This standard specifies the safety performance requirements, test methods and inspection rules for flameproof low-voltage three-phase asynchronous motors for coal mines. This standard applies to motors with a rated voltage of up to 1140V (hereinafter referred to as motors) used in coal mines with methane explosion hazards. MT 451-1995 General Technical Specification for Safety Performance of Flameproof Low-voltage Three-phase Asynchronous Motors for Coal Mines MT451-1995 Standard download decompression password: www.bzxz.net

Coal Industry Standard of the People's Republic of China
General Technical Specification for Safety Performance of Flameproof Low-voltage Three-phase Asynchronous Motors for Coal Mines
1 Subject Content and Scope of Application
MT451-1995
This standard specifies the safety performance requirements, test methods and inspection rules for flameproof low-voltage three-phase asynchronous motors for coal mines. This standard applies to motors with a rated voltage of up to 1140V (hereinafter referred to as motors) used underground in coal mines with methane explosion hazards.
2Reference standards
GB/T228Metal tensile test method
GB/T 755
Basic technical requirements for rotating electrical machines
GB/T 1032
Test methods for three-phase asynchronous motors
GB/T 1410
Test methods for volume resistivity and surface resistivity of solid insulating materialsBasic environmental testing procedures for electrical and electronic productsTest Db: Alternating damp heat test methodGB/T 2423.4
General requirements for explosion-proof electrical apparatus for explosive atmospheresGB 3836.12
GB 3836. 2#
Explosion-proof electrical apparatus for explosive atmospheresFlameproof electrical apparatus "d"GB3836.3Explosion-proof electrical apparatus for explosive atmospheresIncreased safety electrical apparatus\e"GB/T 4942.1 Japan
Motor housing protection classification
GB/T 10111
Random sampling method using random number generators 3 Safety performance requirements
3.1 Flameproof housing material
3.1.1 The base of the motor for mining working face must be made of steel plate or cast steel, and other parts can be made of cast iron with a tensile strength of not less than HT250.
3.1.2 The housing of the motor for non-mining working face can be made of cast iron with a tensile strength of not less than HT250. 3.2 Flameproof housing strength
3.2.1 Cast iron housing The shell or shell parts and fan cover should be able to withstand an impact test with an impact energy of 20J without causing deformation or damage that affects the explosion-proof performance (the impact energy of 7J can be used for motors used in non-mining working faces, but the mark "X" should be added after the explosion-proof certificate number). 3.2.2 The explosion-proof shell and shell parts should be subjected to a water pressure test with a pressure of 1MPa and a duration of 1min after fine processing. The test result is qualified if it is discontinuous dripping (one drop of water every interval greater than 10s is considered discontinuous dripping). 3.3 Non-threaded explosion-proof Joint surface
3.3.1 The minimum effective length of the flameproof joint surface (L,), the minimum effective length from the edge of the bolt through hole to the edge of the flameproof joint surface (Lz) and the maximum gap or diameter difference (b) of the flameproof joint surface must comply with the provisions of Table 1. Approved by the Ministry of Coal Industry of the People's Republic of China on December 28, 1995 and implemented on April 1, 1996
Joint surface type
Flat surface, stopper or cylindrical structure
Cylinder structure with sliding bearing1)||t t||Circular structure with rolling bearing?)
MT451—1995
Table 1 Structural parameters of non-threaded flameproof joint surface
1) Only applicable to submersible pump motors, see 3.7.4, 2) See 3.7.3
V≤100
Net volume of housing (V)
3.3.2 Due to the need for repair, when designing flameproof components, the flange thickness of the flat flameproof joint surface should be increased by 15%, but at least 1.0mm.
3.3.3 The roughness of the flameproof joint surface shall be processed according to Ra6.3um. 3.4 Threaded flameproof joint surface
3.4.1 The minimum axial engagement length, minimum number of engagement buckles, matching accuracy and pitch of the thread must comply with the provisions of Table 2. Table 2 Structural parameters of threaded flameproof joint surface
Net volume of housing (V)wwW.bzxz.Net
V≤100
1002 000
Minimum axial engagement length
Minimum number of engagement buckles
3.4.2 Measures should be taken to prevent the thread structure from loosening. Fitting accuracy
3.5 Anti-rust measures should be taken on the flameproof joint surface, such as electroplating, phosphating, acid-free anti-rust oil, etc., but paint should not be applied. 3.6 Adhesion
3.6.1 When the shell parts adopt the adhesive structure (such as the insulating sleeve), the shell strength should not depend on the adhesive. The adhesive should have sufficient resistance to mechanical, chemical and other effects and solvents, and should be able to withstand the highest temperature and the lowest ambient temperature during normal operation of the motor for a long time and maintain its thermal stability. The ultimate thermal stability temperature of the adhesive should be more than 20℃ higher than its maximum operating temperature, but not less than 120'C.
