faults that can lead to a loss of the safety function is equal to 1 + 1 (= 2). The requirement to achieve a hardware fault tolerance of 1 for SIL3 is derived from section 7.4 "Design and Development of the E / E / PE System" and the associated Table 3, page 27 of the standard DIN EN 61508-2 (VDE 0803-2):2011-02. The alternative shown in the table, achieving SIL3 with a hardware fault tolerance of 0 but a safe failure rate of 99 percent or greater, is not feasible in practice.The reason for this is that the proportion of dangerous failures will be higher than 1% due to the complexity of the circuitry required for the safety function under consideration here.

[0011] Summary of invention 202408802

[0012] 2

[0013] The object of the present invention is to improve the STO safety function in engine starters.

[0014] This problem is solved according to the invention by a method with the features specified in claim 1. This method is for operating a motor starter. The motor starter has a load current path for conducting a load current. The method includes receiving an input signal at an interface of the motor starter. The method includes evaluating the received input signal for the presence of an STO signal. If the presence of an STO signal is detected, the method includes initiating an interruption of the load current path on at least two independent command paths. On a first command path, an interruption of the load current path is triggered at a first time point that is in a defined relationship to a zero crossing of the load current in the load current path.And on a second command path, an interruption of the load current path is triggered at a second time point, which is a predetermined time interval after a detection time point at which the presence of the STO signal was detected, wherein said predetermined time interval is chosen to be longer than the time interval between the detection time and the first time point.

[0015] This problem is further solved according to the invention by a motor starter with the features specified in claim 5. The motor starter has a load current path running through it for conducting a load current. The motor starter has a switching device for interrupting the load current path. The switching device is configured to interrupt the load current path running through the motor starter upon detection of an STO signal. The motor starter has an interface for receiving an input signal. The motor starter has a detection circuit for detecting zero crossings of the load current in the load current path. The motor starter has two independent command paths, namely a first and a second command path.The motor starter has an evaluation circuit configured to assess a control command received at the interface for the presence of an STO signal and, if an STO signal is detected, to send an interrupt command on each of the two command paths. The first command path has a first trigger unit configured to initiate an interruption of the load current path at a first time defined relative to a zero crossing of the load current in the load current path, in response to a received interrupt command. The second command path has a second trigger unit configured to initiate an interruption of the load current path at a second time, in response to a received interrupt command.

[0016] 3. To trigger; the second time point is a predetermined time interval after a detection time point at which the evaluation circuit has detected the presence of the STO signal. This predetermined time interval is chosen to be longer than the time interval between the detection time and the first time point.

[0017] The invention relates to an architecture within a motor starter for motors, preferably with a fixed speed. The motor starter according to the invention implements the safety function "Safe Torque Off" (safe disconnection of the torque-generating energy supply to the motor, preventing automatic restart). When STO is requested, the motor starter attempts to disconnect the motor from the voltage source at a first point in time, preferably at the zero crossing of the load current, in order to protect the switching components. The first point in time, which is in a defined relation to a zero crossing of the load current in the load current path, can, for example, be the point in time of the zero crossing of the current or, for example, a point in time that is a few milliseconds, e.g., 1 ms or 2 ms, before the point in time of the zero crossing of the current.

[0018] If the load current path is not interrupted at the initial time due to a fault, at least one redundant shutdown path, acting as a fallback level, ensures that the motor is disconnected from the voltage source with a time delay relative to the initial time. This fallback level achieves a hardware fault tolerance of 1, which is sufficient to achieve a SIL level of SIL3.

[0019] The STO command arrives at the motor starter from an external source via at least one interface configured to receive an input signal. This interface can be a voltage input, such as a 24 V FDI terminal, where an STO command is signaled by a change in voltage level, or a bus communication interface, where an STO command is sent as part of a data packet secured with a failsafe communication protocol (FDI = Failsafe Digital Input). A data packet received or sent via the data bus can also be referred to as a "telegram" in the following.

