Basic knowledge of motors
Thread Content
Basic knowledge of motors I: Small three-phase asynchronous motors, typically ranging from H80 to 315 MM in size, are produced in large quantities and have a wide range of applications. They account for around 40% of the total electrical consumption in power grids. In the early 1960s, the JO2 series of motors were popular. The power ratings and installation dimensions of this series differed from the standard specifications used in the international market. Additionally, these motors had a low starting torque and lacked noise control features; therefore, the motors currently in use in China are of the Y series. This motor is robust, durable, safe, and reliable, which is why its range of applications is expanding. However, some users experience an annual failure rate of up to 5% for their motors, and the main reasons for this are often improper selection, incorrect usage, and inadequate protection. Therefore, the main purpose of this lecture is to identify quality issues that arise during the use of motors and to resolve them properly. Systems of small asynchronous motors: Small asynchronous motors can be classified into: basic series, derivative series, and special-purpose series. Basic series – widely used and produced in large quantities; they are general-purpose motors, such as the Y series (IP44) small three-phase asynchronous motors. Derivative series – Based on the basic series, certain modifications are made to meet different usage requirements; the additional components share a high degree of compatibility and consistency with those of the basic series. The derivative series include electrical derivatives (such as high-efficiency motors, YX series), structural derivatives (such as wound-rotor motors, YR series), and derivatives for special environments (explosion-proof motors, YB series), among others. Special series – Unlike those for general use, these are series with specific requirements for operation and particular protection conditions, such as YZ and YZR asynchronous motors for metallurgical and lifting applications. Basic Knowledge of Motors II: Basic Series Technical Parameters 1. Standard number: JB/T9616-1996 2. Enclosure protection rating: The Y series of small three-phase asynchronous motors comes in two enclosure protection grades: IP23 and IP44. The meanings of IP23 and IP44 are as follows: IP is the symbol used to indicate the level of protection, and the two digits that follow have the requirements specified in the table below.Level | Requirements
------|-------------
IP23 | First digit: Protects against finger contact as well as access to the live or moving parts inside the enclosure; prevents small solid objects with a diameter greater than 12 MM from entering. Second digit: Exposure to water spray at an angle of 60 degrees or less relative to the vertical direction should not have any harmful effect on the motor.
IP44 | First digit: Protects against tools, metal wires, or similar objects with a thickness greater than 1 MM from coming into contact with the live or moving parts inside the enclosure; prevents small solid objects with a diameter greater than 1 MM from entering. However, this does not apply to ventilation openings through which air is drawn in or blown out by external fans, nor to the drainage holes in enclosed motors – these areas must have a protection level of 2. Second digit: Exposure to water splashes from any direction should not have any harmful effect on the motor. 3. Installation structure and type: The installation structures for Y-series motors include three types: installation using footings, installation using a flanged end cover together with footings, and installation using a single flanged end cover. Based on the three basic installation structures, the installation types of motors are further divided into horizontal or vertical installation, with the shaft extension facing upward or downward; these include installation types such as B3, B35, B5, V1, V15, etc. For specific models, refer to the standards. 