CN111049097A - Circuit overload protection method and overcurrent protection device - Google Patents

Circuit overload protection method and overcurrent protection device Download PDF

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Publication number
CN111049097A
CN111049097A CN201811186671.6A CN201811186671A CN111049097A CN 111049097 A CN111049097 A CN 111049097A CN 201811186671 A CN201811186671 A CN 201811186671A CN 111049097 A CN111049097 A CN 111049097A
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Prior art keywords
current
circuit
current value
overload
protection device
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CN201811186671.6A
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Chinese (zh)
Inventor
杨鹏
乐成彦
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Hella Shanghai Electronics Co Ltd
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Hella Shanghai Electronics Co Ltd
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Priority to CN201811186671.6A priority Critical patent/CN111049097A/en
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02HEMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current

Abstract

The invention provides a method for protecting circuit overload, which is applied to an electric appliance system and comprises the following steps: s1: detecting a current value in a circuit of an electrical appliance system; s2: sampling current value detection results in a preset time interval before the current moment for a preset number of times, wherein the time intervals between two adjacent sampling times are the same, calculating an effective current value in the preset time interval according to the sampling times and the current value obtained by each sampling, then comparing the effective current value with a preset maximum allowable value of overload current, and judging the current in the circuit at the current moment to be the overload current when the effective current value is greater than the preset maximum allowable value of the overload current; s3: and when the current in the circuit at the current moment is the overload current, cutting off the power supply of the electrical appliance system. The invention also provides an overcurrent protection device. After the technical scheme is adopted, the overcurrent protection device can not be influenced by the ambient temperature, can judge the overcurrent, and does not need to replace the fuse.