[0020] The STO safety function is not designed to protect the motor starter itself. The STO safety function protects people from hazards emanating from a drive or machine powered by a motor that is operated by the motor starter. 202408802

[0021] 4

[0022] The present invention can be used, among other things, to protect persons from the hazards emanating from a drive by means of a motor starter, i.e., a device for switching and controlling three-phase motors, and the STO (Safe To Go) safety function. For example, STO can be triggered when a light barrier detects that a person has entered a danger zone near a drive or a driven machine. The combination of all elements in the safety chain, such as sensors (e.g., light barrier) or evaluation units (e.g., PLC), must, as a whole, meet the requirements for SIL3 (Safety Integrity Level 3) so that the safety function as a whole achieves SIL3 (PLC = Programmable Logic Controller).

[0023] Embodiments of the invention

[0024] Advantageous embodiments and further developments of the invention are specified in the dependent claims. The method according to the invention can also be further developed according to the dependent apparatus claims, and vice versa.

[0025] According to a preferred embodiment of the invention, the first time point coincides with the first zero crossing of the load current in the load current path after the interruption of the load current path has been initiated. An advantage of this is that the interruption of the load current path is carried out as quickly as possible, while simultaneously protecting the switching device used to interrupt the load current path.

[0026] According to a preferred embodiment of the invention, the predetermined time interval is at least one period of the load current. The second time interval must always be later than the first; that is, the predetermined time interval must be longer than the time interval between the detection time of the STO signal and the first time interval. With a sinusoidal load current of a three-phase AC motor, it is ensured after one period of the load current that the zero crossing of the current has already passed in all three phases. An advantage of this is that the interruption of the

[0027] The load current path, except in a case where there was a fault when the load current path was interrupted at the first time, is already de-energized at the second time, which protects the switching components.

[0028] According to a preferred embodiment of the invention, the switching device includes a semiconductor switch for interrupting the load current path; that is, the interruption of the load current path is effected by means of a semiconductor switch. Switching with semiconductor switches instead of electromechanical switching elements has several advantages. One advantage is that the 202408802

[0029] 5

[0030] Losses caused by switching operations are reduced. A further advantage is that switching processes are faster, wear-free, and can occur at any defined time, which is an important prerequisite for zero-crossing current shutdown. In each phase of the load current path, there is at least one semiconductor switch, such as a transistor (MOSFET, IGBT, etc.), which can interrupt the phase and thus disconnect a motor from the mains voltage. The switching device can include additional switches (semiconductor switches such as transistors and / or electromechanical switches such as relays) in series with the aforementioned semiconductor switch. The motor starter, for example, can have a power section with a switching device containing at least one switch per phase conductor.

[0031] According to a preferred embodiment of the invention, the evaluation circuit is part of a technology controller. A technology controller of a motor starter is a controller configured to manage the switching functions of the motor starter. Thus, a technology controller already present in the motor starter is used for evaluating the STO command. An advantage of this is that the existing resources of a motor starter are utilized more efficiently and unnecessary costs are avoided.

[0032] Preferably, the technology controller cyclically evaluates an input signal for the presence of a STO signal and forwards any STO signal present on two channels. Firstly, the technology controller controls the cell controller(s) in the relevant phase(s), e.g., via a data packet on a bus line, to trigger an interruption of the load current path at a first time point that is related to a defined zero crossing of the load current in the load current path. The switching device is controlled by the cell controller such that a semiconductor switch in the load current path is switched first, and only then, with a delay, is a serial electromechanical switch in the load current path switched to block current.Secondly, the technology controller sends a digital signal to a hardware circuit, which it uses to control the hardware circuit so that it triggers an interruption of the load current path at a second time, which is a predetermined time interval after the time of detection of the STO signal and always after the first time; in this way, the load current path is interrupted at the second time if the interruption of the load current path at the first time did not occur due to a fault.

[0033] According to a preferred embodiment, the first command path includes a cell controller configured to trigger an interruption of the load current path at a first time point in a defined relationship to a zero crossing of the load current in 202408802

[0034] 6

[0035] The load current path is defined. A cell controller is a controller assigned to exactly one phase of the load current path and configured to communicate and coordinate with a hierarchically superior technology controller of the motor starter. This control is based on the content of a command, such as a cyclic bus telegram (e.g., SPI bus), which the cell controller receives from the technology controller of the motor starter. This command is used to control the switches of the switching device (SPI = Serial Peripheral Interface). The cell controller is preferably capable of detecting a zero crossing of the current in its assigned phase.