4. Cooling method: Y-series motors are basically cooled by the circulation of surrounding air. The IP23 motor uses the blades on the rotor end rings as driving elements; cold air enters from the end covers, is pressurized by these blades, thereby carrying away some of the heat from the rotor. This cooled air then cools the ends of the stator windings and the back side of the core, before being expelled outside the machine through the middle of the casing. It is an IP44 motor; the heat generated by internal losses during operation (iron loss, copper loss, mechanical loss) is transferred entirely to the surface of the motor. A fan installed at the end that is not connected to the shaft drives the surrounding air to continuously blow over the motor’s surface, carrying away this heat and thus cooling the motor. 5. Check the table for power rating and installation dimensions. 6. Key performance indicators: Compared with motors from other manufacturers, these motors may have shorter cores and thinner enameled wires, but all their performance parameters such as power meet the standard requirements. 7. Winding temperature rise: Y-series motors use Class B insulation, allowing a winding temperature rise of 80K. Additionally, Class F insulation allows a winding temperature rise of 115K. 8. Operating conditions: (1) The altitude shall not exceed 1,000 meters; the ambient temperature shall not be higher than 40°C, and the lowest temperature shall be –15°C. The average maximum humidity in the wettest month at the location of operation is 90%, while the average minimum temperature during that month does not exceed 25°C. (2) The supply voltage is 380V ±5%, with a frequency of 50HZ that varies by no more than ±1%. The imbalance in three-phase current is no more than 10% when the load is empty, and no more than 5% when the load is moderate. The no-load current is generally 30–55% of the load current. Basic Knowledge of Motors III: Nameplate Data: Contents on the nameplate of a standard motor. Type (TYPE): Voltage (VOLT): 380V Frequency (HZ): 50HZ Connection method (CONN.). ) Generally, motors of 3KW and below are connected in star configuration, while motors over 3KW are connected in delta configuration. Power: Serial number (SER. NO. ) Protection class (ENCL), Insulation class (INS). CLASS): Applicable standard: Generally JB/T9616-1996. Noise, Rotational speed (R/MIN), Rated current (AMP): Date of production (DATE), Duty cycle, Weight (WGT). Special motors have the following additional markings: THREE PHASE INDUCTION MOTOR, Service factor (S.). F. ) Current at service factor (S.F.A.) Efficiency EFF at 100% load. (100%FL) Efficiency EFF at 75% load. (75%FL) Maximum ambient temperature limit. The bearing model for the shaft extension end of AMB is BRGS. P. E Non-axial end bearing model O.P.E. The user’s alternative part number (PART. NO)
Quite detailed, I’ve learned it! ~! :victory:
A detailed introduction to the motor, but it seems to focus only on its exterior, with no description of its internal structure.
They are all basic, but very practical pieces of knowledge. Thank you~:handshake :handshake
Classification of Explosion Protection Grades
I. Classification of Hazardous Areas: Explosive Substances
Area Definitions
Chinese Standards
North American Standards
Gases
CLASS I: Areas where explosive gas mixtures are present continuously or for extended periods under normal conditions
Zone 0, Div.1: Areas where explosive gas mixtures may occur under normal conditions
Zone 1: Areas where explosive gas mixtures cannot occur under normal conditions, but may appear occasionally or for short periods only under abnormal conditions
Zone 2, Div.2
Dusts
CLASS II
Fibers
CLASS III: Areas where explosive dusts or combustible fibers mixed with air may be present continuously, frequently for short periods, or for extended periods under normal conditions
Zone 10, Div.1: Areas where explosive dusts or combustible fibers mixed with air cannot occur under normal conditions, but may appear occasionally or for short periods only under abnormal conditions
Zone 11, Div.2
II. Applicability of Explosion Protection Methods to Hazardous Areas:
Serial Number | Explosion Protection Type | Code | Standard | Explosion Protection Measures | Applicable Areas
1 | Flameproof type | d | GB3836.2 | Isolate ignition sources | Zone 1, Zone 2
2 | Increased safety type | e | GB3836.3 | Prevent the generation of ignition sources | Zone 1, Zone 2
