Method for controlling a circuit breaker with active current limiting and circuit breaker set up for executing such a method

Abstract

The invention relates to a method for controlling a circuit breaker with active current limiting. Furthermore, the invention relates to an electronic circuit breaker with active current limiting with a control system set up for carrying out such a method.

Description

[0001] The invention relates to a method for controlling a circuit breaker with active current limiting. Furthermore, the invention relates to an electronic circuit breaker with active current limiting, comprising a control unit configured for executing such a method. background

[0002] Current-limiting or current-switching elements can be found in many areas of electrical systems and devices.

[0003] For example, in industrial applications, switching power supplies with an output power of only up to 1000 W are typically used to supply low-voltage protection networks of 12–48 V DC. Correspondingly, the available output current is also low.

[0004] To ensure voltage stability in low-power power supplies, short-circuit currents and fault-related current increases must be switched off very quickly, or alternatively limited to a small value, because otherwise the voltage at other consumers can drop so drastically that they no longer function properly or at all.

[0005] The applicant offers the CBM E... product family as an example of an active current-limiting circuit breaker. In this product, the short-circuit current is typically limited to a predetermined, fixed current higher than the rated current for a predefined, fixed duration before the circuit breaker completely trips. In the example given, a semiconductor MOSFET is operated in linear mode for current limiting.

[0006] The disadvantage here is that the current is always limited to a small value, typically optimized for low-power power supplies as a worst-case scenario. The current limiting level remains constant, even with more powerful power supplies, regardless of whether it's a fault-induced short-circuit current or a regular / desired inrush current, such as for charging batteries in a device.

[0007] As a result, some consumers can only be started with a significant time delay, e.g. due to long "charging times" of capacity, or not at all. Task

[0008] Based on this, one object of the invention is to provide an improvement that allows safe operation to be guaranteed and also restricts the characteristics of normal operation less. Brief description of the invention

[0009] The problem is solved by a method for controlling a circuit breaker with active current limiting according to claim 1 and a circuit breaker configured for executing such a method according to claim 6. Further advantageous embodiments are the subject of the dependent claims, the description and the figures. Brief description of the characters

[0010] The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0011] It shows: Fig. 1 schematically a variant of a flowchart according to embodiments of the invention Detailed description of the invention

[0012] The invention will now be described in more detail with reference to the figures. It should be noted that different aspects are described, each of which can be used individually or in combination. That is, each aspect can be used with different embodiments of the invention, unless explicitly presented as a pure alternative.

[0013] Furthermore, for the sake of simplicity, reference will generally be made to only one entity at a time. Unless explicitly stated otherwise, the invention may also include several of the entities concerned. Therefore, the use of the words "a," "an," and "one" should only be understood as an indication that at least one entity is used in a simple embodiment.

[0014] Information with numerical values ​​should generally not be understood as exact values, but also include a tolerance of + / - 1% to + / - 10%.

[0015] Insofar as standards, specifications, or the like are mentioned in this application, reference is always made to at least those standards, specifications, or the like applicable on the filing date. That is to say, if a standard / specification, etc., is updated or replaced by a successor, the invention is also applicable to it.

[0016] In one embodiment of the invention, which is exemplified by the Fig. As described in section 1, a method for controlling a circuit breaker with active current limiting is provided.

[0017] Unless explicitly stated as being to be carried out in a specific order, the steps described below can be arranged in any order or considered in parallel.

[0018] The following describes an ongoing operation, but the considerations are equally applicable to a start-up operation.

[0019] First, it is assumed that in step 100 a current I is measured through the circuit breaker.

[0020] In step 200, it is first checked whether the measured current I is equal to the nominal value I N exceeds. If the measured current I exceeds the nominal value I N In a further step, 300 can be checked to see if the input voltage has dropped compared to a previous measurement.

[0021] Several scenarios are now possible. Three examples are defined below, although the invention is not limited to three scenarios; more scenarios can be statically defined, or dynamic adjustments based on measured values ​​can be made.

[0022] If the input voltage has not decreased by more than a predetermined first limit value compared to a previous measured value, e.g. a drop of up to 0.5...2.5% compared to a previously determined input voltage or a nominal input voltage, the maximum current I max to a first maximum value I max1 in a step 400a, which is larger than the nominal value I N is, for example, 5 times the rated current, and furthermore a monitoring interval t I to a first value t I1 , for example 3 ms, set.

