Method and system for operating an electromagnetic switch

Abstract

A method for operating an electromagnetic switch (100), particularly a contactor or relay, is proposed, comprising the steps of: applying an initial supply voltage (U) S )Activate switch (100) to connect the magnetic circuit of switch (100), and after activation switch (100) according to the initial supply voltage (U) S The switch (100) is controlled by a limited or decreasing control voltage and / or by a limited or decreasing control current, the control voltage is increased for a specified time period (Δt), and the inductance (L) of the magnetic circuit of the switch (100) is determined during and / or after the specified time period (Δt).

Description

Technical Field

[0001] The present invention relates to a method and system for operating an electromagnetic switch, such as a contactor or a relay.

[0002] The present invention also relates to the use of this method or system in a motor vehicle power supply, wherein the motor vehicle may be, for example, a motor vehicle that is at least partially electrically driven, such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle. Background Technology

[0003] Practice in vehicle technology has shown that electromagnetic switches, such as contactors, are used, particularly in at least partially electrically driven motor vehicles, to selectively connect and disconnect the vehicle's power electronics, for example, from an energy storage device, such as a battery. This can be implemented, for example, in the vehicle's high-voltage power supply.

[0004] The switch can be activated, for example, by the vehicle's low-voltage power supply. During the vehicle's product lifecycle, a situation may arise where, for example, the corresponding vehicle battery of the low-voltage power supply is deeply discharged, the low-voltage power supply can only provide a voltage lower than its actual rated voltage (e.g., 12V). For example only, this reduced voltage can be less than 10V, for example, only about 7V. When the switch is activated and / or controlled at such a low voltage, although the switch contacts are in contact, the switch magnetic circuit may not be fully closed or not closed with full contact force. Even when the switch is now controlled at a lower voltage (reduced via PWM) in the "hold" state to, for example, reduce the switch's drive power, the magnetic circuit remains partially open.

[0005] Practice has shown that when the magnetic circuit of a switch is not fully closed, the corresponding holding force at the contacts may decrease, and in extreme cases, this decrease can be significant, exceeding 50% of the target holding force. This can cause the switch to undesirably open under load current during vehicle operation, which may adversely affect functional safety or driving safety, and may also damage the switch due to, for example, arcing. Summary of the Invention

[0006] The objective of this invention is therefore to improve the functional safety of its operation, particularly that of electromagnetic switches.

[0007] This task is accomplished through the subject matter of the independent claims. Advantageous improvements of the invention are described in the dependent claims, the specification, and the drawings.

[0008] The first aspect provides a method for inspecting electromagnetic switches, particularly contactors or relays. The method comprises the following steps:

[0009] The switch is activated with the initial supply voltage to connect its magnetic circuit.

[0010] After the switch is activated, it is controlled by a control voltage and / or a control current, especially a holding current, that is limited or decreasing relative to the initial supply voltage.

[0011] Increase the control voltage and / or control current for a specified period of time.

[0012] Determine the inductance of the magnetic circuit of the switch during the specified time period and / or after its expiration.

[0013] This method can be implemented at least partially or entirely by a computer, preferably in hardware and / or software form. For this purpose, a system according to the second aspect below can be employed. The above-described method steps can be performed, in particular, by one or more microcontrollers and perhaps with the aid of additional measuring devices such as current measuring devices, resistance measuring devices, voltage measuring devices, etc.

[0014] The switch, particularly the contactor, can be specified for high switching power and can be remotely operated. The switch or its circuitry may include two circuits: a control circuit and a main circuit. If a control current flows through the switch's magnetic circuit or coil, the magnetic field attracts the contacts, which are specifically designed mechanically, into the active state. If no current flows, the spring returns to its resting state, causing the contacts to return to their initial position. In the active state, the switch's magnetic circuit is closed, where the air gap in the magnetic circuit is reduced, or even becomes zero.

[0015] The specified time period can be in the range of less than 1 second, for example, in the range of milliseconds, wherein, for example, 1 to 50 ms, preferably 5 to 20 ms, and particularly preferably 10 ms, has proven to be suitable. This allows for convincing inductance measurements without interference or threat to switching operation caused by thermal overload, such as high current.

[0016] The temporary increase in control voltage and / or control current allows the closing force to be reapplied to the switch's magnetic circuit or contacts after the switch has been activated, thus enabling the switch to change its closed state again during control or when the control voltage and / or control current is increased. This increase in control voltage can be achieved, for example, by controlling or adjusting the control circuitry based on hardware and / or software.