3 | Intrinsic safety type | ia | GB3836.4 | Limit the energy of ignition sources | Zone 0, Zone 2; Intrinsic safety type ib | GB3836.4 | Limit the energy of ignition sources | Zone 1, Zone 2
4 | Positive pressure type | p | GB3836.5 | Separate hazardous substances from ignition sources | Zone 1, Zone 2
5 | Oil-filled type | o | GB3836.6 | Separate hazardous substances from ignition sources | Zone 1, Zone 2
6 | Sand-filled type | q | GB3836.7 | Separate hazardous substances from ignition sources | Zone 1, Zone 2
7 | Spark-free type | n | GB3836.8 | Prevent the generation of ignition sources | Zone 2
8 | Sealed type | m | GB3836.9 | Prevent the generation of ignition sources | Zone 1, Zone 2
9 | Hermetically sealed type | h | GB3836.10 | Prevent the generation of ignition sources | Zone 1, Zone 2
III. Applicability of Explosion Protection to Hazardous Areas: Classification of Explosive Gases
Based on the minimum spark energy required to initiate an explosion, China, Europe, and most other countries and regions classify explosive gases into four hazard levels, as shown in the table below:
Operating Condition Category | Gas Classification | Representative Gases | Minimum Ignition Spark Energy
Underground mines | I | Methane | 0.280 mJ
Factories outside mines | IIA | Propane | 0.180 mJ
| IIB | Ethylene | 0.060 mJ
| IIC | Hydrogen | 0.019 mJ
IV. Classification of Gas Temperature Groups:
Temperature Group | Safe Surface Temperature of Equipment | Common Explosive Gases
T1 | ≤ 450°C | Hydrogen, acrylonitrile, etc. (46 types)
T2 | ≤ 300°C | Acetylene, ethylene, etc. (47 types)
T3 | ≤ 200°C | Gasoline, butyraldehyde, etc. (36 types)
T4 | ≤ 135°C | Acetaldehyde, tetrafluoroethylene, etc. (6 types)
T5 | ≤ 100°C | Carbon disulfide
T6 | ≤ 85°C | Ethyl nitrate and ethyl nitrite
V. Meaning of the Explosion Protection Marking Ex(ia)ⅡC T6:
Marking Content | Symbol | Meaning
Explosion protection declaration | Ex | Complies with a certain explosion protection standard, such as China’s standards
Explosion protection method | ia | Uses an ia-level intrinsic safety explosion protection method; can be installed in Zone 0
Gas category | ⅡC | Permitted to operate in environments with ⅡC-class explosive gases
Temperature group | T6 | The surface temperature of the equipment does not exceed 85°C
Meaning of Ex(ia)ⅡC:
Marking Content | Symbol | Meaning
Explosion protection declaration | Ex | Complies with European explosion protection standards
Explosion protection method | ia | Uses an ia-level intrinsic safety explosion protection method; can be installed in Zone 0
Gas category | ⅡC | Permitted to operate in environments with ⅡC-class explosive gases
Note: The absence of a temperature group indicator indicates that the equipment does not come into direct contact with explosive gases.
VI. Explosion Protection Terminology: Definition of Safety Barrier Parameters:
Maximum allowable voltage of the safety barrier: Um – The highest voltage that can be applied to the non-intrinsic safety side while ensuring the intrinsic safety performance of the intrinsic safety side of the safety barrier； Maximum open-circuit voltage of the safety barrier: Uoc, the maximum voltage when the intrinsically safe terminal is open within the maximum allowable voltage range ； Maximum short-circuit current of the safety barrier: Isc is the maximum current when the intrinsically safe side is short-circuited within the maximum allowable voltage range ； Safety barrier allowable distributed capacitance: Ca – the maximum allowable external capacitance at the intrinsically safe terminal while ensuring intrinsically safe performance ； Safety barrier allows distributed inductance: La represents the maximum allowable external inductance at the intrinsically safe side while ensuring intrinsic safety ； VII. Explanation of the format for explosion-proof markings: The explosive hazardous materials present in factories or mining areas are scientifically classified and graded based on their ignition energy, minimum ignition temperature, and the duration for which explosive gases are present at that location, in order to determine the appropriate explosion-proof markings and types of explosion-proof equipment required. Explanation of explosion protection rating: Class ia: Electrical equipment that cannot ignite explosive gas mixtures under normal operating conditions, as well as in the presence of