[0036] According to a preferred embodiment, the second command path includes a hardware circuit configured to trigger an interruption of the load current path at a second time interval a predetermined time after the first. An advantage of this is that a hardware circuit costs less than a controller and is, under certain circumstances, less prone to failure. Furthermore, one measure to achieve a level of safety can be the use of diverse technologies to achieve the same result. Diversity would be achieved in this case if the first command path uses a controller and the second command path uses a hardware circuit.

[0037] According to a preferred embodiment of the invention, the motor starter includes a delay circuit configured to provide the aforementioned time interval for delaying the trigger command of the second command path. Preferably, this delay circuit is implemented as a delay element of the aforementioned hardware circuitry of the second command path. An advantage of this is that a delay element can be implemented very simply and cost-effectively as a hardware circuit, and diversity is achieved by using only hardware circuitry, rather than a controller, in the second command path. The use of diverse technologies to achieve the same result can be a measure to achieve a certain level of safety.

[0038] According to a preferred embodiment of the invention, the interface is a voltage input for tapping a voltage and / or a bus interface for receiving and sending data packets via a bus. The motor starter can have a voltage input to which a voltage can be applied, whereby by selecting a defined voltage level, the so-called "voltage level," the motor starter can be signaled whether an STO signal is present (e.g., voltage level approximately 0 V) ​​or not (e.g., voltage level 24 V). Alternatively or additionally, the motor starter can have a bus interface to which a data bus, hereinafter also simply referred to as "bus," can be connected.

[0039] The bus interface, labeled 7, can be connected. It is used to receive and send data packets via the data bus.

[0040] The motor starter can have suitable interfaces, i.e., receiving devices, with which it can receive both an STO signal signaled by a voltage level and an STO signal transmitted via a data bus. The signal that triggers STO can therefore be transmitted to the motor starter either via a voltage level at an input terminal, or as part of a data packet (e.g., a telegram) preferably received cyclically via a bus and secured using a safe bus protocol (e.g., PROFIsafe), or via both methods. The motor starter is capable of receiving an STO signal both as a voltage signal and in a data packet. For STO via the safe input terminal and for STO via bus communication secured using a safe bus protocol (e.g., PROFIsafe), there can be redundant paths for evaluating and executing the STO command.

[0041] According to a preferred embodiment of the invention, the motor starter has two or more redundant evaluation paths, each configured to evaluate whether a voltage applied to the voltage input signals an STO signal or whether a data packet received at the bus interface contains an STO signal. These additional evaluation paths can be implemented using controllers, e.g., a communication controller of the motor starter, and / or using hardware circuits. It is possible for the motor starter to have, in addition to the evaluation circuit, at least one further evaluation circuit configured to evaluate a control command received at the interface for the presence of an STO signal and, if an STO signal is present, to send an interrupt command on the second command path of the motor starter at this further evaluation circuit.One advantage of this is that a failsafe level is achieved: thus, if detection of an incoming STO signal is not possible in a first evaluation path, the incoming STO signal can be detected in a second or further evaluation path.

[0042] According to a preferred embodiment of the invention, the load current path has one or more phases, each comprising a first triggering unit and an OR gate in which the command paths converge. The OR gate can be a logic gate or an electronic circuit that performs the function of a logic gate. An advantage of the OR logic is that the load current path is interrupted even if only one of the evaluation paths correctly detects an STO signal and correctly transmits an interrupt command on one of the command paths. This redundancy provides hardware fault tolerance.

[0043] 8 out of 1 achieved, which is sufficient to achieve a SIL level of SIL3 for the safety function STO.

[0044] According to a preferred embodiment of the invention, the detection circuit for detecting zero-crossing currents of the load current in the load current path is integrated into the first tripping unit. An advantage of this is that the available resources of a motor starter are utilized more efficiently, and unnecessary costs and space requirements are avoided. Furthermore, the threshold for detecting the zero-crossing currents can be parameterized or calibrated.

[0045] According to a preferred embodiment of the invention, the motor starter is configured to control a fixed-speed motor. To control a variable-speed motor, a frequency converter can be used instead of a motor starter; in this case, an STO signal is sent to the frequency converter.