[0017] According to an improved version of this method, it can be achieved by using voltage from U... i Jump to U BN (where U) i For example, 4V, U BNThe current increment in response to a voltage of 12V is used to identify whether the switch is closed. Another conceivable implementation is that the switch, especially the contactor, is opened and the voltage jumps from U0 = 0V to U1 (e.g., 4V). Then, the current increment within Δt (e.g., 10ms) indicates whether the switch is effectively opened; that is, in the case of a contactor, there is no so-called contactor sticking.

[0018] Inductance can be determined directly or indirectly, for example by calculating inductance based on the following values: initial supply voltage, control voltage and / or control current, current increase caused by increasing control voltage and / or control current, and a specified time period.

[0019] The inductance of at least one magnetic circuit with an air gap is related to, for example, the size of the air gap, especially its width. If the magnetic circuit is fully or as intended connected, there is a corresponding value of inductance, for example, about 310 mH. If the air gap in the magnetic circuit is not properly closed, for example, if there is still an air gap of 0.8 mm, there is another reduced inductance value, for example, about 170 mH. This inductance determination thus allows for the inspection or diagnosis of the on / off and / or closed state of the switch.

[0020] Using this method, the operation of the switch can be improved in terms of its functional safety, because the on / off state and / or closed state of the switch can be checked or diagnosed. This allows for early intervention in suboptimal on / off or closed states, and perhaps appropriate alternatives. Appropriate alternatives can also reduce the thermal load on the switch, by reacting before, for example, an arc is generated due to accidental opening of the contacts due to insufficient holding force. However, the switch still operates after startup with a limited or reduced control voltage relative to the initial supply voltage and / or a limited or reduced control current (holding current), thereby reducing the control power and / or thermal load of the switch during operation.

[0021] According to an improved method, the on / off state of the switch is checked based on the inductance of the determined magnetic circuit. The check result may include whether the actual on / off state corresponds to or does not correspond to the ideal on / off state. Based on this result, various alternative measures can be taken, such as controlling the switch again in the absence of a power-saving circuit, or shutting off the vehicle or parts thereof.

[0022] In one improved scheme, the closed state of the switch is inferred by comparing the inductance of the determined magnetic circuit with an inductance threshold, wherein a specified inductance less than the inductance threshold indicates a partially closed state, and a specified inductance greater than or equal to the inductance threshold indicates a fully closed state.

[0023] According to an improved scheme, the control voltage and / or control current are reduced or limited by a power-saving circuit or energy-saving device. The term "energy-saving device" refers to a device that allows for a reduction in control power, thereby mitigating power consumption and heat generation in the switching coil.

[0024] In an improved approach, the control voltage and / or control current can be provided using pulse width modulation (PWM). PWM can be implemented, for example, by a microcontroller with one or more integrated PWM modules, thereby generating PWM signals without CPU load. However, a software solution is also feasible. Here, for example, the CPU of the microcontroller can generate the PWM. This reduces control power, thereby mitigating power consumption and heat generation in the switching coils.

[0025] According to an improved scheme, the step of increasing the control voltage and / or control current for a specified time period may include:

[0026] Increase the duty cycle of pulse width modulation (PWM) when using a current supply voltage higher than the initial supply voltage.

[0027] In other words, the duty cycle can be increased from a first value used to drive the switch during the specified operating period to a second, higher value. In particular, the control voltage and / or control current can be temporarily increased to apply additional or higher closing force.

[0028] In an improved version, the method may also include the following steps:

[0029] Determine the current supply voltage before increasing the control voltage and / or control current for a specified period of time.

[0030] Among them, when the supply voltage is less than the supply voltage threshold, the steps of increasing the control voltage and / or control current for a specified period of time are taken until the supply voltage threshold is reached or exceeded.

[0031] This limits the execution of this step to applicable scenarios where the supply voltage is high enough to provide effective closing force.

[0032] According to an improved approach, the step of determining the inductance of the magnetic circuit of the switch during and / or after the specified time period may include:

[0033] Determine the starting current value before the start of the specified time period.

[0034] Determine the current increment within the specified time period or determine the end current value after the specified time period expires, and calculate the current increment from the end current value and the start current value.

[0035] The inductance is calculated using the determined or calculated current increment.

[0036] Current measurement can be performed directly or indirectly using a suitable current measuring device. The specified time period can be set and determined using the microcontroller's system clock, timer, etc. The corresponding information can be fixedly written into, for example, memory or registers. This allows for precise, fast, and / or resource-efficient determination of the inductance.