one or two faults. During normal operation, the safety factor is 2.0 ； In the event of a failure, the safety factor is 1.5 ； For two failures, the safety factor is 1.0. Note: Contacts that generate sparks must be equipped with an explosion-proof enclosure, a hermetically sealed enclosure, or the safety factor must be doubled. IB rating: Electrical equipment that cannot ignite explosive gas mixtures under normal operation and in the event of a fault. During normal operation, the safety factor is 2.0 ； In the event of a failure, the safety factor is 1.5. During normal operation, contacts that generate sparks must be protected by an explosion-proof or airtight enclosure, and there must be measures for fault self-detection; the safety factor in the event of one fault is 1.0. Source: http://www.sysbetter.com The national explosion protection rating standard is “GB3836.1-2000 Electrical equipment for explosive gas environments”; this standard is supplemented or modified by the following special standards for various explosion protection types. GB 3836.2 Electrical equipment for use in explosive gas environments – Part 2: Flameproof type “d” GB 3836.3 Electrical equipment for use in explosive gas environments – Part 3: Increased safety type “e” GB 3836.4 Electrical equipment for use in explosive gas environments – Part 4: Inherently safe type “i” GB 3836.5 Electrical equipment for use in explosive gas environments – Part 5: Positive pressure type “p” GB 3836.6 Electrical equipment for use in explosive gas environments – Part 6: Oil-immersed type “O” GB 3836.7 Electrical equipment for use in explosive gas environments – Part 7: Sand-filled type “q” GB 3836.9 Electrical equipment for use in explosive gas environments – Part 9: Encased type “m” GB 7957 Safety helmet lamps for use in mines. The above standards and this standard do not apply to medical electrical equipment, detonators, detonator testers, and ignition circuit testers. Common symbols include “ExdⅠ/Ⅱ BT3”. “Ex” is a general symbol meaning “explosive” (this is my personal interpretation); “d” indicates that the protection type is flameproof type “d”. “Ⅰ” or “Ⅱ” denotes the classification of the electrical equipment – Ⅰ refers to equipment used in coal mines, while Ⅱ refers to equipment used in other explosive gas environments besides coal mines. Among them, flameproof type “d” and inherently safe type “i” electrical equipment are further divided into categories ⅡA, ⅡB, and ⅡC. “T3” indicates the temperature group. For specific classifications and their meanings, please refer to “GB3836.1-2000 Electrical equipment for use in explosive gas environments”. I. Concept of explosion protection 1. Three necessary conditions for an explosion to occur; when all three conditions are met, an explosion takes place. Energy required for ignition, source of migration ； Air or oxygen air or oxygen ； Flammable air, flammable dust. 2. To prevent explosions, it is necessary to consider three essential conditions; by restricting any one of these conditions, the occurrence of an explosion can be prevented. In industrial processes, handling of flammable and explosive environments is usually approached from the following three aspects. 1) Prevent or minimize the likelihood of leaks of flammable substances ； 2) Avoid using, or use as little as possible, electrical components that are prone to generating sparks ； 3) Adopt methods such as filling with nitrogen to maintain an inert state. II. Classification of Hazardous Areas, Explosion Protection Classification of Electrical Components, and Allowable Temperature Ranges
1. Classification of Hazardous Areas
Zone 0: Explosive gases are present all the time or for extended periods.
Zone 1: Flammable gases may occur or be present during the normal operation of instruments.
Zone 2: Under normal conditions, no flammable gases are present; even if they do occur occasionally, their presence is short-lived.
Comparison between International Standards and American Standards for Hazardous Area Classification
I.E.C. N.E.C.
Gases: Zone 0 – Class I, Division I; Zone 1 – Class I, Division I; Zone 2 – Class I, Division II
Dusts: Zone 10 – Class II, Division I; Zone 11 – Class II, Division II
I.E.C.: International Electrotechnical Commission
N.E.C.: National Electrical Code, U.S.A.