[0023] If the input voltage drops more than a predetermined first limit value compared to a previous measured value, e.g., a drop of up to 0.5...2.5% compared to a previously determined input voltage or a nominal input voltage, but less than or equal to a second limit value, e.g., a drop of up to 10% compared to a previously determined input voltage or a nominal input voltage, the maximum current I max to a second maximum value I max2 in a step 400b, which is larger than the nominal value I N , but smaller than the first maximum value I max1 is, for example, 3 times the rated current, and furthermore a monitoring interval t is used. I to a second value t I2 specified, where the second value is t I2 , greater than the first value t I1 is, for example, 10 ms.

[0024] If the input voltage has dropped by more than a predetermined second limit value compared to a previous measured value, e.g. a drop of 10% or more compared to a previously determined input voltage or a nominal input voltage, the maximum current I max to a third maximum value I max3 , set in a step of 400c, which is greater than the nominal value I N , but smaller than the second maximum value I max2 is, for example, 1.1 times the rated current, and furthermore, a monitoring interval t is specified. I to a third value t I3 specified, where the third value is t I3 greater than the second value t I2 , is, for example, 30 ms.

[0025] Now that both a maximum current and a monitoring interval have been determined, in step 500 the current I through the circuit breaker is measured again after the defined monitoring interval t. I certainly.

[0026] If the measured current I is greater than the nominal value I N In step 550, the input voltage and output voltage are determined in step 700.

[0027] Furthermore, unlike the previous procedure, the input voltage can now also be taken into account. Therefore, in step 600, it can be checked whether the input voltage has dropped compared to a previous measured value, e.g., a drop of up to 0.5...2.5% compared to a previously determined input voltage or a nominal input voltage.

[0028] Now, in step 700, both the input voltage and the output voltage can also be determined.

[0029] Obviously, the input and output voltages can be determined simultaneously or sequentially. It can also be provided that the process terminates when certain limits are reached for one of the voltages, so that, for example, during sequential processing, the other voltage is no longer measured.

[0030] If the input voltage U in compared to a previous measured value, it is no more than a predetermined first limit value, e.g. a drop compared to a previously determined input voltage or a nominal input voltage of up to 0.5...2.5%, and the output voltage U out greater than or equal to a first voltage value U out1 e.g. greater than or equal to 0.3 U in If the adjustable maximum current I is reached, it will be... max in one step 800a to a first maximum value I max1 specified, which is greater than the nominal value I N) is, for example, 5 times the rated current, and a monitoring interval t I to a first value t I1 e.g. set to 3 ms.

[0031] If the input voltage U in compared to a previous measured value, the value is lower than a predetermined first limit but less than or equal to a fourth limit, e.g. less than or equal to 5%, or if the output voltage U has dropped. out If the voltage value is smaller than the first voltage value but greater than or equal to a second voltage value, the maximum current I is max in one step 800b to a second maximum value I max2 specified, which is greater than the nominal value I N ), but smaller than the first maximum value I max1 is, for example, 3 times the rated current, and a monitoring interval t I to a second value t I2 is set where the second value is greater than the first value, e.g. 10 ms.

[0032] If the input voltage has dropped by more than a predetermined fifth limit value, which is greater than the fourth limit value (e.g., more than 5%) compared to a previous measurement, the maximum current I will be max to a third maximum value I max3 in a step 800c, which is larger than the nominal value I N , but smaller than the second maximum value I max2 is, for example, 1.1 times the rated current, and a monitoring interval t I to a third value t I3 specified, where the third value is greater than the second value, e.g. 30 ms.

[0033] It should be noted that the adjustable values ​​for current and monitoring interval may differ in the 400a...c and 800a...c steps.

[0034] According to one embodiment of the invention, the maximum current can be increased continuously or in discrete steps, particularly during a start-up phase 50. Without limiting the generality, it is also possible to increase the maximum current I max This can also be increased continuously or in discrete steps.

[0035] In a further embodiment of the invention, after the expiry of a maximum limitation period Tmax or upon reaching a maximum number of iterations of the previous steps 500 ... 800a...c, the maximum current I max The value is set to 0 in a step of 900. In such a case, it is assumed that there is no charging of a capacitor, but rather a short circuit.

[0036] According to another embodiment of the invention, the current limiting ends when, in step 1000, it is determined that the output voltage U outhas reached a predetermined value in relation to the input voltage, e.g. 0.8 times the input voltage.

[0037] In another embodiment of the invention, the monitoring interval and the maximum current can be dynamically adjusted, e.g., based on the measured voltage drop in steps of 400a, 400b, 400c, 800a, 800b, 800c. For example, the current can be changed in a ramp-like manner (stepwise or continuously). It can also be provided, for example, that the maximum current is increased to its maximum value up to a certain voltage drop and then reduced again when this specific voltage drop is reached or exceeded.

