Current parameters of the hottest low voltage circ

2022-08-20
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The current parameter of low-voltage circuit breaker

circuit breaker is one of the main protective appliances in the distribution system, and it is also the most perfect protective appliance. Its main function is to protect against short circuit, overload, grounding fault, voltage loss and undervoltage. The circuit breaker can be equipped with different relays or releases according to different needs. The release is an integral part of the circuit breaker, and the relay controls the circuit breaker through the undervoltage release and shunt release connected to the circuit breaker operating mechanism

the protection function of low-voltage circuit breaker is generally completed by the release. There are many parameters indicating the current characteristics of low-voltage circuit breakers, which are easy to be confused. In the design documents, the current value of the circuit breaker is often marked without explaining the significance of the current value, causing confusion to the order. To select the circuit breaker completely and accurately, it is necessary to clearly calibrate each current parameter of the circuit breaker

1 the national standard of rated current parameters of circuit breakers "low voltage circuit breakers for low voltage switchgear and control equipment" gbl4048.2-94 (equivalent to iec947-2) uses two concepts for the rated current of circuit breakers. The rated current of circuit breakers is 1n and the rated current of circuit breaker shell level is 1nm, and gives the following definitions: -- the rated current of circuit breakers is 1n, which refers to the current that the release can pass for a long time, that is, the rated current of the release. For the circuit breaker with adjustable release, it is the maximum current that the release can pass for a long time—— The rated current of the circuit breaker shell level is LNM, which is expressed by the maximum rated current of the release installed in the frame or plastic shell with the same basic geometric size and similar structure. The definition of rated current of circuit breaker in national standard gbl4048.2-94 is somewhat different from the concept we usually say. When we refer to the concept of "rated current of circuit breaker", we usually refer to "rated current of circuit breaker shell level" rather than "rated current of release". For example, when we choose a dz20y-100/3300-80a circuit breaker, we usually simply say that its rated current is 100A and the rated current of the release is 80A. In the product data provided by most low-voltage circuit breaker suppliers, the complex statement of "rated current of circuit breaker shell level" is generally not mentioned, but only the parameter of "rated current of circuit breaker" is given. In fact, it seems that "rated current of circuit breaker" as a short form of "rated current of circuit breaker shell level" is more appropriate. Perhaps the inconsistency between the definition of rated current in the standard and that in normal use is one of the reasons for the confusion. "Rated current of circuit breaker shell level" is a parameter indicating the current carrying capacity of the circuit breaker frame, which is mainly determined by the current carrying capacity of the main contact, and it also determines the maximum rated current value of the tripper that can be installed. This parameter is indispensable when selecting circuit breaker

2 current parameters of overcurrent release the release types of circuit breaker include overcurrent release, undervoltage release, shunt release, etc. The over-current release can also be divided into overload release and short-circuit (electromagnetic) release, and can be divided into long time delay, short time delay and instantaneous. Overcurrent release is the most commonly used. The setting value of the action current of the overcurrent release can be fixed or adjustable, and the knob or adjusting lever is usually used for adjustment. The electromagnetic over-current release can be fixed or adjustable, while the electronic over-current release is usually adjustable. According to the installation mode, the over-current release can be divided into fixed installation type or modular installation type. The fixed release and the circuit breaker shell are processed into one. Once they leave the factory, the rated current of the release is not adjustable, such as DZ20; As an installation module of the circuit breaker, the modular installation tripping can be replaced at any time with strong flexibility, such as the NS type of merlingerin company. The current indicating the overcurrent release has the following parameters: -- the rated current of the release is 1n, which refers to the maximum current that the release can pass for a long time—— The action current setting value IR of long-time overload release, 1r=in for fixed release, and IR for adjustable release is a multiple of the rated current 1n of the release, such as 1r=0.4 ~ 1 × 1n。 —— The action current setting value im of the short time-delay electromagnetic release is the multiple of the action current setting value IR of the overload release. The multiple is fixed or adjustable, such as im=2 ~ 10 × Ir。 For the non adjustable type, an appropriate setting value can be selected—— The rated value of the action current im 'of the instantaneous electromagnetic release is the multiple of the rated current in of the release. The multiple is fixed or adjustable, such as Im' =1.5 ~ 11 × In。 For the non adjustable type, an appropriate setting value can be selected