2. Explosion Protection Classification of Electrical Components
1. General protection: EN50.014
2. Oil-immersed protection: 0 EN50.015
3. Pressurized protection systems: p EN50.016
4. Powder filling: q EN50.017
5. Flame-retardant enclosures: d EN50.018
6. Increased safety factors: e EN50.019
7. Intrinsic safety protection: i EN50.0120
8. Airtight protection: h – No standard specified
9. Pressure relief protection: n – No standard specified
10. Special measures: s – No standard specified
3. Allowable Temperature Ranges for Electrical Equipment
Temperature class code of electrical components | Maximum allowable surface temperature (°C) | Ignition point of gas (°C)
T1 | 200 | T | 450 | 450
T2 | 200 | T | 300 | 300
T3 | 135 | T | 200 | 200
T4 | 100 | T | 135 | 135
T5 | 85 | T | 100 | 100
T6 | T | 85 | 85
III. Explosion Properties of Some Common Substances
Name | Ignition point (°C) | Temperature class | Explosion group number
—— | —— | —— | ——
Propane | 540 | T1 | IIA
Acetylene | 305 | T2 | IIC
Acetic anhydride | 330 | T2 | IIA
Benzene | 555 | T1 | IIA
Butane | 365 | T2 | IIA
n-Butanol | 340 | T2 | IIA
Benzenochloride | 590 | T1 | IIA
Ethanol | 425 | T2 | IIA
Ethyl acetate | 460 | T1 | IIA
Methanol | 455 | T1 | IIA
*** | 430 | T1 | IIA
n-Pentane | 285 | T3 | IIA
Propane | 470 | T1 | IIA
Toluene | 535 | T1 | IIA
Hydrogen | 560 | T1 | IIC
Hydrogen sulfide | 270 | T3 | IIB
Carbon disulfide | 102 | T5 | IIC
IV. Power Supply Restrictions for Intrinsic Safety Sensor Circuits
Power supply restrictions are mainly reflected in the following three aspects:
1. Isolating the power supply from electronic components. 2. Take measures to prevent external interference from coupling electromagnetic fields into electronic components via the relay or current output terminals. 3. Limiting the operating power supply and voltage of the sensing circuit. Intrinsic safety circuits can be divided into two categories: ia and ib. Ib intrinsically safe circuits must ensure that the circuit components do not catch fire or explode, both when the circuit is operating normally and in the event of a fault within the system. Intrinsic safety circuits require that components do not catch fire or explode under normal operating conditions as well as in the presence of two faults. V. Main explosion-proof standards followed by EH instruments: 1. IEC / CENELEC / EUROPE and NORTH AMERICA / FM standards are commonly used, whereas the CANADA / CSA standard is hardly used in China. Example: CENELEC: Eex de/Eex d ib IIC T2-T6 FM: NI/I/Z/ABCD DIP/II, III/1/EFG XP/I/1/ABCD DIP/II, III/1/EFG CSA: Class I, Div 2, ABCD. The new European explosion-proof standard ATEX100a will replace the previous CENELEC standards (as of 2003). ATEX 100a: II IG Ee*a IIB T6 I II 1G Zone 0 1D, 2D, 3D – dust explosions; Mining, other applications. 2G Zone 1 – Industrial applications. 3G Zone 2. VI. Classification of protection levels for instrument enclosures: For instruments used in explosive hazard areas, it is also necessary to specify the protection level of their enclosures, which is represented by a certain code, namely the IP rating. The enclosure protection rating specified by IEC144 is represented by a code that corresponds to its resistance to impact and penetration by external objects as well as its waterproofing capability. For example, the measurement circuit board of an intrinsically safe instrument should not be removed from its enclosure, as this would violate the minimum requirements specified by IP40. The protection rating consists of two digits, preceded by the word IP. IP1 2 First digit Second digit Resistance to impact by external objects Waterproofing capacity 0: No resistance to penetration 0: No waterproofing capability 1: External object size greater than 50 mm (very large) 1: Water droplets falling vertically 2: External object size greater than 120 mm (medium) 2: Water droplets at an angle of -15° 3: External object size greater than 2.5 mm (small) 3: Water sprayed at a 60° angle 4: Granular external objects with particle sizes greater than 1 mm 4: Spraying from all directions 5: Hazardous dust 5: Water jet of 50 liters per minute 6: Penetrating dust (applicable only to special enclosures) 6: Water jet of 100 liters per minute 7: Immersion in water at a speed of 1 meter per minute 8: Immersion in water in a pre-agreed manner 1: Category, grade, and temperature group of explosion-proof electrical equipment 1.1 Classification of hazardous areas in explosive gas environments Zone 0: An environment where explosive gas mixtures are present continuously or for extended periods of time. Zone 1: An environment where explosive gas mixtures may occur during normal operation. Zone 2: An environment in which explosive gas mixtures cannot occur under normal operating conditions, or in which such mixtures exist only for a short period of time. Zone 0 generally exists only within the gas-filled spaces inside enclosed containers, storage tanks, etc. In actual design, Zone 1 is also rare; in most cases, it falls under Zone 2. 