[0037] According to an improved embodiment, the step of determining the inductance (L) of the magnetic circuit of the switch during and / or after a specified time period may include:

[0038] After the specified time period expires, the current increase, which is a response to the increase in control voltage, is measured, and

[0039] The inductance of the magnetic circuit is determined by the product of the change in control voltage and the change in control current during that time period.

[0040] In one improved embodiment, the step of determining the inductance of the magnetic circuit of the switch during and / or after the specified time period may include:

[0041] Compare the determined inductance with earlier inductance measurements, and / or

[0042] The algorithm uses a machine learning approach based on training data from earlier inductance measurements.

[0043] The comparison can be performed using statistical algorithms such as the k-nearest neighbor algorithm. This allows for a more accurate determination of the inductance.

[0044] The second aspect relates to a system for operating an electromagnetic switch. This system is preferably configured to perform the aforementioned method. The system has:

[0045] An electromagnetic switch that can be activated by an initial supply voltage to connect its magnetic circuit, and can be controlled to maintain the connected state after activation.

[0046] At least one microcontroller configured to:

[0047] After the switch is activated, it is controlled with a limited or reduced control voltage and / or a limited or reduced control current relative to the initial supply voltage.

[0048] Increase the control voltage and / or control current for a specified period of time, and

[0049] Determine the inductance of the magnetic circuit of the switch during the specified time period and / or after its expiration.

[0050] The switch can be the switch described above with respect to the method, i.e., in particular a contactor. The microcontroller does not necessarily have to be a single component, but can also be designed as a distributed system, i.e., having multiple constituent components. The microcontroller may itself have one or more integrated circuits, software modules, etc., to perform the aforementioned functions or the functions described in relation to the method, such as current measurement, resistance measurement, etc. However, the microcontroller can also cooperate with external devices such as measuring devices and acquire and process corresponding signals from external devices.

[0051] The third aspect relates to the use of the system for operating an electromagnetic switch according to the preceding claims in a motor vehicle power supply, wherein the switch connects the motor vehicle's power electronics to the motor vehicle battery in an on / off state, and the system checks the on / off state of the switch and affects the function of the motor vehicle based on the check result.

[0052] This application allows for high functional safety because the on / off and / or closed states of the switch can be reliably monitored or diagnosed.

[0053] Other features, advantages, and applications of the present invention are derived from the following description of advantageous embodiments and the accompanying drawings. Attached Figure Description

[0054] Hereinafter, advantageous embodiments of the invention will be explained with reference to the accompanying drawings, in which:

[0055] Figure 1 A side view schematic diagram shows a motor vehicle having a system according to one embodiment.

[0056] Figure 2 A schematic block diagram illustrates a system according to one implementation.

[0057] These figures are merely illustrative and are used only to explain the invention. Identical or functionally equivalent parts are always marked with the same reference numerals. Detailed Implementation

[0058] Figure 1 A side view schematic diagram shows a motor vehicle 1, which is, for example, a battery-powered electric vehicle. The motor vehicle 1 has an energy storage device 10 in the form of a battery system and a power electronic device 20, including, for example, a transformer. One or more switches 100 are provided between the energy storage device 10 and the power electronic device 20 for disconnecting the terminals of the energy storage device 10 from the power electronic device as needed.

[0059] Switch 100 is an electromagnetic switch in the form of a contactor, which basically has a control circuit and a main circuit. The control circuit is used to control the contactor, and the main circuit is the circuit that is switched on and off. In addition, switch 100 has a magnetic circuit with an air gap. Such switch 100 is well known, so it will not be described in more detail here.

[0060] Figure 2 A schematic block diagram illustrates a system for operating switch 100. It can be started with an initial supply voltage U to connect its magnetic circuit, said initial supply voltage being provided by the power supply of vehicle 1, particularly a low-voltage power supply, and after startup, to maintain its closed state (which typically ends after a few milliseconds), it can be subjected to pulse width modulation (PWM) as a power-saving circuit, in order to reduce power consumption and thus save energy, especially during the holding state. The PWM is specifically designed to control switch 100 with a control voltage limited or reduced relative to the initial supply voltage and / or with a limited or reduced control current. PWM can also be referred to as a power-saving circuit or energy-saving device. Functionally, the PWM limits the control current and / or control voltage of switch 100.