[0046] According to a preferred embodiment of the invention, the interface is a voltage input configured as a safe digital input. This means that the voltage input is certified according to a functional safety standard and meets the requirements stipulated in that standard. One such requirement might be that the probability of a stuck-at-1 fault occurring at the evaluation units due to a defect in an electronic component must be below a certain value. Achieving this requires specific measures in the design of the electronics, such as a redundant circuit design or a cyclic dark test. In a dark test, a controller applies a test signal to the electronic circuit of a safe input and tests whether the level changes from high to low, which would prove that no stuck-at-1 fault is present.

[0047] According to a preferred embodiment of the invention, the evaluation of a data packet received via the interface is secured by means of a secure bus protocol. According to a preferred embodiment of the invention, the receiving and sending of data packets via the data bus is carried out using a secure bus protocol.

[0048] According to a preferred embodiment of the invention, in the event of a transmission error in a data packet, STO (Safe Transmission Error) is triggered if the transmission error is not rectified within a specified time period by a correct retransmission of the data packet. This is one of the reasons why a safe bus protocol is used. With regard to a safe protocol for securing data packets (e.g., telegrams), securing means 202408802

[0049] 9 does not mean that the data packets are protected against transmission errors, but only that such transmission errors are reliably detected.

[0050] Exemplary embodiments of the drawing

[0051] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more easily understood through the following description of exemplary embodiments, which will be explained in more detail with reference to the drawings. The drawings are schematic and not to scale.

[0052] Fig. 1 shows a motor branch; and

[0053] Fig. 2 shows a motor starter according to the invention in a first embodiment;

[0054] Fig. 3 shows a flowchart of the procedure for operating a motor starter;

[0055] Fig. 4 shows a temporal sequence of switching operations; and

[0056] Fig. 5 shows a motor starter according to the invention in a different embodiment.

[0057] Detailed description of the exemplary implementations

[0058] Fig. 1 shows a motor branch. From a power supply network 40 with three phase conductors L1, L2, L3, e.g., a three-phase network, a three-phase load circuit 41 branches off at connection points 42, via which electrical energy can be transported to an electric motor 43. The motor can be a low-voltage three-phase asynchronous motor or any other electrically operated motor.

[0059] A motor starter 50 is connected between connection points 42 and the motor 43, in the phase conductors L1, L2, L3 of the load circuit 41. The motor starter has input terminals 31 on the mains side and output terminals 32 on the load side, to which the phase conductors L1, L2, L3 are connected. Inside the motor starter 50, load current paths run between the input terminals 31 and the output terminals 32, which can be interrupted by means of switching devices in the motor starter 50.

[0060] The motor starter 50 switches all three phase conductors L1, L2, L3 of the load circuit 41. For this purpose, the motor starter 50, which can be divided into a power section and a control section, has the following features: 202408802

[0061] 10. The power section of the motor starter contains at least one switch per phase L1, L2, L3. The switch can be electromechanical, e.g., a relay, or electronic, e.g., a transistor (MOSFET, IGBT, etc.). It is also possible that at least one electromechanical switch, e.g., a relay or a galvanically isolating disconnect switch, and one electronic semiconductor switch, e.g., a transistor switch, are arranged in series in at least one phase conductor. The motor starter is configured for a fixed-speed motor.

[0062] The motor starter 50 has a bus interface 3 and a voltage input 4. The bus interface 3 is used to receive and send data packets via a bus line 10B. The voltage input 4 is connected to an electrical line 10U; in this way, a voltage is applied to the voltage input 4, the voltage level of which can signal the motor starter.

[0063] A command, such as an STO signal, can be transmitted to the motor starter 50 via both bus interface 3 and voltage input 4. Other devices are also connected to bus line 10B: a bus node 62 in the form of a PLC, which sends commands such as an STO signal to the motor starter 50, and a parameterization device 61 (PLC = Programmable Logic Controller). The parameterization device 61, e.g., a PC (Personal Computer) with an engineering tool such as the Siemens TIA Portal (TIA = Totally Integrated Automation), does not send parameterization data directly to the motor starter 50, but rather to the PLC 62. The parameterization data is stored there permanently, and the PLC 62 sends the parameterization data to the motor starter 50 whenever the motor starter 50 "reports" to bus 10B after starting up."Start-up" of the motor starter 50 means that the motor starter 50 is switched on by connecting a 24 V supply voltage to its control unit. The parameterization device 61 is therefore only required for initial parameterization and if the parameterization data is to be changed after the initial parameterization.