1.2 Explosion-proof electrical equipment is divided into two categories: Category I – electrical equipment used in coal mines; Category II – electrical equipment used in locations other than mines. 1.3 Electrical equipment of Category II is further divided into three subcategories, IIA, IIB, and IIC, based on their maximum allowable safety gap or minimum ignition current when exposed to explosive gas mixtures ； And they are divided into six groups, T1 to T6, according to their highest surface temperature. 1.4 Explosive gas mixtures are classified by ignition temperature, as shown in Table 1. 2. Noun predicates 2.1 Flameproof electrical equipment: Electrical equipment whose enclosure is capable of withstanding the explosive pressure of internal explosive gas mixtures and preventing the spread of an internal explosion to the explosive mixtures surrounding the enclosure; such equipment is marked with “d”. 2.2 Increased safety electrical equipment does not generate arcs, sparks, or high temperatures that could ignite explosive mixtures under normal operating conditions; structural measures are taken to increase safety margins in order to prevent the occurrence of arcs, sparks, or high temperatures under normal and permitted overload conditions. Such equipment is marked with the symbol “e”. 3. Explosion prevention principle: There are two reasons why electrical equipment can ignite a flammable gas mixture: one is the sparks and arcs generated by the electrical equipment, and the other is the heating of the surface of the electrical equipment (i.e., the surface in contact with the flammable gas mixture). To achieve explosion protection, the components of the equipment that can generate arcs or sparks during normal operation should be placed within an explosion-proof enclosure, or other explosion-proof designs such as encapsulation, sand filling, oil filling, or positive pressure systems can be employed. Safety-enhanced electrical equipment refers to devices that do not generate arcs, sparks, or dangerous high temperatures during normal operation. By implementing additional protective measures in their design, it is possible to ensure that such devices do not experience arcs, sparks, or overheating under normal operating conditions or under approved overload conditions, thereby further enhancing their safety and reliability. Therefore, such equipment has no ignition source when operating normally, and can be used in explosive hazardous environments. 4. Examples of explosion-proof markings 4.1 If the electrical equipment is of IIB category, explosion-proof type T3, the marking will be Exd II BT3. 4.2 If the electrical equipment is of Category II increased safety type, with temperature group T2, the marking is Exe II T2. 4.3 If an electrical device adopts more than one composite protection type, the main explosion protection type shall be indicated first, followed by the other protection types. For example, if the main type is enhanced safety with internal IIC classification explosion-proof components and the temperature group is T4, the marking will be Exed II CT4. 4.4 If the electrical equipment is of dust-proof and explosion-proof type, Group T11. The identifier is: DIPDPT11.
I. Classification of Hazardous Areas: Explosive Substances
Area Definitions
Chinese Standards
North American Standards
Gases
CLASS I: Areas where explosive gas mixtures are present continuously or for extended periods under normal conditions
Zone 0, Div.1: Areas where explosive gas mixtures may occur under normal conditions
Zone 1: Areas where explosive gas mixtures cannot occur under normal conditions, but may appear occasionally or for short periods only under abnormal conditions
Zone 2, Div.2
Dusts
CLASS II
Fibers
CLASS III: Areas where explosive dusts or combustible fibers mixed with air may be present continuously, frequently for short periods, or for extended periods under normal conditions
Zone 10, Div.1: Areas where explosive dusts or combustible fibers mixed with air cannot occur under normal conditions, but may appear occasionally or for short periods only under abnormal conditions
Zone 11, Div.2
II. Applicability of Explosion Protection Methods to Hazardous Areas:
Serial Number | Explosion Protection Type | Code | Standard | Explosion Protection Measures | Applicable Areas
1 | Flameproof type | d | GB3836.2 | Isolate ignition sources | Zone 1, Zone 2