[0061] Furthermore, the system for operating switch 100 includes a microcontroller 200 functionally connected to switch 100. The microcontroller is, for example, part of an electronic controller or integrated control device of the vehicle 1. Specifically, the microcontroller 200 is configured to determine the inductance of the magnetic circuit of switch 100 within a specified time period and / or after its expiration. The aforementioned PWM can also be part of the microcontroller 200, for example, in the form of a PWM module. Additionally, the microcontroller 200 is configured to increase the control voltage and / or control current of switch 100 for a specified time period, preferably within milliseconds (ms). This can be achieved using the power supply voltage of vehicle 1, or perhaps by a voltage source common to the aforementioned supply voltage U, such as a vehicle battery. To increase the control voltage and / or control current, a current supply voltage U higher than the initial supply voltage can be used to implement the duty cycle of the PWM. Furthermore, the microcontroller 200 is configured to determine the inductance L of the magnetic circuit of switch 100 within and / or after the specified time period, for example, by measuring current, current difference, or current increment, and thereby calculating the inductance L. The microcontroller 200 is also configured to determine the supply voltage U, for example by voltage measurement or by information from the power supply signal, before increasing the control voltage and / or control current for a specified period of time. S Furthermore, if the supply voltage is lower than a supply voltage threshold, steps are taken to increase the control voltage and / or control current until the supply voltage threshold is reached or exceeded. The supply voltage threshold can be, for example, approximately 8V to 12V, preferably approximately 9.5V.

[0062] The procedure for operating switch 100 or the corresponding applicable method can be described as follows.

[0063] As an example initial condition, it can be assumed that the vehicle 1 or the aforementioned system is configured to start the switch 100, for example, by means of a low-voltage power supply, such as a 12V vehicle battery. For example, after the vehicle 1 has been stationary for an extended period, under adverse weather conditions or similar boundary conditions, the supply voltage U provided in the low-voltage power supply may be [not specified].S It can be relatively low, for example, only about 7V. That is, a relatively low control voltage is used to start switch 100, which may be sufficient to make the contacts of switch 100 contact each other, but switch 100 cannot be fully closed or has only a small holding force at the contacts.

[0064] Therefore, after switch 100 is activated (using the initial supply voltage U, which is approximately 7V in this case), switch 100 initially operates using the aforementioned PWM, i.e., relative to the supply voltage U. S The control voltage is limited or reduced, and / or the control current is limited or reduced, wherein the control voltage and / or control current are then increased for a defined, i.e., a known or specified time period Δt. This can be achieved, for example, by converting the PWM to a sufficiently high voltage value. That is, in particular, the duty cycle of the PWM is controlled, i.e., a voltage higher than or equal to the aforementioned supply voltage threshold is applied at switch 100. If switch 100 is still not fully closed, an additional or, in terms of time, subsequent closing force can be applied to the magnetic circuit or contacts of switch 100 by temporarily increasing the control voltage and / or control current.

[0065] Next, within a specified time period Δt, the current, current difference, or current increment ΔI can be determined using the microcontroller 200, for example, by direct or indirect current measurement. For this purpose, for example, the initial current value before the start of the specified time period Δt can be determined first. Then, the current increment ΔI within the specified time period Δt can be determined. Alternatively, the final current value after the end of the specified time period Δt can be determined, and the current increment ΔI can be calculated from the final current value and the initial current value. Thus, the inductance L can be calculated by the microcontroller 200, which can, for example, calculate or determine the following:

[0066] L=(U S -I PWM R)Δt / ΔI

[0067] Where L represents inductance, R represents coil resistance, and I PWM Δt represents the control current of PWM, Δt represents the specified time period, and ΔI represents the current difference or current increment.

[0068] For better illustration, the inductance L should be calculated simply using the exemplary value used for the exemplary switch 100. It can be assumed here that the PWM (i.e., power-saving circuit or energy-saving device) directs the current I... PWM Control or regulate to approximately 0.74A. R is determined, for example, by resistance measurement or based on the specifications of switch 100, to be approximately 5.7 ohms. Then, for example, by increasing the duty cycle of the PWM, the voltage U is... SThe voltage is increased to approximately 12V, and determined, for example, by measurement techniques, specifically for a specified time period Δt of approximately 10ms. In this case, the current increases from 0.74A to, for example, approximately 0.98A, thus resulting in a current difference ΔI of approximately 0.24A. The inductance L is thus obtained using the aforementioned exemplary values:

[0069]

[0070] If the magnetic circuit fails to close or does not close completely under fault conditions, leaving a 0.8mm gap, the current increase within 10ms will be 0.5A. The inductance is then determined by the diagnostic unit as follows:

[0071]

[0072] The currently determined inductance L of the magnetic circuit can be compared with an inductance threshold to infer the closed and / or open state of switch 100. In the exemplary values ​​above, for example, an inductance L greater than or equal to 300 mH can be considered fully activated or closed or normal, while an inductance L less than 200 mH can be considered insufficiently activated or closed or abnormal. Obviously, specific thresholds may differ from the exemplary values. In the case of inductance thresholds within the range, the determination and / or measurement of inductance L can be repeated once or multiple times, i.e., by increasing the voltage again, and so on.

