The parameters of explosion proof AC motors should first meet safety standards and then match the requirements of working conditions.
Explosion proof rating (safety core)
This is the primary indicator for distinguishing explosion-proof motor types, directly corresponding to the hazardous environment level, consisting of "explosion-proof type+gas/dust category+temperature group".
Explosion proof motors type: Different structural designs correspond to different protection principles, and common types are as follows:
Ex d: Explosion proof type, which prevents internal explosion diffusion through a sturdy shell, suitable for Zone 1 and Zone 2 (flammable gas environment).
Ex ia: Intrinsically safe type, with extremely low circuit energy, unable to ignite flammable substances, suitable for Zone 0 and Zone 1 (the most dangerous areas).
Ex tD: Dust explosion proof AC motors type, preventing dust from entering the interior of the motor or accumulating high temperatures, suitable for zones 20, 21, and 22 (dust environment).
Gas/dust category
Gas environment: divided into Class I (coal mine gas) and Class II (combustible gases in factories, such as methane and propane).
Dust environment: divided into Class III (combustible dust, such as flour and aluminum powder).
Temperature group: Refers to the highest surface temperature of the motor, which should be lower than the ignition temperature of flammable substances in the environment. Common groups:
T1 (≤ 450 ℃), T2 (≤ 300 ℃)... T6 (≤ 85 ℃), T6 has the highest safety and is suitable for low ignition temperature substances such as ethanol and ether.
Basic parameters of the motor (adaptation to working conditions)
Similar to ordinary motors, but needs to be adjusted in conjunction with explosion proof motor' design to ensure operational stability:
| First-level classifications | Secondary parameter | Key note |
| Foundation performance parameter | Power (Power) | Scope: 0.12kW (small equipment) ~ thousands of kW (large compressor); need to match the load power, to prevent overload and high temperature. |
| Rotational Speed | Determined by the number of poles: 2 poles (2900r/min), 4 poles (1450r/min); it needs to match the rated speed of the equipment (such as pump, fan). | |
| Voltage / Frequency (Voltage/Frequency) | Domestic commonly used: 380V/50Hz; large industrial equipment: 6kV, 10kV; export compatibility with 110V/60Hz and other specifications. | |
| Efficiency (Efficiency) | It is divided into three levels: IE1 (standard), IE2 (high efficiency), and IE3 (ultra high efficiency). High-efficiency motors can reduce energy consumption, reduce temperature rise, and improve safety. | |
| Environmental adaptability parameters | Protection level (IP code) | Indicates dust proof and waterproof capability: IP54 (dust proof and splash proof), IP55 (dust proof and spray proof); dust environment requires at least IP65 (fully dust proof). |
| Ambient Temperature | Conventional application: -20℃ ~ 40℃; can be customized for special needs (such as low temperature-40℃, high temperature above 100℃). | |
| Humidity / Corrosives (H/C) | Humid/corrosive environment (such as chemical industry): stainless steel shell or anti corrosive coating is required to prevent structural failure. | |
| Security certificate | Domestic certification | Must comply with GB 3836 standard (for combustible dust environments). |
| International certification | The European Union (CE), International Electrotechnical Commission (IEC), and United States (UL) must comply with the regulations of the target region. |
Typical application scenarios
The core commonality of all scenarios is the presence of "flammable and explosive substances", and explosion proof AC motors with corresponding explosion-proof levels need to be selected based on the type of substance (gas/dust):
Combustible gas environment (Class II explosion-proof motor)
Petrochemical industry: Oil pumps for oilfield extraction, compressors for refineries, and stirring motors for chemical plants' reaction vessels need to withstand gases such as methane, propane, and benzene, and are commonly classified as Ex d IIB T4 grade.
Gas industry: booster pumps for urban natural gas transmission and distribution stations, cooling fans for LNG storage tanks, require explosion-proof rating Ex d IIC T4 (suitable for IIC class gases such as natural gas).
Painting industry: Ventilation fans in automotive spray painting workshops and conveyor motors in furniture spray painting lines need to be protected from steam ignition of paint solvents (such as toluene and xylene), and Ex d IIB T5 is commonly used.
Combustible dust environment (Class III explosion-proof motor)
Grain processing industry: Flour mills in flour mills and mixers in feed mills need to prevent dust clouds from exploding from flour and feed powder, using Ex tD A21 IP65 T135 (dust explosion-proof type).
Metallurgical/metal processing industry: Conveyor equipment in aluminum powder plants, dust collector motors in zinc powder workshops, and low ignition temperature of metal dust (such as aluminum powder) require Ex tD A20 level (applicable to Zone 20, areas with long-term dust layers).
Pharmaceutical industry: Granulators in traditional Chinese medicine powder workshops and motors for mixing Western medicine raw materials need to be explosion-proof and meet hygiene requirements. Ex tD motors with stainless steel casings are commonly used.
Special hazardous environments
Coal mining industry: underground ventilation fans and scraper conveyors require Class I explosion-proof motors (Ex d I) that can withstand mixed environments of gas (methane) and coal dust.
Military industry: Ventilation equipment for ammunition warehouses and mixing motors for explosive production lines must be of intrinsic safety (Ex ia) or explosion-proof type, with a grade of IIC T6.
Selection precautions
Priority matching of "hazardous area level": Zone 0/20 must use intrinsic safety type (Ex ia/Ex tD A20), Zone 1/21 can use explosion-proof type, and Zone 2/22 can use increased safety type (Ex e).
Avoid "over class selection" or "downgraded use": using T4 motor (up to 450 ℃) in T6 environment (ignition temperature 85 ℃) may cause safety hazards, otherwise it will increase costs.
Pay attention to "temperature rise control": Even if the explosion-proof level meets the standard, long-term overload may cause the explosion proof AC motors temperature to rise too high, which may still exceed the temperature group limit, and a power margin of 10% -20% needs to be reserved.
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