2 | Increased safety type | e | GB3836.3 | Prevent the generation of ignition sources | Zone 1, Zone 2
3 | Intrinsic safety type | ia | GB3836.4 | Limit the energy of ignition sources | Zone 0, Zone 2; Intrinsic safety type ib | GB3836.4 | Limit the energy of ignition sources | Zone 1, Zone 2
4 | Positive pressure type | p | GB3836.5 | Separate hazardous substances from ignition sources | Zone 1, Zone 2
5 | Oil-filled type | o | GB3836.6 | Separate hazardous substances from ignition sources | Zone 1, Zone 2
6 | Sand-filled type | q | GB3836.7 | Separate hazardous substances from ignition sources | Zone 1, Zone 2
7 | Spark-free type | n | GB3836.8 | Prevent the generation of ignition sources | Zone 2
8 | Sealed type | m | GB3836.9 | Prevent the generation of ignition sources | Zone 1, Zone 2
9 | Hermetically sealed type | h | GB3836.10 | Prevent the generation of ignition sources | Zone 1, Zone 2
III. Applicability of Explosion Protection to Hazardous Areas: Classification of Explosive Gases
Based on the minimum spark energy required to initiate an explosion, China, Europe, and most other countries and regions classify explosive gases into four hazard levels, as shown in the table below:
Operating Condition Category | Gas Classification | Representative Gases | Minimum Ignition Spark Energy
Underground mines | I | Methane | 0.280 mJ
Factories outside mines | IIA | Propane | 0.180 mJ
| IIB | Ethylene | 0.060 mJ
| IIC | Hydrogen | 0.019 mJ
IV. Classification of Gas Temperature Groups:
Temperature Group | Safe Surface Temperature of Equipment | Common Explosive Gases
T1 | ≤ 450°C | Hydrogen, acrylonitrile, etc. (46 types)
T2 | ≤ 300°C | Acetylene, ethylene, etc. (47 types)
T3 | ≤ 200°C | Gasoline, butyraldehyde, etc. (36 types)
T4 | ≤ 135°C | Acetaldehyde, tetrafluoroethylene, etc. (6 types)
T5 | ≤ 100°C | Carbon disulfide
T6 | ≤ 85°C | Ethyl nitrate and ethyl nitrite
V. Meaning of the Explosion Protection Marking Ex(ia)ⅡC T6:
Marking Content | Symbol | Meaning
Explosion protection declaration | Ex | Complies with a certain explosion protection standard, such as China’s standards
Explosion protection method | ia | Uses an ia-level intrinsic safety explosion protection method; can be installed in Zone 0
Gas category | ⅡC | Permitted to operate in environments with ⅡC-class explosive gases
Temperature group | T6 | The surface temperature of the equipment does not exceed 85°C
Meaning of Ex(ia)ⅡC:
Marking Content | Symbol | Meaning
Explosion protection declaration | Ex | Complies with European explosion protection standards
Explosion protection method | ia | Uses an ia-level intrinsic safety explosion protection method; can be installed in Zone 0
Gas category | ⅡC | Permitted to operate in environments with ⅡC-class explosive gases
Note: The absence of a temperature group indicator indicates that the equipment does not come into direct contact with explosive gases.
VI. Explosion Protection Terminology: Definition of Safety Barrier Parameters:
Maximum allowable voltage of the safety barrier: Um – The highest voltage that can be applied to the non-intrinsic safety side while ensuring the intrinsic safety performance of the intrinsic safety side of the safety barrier； Maximum open-circuit voltage of the safety barrier: Uoc, the maximum voltage when the intrinsically safe terminal is open within the maximum allowable voltage range ； Maximum short-circuit current of the safety barrier: Isc is the maximum current when the intrinsically safe side is short-circuited within the maximum allowable voltage range ； Safety barrier allowable distributed capacitance: Ca – the maximum allowable external capacitance at the intrinsically safe terminal while ensuring intrinsically safe performance ； Safety barrier allows distributed inductance: La represents the maximum allowable external inductance at the intrinsically safe side while ensuring intrinsic safety ； VII. Explanation of the format for explosion-proof markings: The explosive hazardous materials present in factories or mining areas are scientifically classified and graded based on their ignition energy, minimum ignition temperature, and the duration for which explosive gases are present at that location, in order to determine the appropriate explosion-proof markings and types of explosion-proof equipment required. Explanation of explosion protection rating: Class ia: Electrical equipment that cannot ignite explosive gas mixtures under normal operating conditions, as well as in the presence of one or two faults. During normal operation, the safety factor is 2.0 ； In the event of a failure, the safety factor is 1.5 ； For two failures, the safety factor is 1.0. Note: Contacts that generate sparks must be equipped with