[0064] An STO (Safe Torque Off) device 65, such as a light barrier, light curtain, safety mat, emergency stop switch, safety door, or safety scanner, can be connected to the electrical line 10U, which is connected to the voltage input 4. This device sends a safety command in the form of an STO signal to the motor starter 50 when a defined condition is present. The safety command can be signaled to the motor starter 50 by a defined voltage level, e.g., a voltage < 5 V, at the voltage input 4. 202408802

[0065] 11

[0066] Fig. 2 shows a first embodiment of a motor starter 50 according to the invention. The motor starter 50 has a load current path 9 running through the motor starter 50, which runs from an input 31 of the load current line (mains side / power supply side) to an output 32 of the load current line (load side) for conducting a load current.

[0067] The motor starter 50 has an interface 3 for receiving an input signal 101. Interface 3 can be a voltage input for connecting an electrical line; a voltage can be applied to the voltage input via this line, and the voltage level of this voltage signals an STO signal to the motor starter 50. The voltage input can also be a safe digital input.

[0068] Alternatively, interface 3 can be a bus interface for receiving and sending data packets 101 via a bus line; thus, a bus data packet 101 can signal an STO signal to the motor starter 50. Each data packet can be secured using a secure bus protocol. The motor starter 50 can alternatively have two independent inputs (voltage input and bus interface) for receiving an STO signal, with the two inputs operating using different communication methods.

[0069] The motor starter 50 has a switching device 7, 8 for interrupting the load current path 9. The switching device 7, 8 can operate electromechanically, with an actuator 7 and a relay 8. Alternatively, the switching device 7, 8 can operate electronically, with a control unit 7, e.g., a gate driver, and a semiconductor switch 8, e.g., a transistor.

[0070] The motor starter 50 has two independent command paths P1, P2, namely a first command path P1 and a second command path P2.

[0071] The motor starter 50 has a technology controller 1, which is connected to the interface 3 via a first transmission line 140. Input signals 101 received at the interface 3 are forwarded to the technology controller 1 via the first transmission line 140. The technology controller 1 has an evaluation circuit configured to evaluate a control command 101 received at the interface 3 for the presence of an STO signal and, if an STO signal is present, to send an interrupt command to the evaluation circuit on each of the two command paths P1 and P2. The evaluation circuit can operate using any suitable evaluation method, e.g., based on data packets or on voltage levels.

[0072] 12

[0073] The first command path P1 includes a first trigger unit 80, which is in the form of a cell controller, and a second transmission line 144 for routing the interrupt command from the technology controller 1 to the first trigger unit 80. The first trigger unit 80 is configured to trigger an interruption of the load current path 9 at a first time t1 in response to an interrupt command received from the technology controller 1. This first interruption is related to a defined zero crossing of the load current in the load current path 9. For this purpose, the cell controller 80 includes a detection circuit for detecting zero crossings of the load current in the load current path 9. At the first time t1, the first trigger unit 80 sends a first STO signal 105 to an OR gate 16 of the motor starter 50. The OR gate 16 can be a logic gate or an electronic circuit that performs the function of a logic gate.As soon as the first STO signal is present at the OR gate 16, a switching signal 111 is sent from the OR gate 16 to the switching device 7, 8 in order to open the switch 8 without delay.

[0074] The second command path P2 includes a second triggering unit 19, which is implemented as a hardware circuit with a delay element, and a third transmission line 143 for routing the interrupt command from the technology controller 1 to the second triggering unit 19. The second triggering unit 19 is configured to trigger an interruption of the load current path 9 at a second time t2 in response to an interrupt command received from the technology controller 1. This second time t2 is located a predetermined time interval At after the detection time at which the STO signal was detected. To this end, the second triggering unit 19 sends a second STO signal 106 to the OR gate 16 at the second time t2. As soon as the second STO signal is present at the OR gate 16, a switching signal 111 is sent from the OR gate 16 to the switching device 7, 8 to open the switch 8 without delay.

