Method for controlling a circuit breaker with an active current limitation function, and circuit breaker designed to carry out such a method

Abstract

The invention relates to a method for controlling a circuit breaker with an active current limitation function. The invention additionally relates to an electronic circuit breaker with an active current limitation function, comprising a controller designed to carry out such a method.

Description

[0001] Method for controlling a circuit breaker with active current limiting and circuit breaker set up for executing such a method

[0002] 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.

[0003] background

[0004] Current-limiting or current-switching elements can be found in many areas of electrical systems and devices.

[0005] 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 (12–48 V DC). Correspondingly, the available output current is also low.

[0006] 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.

[0007] The applicant offers the CBM E... product family as an example of an active current-limiting circuit breaker. In this system, 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 this example, a semiconductor MOSFET is operated in linear mode for current limiting. A disadvantage of this approach is that the current is always limited to a small value, typically optimized for low-power power supplies as a worst-case application. The current limiting level remains constant, even in higher-powered power supplies, regardless of whether it is a fault-induced short-circuit current or a regular or desired load inrush current, such as for charging capacitors in a load.

[0008] 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.

[0009] Task

[0010] 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.

[0011] Brief description of the invention

[0012] 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.

[0013] Brief description of the characters

[0014] The invention will now be explained in more detail with reference to a drawing and exemplary embodiments.

[0015] The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0016] Figure 1 schematically shows a variant of a flowchart according to embodiments of the invention.

[0017] Detailed description of the invention

[0018] 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.

[0019] 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.

[0020] Information with numerical values ​​should generally not be understood as exact values, but also include a tolerance of + / - 1% to + / - 10%.

[0021] 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.

[0022] In one embodiment of the invention, which is described by way of example with reference to Figure 1, a method for controlling a circuit breaker with active current limiting is provided.

[0023] Unless explicitly stated as being to be carried out in a specific order, the steps described below can be arranged in any sequence or considered in parallel. The following section describes an ongoing operation, but the considerations are equally applicable to a start-up phase.

[0024] First, it is assumed that in step 100 a current I is measured through the circuit breaker.

[0025] In step 200, it is first checked whether the measured current I is equal to the nominal value l N exceeds. If the measured current I exceeds the nominal value l NIn a further step, 300 can be checked to see if the input voltage has dropped compared to a previous measurement.

[0026] 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.

[0027] 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 l m ax to a first maximum value l maxi in a step 400a, which is larger than the nominal value l Nis, for example, 5 times the rated current, and furthermore a monitoring interval ti is set to a first value tu, for example 3 ms.

[0028] 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 l m ax to a second maximum value I m ax2 set in a step 400b, which is larger than the nominal value l N , but smaller than the first maximum value l maxiThe input voltage is, for example, 3 times the rated current, and a monitoring interval ti is further defined based on a second value tiz, where the second value tiz is greater than the first value tu, for example, 10 ms. If the input voltage has dropped by more than a predetermined second limit value compared to a previous measurement, for example, a drop of 10% or more compared to a previously defined input voltage or a rated input voltage, the maximum current l is set. m ax to a third maximum value I m ax3, set in a step of 400c, which is greater than the nominal value l N , but smaller than the second maximum value I m ax2 is, for example, 1.1 times the rated current, and furthermore, a monitoring interval ti is set to a third value tß, where the third value tß is greater than the second value tiz, for example, 30 ms.

[0029] After both a maximum current and a monitoring interval have been determined, in step 500 the current I through the circuit breaker is determined again after the specified monitoring interval ti.

[0030] If the measured current I is greater than the nominal value l N In step 550, the input voltage and output voltage are determined in step 700.

[0031] 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.

[0032] Now, in step 700, both the input voltage and the output voltage can also be determined.

[0033] Obviously, the determination of the input and output voltages can take place simultaneously or sequentially. It can also be provided that the process terminates when certain limits of one of the voltages are reached, so that, for example, during sequential processing, the other voltage is no longer measured. This applies if the input voltage U is no 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 defined input voltage or a nominal input voltage, and the output voltage U ou t is greater than or equal to a first voltage value U ou ti, e.g. greater than or equal to 0.3 Uj n If the adjustable maximum current is l m ax in one step 800a to a first maximum value Imaxi, which is greater than the nominal value l N) is, for example, 5 times the rated current, and a monitoring interval ti is set to a first value tu, for example, 3 ms.

[0034] If the input voltage Um has dropped by more than a predetermined first limit value, but less than or equal to a fourth limit value, e.g. less than or equal to 5%, compared to a previous measured value, or if the output voltage U ou If t is smaller than the first voltage value but greater than or equal to a second voltage value, the maximum current l m ax in one step 800b to a second maximum value I m ax2 is set, which is greater than the nominal value l N ), but smaller than the first maximum value l maxi is, for example, 3 times the rated current, and a monitoring interval ti is set to a second value tiz, where the second value is greater than the first value, for example, 10 ms.

[0035] 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 l m ax to a third maximum value I m ax3 set in a step of 800c, which is larger than the nominal value l N , but smaller than the second maximum value I m ax2 is, for example, 1.1 times the rated current, and a monitoring interval ti is set to a third value tß, where the third value is greater than the second value, for example, 30 ms.

[0036] It should be noted that the adjustable values ​​for current and monitoring interval may differ in the 400a...c and 800a...c steps.

[0037] 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 l m This can also be increased continuously or in discrete steps. In a further embodiment of the invention, after a maximum limiting time Tmax has elapsed or upon reaching a maximum number of iterations of the previous steps 500 ... 800a...c, the maximum current l m ax 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.