[0038] Without limiting the generality, the invention can also be embodied in an electronic circuit breaker with active current limiting and a control unit, wherein the control unit is set up to execute one of the previously described methods.

[0039] In particular, the electronic circuit breaker can have an active component that can be operated in linear mode, at least temporarily. This active component can be, for example, a power transistor, especially a MOSFET transistor.

[0040] According to the invention, a method is thus provided which enables an automatic adjustment of the current limiting level, adapted to the strength of the available energy source, in the event of an inrush current.

[0041] For this purpose, the combination of certain indicators can be used as a limiting factor. • Drop in supply voltage Uin • Level of output voltage Uout, • Height of the current I

[0042] The process can be divided as follows: Overcurrent during ongoing channel operation (as previously described)

[0043] First, a current demand exceeding the nominal value can be detected. This triggers active current limiting.

[0044] When the combinations of predefined nominal current multiples (x In) and supply voltage dips Uin are exceeded, the current flow to the protected channel output can be limited as follows, for example: • In case of a small voltage drop (e.g. less than 2.5%) -> limitation to 5 x In • In case of moderate voltage drop (e.g. ≤ 10%) -> limitation to 3 x In • In case of a significant voltage drop (e.g., > 10%) -> limitation to 1.1 x In

[0045] This allows for a more sensitive response to significant voltage drops.

[0046] While this makes regulated, current-limited operation fundamentally possible, it must also be monitored to prevent the circuit breaker from being overloaded.

[0047] In subsequent continuous monitoring, the limit can therefore be reassessed after each monitoring interval. The limit can be based on the previous limits or chosen differently.

[0048] Depending on the stability of the supply voltage Uin and the time course of the output voltage Uout, the current limiting phase can be initiated after a predefined time, for example. • 3 ms for limiting to 5x In • 10 ms for limiting to 3x In • 30 ms for limiting to 1.1 in The output channel can be adjusted to a new value or repeated, or the output channel can be completely de-energized.

[0049] If the conditions shown below are not met, or if the repetition of the limiting phases has exceeded a predefined number / duration, the channel can be switched off: • In case of a small voltage drop (e.g. less than 2.5%) and Uout = 0.3 x Uin -> limitation to 5 x In • In case of moderate voltage drop (e.g. ≤ 5%) or Uout > 0.2 x Uin...< 0.3 x Uin -> limitation to 3 x In • In case of a significant voltage drop (e.g., ≤ 10%) or Uout > 0.1 x Uin...< 0.2 x Uin -> limitation to 1.1 x Uin

[0050] The current limiting routine can also end.

[0051] The limiting routine ends when the channel has been completely switched off or de-energized, or when, after the maximum limiting duration has elapsed, the output voltage Uout has almost reached the level of the supply voltage and the supply voltage has not fallen below its predefined minimum value, e.g. 0.8 x Un. Initial phase

[0052] However, an analogous procedure can also take place during a start-up phase, i.e., when the circuit breaker is put into operation on the network, for example by switching on a channel, which is outlined below.

[0053] The current flow in the protected channel output can be increased continuously up to the desired limiting threshold (e.g., ramp-like), whereby the limiting threshold can be varied depending on the stability of the supply voltage Uin, i.e., and the time course of the output voltage (Uout).

[0054] Smaller thresholds can be set in the case of strong supply voltage dips and weak output voltage increases, for example • In case of a small voltage drop (e.g. ≤ 2.5%) -> limitation to 5 x In • In case of moderate voltage drop (e.g. ≤ 10%) -> Limit to 3 x In • In case of a significant voltage drop (e.g., > 10%) -> limitation to 1.1 x In

[0055] Obviously, different thresholds may be set during start-up than during ongoing operation.

[0056] Following the setting of a limit, continuous monitoring can follow in an analogous manner with repeated selection of a limit level.

[0057] Depending again on the stability of the supply voltage (Uin) and the time course of the output voltage (Uout), the current limiting phase can be adjusted to a new value or repeated after a predefined time (e.g. 3 ms for 5 x In, 10 ms for 3 x In, 20 ms for 1.1 In), or the output channel can be completely switched off.