[0075] The load current path 9 can have one or more phases. For each phase, the motor starter 50 has a phase-specific part 50b, which includes a switching device 7, 8, an OR gate 16, and a first trip unit 80. The motor starter 50 also has a common part 50a, which is shared by all phases: this includes the interface 3, the technology controller 1, and the second trip unit 19.

[0076] Fig. 3 shows a flowchart of the method for operating a motor starter as shown in Fig. 2. In a first step 201, an input signal is received at an interface of the motor starter. In a second step 202, the received input signal is evaluated for the presence of an STO signal, for example by a 202408802

[0077] 13

[0078] Evaluation circuit of a technology controller. In a third step 203, a decision is made: If no STO signal is present 204, the procedure jumps back to the first step 201. If, at a detection time tO, it is detected that an STO signal is present in the received input signal 205, the parallel steps 206 and 207 are carried out. In the fourth step 206, an interruption of the load current path is triggered on a first command path, which is to take place at a first time t1 that is in a defined relation to a zero crossing of the load current in the load current path.

[0079] In the fifth step 207, an interruption of the load current path is triggered on a second command path, which is to take place at a second time t2, which is a predetermined time interval At after the detection time tO. In a sixth step 208, a switching operation is carried out to interrupt the load current path at the first time t1. In a seventh step 209, a switching operation is carried out to interrupt the load current path at the second time t2.

[0080] Fig. 4 shows a timeline t illustrating an exemplary sequence of switching operations. tO is the so-called detection time, i.e., the time at which it is detected, for example by an evaluation circuit of a technology controller, that an STO signal is present. t1 is a first time point after the detection time tO: t1 > tO. The first time point t1 is related to a zero crossing Z of the load current in the load current path in a defined way: in the illustrated configuration, the first time point t1 is located a reference time interval öt before the zero crossing Z. The reference time interval öt can be any time interval, e.g., any number of milliseconds such as 1 ms. In other configurations, the first time point t1 can be located a reference time interval öt after the zero crossing Z. The reference time interval öt is preferably chosen so that the switching elements are subjected to the lowest possible load.In other embodiments, the first time t1 coincides with the first zero crossing of the load current in load current path 9 after the interruption of the load current path has been initiated, preferably with the first zero crossing of the load current in load current path 9 after the detection time tO. t2 is a second time point that lies a predetermined time interval At after the detection time tO: t2 = tO + At. The predetermined time interval At is chosen such that the second time point t2 lies after the first time point t1: At > t1 - tO. Preferably, the time interval At is therefore at least one period of the mains frequency of the voltage source that causes the load current. 202408802.

[0081] 14

[0082] Fig. 5 shows a further embodiment of a motor starter 50 according to the invention. The motor starter 50 has a load current path 9 running through the motor starter 50, which runs from an input 31 of the load current line (mains side / power supply side) to an output 32 of the load current line (load side), for conducting a load current.

[0083] The motor starter 50 has an interface 3 for receiving an input signal 101. The interface 3 can be a voltage input for connecting an electrical line 10; a voltage can be applied to the voltage input via the electrical line 10, the voltage level of which signals an STO signal to the motor starter 50. The voltage input can be a safe digital input.

[0084] Alternatively, interface 3 can be a bus interface for receiving and sending data packets 101 via a bus line 10; thus, a STO signal can be sent to the motor starter 50 by a bus data packet 101. Each data packet can be secured using a secure bus protocol. Alternatively, the motor starter 50 can have two independent inputs (voltage input and bus interface) for receiving an STO signal, with the two inputs operating using different communication methods.

[0085] The motor starter 50 has a switching device 7, 8 for interrupting the load current path 9. The switching device 7, 8 can operate electromechanically, with an actuator 7 and a relay 8. Alternatively, the switching device 7, 8 can operate electronically, with a control unit 7, e.g., a gate driver, and a semiconductor switch 8, e.g., a transistor.

[0086] The motor starter 50 has two independent command paths P1, P2, namely a first command path P1 and a second command path P2.

[0087] The motor starter 50 has a technology controller 1, which is connected to the interface 3 via a first transmission line 140. Input signals 101 received at the interface 3 are forwarded to the technology controller 1 via the first transmission line 140. The technology controller 1 has an evaluation circuit 13, which is configured to evaluate a control command 101 received at the interface 3 for the presence of an STO signal and, if an STO signal is present, to send an interrupt command to the evaluation circuit 13 on the two command paths P1 and P2. The evaluation circuit 13 can operate using any suitable evaluation method, e.g., based on data packets or on voltage levels.