Description

Circuit overload protection method and overcurrent protection device
Technical Field
The invention relates to the technical field of electrical appliance systems, in particular to a circuit overload protection method and an overcurrent protection device.
Background
Usually, a thermal relay or a fuse is adopted in an electrical system to perform overload and short-circuit protection, and the protection method has the advantages of simple circuit structure, easiness in implementation and the like, but the overcurrent protection device implemented based on electrical hardware also has some problems in practical application.
Firstly, the overcurrent protection devices such as fuses are easily affected by the ambient temperature during operation, which causes protection failure or malfunction, and affects the accuracy of the set protection current value. On one hand, the change of the environmental temperature can influence the heat dissipation condition of the related melt in the air, and the temperature rise curve of the melt is inevitably influenced by heat dissipation under the condition of long-time overload, so that the accurate control of the overload set value is not facilitated. On the other hand, the fuse melt is sensitive to temperature, and under the action of a certain high temperature for a long time, the melting point and the impedance of the fuse melt change, and the change affects the accuracy of the fuse, namely the aging of the fuse. Due to the long-term accumulation of heat, the fuse is aged to cause the protection value to deviate from the set current value, and the aged fuse is very dangerous to use in a circuit.
Secondly, the current of some circuits at the switching instant is several times larger than the normal operating current, and although this current peak is high, it occurs for a short time, which we call it a pulse current, also called a rush current or surge current. Such pulse type overcurrent does not pose a threat to many electrical systems, but may cause the actions of many overcurrent protection devices such as ordinary fuses and relays, and unnecessary frequent protection will make the circuit unable to work normally; if a larger size fuse is used, it is not protected when the circuit is overloaded.
Finally, the fuse type overcurrent protection device needs to be replaced after the overcurrent is blown, even if the fuse is not blown after a long time use, the fuse may be aged, and the fuse needs to be replaced at the moment, so that nonferrous metals are consumed, and the hardware cost of the protection device is increased.
Therefore, it is necessary to develop a circuit overload protection method and an overcurrent protection device that can discriminate an overcurrent without being affected by an ambient temperature and that does not require hardware replacement.
Disclosure of Invention
In order to overcome the above technical drawbacks, an object of the present invention is to provide a method for protecting an overload circuit and an overcurrent protection device, which are not affected by ambient temperature, can determine an overload current, and do not require hardware replacement.
The invention discloses a method for protecting circuit overload, which is applied to an electric appliance system and comprises the following steps: s1: detecting a current value in the electric appliance system circuit; s2: sampling current value detection results in a preset time interval before the current moment for a preset number of times, wherein the time intervals between two adjacent sampling times are the same, calculating an effective current value in the preset time interval according to the sampling times and the current value obtained by each sampling, then comparing the effective current value with a preset maximum allowable value of overload current, and when the effective current value is greater than the preset maximum allowable value of the overload current, judging that the current in the circuit at the current moment is the overload current; s3: and when the current in the circuit at the current moment is the overload current, cutting off the power supply of the electrical appliance system.
Preferably, the effective current value is calculated according to the following formula:
Figure BDA0001826394880000021
wherein:
Figure BDA0001826394880000022
is the effective current value; k is the preset times; i.e. inIs the current value of the nth sample.
The invention also discloses an overcurrent protection device, which is applied to an electrical system and comprises:
the current detection circuit is used for detecting the current value in the electrical system circuit;
the signal conditioning circuit is connected with the current detection circuit and is used for converting the detection result of the current detection circuit from an analog signal to a digital signal;
the single chip microcomputer is connected with the signal conditioning circuit, reads the digital signal, samples current value detection results in a preset time interval before the current moment for preset times, calculates an effective current value in the preset time interval according to the sampling times and the current value obtained by each sampling, compares the effective current value with a preset maximum allowable value of overload current, and judges that the current in the circuit at the current moment is the overload current when the effective current value is greater than the preset maximum allowable value of the overload current;
and the execution mechanism is connected with the single chip microcomputer and is used for cutting off the power supply of the electrical appliance system when the single chip microcomputer judges that the current in the circuit at the current moment is the overload current.
Preferably, the effective current value is calculated according to the following formula:
Figure BDA0001826394880000031
wherein:
Figure BDA0001826394880000032
is the effective current value; k is the preset times; i.e. inIs the current value of the nth sample.
Preferably, the overcurrent protection device further comprises a display screen, and the display screen is electrically connected with the single chip microcomputer.