3.6.2 The minimum adhesive length from the inner edge to the outer edge of the shell must comply with the provisions of Table 3. 331
Net volume of housing (V)
Minimum adhesive length
MT451—1995
Table 3 Minimum adhesive length
10V≤100
3.6.3 The adhesive structure shall meet the explosion-proof requirements after the thermal stability test. 3.7 Shaft and bearing
3.7.1 Flameproof bearing cover shall be provided wherever the shaft passes through the wall of the flameproof housing. The bearing cover shall not be damaged due to wear or eccentricity of the bearing.
3.7.2 The minimum single-side clearance (b2) between the shaft and the shaft hole shall not be less than 0.075mm. 3.7.3 For motors with rolling bearings, the maximum single-sided clearance (b) between the shaft and the shaft hole shall not be greater than 2/3 of the b value in Table 1. 3.7.4 For motors with sliding bearings, the material of the bearing cover and one of the flameproof joint surfaces of the shaft shall be made of spark-free material (such as brass).
3.8 Housing fastening
3.8.1 Bolts and nuts for fastening shall not be made of plastic or light alloy materials. Anti-loosening measures shall be taken for housing fastening. 3.8.2 After the bolts and non-penetrating screw holes are fastened, a thread margin greater than 2 times the thickness of the anti-loosening washer shall be left. 3.8.3 The fastening screw holes shall not penetrate the housing wall. The thickness of the screw hole wall and bottom shall not be less than 1/3 of the true diameter of the bolt, but at least 3.0mm.
3.8.4 For process through holes or screw holes that must penetrate the housing in structure, their matching shall adopt a circular flameproof structure or a threaded flameproof structure. The exposed end should be permanently fixed or buried in the guard ring. 3.8.5 Anti-rust measures should be taken for fasteners.
3.9 Housing protection
The protection level of the motor housing should not be lower than IP44, and the junction box should not be lower than IP54.3.10 Lead-in device
3.10.1 The sealing ring, gasket, plugging plate, etc. selected in the lead-in device should comply with the provisions of GB3836.1. 3.10.2 After the clamping test of the lead-in device, the displacement of the test rod should not be greater than 6mm, and its structure should not be damaged. 3.10.3 After the sealing test, the lead-in device shall not drip or be damaged (except the sealing ring). 3.10.4 After the aging test, the Shore hardness change of the rubber sealing ring in the lead-in device should not exceed 20%. 3.11 Junction box
3.11.1 The design of the structural dimensions of the junction box should be convenient for wiring, and leave space suitable for the bending radius of the cable. After the cable is correctly connected, its electrical clearance and creepage distance shall comply with the provisions of Table 4. Table 4 Electrical clearance and creepage distance
Rated voltage
Minimum electrical clearance
Note: I, I, IIa are groups divided according to the comparative tracking index (CTI) of the insulating material 3.11.2 The inner wall of the junction box shall be evenly coated with arc-resistant paint Minimum creepage distance, mm
3 The insulating sleeve shall be made of materials with low hygroscopicity. When the insulating sleeve is subjected to torque during the wiring process with the connector, it shall not rotate or be damaged after 335
Torsion test. MT451-1995
3.11.4 The connector and the grounding terminal shall have sufficient mechanical strength and shall be reliably connected. When affected by temperature changes, vibrations, etc., poor contact shall not occur.
3.12 Grounding
3.12.1 The housing of the fixed motor shall be provided with an external grounding device. Mobile motors should use cables with grounding core wires. The specifications of the external grounding bolt diameter should meet the following requirements:
For motors with power greater than 10kW, not less than M12; a.
For motors with power greater than 5kW~10kW, not less than M10; b.
For motors with power greater than 0.25kW~5kW, not less than M8; c.
d. For motors with power less than 0.25kW and current less than 5A, not less than M6. 3.12.2 A special internal grounding device should be installed inside the motor junction box. The specifications of the internal grounding bolt diameter should meet the following requirements: a. When the cross-sectional area of ​​the conductive core wire is not greater than 35 mm2, it should be the same as the diameter of the terminal bolt; b. When the cross-sectional area of ​​the conductive core wire is greater than 35mm2, it should be not less than the bolt diameter of 1/2 of the cross-sectional area of ​​the conductive core wire, but at least equal to the bolt diameter of the 35mm core wire.
3.12.3 A grounding mark "-" should be provided near the grounding bolt, and the mark should not be worn out during the entire use of the motor. 3.12.4 Anti-rust measures should be taken for the grounding device, or it should be made of stainless metal materials. 3.13 Fan of external fan-cooled motor
3.13.1 The protection level of the ventilation hole: the air inlet end shall not be less than IP20; the air outlet end shall not be less than IP10. 3.13.2 Vertical motors should be able to prevent foreign objects from falling vertically into the ventilation hole. 3.13.3 The fan blades, fan cover, and partitions should have sufficient mechanical strength and be reliably fixed; after they have undergone the impact test specified in 3.2.1, the stationary parts and the moving parts shall not collide or rub against each other. 3.13.4 Under normal working conditions, the distance between the fan blade and the stationary parts should not be less than 1% of the diameter of the fan blade, at least 1mm, but not more than 5mm.