[0088] 15

[0089] The first command path P1 includes a first triggering unit 80, which is in the form of a cell controller, and a second transmission line 144 for routing the interrupt command from the technology controller 1 to the first triggering unit 80. The first triggering unit 80 is configured, in response to an interrupt command received from the technology controller 1, to trigger an interruption of the load current path 9 at a first time t1 using a software program 81. This first interruption is related to a defined current zero crossing Z of the load current in the load current path 9. For this purpose, the cell controller 80 includes a detection circuit 82 for detecting current zero crossings of the load current in the load current path 9. At the first time t1, the first triggering unit 80 sends a first STO signal 105 to an OR gate 16 of the motor starter 50.The OR gate 16 can be a logic gate or an electronic circuit that performs the function of a logic gate. As soon as the first STO signal is present at the OR gate 16, a switching signal 111 is sent from the OR gate 16 to the switching device 7, 8 in order to open the switch 8 without delay.

[0090] The second command path P2 includes a second trigger unit 19, which is implemented as a hardware circuit with a delay element, and a third transmission line 143 for routing the interrupt command from the technology controller 1 to the second trigger unit 19. The second trigger unit 19 is configured to trigger an interruption of the load current path 9 at a second time t2 in response to a received interrupt command. This second time t2 is located a predetermined time interval At after the detection time tO, at which the STO signal was detected. To this end, the second trigger unit 19 sends a second STO signal 106 to the OR gate 16 at the second time t2. As soon as the second STO signal is present at the OR gate 16, a switching signal 111 is sent from the OR gate 16 to the switching device 7, 8 to open the switch 8 without delay.

[0091] The motor starter 50, apart from the evaluation circuit 13 of the technology controller 1, has a further evaluation circuit 23; this further evaluation circuit 23 is provided in a first embodiment by a controller 2 and in an alternative embodiment by a hardware circuit 5. The further evaluation circuit 23 is connected to the interface 3 via the first transmission line 140 and a fourth transmission line 141; input signals 101 arriving at the interface 3 are forwarded to the further evaluation circuit 23 via these transmission lines 140, 141. The further evaluation circuit 23 can operate with any suitable evaluation method, e.g., based on data packets or on voltage levels. If an STO signal is present at the further evaluation circuit 23, the further evaluation circuit 23 sends an interrupt command 142 to the second trigger unit 19.

[0092] 16

[0093] The load current path 9 can have one or more phases. For each phase, the motor starter 50 has a phase-specific part 50b, which includes a switching device 7, 8, an OR gate 16, and the first trip unit 80. The motor starter 50 also has a common part 50a, which is shared by all phases: this includes the interface 3, the technology controller 1, the further evaluation circuit 23, and the second trip unit 19.

[0094] 202408802

[0095] 17

[0096] Reference symbol list

[0097] 1 Controller, first; Technology Controller

[0098] 2 controllers, second; communication controller

[0099] 3 Interface (Bus interface; voltage input terminal, digital input, FDI terminal)

[0100] 5 HW circuit

[0101] 7 Actuator, control unit

[0102] 8 switches

[0103] 9 Load current path

[0104] 10 Input lines (bus lines, electrical lines)

[0105] 13 Evaluation circuit of 1

[0106] 16 Oder gates

[0107] 19 HW circuit with delay element

[0108] 23 Evaluation circuit of 2, 5

[0109] 31 Input of the load current line (power supply side)

[0110] 32 Output of the load current line (load side)

[0111] 40 Power supply network

[0112] 41 Motor supply line

[0113] 43 Engine

[0114] 50 engine starters

[0115] 50a common part of 50

[0116] 50b phase-specific part of 50

[0117] 61 Parameterization device

[0118] 62 bus nodes, F-PLC

[0119] 65 STO release device

[0120] 80-cell controller

[0121] 81 SW program, algorithm

[0122] 82 Detection circuit

[0123] 101 Input signal (bus data packet, voltage signal)