Preferably, the display screen is a touch display screen and is used for realizing human-computer interaction; or the current protection device further comprises an operation key, and the operation key is electrically connected with the display screen and used for realizing human-computer interaction.
Preferably, the current detection circuit comprises a current transformer.
Preferably, the current detection circuit comprises a rectifier bridge.
Preferably, the current detection circuit comprises a hall-type current sensor.
Preferably, the actuator comprises an electric actuator.
After the technical scheme is adopted, compared with the prior art, the method has the following beneficial effects:
1. is not influenced by the ambient temperature.
2. The overload current can be judged, the circuit is protected when the overload occurs, and unnecessary frequent protection can not be carried out on the circuit due to the pulse current.
3. The fuse does not need to be replaced, the operation is simplified, and the consumption of nonferrous metals is reduced.
Drawings
Fig. 1 is a schematic diagram of an overcurrent protection apparatus according to an embodiment of the invention.
Detailed Description
The advantages of the invention are further illustrated in the following description of specific embodiments in conjunction with the accompanying drawings.
The terminology used in the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used in this disclosure and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.
In the description of the present invention, unless otherwise specified and limited, it is to be noted that the terms "mounted," "connected," and "connected" are to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, a communication between two elements, a direct connection, or an indirect connection via an intermediate medium, and specific meanings of the terms may be understood by those skilled in the art according to specific situations.
In the following description, suffixes such as "module", "component", or "unit" used to denote elements are used only for facilitating the explanation of the present invention, and have no specific meaning in themselves.
The invention discloses a method for protecting circuit overload, which is applied to an electric appliance system and comprises the following steps:
s1: detecting the current value in the electric appliance system circuit through a current detection circuit;
s2: and sampling the current value detection result in a preset time interval before the current moment by using the single chip microcomputer for a preset number of times, wherein the time intervals between two adjacent samplings are the same. Specifically, the sampling time interval (i.e., the preset time interval) and the sampling number (i.e., the preset number) are preset according to the current condition of the electrical system. For example, if the preset time interval is 10ms and the preset sampling frequency is 5 times, it means that the current value detected by the current detection circuit is sampled 5 times in a time segment 10ms before the current time, and the time interval of each sampling is 2 ms.
And then, calculating the effective current value in the preset time interval according to the sampling times and the current value obtained by each sampling.
According to the active current calculation method, the effective current is calculated within a preset time interval delta t from the current time t
Figure BDA0001826394880000041
Is provided with
Figure BDA0001826394880000042
Where i (t) is a real-time current function, Δ t is a preset time interval, and may be taken as a calculation judgment period. Thus, the discretized effective current value
Figure BDA0001826394880000043
Is composed of
Figure BDA0001826394880000044
Wherein k is the number of current samples within a predetermined time interval Δ t, i.e. the predetermined number of times, inIs the current value at the nth sampling. In application, the time interval t of each samplingrIs composed of
Figure BDA0001826394880000045
Then, the effective current value is measured
Figure BDA0001826394880000046
And a preset maximum allowable value I of the overload currentMComparing when the effective current value is larger than the preset maximum allowable value of the overload current, namely
Figure BDA0001826394880000047
And judging that the current in the circuit at the current moment is overload current, namely the circuit of the electrical appliance system is overloaded.
S3: and when the current in the circuit at the current moment is the overload current, the power supply of the electrical appliance system is cut off, so that the electrical appliance system is prevented from being damaged by overload.
The method for circuit overload protection judges whether the circuit is overloaded or not by calculating the effective current value in a period of time and comparing the effective current value with the preset maximum allowable value of the overload current. Knowing that the overload current is long-term and the pulse current is transient, according to the time delay characteristic of the circuit, calculating the effective current value in a period of time through discretized time current integration, and distinguishing the overload current from the pulse current so as to judge whether the circuit is overloaded or not. And the power supply is cut off under the condition of overload, so that the safety of an electrical appliance system is ensured. The method can not cause unnecessary frequent protection due to the pulse current, and can not influence the normal work of an electric appliance system. The circuit is protected only in the event of overload.
Meanwhile, for different maximum current requirements and delay characteristic requirements of various electrical system circuits, only the maximum allowable value I of the overload current of the parameter needs to be adjustedMThe preset time interval delta t and the preset sampling times k can be realized, and the method has wide applicability.
Referring to fig. 1, the present application also discloses an overcurrent protection device applied to an electrical system, the overcurrent protection device comprising:
