This standard specifies the use conditions, structure and performance requirements, test and inspection rules of modular terminal combination electrical appliances (hereinafter referred to as combination electrical appliances). This standard applies to indoor fixed combination electrical appliances with an AC frequency of 50Hz and a rated voltage of 380V, with a rated current not exceeding 250A and a rated current of each short-circuit protection device not exceeding 125A. For combination electrical appliances for certain special purposes, in addition to meeting the relevant requirements of this standard, their special requirements shall be negotiated by the user and the manufacturer. JB/T 7121-1993 Modular Terminal Combination Electrical Appliances JB/T7121-1993 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
JB/T 7121 -1993
Modular Terminal Combination Electrical Appliances
Published on October 8, 1993
Ministry of Machinery Industry of the People's Republic of China
Implemented on January 1, 1994
Mechanical Industry Standard of the People's Republic of China
Modular Terminal Combination Electrical Appliances
Subject Content and Scope of Application
JB/T7121-1993
This standard specifies the use conditions, structural and performance requirements, test and inspection rules of modular terminal combination electrical appliances (hereinafter referred to as combination electrical appliances).
This standard applies to indoor fixed combination electrical appliances with an AC frequency of 50Hz and a rated voltage of up to 380V, with a rated current not exceeding 250A and a rated current of each short-circuit protection electrical appliance not exceeding 125A. For some special purpose combined electrical appliances, in addition to meeting the relevant requirements of this standard, the special requirements shall be negotiated between the user and the manufacturer. Reference standards
GB14048.1
JB6525
GB2828
3 Terms
Low voltage switchgear and controlgear
Low voltage electrical enclosure protection grade
Electrical installation rail
Basic environmental test procedures for electrical and electronic products: Test Db: Alternating damp heat test method Batch inspection Count sampling inspection and sampling table In addition to those specified in CB14048, this standard supplements the following terms. Modularization
Make the appearance, installation and connection dimensions of the card-mounted electrical appliances fully or partially meet the specified size series. 3.2
Modular terminal combination electrical appliances
Mainly used at the end of power lines, a combination of modular electrical appliances (hereinafter referred to as electrical appliances) and their electrical, mechanical connections and casing.
4.1 According to the main function, it is divided into
Protection:
Control;
Others.
4.2 According to the place of use, it is divided into
For skilled personnel (mainly used in industrial places); b.
For unskilled personnel (mainly for household and similar purposes). 4.3
Classification by enclosure protection level
See 7.1.3.
4.4Classification by installation form
Suspended type:www.bzxz.net
Embedded type:
Approved by the Ministry of Machinery Industry on October 8, 1993
Implementation on January 1, 1994
General type (applicable to both suspended and embedded types). 4.5Classification by enclosure material
Plastic enclosure;
Metal enclosure.
5Characteristics (basic parameters)
5.1Rated voltage
5.1.1Rated insulation voltage
JB/T 7121 - 1993
The rated insulation voltage of combination electrical appliances is 380V AC. 5.1.2 Rated working voltage
The rated working voltage of the combination appliance is AC 220, 220/380, 380V. 5.2 Rated current
For a combination appliance with a given circuit combination, the current (incoming current) that ensures normal operation under the conditions specified in Chapter 6, the rated current of the combination appliance should be selected from the following values: 6, 10, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250A. 5.3 Conventional thermal current
For a given enclosure, the circuit combination that may produce the highest temperature rise in the predetermined circuit combination, under the test conditions of 8.2.2, the sum of the output load currents that each component may withstand when the temperature rise does not exceed the provisions of 7.2.2 (for a three-phase circuit, it should be converted to the sum of the single-phase currents). The conventional thermal current should be selected from the values ​​listed in 5.2. 5.+Rated frequency
The rated frequency of the combination device is AC 50Hz. 5.5 Short-circuit characteristics
Rated short-time withstand current
The rated short-time withstand current of the combination device is the current specified in the product standard that the device can carry without any damage under the test conditions of 8.2.4.3.
For current, the rated short-time withstand current refers to the effective value of the AC symmetrical component, and it is considered that the maximum peak-to-peak value that may occur will not exceed n times this effective value. The coefficient n is as specified in Table 26 of GB14048.1. Unless otherwise specified, the current duration is 1s. 5.5.2 Rated short-circuit breaking capacity
The rated short-circuit breaking capacity of the combination device is the short-circuit current that can be broken under the test conditions of 8.2.4.2 specified in the product standard. For AC, it is expressed by the effective value of the AC symmetrical component of the expected breaking current. 5.5.3 Rated limiting short-circuit current
The rated limiting short-circuit current of a combination electrical appliance is specified in the product standard. Under the test conditions of 8.2.4.4, the specified short-circuit protection device is used as the protection device, and the expected short-circuit current that can be well tolerated within the action time of the short-circuit protection device. For AC, the rated limiting short-circuit current is expressed as the effective value of the AC symmetrical component. The specified short-circuit protection device can be the protection device in the incoming circuit or output circuit of the combination electrical appliance, or it can be a short-circuit protection device specified by the manufacturer outside the combination electrical appliance.
6 Normal operating conditions and installation conditions
Except for the following provisions, the provisions of Chapter 6 of GB11048 apply. 6.1 Pollution degree
a. Industrial use: Level 3
b. Household and similar use: Level 2
2 Installation category (overvoltage category)
The installation category is "class, subclass.
Structural and performance requirements
7.1 Structural requirements
7.1.1 Materials
7.1.1 of GB14048.1 is applicable.
JB/T7121-1993
7.1.10 of GB14048.1 is applicable, and the following provisions are supplemented. Dimensional coordination of enclosure, installation structure and electrical appliances 7.1.2.15
7.1.2.1. 1
Electrical equipment mounting rails
This standard recommends the use of TH357.5 type mounting rails that comply with JB6525. For heavier electrical equipment, the TH35-15 type mounting rails with better rigidity can be used. Width dimensions of electrical equipment
7.4.2. 1.2
This standard recommends the use of modular card-mounted electrical appliances. The width dimension (B) of modular card-mounted electrical appliances should be in the dimension series with a module of 9mm or 12.5mm. The modular dimension tolerance is (.0.25)mm, that is:
B=n×9-8.2mm or B=nX12.5-0.2mm, where n is a positive integer.
7.1.2.1.3 Dimension coordination
The main dimensions of the electrical appliance, casing and mounting structure are recommended to adopt the values ​​in Table 1, and the dimensional relationship is shown in Figure 1. Dimension coordination must generally follow the following relationship: Q+≤P,min.
For structures with baffles:
P2max≤Q≤Q
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