[0124] 105 first STO signal

[0125] 106 second STO signal

[0126] 111 Switching signal

[0127] 140 transmission line

[0128] 141 Transmission line

[0129] 142 Transmission line

[0130] 143 Transmission line 202408802

[0131] 18

[0132] 144 Transmission line

[0133] 201-209 Procedural steps

[0134] P1 first command path; regular shutdown path

[0135] P2 second command path; fallback shutdown path, delayed tO detection time t1 first time t2 second time

[0136] At time span

[0137] 5t reference period

Claims

202408802 19 Patent claims 1. Method for operating a motor starter (50) having a load current path (9) for conducting a load current, comprising the following steps: - Receiving an input signal (101) at an interface (3) of the motor starter (50); - Evaluating the received input signal (101) for the presence of an STO signal; - If the presence of an STO signal is detected, initiate an interruption of the load current path (9) on at least two independent command paths (P1 , P2), thereby - on a first command path (P1) an interruption of the load current path (9) is triggered at a first time (t1) which is in a defined relation to a current zero crossing of the load current in the load current path (9), and - on a second command path (P2) an interruption of the load current path (9) is triggered at a second time (t2) which is a predetermined time interval (At) after a detection time (tO) at which the presence of the STO signal was detected, wherein the predetermined time interval (At) is chosen to be longer than the time interval between the detection time (tO) and the first time (t1).

2. Method according to claim 1, wherein the first time point (t1) coincides with the first zero crossing of the load current in the load current path (9) after the interruption of the load current path has been initiated.

3. Method according to one of the preceding claims, wherein the specified time period (At) is at least one period of the load current.

4. Method according to one of the preceding claims, wherein the interruption of the load current path (9) is carried out using a semiconductor switch.

5. Motor starter (50), comprising - a load current path (9) passing through the motor starter (50) for conducting a load current; - a switching device (7, 8) for interrupting the load current path (9); - an interface (3) for receiving an input signal (101); - a detection circuit for detecting current zero crossings of the load current in the load current path (9); 202408802 20 - two independent command paths (P1 , P2), having a first and a second command path (P1 , P2); - an evaluation circuit (13) configured to evaluate a control command (101) received at the interface (3) for the presence of an STO signal and, if it detects the presence of an STO signal, to send an interrupt command on each of the two command paths (P1 , P2);wherein the first command path (P1) has a first trigger unit (80) configured to trigger an interruption of the load current path (9) at a first time (t1) in response to a received interruption command, which is in a defined relation to a current zero crossing of the load current in the load current path (9), and wherein the second command path (P2) has a second trigger unit (19) configured to trigger an interruption of the load current path (9) at a second time (t2) in response to a received interruption command, which is a predetermined time interval (At) after a detection time (tO) at which the evaluation circuit (13) has detected the presence of the STO signal, wherein the predetermined time interval (At) is chosen to be longer than the time interval between the detection time (tO) and the first time (t1).

6. Motor starter according to claim 5, wherein the evaluation circuit is part of a technology controller.

7. Motor starter according to one of claims 5 or 6, comprising a delay circuit configured to provide the specified time interval (At).

8. Motor starter according to one of claims 5 to 7, wherein the interface (3) is a voltage input for tapping a voltage and / or a bus interface for receiving and sending data packets via a bus.

9. Motor starter according to one of claims 5 to 8, wherein the load current path (9) has one or more phases (L1 , L2, L3) each having a first trigger unit (80) and an OR gate (16) in which the command paths (P1 , P2) converge.

10. Motor starter according to one of claims 5 to 9, 202408802 21 wherein the load current path (9) has one or more phases (L1 , L2, L3) to which a controller is assigned which has the first trip unit (80).

11. Motor starter according to one of claims 5 to 10, wherein the motor starter has, in addition to the evaluation circuit (13), at least one further evaluation circuit (23) which is configured to evaluate a control command (101) received at the interface for the presence of an STO signal and, if an STO signal is present at the further evaluation circuit, to send an interrupt command on the second command path (P1 , P2) of the motor starter (50).

12. Motor starter according to one of claims 5 to 11, wherein the detection circuit is integrated into the first triggering unit (80).

13. Motor starter according to one of claims 5 to 12, wherein the switching device (7, 8) has a semiconductor switch (8) for interrupting the load current path (9).

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