[0073] List of reference numerals

[0074] 1 Motor vehicles

[0075] 10. Accumulator

[0076] 20 Power Electronic Devices

[0077] 100 switch

[0078] 200 microcontrollers

Claims

1. A method for operating an electromagnetic switch, the method having the steps of: starting the electromagnetic switch at an initial supply voltage for switching on a magnetic circuit of the electromagnetic switch, controlling the electromagnetic switch at a limited or reduced control voltage and / or control current relative to the initial supply voltage after starting the electromagnetic switch, determining a current supply voltage and, in case the current supply voltage is less than a supply voltage threshold, increasing the control voltage and / or the control current for a defined time period until the current supply voltage reaches or exceeds the supply voltage threshold, and determining an inductance of the magnetic circuit of the electromagnetic switch within the defined time period and / or after the defined time period has expired.

2. The method of claim 1, wherein, checking an on-off state of the electromagnetic switch in dependence on the determined inductance of the magnetic circuit.

3. The method of claim 1 or 2, wherein, inferring a closed state of the electromagnetic switch in dependence on the determined inductance of the magnetic circuit compared to an inductance threshold, the determined inductance of the magnetic circuit being less than the inductance threshold indicating a non-full closed state of the electromagnetic switch and the determined inductance of the magnetic circuit being greater than or equal to the inductance threshold indicating a full closed state of the electromagnetic switch.

4. The method of claim 1 or 2, wherein, the control voltage and / or the control current being reduced or limited by a power saving circuit or economizer.

5. The method of claim 1 or 2, wherein, the control voltage and / or the control current being provided by means of pulse width modulation, PWM.

6. The method of claim 1 or 2, wherein, the step of increasing the control voltage and / or the control current for a defined time period comprises increasing a duty cycle of a pulse width modulation, PWM, in case a current supply voltage higher than the initial supply voltage is used.

7. The method of claim 1 or 2, wherein, the electromagnetic switch comprises a contactor or a relay.

8. The method of claim 1 or 2, wherein, the step of determining an inductance of the magnetic circuit of the electromagnetic switch within the defined time period and / or after the defined time period has expired comprises: determining a current increase within the defined time period; or determining a start current value before the start of the defined time period and an end current value after the defined time period has expired and calculating a current increase based on the end current value and the start current value, and calculating the inductance using the determined or calculated current increase.

9. The method of claim 1 or 2, wherein, the step of determining an inductance of the magnetic circuit of the electromagnetic switch within the defined time period and / or after the defined time period has expired comprises: measuring a current increase as a reaction to an increase of the control voltage after the defined time period has expired, and determining the inductance of the magnetic circuit by multiplying the quotient of a change of the control voltage and a change of the control current by the defined time period.

10. The method of claim 1 or 2, wherein, the step of determining an inductance of the magnetic circuit of the electromagnetic switch within the defined time period and / or after the defined time period has expired comprises: comparing the determined inductance to an earlier measured inductance value, and / or using a machine learning algorithm based on training data from earlier measured inductance values.

11. A system for operating an electromagnetic switch, comprising: an electromagnetic switch, the electromagnetic switch being startable at an initial supply voltage for switching on a magnetic circuit of the electromagnetic switch and being controllable for maintaining an on state after starting, and at least one microcontroller, the microcontroller being arranged for: controlling the electromagnetic switch with a limited or reduced control voltage and / or control current relative to the initial supply voltage after the electromagnetic switch has been activated, determining a current supply voltage and, in the event that the current supply voltage is less than a supply voltage threshold, increasing the control voltage and / or the control current for a defined period of time until the current supply voltage reaches or exceeds the supply voltage threshold, and determining the inductance of the magnetic circuit of the electromagnetic switch over the defined period of time and / or after the defined period of time has expired.

12. Use of a method for operating an electromagnetic switch according to any one of claims 1-10 or a system for operating an electromagnetic switch according to claim 11 in a power supply of a motor vehicle, wherein, The power electronics of the motor vehicle are connected to the battery of the motor vehicle in dependence on the on / off state of the electromagnetic switch, and the on / off state of the electromagnetic switch is checked and the function of the motor vehicle is influenced in dependence on the result of the check.

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