-current detection circuit
The current detection circuit is used for detecting the current value in the electric appliance system circuit and outputting an analog signal. Preferably, the current detection circuit comprises a hall-type current sensor. In some embodiments, the current detection circuit further includes a current transformer for converting a large primary-side current into a small secondary-side current so as to detect a current value of the large-current circuit. In some embodiments, the current sensor further comprises a rectifier bridge for converting the ac voltage to an output dc voltage for detecting a value of current in the ac circuit.
-signal conditioning circuit
The signal conditioning circuit is connected with the current detection circuit and used for converting the detection result of the current detection circuit from an analog signal to a digital signal.
-single-chip microcomputer
The single chip microcomputer is connected with the signal conditioning circuit, reads the digital signal, samples current value detection results in a preset time interval before the current moment for preset times, calculates effective current values in the preset time interval according to the sampling times and current values obtained by each sampling, compares the effective current values with a preset maximum allowable value of overload current, and judges that the current in the circuit at the current moment is the overload current when the effective current values are larger than the preset maximum allowable value of the overload current. Specifically, according to the active current calculation method, within a preset time interval Δ t to the present time t, for the effective current
Figure BDA0001826394880000051
Is provided with
Figure BDA0001826394880000061
Where i (t) is a real-time current function, Δ t is a preset time interval, and may be taken as a calculation judgment period. Thus, the discretized effective current value
Figure BDA0001826394880000062
Is composed of
Figure BDA0001826394880000063
Wherein k is the number of current samples within a predetermined time interval Δ t, i.e. the predetermined number of times, inIs the current value at the nth sampling. In application, the time interval t of each samplingrIs composed of
Figure BDA0001826394880000064
Then, the effective current value is measured
Figure BDA0001826394880000065
And a preset maximum allowable value I of the overload currentMComparing when the effective current value is larger than the preset maximum allowable value of the overload current, namely
Figure BDA0001826394880000066
And judging that the current in the circuit at the current moment is overload current, namely the circuit of the electrical appliance system is overloaded.
-an actuator
The executing mechanism is connected with the single chip microcomputer and used for cutting off the power supply of the electrical appliance system when the single chip microcomputer judges that the current in the circuit at the current moment is the overload current. Preferably, the executing mechanism comprises an electric actuator and a protection switch, when the single chip microcomputer judges that the current in the circuit at the current moment is the overload current, the single chip microcomputer controls the electric actuator to act, and the electric actuator drives the protection switch to be disconnected, so that the power supply is cut off, and the purpose of protecting the circuit is achieved. Preferably, the electric actuator may be a motor.
Further, the overcurrent protection device further comprises a display screen, and the display screen is electrically connected with the single chip microcomputer.
In some embodiments, the display screen is a touch display screen for human-computer interaction. Specifically, a parameter overcurrent maximum allowable value (I) is preset in a single chip microcomputerM) The corresponding relation between the preset time interval (delta t) and the preset sampling times (k) and the existing fuse type is realized through the human-computer interaction of the touch display screen, and the maximum allowable value (I) of the overload current can be correspondingly realized by the singlechip if the fuse type is selected on the touch display screenM) The preset time interval (delta t) and the preset number of sampling times (k) are set, so that the current protection device can achieve the technical effect basically the same as the fuse type. However, the difference is that the fuse blows at a specific overcurrent or pulse current, and the overcurrent protection device of the present application cuts off the power supply at the overcurrent and does not operate at the allowable pulse current.
In other implementations, the overcurrent protection device further includes a physical key, and the operation key is electrically connected to the display screen and is used for implementing human-computer interaction. Similar to the above embodiment of the touch display screen, the maximum allowable value (I) of the overload current is preset in the single chip microcomputerM) The difference is that the embodiment is operated through an entity key, and the embodiment is operated through a touch display screen.
The overcurrent protection device does not have a fuse body of a fuse wire type, cannot influence the function and the effect of the overcurrent protection device due to the environment temperature, does not need to replace the fuse wire, simplifies the manual operation, reduces the consumption of nonferrous metals, and saves the hardware cost. Simultaneously, the overcurrent protection device of the application can judge the overload current, protect the circuit when in overload, and avoid carrying out unnecessary frequent protection on the circuit due to the pulse current.
It should be noted that the embodiments of the present invention have been described in terms of preferred embodiments, and not by way of limitation, and that those skilled in the art can make modifications and variations of the embodiments described above without departing from the spirit of the invention.