[0058] If the conditions, as illustrated below, are not met, or if the repetition of the limiting phases has exceeded a predefined number / time, the channel can be switched off: • In case of a small voltage drop (e.g. less than 2.5%) and Uout = 0.3 x Uin -> limitation to 5 x In • In case of moderate voltage drop (e.g. ≤ 5%) or Uout > 0.2 x Uin...< 0.3 x Uin -> limitation to 3 x In • In case of a significant voltage drop (e.g., ≤ 10%) or Uout > 0.1 x Uin...< 0.2 x Uin -> limitation to 1.1 x Uin

[0059] The current limiting routine can also end.

[0060] The limiting routine ends when the channel has been completely switched off or de-energized, or when, after the maximum limiting duration has elapsed, the output voltage Uout has almost reached the level of the supply voltage and the supply voltage has not fallen below its predefined minimum value, e.g. 0.8 x Un.

Claims

[1] Method for controlling a circuit breaker with active current limiting comprising the steps: • Measurement (100) of a current (I) through the circuit breaker, • If the measured current (I) is greater than the nominal value (I) N ) (200) is, check (300) whether the input voltage has dropped compared to a previous measurement, • If the input voltage has not dropped by more than a predetermined first limit value compared to a previous measured value, the maximum current (I) max ) to a first maximum value (I max1 ) determine (400a) which is greater than the nominal value (I N ) is, and setting (400a) a monitoring interval (t I ) to a first value (t I1 ), • If the input voltage is higher than a predetermined first limit value compared to a previous measurement, but lower than or equal to a second limit value, the maximum current (I) max) to a second maximum value (I max2 ) determine (400b), which is greater than the nominal value (I N ), but smaller than the first maximum value (I max1 ) is, and setting (400b) a monitoring interval (t I ) to a second value (t I2 ), where the second value (t I2 ), greater than the first value (t I1 ) is, • If the input voltage has dropped by more than a predetermined second limit value compared to a previous measured value, the maximum current (I) max ) to a third maximum value (I max3 ) set (400c), which is greater than the nominal value (I N ), but smaller than the second maximum value (I max2 ) is, and setting (400c) a monitoring interval (t I ) to a third value (t I3 ), where the third value (t I3 ), greater than the second value (t I2 ) is, • After setting the maximum current, measure (500) a current (I) after the set monitoring interval (t I ) . • if the measured current (I) is greater than the nominal value (I) N ) (550) Determination (700) of the input voltage and the output voltage, • Check (600) whether the input voltage has dropped compared to a previous measurement, • If the input voltage has not dropped by more than a predetermined first limit value compared to a previous measured value and the output voltage (U out ) greater than or equal to a first voltage value (U) out1 ) is, the maximum current (I max ) to a first maximum value (I max1 ) determine (800a) which is greater than the nominal value (I N ) is, and setting a monitoring interval (t I ) to a first value (t I1 ), • If the input voltage has dropped by more than a predetermined first limit value but less than or equal to a fourth limit value compared to a previous measured value, or if the output voltage is less than the first voltage value but greater than or equal to a second voltage value, the maximum current (I max ) to a second maximum value (I max2 ) set (800b) which is greater than the nominal value (I N ), but smaller than the first maximum value (I max1 ) is, and setting a monitoring interval (t I ) to a second value (t I2 ), where the second value is greater than the first value, • If the input voltage has dropped by more than a predetermined fifth limit value, which is greater than the fourth limit value, compared to a previous measurement, the maximum current (I) max ) to a third maximum value (I max3 ) set (800c), which is greater than the nominal value (I N), but smaller than the second maximum value (I max2 ) is, and setting a monitoring interval (tl) to a third value (tl3), where the third value is greater than the second value. [2] Method according to claim 1, characterized by , that during a start-up phase (50) the current continuously or in discrete steps the maximum current (I max ) is increased. [3] Method according to claim 1 or 2, characterized by , that after the expiry of a maximum limit duration (Tmax) or upon reaching a maximum number of cycles (900) the maximum current (I max ) is set to 0. [4] Method according to any one of the preceding claims, characterized by , that the current limiting ends (1000) as soon as the output voltage reaches a predetermined value relative to the input voltage. [5] Method according to any one of the preceding claims, characterized by, that the monitoring interval and the maximum current are dynamically set based on the measured voltage drop (400a 400b, 400c, 800a, 800b, 800c), e.g. by increasing the current gradually or continuously up to the maximum value. [6] Electronic circuit breaker with active current limiting comprising a control system configured to execute one of the methods according to any of the preceding claims. [7] Electronic circuit breakers according to claim 6, comprising an active component which can be operated in linear mode at least temporarily. [8] Electronic circuit breakers according to claim 6, comprising a power transistor, in particular a MOSFET transistor.

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