3.13.5 If the fan blade is made of plastic, the surface insulation resistance value should not be greater than 1×10°Q. , 3.13.6 If the fan blades are made of light alloy, the light alloy shall comply with the relevant provisions of GB13813. 3.14 After the strength test, the motor shall not produce deformation and damage that affects the flameproof performance; during the flameproof performance test, no explosion shall be transmitted. 3.15 Under rated working conditions, the surface temperature of the motor casing shall not exceed 150°C, and the temperature at the cable entry shall not exceed 70°C. 3.16 The insulation resistance value of the motor stator winding shall comply with the provisions of Table 5 when it is hot or after the temperature rise test. Table 5 Insulation resistance value
Rated voltage
Minimum insulation resistance value, MO
When hot or after the temperature rise test
3.17 The motor stator winding shall not be broken down after the voltage withstand test. After alternating damp heat test
3.18 After the alternating damp heat test, the insulation resistance value of the motor stator winding shall comply with the provisions of Table 5, the withstand voltage test shall comply with the provisions of 3.17, and there shall be no rust on the flameproof surface. 3.19 The motor stator winding shall be able to withstand a short-term elevated voltage test without breakdown of the inter-turn insulation. 3.20 Marking
3.20.1 Clear permanent embossed markings \ExdI and coal mine safety markings \MA" should be set on the obvious part of the motor housing. 336
MT451-1995
3.20.2 A copper or stainless steel nameplate with a thickness of not less than 1mm should be set on the obvious part of the motor housing and fixed securely. The following contents should be clearly marked on the nameplate:
Product name and model;
Explosion-proof mark;
Explosion-proof certificate number;
Safety mark number;
Factory date and number;
Manufacturer name.
Test method
Tensile strength test shall be carried out in accordance with GB/T228.
4.2 Impact test is carried out in accordance with GB3836.1.
4.3 Water pressure test is carried out in accordance with Appendix A of GB3836.2. 4.4 Thermal stability test is carried out in accordance with GB3836.1. 4.5 Protection test is carried out in accordance with GB/T4942.1. 4.6 Clamping test of introduction device is carried out in accordance with GB3836.1. Sealing test of introduction device is carried out in accordance with GB3836.2. 4.7
4.8 Aging test of rubber material is carried out in accordance with GB3836.1. 4.9 Torsion test of connecting parts is carried out in accordance with GB3836.1. 4.10
Surface insulation resistance test is carried out in accordance with GB/T1410. 4.11
Strength test and flameproof test are carried out in accordance with GB3836.2. Temperature test is carried out in accordance with GB3836.1.
Insulation resistance test is carried out in accordance with GB/T1032. Withstand voltage test is carried out in accordance with GB/T1032. The effective value of voltage shall comply with the provisions of Table 6. Table 6 Withstand voltage value
Rated voltage
Before alternating damp heat test
Effective value of voltage
After alternating damp heat test
4.15 Alternating damp heat test is carried out in accordance with GB/T2423.4. The severity level is high temperature +40℃, and the test cycle is 12d. 4.16 Short-time rise voltage test is carried out in accordance with GB/T755. 4.17 The inspection of flameproof parameters, flameproof joint surface roughness, rust prevention, fastening, electrical clearance, creepage distance, grounding and marking is carried out by measuring tools and visual inspection.
5 Inspection rules
5.1 The factory inspection items of motor safety performance shall be carried out in accordance with the provisions of Table 7. 337
MT451—1995
Table 7 Inspection items for safety performance of electric motors
Technical requirements clauses
Factory inspection
All inspections
MT451--1995
Table 7 (end)
Technical requirements clauses
Factory inspection
Items with “￥” marked as key items, “” marked as general items, and the rest as important items. 2Items with “√” marked as items to be inspected, “-” marked as items not to be inspectedAll inspections
5.2All inspection items for safety performance of electric motors shall be inspected during product type inspection. Samples shall be randomly selected from qualified products of factory inspection according to the provisions of GB/T10111. For key items, if any item fails to meet the standards, the safety of the batch of products shall be judged as unqualified. For important items, if two items fail to meet the standards, the safety of the batch of products is judged to be unqualified; if one item fails to meet the standards, the batch of products is judged to be unqualified in terms of safety. If one item fails to meet the standards, the batch of products is judged to be unqualified in terms of safety. 5.3 If the safety of the motor fails to meet the standards, the batch of products is judged to be unqualified. Additional notes:
This standard is proposed by the Coal Mine Safety Standardization Technical Committee. This standard is under the jurisdiction of the Explosion-proof Branch of the Coal Mine Safety Standardization Technical Committee. This standard was drafted by the Fushun Branch of the China Coal Research Institute, and the Shanghai Branch and Chongqing Branch of the China Coal Research Institute participated in the drafting. The main drafters of this standard are Li Shuanghui, Chen Zaixue, Wang Wenzhao, Wang Pingtang, and Liu Xiaobo. This standard is entrusted to the Fushun Branch of the China Coal Research Institute for interpretation. 339
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