Claims (10)

1. A method for protecting circuit overload is applied to an electrical system, and is characterized by comprising the following steps:
s1: detecting a current value in the electric appliance system circuit;
s2: sampling current value detection results in a preset time interval before the current moment for a preset number of times, wherein the time intervals between two adjacent sampling times are the same, calculating an effective current value in the preset time interval according to the sampling times and the current value obtained by each sampling, then comparing the effective current value with a preset maximum allowable value of overload current, and when the effective current value is greater than the preset maximum allowable value of the overload current, judging that the current in the circuit at the current moment is the overload current;
s3: and when the current in the circuit at the current moment is the overload current, cutting off the power supply of the electrical appliance system.
2. The method of claim 1, wherein the effective current value is calculated according to the following equation:
Figure FDA0001826394870000011
wherein:
Figure FDA0001826394870000012
is the effective current value; k is the preset times; i.e. inIs the current value of the nth sample.
3. An overcurrent protection device applied to an electrical system, the overcurrent protection device comprising:
the current detection circuit is used for detecting the current value in the electrical system circuit;
the signal conditioning circuit is connected with the current detection circuit and is used for converting the detection result of the current detection circuit from an analog signal to a digital signal;
the single chip microcomputer is connected with the signal conditioning circuit, reads the digital signal, samples current value detection results in a preset time interval before the current moment for preset times, calculates an effective current value in the preset time interval according to the sampling times and the current value obtained by each sampling, compares the effective current value with a preset maximum allowable value of overload current, and judges that the current in the circuit at the current moment is the overload current when the effective current value is greater than the preset maximum allowable value of the overload current;
and the execution mechanism is connected with the single chip microcomputer and is used for cutting off the power supply of the electrical appliance system when the single chip microcomputer judges that the current in the circuit at the current moment is the overload current.
4. The overcurrent protection device as set forth in claim 3, wherein said effective current value is calculated according to the following formula:
Figure FDA0001826394870000021
wherein:
Figure FDA0001826394870000022
is the effective current value; k is the preset times; i.e. inIs the current value of the nth sample.
5. The overcurrent protection device as recited in claim 3, wherein the overcurrent protection device further comprises a display screen, the display screen being electrically connected to the single-chip microcomputer.
6. The overcurrent protection device as recited in claim 5, wherein the display screen is a touch display screen for human-computer interaction;
or the current protection device further comprises an operation key, and the operation key is electrically connected with the display screen and used for realizing human-computer interaction.
7. The overcurrent protection device as recited in claim 3, wherein said current sensing circuit comprises a current transformer.
8. The overcurrent protection device as set forth in claim 3, wherein said current sensing circuit comprises a rectifier bridge.
9. The overcurrent protection device as set forth in claim 3, wherein said current detection circuit comprises a Hall type current sensor.
10. The overcurrent protection device as set forth in claim 3, wherein said actuator comprises an electric actuator and a protection switch.
CN201811186671.6A 2018-10-12 2018-10-12 Circuit overload protection method and overcurrent protection device Withdrawn CN111049097A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111668804A (en) * 2020-06-22 2020-09-15 联想(北京)有限公司 Overcurrent protection method and device and electronic equipment

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1667905A (en) * 2004-03-10 2005-09-14 上海电器科学研究所(集团)有限公司 Current sampling and effective value determination method for circuit breaker release
CN101242096A (en) * 2008-02-04 2008-08-13 南京因泰莱配电自动化设备有限公司 Current protection control method and device
CN201707389U (en) * 2010-04-28 2011-01-12 维嘉数控科技(苏州)有限公司 Supply current detection device of high speed alternating current motor
CN103116128A (en) * 2013-01-25 2013-05-22 河北工业大学 Breaker overload testing device and operation method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1667905A (en) * 2004-03-10 2005-09-14 上海电器科学研究所(集团)有限公司 Current sampling and effective value determination method for circuit breaker release
CN101242096A (en) * 2008-02-04 2008-08-13 南京因泰莱配电自动化设备有限公司 Current protection control method and device
CN201707389U (en) * 2010-04-28 2011-01-12 维嘉数控科技(苏州)有限公司 Supply current detection device of high speed alternating current motor
CN103116128A (en) * 2013-01-25 2013-05-22 河北工业大学 Breaker overload testing device and operation method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111668804A (en) * 2020-06-22 2020-09-15 联想(北京)有限公司 Overcurrent protection method and device and electronic equipment
CN111668804B (en) * 2020-06-22 2021-10-22 联想(北京)有限公司 Overcurrent protection method and device and electronic equipment

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Application publication date: 20200421