3 short circuit characteristic current parameter of circuit breaker 3.1 rated short-circuit breaking capacity ICN the rated short-circuit breaking capacity ICN of circuit breaker shall be expressed by ICU and ICs and determined in specific product standards. 3.2 rated limit short-circuit breaking capacity ICU rated limit short-circuit breaking capacity ICU is the value of breaking circuit to help you further understand the specified test voltage of the equipment and the limit short-circuit breaking current under other specified conditions, which can be expressed by the expected short-circuit current. After the o-t-co action according to the specified test procedure, the rated current of the circuit breaker will not be considered. O - indicates breaking operation; Co - indicates that the on operation is followed by the off operation; T - represents the time interval between two successive operations, generally not less than 3min. 3.3 rated operating short-circuit breaking capacity ICs rated operating short-circuit breaking capacity ICs refers to a breaking current value smaller than the rated limit short-circuit breaking current of the circuit breaker under the specified test voltage and other specified conditions, and ICs is a percentage of ICU. After the operation of o-t-co-t-co according to the specified test procedure, the circuit breaker shall have the ability to continue to carry its rated current. For miniature circuit breakers with rated short-circuit breaking capacity greater than 1500A, the national standard circuit breakers for household and similar places gbl0963 (equivalent to iecb98) stipulates that the tests of rated limit short-circuit breaking capacity ICU and rated operating short-circuit breaking capacity ICS should be carried out. When ICU ≤ 6000a, icu=ics, so only ICs test is required. Therefore, for miniature circuit breakers with short-circuit breaking capacity of 4500a and 6000a, its icu=ics=icn, so generally only its rated short-circuit breaking capacity ICN value is mentioned. 3.4 rated short-time withstand current ICW rated short-time withstand current ICW refers to the current value borne by the circuit breaker for a short time under the specified test conditions. For AC, this current value is the effective value of the periodic component of the expected short-circuit current, and the time related to the rated short-time withstand current is at least 0.05s

4 calibrate the current parameters of the circuit breaker. The short-circuit current parameters ICU, ICs and ICW of the circuit breaker need to be considered on May 7 when selecting the circuit breaker. The model of the circuit breaker and the rated current of the shell frame level INM have been determined after selecting, so there is no need to indicate otherwise; The rated current parameters of the circuit breaker and the current parameters of the selected release should be clearly marked according to the actual situation. 4.1 miniature circuit breaker MCB (miniature circuit breaker) for miniature circuit breaker MCB that processes plastic shell and overcurrent release as a whole, such as c45n series of merlingerin company, S230 series of ABB company, e4cb series of Qisheng company, domestic dzxl9 series, etc., only a value of "rated current of circuit breaker" is provided in the general product data. This parameter has the rated current of circuit breaker shell level INM, the rated current of release in The company also cooperates with a number of leading resin companies and some ultimate users, that is, inm=in=ir, while the action current rating im 'of the instantaneous electromagnetic release is generally a fixed value. Therefore, when selecting miniature circuit breakers, it is only necessary to give a current value, which will not cause ambiguity. 4.2 molded case circuit breaker MCCB (moldedcasecircuit breaker) molded case circuit breaker has a wide variety of products, and its current calibration is relatively complex. For example, domestic DZ20 series, sacemodul series of ABB company and compactns series of merlingerin company are commonly used molded case circuit breakers. When the circuit breaker is equipped with a fixed overcurrent release, the rated current in of the release is the same as the action current setting value IR of the long-time overload release, that is, in=ir, such as DZ20 series, TC series, H series circuit breakers. At this time, it is necessary to calibrate two current values, the rated current of the breaker frame level in M and the rated current of the release in (or the setting value of the action current of the long-time-delay overload release IR). The setting value im 'of the action current of the instantaneous release is a fixed value, which generally does not need to be marked. When the circuit breaker is equipped with an adjustable modular overcurrent release, each current of the release needs to be clearly calibrated. First, indicate the rated current of the shell level of the circuit breaker INM, and then indicate the selected release model and each current setting value of the release. For example, when selecting compactns series circuit breaker of merlingerin company, the following complete parameters should be given. Nsl00h type, imm=100a, equipped with str22se-40a type electronic release, in=40a, ir=0.8in (32a), im=5ir (160A), Im '≤ 11in (fixed value). 4.3 ACB (aircircuitbreaker) frame circuit breaker has perfect functions and is equipped with adjustable modular overcurrent release, such as me, dwl5, dwxl5, masterpact series of merlingerin company, asce-megamax-f series of ABB company, etc. When marking the current parameters, first mark the rated current INM of the shell level of the circuit breaker, and then mark the current setting values of the selected release and the release

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