[0038] According to another embodiment of the invention, the current limiting ends when, in step 1000, it is determined that the output voltage U out has reached a predetermined value with respect to the input voltage, e.g. 0.8 times the input voltage.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The combination of certain indicators can be used as a limiting factor. Drop in supply voltage Uin

[0044] Output voltage Uout level

[0045] Height of the current I

[0046] The process can be divided as follows:

[0047] Overcurrent during ongoing channel operation (as previously described)

[0048] First, a current demand exceeding the nominal value can be detected. This triggers active current limiting.

[0049] 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:

[0050] • In case of a small voltage drop (e.g. less than 2.5%) — > Limit to 5 x In

[0051] • in case of moderate voltage drop (e.g. < 10%) — > Limit to 3 x In

[0052] • in case of a significant voltage drop (e.g. > 10%) — > limitation to 1.1 x In

[0053] This allows for a more sensitive response to significant voltage drops.

[0054] While this makes regulated, current-limited operation fundamentally possible, it must also be monitored to prevent the circuit breaker from being overloaded.

[0055] In subsequent continuous monitoring, the current limit can therefore be reassessed after each monitoring interval. The limit can be based on previous limits or chosen differently. Depending on the stability of the supply voltage Uin and the time course of the output voltage Uout, the current limiting phase can be triggered after a predefined time, for example.

[0056] • 3 ms for limiting to 5 x In

[0057] • 10 ms for limiting to 3x In

[0058] • 30 ms for limiting to 1.1 In, adjusted to a new value or repeated, or the output channel completely de-energized.

[0059] 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:

[0060] • In case of a small voltage drop (e.g. less than 2.5%) and Uout = 0.3 x Uin -> limitation to 5 x In

[0061] • In case of moderate voltage drop (e.g., < 5%) or Uout > 0.2 x Uin...< 0.3 x Uin -> limitation to 3 x In

[0062] • 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

[0063] The current limiting routine can also end.

[0064] 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.

[0065] Initial phase

[0066] However, an analogous procedure can also be used during a start-up phase, i.e., when the circuit breaker is activated on the mains, for example by switching on a channel. This procedure is outlined below. The current flow in the protected channel output can be increased continuously (e.g., ramp-like) up to the desired limiting threshold, 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).

[0067] Smaller thresholds can be set in the case of strong supply voltage dips and weak output voltage increases, for example

[0068] • in case of a small voltage drop (e.g. < 2.5%) — > limitation to 5 x In

[0069] • In case of moderate voltage drop (e.g. < 10%) —> Limit to 3 x In

[0070] • in case of a significant voltage drop (e.g. > 10%) — > limitation to 1.1 x In

[0071] Obviously, different thresholds may be set during start-up than during ongoing operation.

[0072] Following the setting of a limit, continuous monitoring can follow in an analogous manner with repeated selection of a limit level.

[0073] 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.

[0074] 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:

[0075] • In case of a small voltage drop (e.g. less than 2.5%) and Uout = 0.3 x Uin -> limitation to 5 x In

[0076] • In case of moderate voltage drop (e.g., < 5%) or Uout > 0.2 x Uin...< 0.3 x Uin -> Limit to 3 x Uin • In case of greater voltage drop (e.g., < 10%) or Uout > 0.1 x Uin...< 0.2 x Uin -> Limit to 1.1 x Uin

[0077] The current limiting routine can also end.

[0078] 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

Claims 1. A 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 (l) 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 (l m ax) to a first maximum value (Imaxi) (400a) that is greater than the nominal value (l N ) is, and setting (400a) a monitoring interval (ti) to a first value (tu), • 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 (l) max) to a second maximum value (Lax?) (400b), which is greater than the nominal value (l) N ), but is smaller than the first maximum value (Imaxi), and setting (400b) a monitoring interval (ti) to a second value (tiz), where the second value (tiz) is greater than the first value (tu), • If the input voltage has dropped by more than a predetermined second limit value compared to a previous measured value, the maximum current (l m ax) to a third maximum value (Laxs) (400c), which is greater than the nominal value (l N ), but is smaller than the second maximum value (lmax?), and setting (400c) a monitoring interval (ti) to a third value (tß), where the third value (tß) is greater than the second value (tß), • After setting the maximum current, measure (500) a current (I) after the set monitoring interval (ti). • if the measured current (I) is greater than the nominal value (l)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 ou t) greater than or equal to a first voltage value (U) ou ti) is, the maximum current (Lax) set to a first maximum value (Imaxi) (800a) that is greater than the nominal value (l) N ) is, and setting a monitoring interval (ti) to a first value (tu), • 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 measurement, 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 (l m ax) to a second maximum value (Lax?) (800b), which is greater than the nominal value (l N ), but is smaller than the first maximum value (Imaxi), and setting a monitoring interval (ti) to a second value (tiz), where the second value is larger 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 measured value, the maximum current (l) m ax) to a third maximum value (Laxs) (800c), which is greater than the nominal value (l N), but is smaller than the second maximum value (lmax?), 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 in that in a switching-on phase (50) the current is continuously or in discrete steps the maximum current (l m ax) is increased.

3. Method according to claim 1 or 2, characterized in that after expiry of a maximum limitation period (Tmax) or upon reaching a maximum number of cycles (900) the maximum current (l m ax) is set to 0.

4. Method according to one of the preceding claims, characterized in that the current limiting ends (1000) as soon as the output voltage reaches a predetermined value with respect to the input voltage.

5. Method according to one of the preceding claims, characterized in that the monitoring interval and the maximum current are dynamically set on the basis of the measured voltage dip (400a 400b, 400c, 800a, 800b, 800c), e.g. by increasing the current stepwise or continuously up to the maximum value.

6. Electronic circuit breaker with active current limiting with a control system configured to execute one of the methods according to one of the preceding claims.

7. Electronic circuit breakers according to claim 6, comprising an active component that 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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