an explosion-proof enclosure, a hermetically sealed enclosure, or the safety factor must be doubled. IB rating: Electrical equipment that cannot ignite explosive gas mixtures under normal operation and in the event of a fault. During normal operation, the safety factor is 2.0 ； In the event of a failure, the safety factor is 1.5. During normal operation, contacts that generate sparks must be protected by an explosion-proof or airtight enclosure, and there must be measures for fault self-detection; the safety factor in the event of one fault is 1.0. Source: http://www.sysbetter.com The national explosion protection rating standard is “GB3836.1-2000 Electrical equipment for explosive gas environments”; this standard is supplemented or modified by the following special standards for various explosion protection types. GB 3836.2 Electrical equipment for use in explosive gas environments – Part 2: Flameproof type “d” GB 3836.3 Electrical equipment for use in explosive gas environments – Part 3: Increased safety type “e” GB 3836.4 Electrical equipment for use in explosive gas environments – Part 4: Inherently safe type “i” GB 3836.5 Electrical equipment for use in explosive gas environments – Part 5: Positive pressure type “p” GB 3836.6 Electrical equipment for use in explosive gas environments – Part 6: Oil-immersed type “O” GB 3836.7 Electrical equipment for use in explosive gas environments – Part 7: Sand-filled type “q” GB 3836.9 Electrical equipment for use in explosive gas environments – Part 9: Encased type “m” GB 7957 Safety helmet lamps for use in mines. The above standards and this standard do not apply to medical electrical equipment, detonators, detonator testers, and ignition circuit testers. Common symbols include “ExdⅠ/Ⅱ BT3”. “Ex” is a general symbol meaning “explosive” (this is my personal interpretation); “d” indicates that the protection type is flameproof type “d”. “Ⅰ” or “Ⅱ” denotes the classification of the electrical equipment – Ⅰ refers to equipment used in coal mines, while Ⅱ refers to equipment used in other explosive gas environments besides coal mines. Among them, flameproof type “d” and inherently safe type “i” electrical equipment are further divided into categories ⅡA, ⅡB, and ⅡC. “T3” indicates the temperature group. For specific classifications and their meanings, please refer to “GB3836.1-2000 Electrical equipment for use in explosive gas environments”. I. Concept of explosion protection 1. Three necessary conditions for an explosion to occur; when all three conditions are met, an explosion takes place. Energy required for ignition, source of migration ； Air or oxygen air or oxygen ； Flammable air, flammable dust. 2. To prevent explosions, it is necessary to consider three essential conditions; by restricting any one of these conditions, the occurrence of an explosion can be prevented. In industrial processes, handling of flammable and explosive environments is usually approached from the following three aspects. 1) Prevent or minimize the likelihood of leaks of flammable substances ； 2) Avoid using, or use as little as possible, electrical components that are prone to generating sparks ； 3) Adopt methods such as filling with nitrogen to maintain an inert state. II. Classification of Hazardous Areas, Explosion Protection Classification of Electrical Components, and Allowable Temperature Ranges
1. Classification of Hazardous Areas
Zone 0: Explosive gases are present all the time or for extended periods.
Zone 1: Flammable gases may occur or be present during the normal operation of instruments.
Zone 2: Under normal conditions, no flammable gases are present; even if they do occur occasionally, their presence is short-lived.
Comparison between International Standards and American Standards for Hazardous Area Classification
I.E.C. N.E.C.
Gases: Zone 0 – Class I, Division I; Zone 1 – Class I, Division I; Zone 2 – Class I, Division II
Dusts: Zone 10 – Class II, Division I; Zone 11 – Class II, Division II
I.E.C.: International Electrotechnical Commission
N.E.C.: National Electrical Code, U.S.A.
2. Explosion Protection Classification of Electrical Components
1. General protection: EN50.014
2. Oil-immersed protection: 0 EN50.015
3. Pressurized protection systems: p EN50.016
4. Powder filling: q EN50.017
5. Flame-retardant enclosures: d EN50.018
6. Increased safety factors: e EN50.019
7. Intrinsic safety protection: i EN50.0120
8. Airtight protection: h – No standard specified
9. Pressure relief protection: n – No standard specified
10. Special measures: s – No standard specified
3. Allowable Temperature Ranges for Electrical Equipment
Temperature class code of electrical components | Maximum allowable surface temperature (°C) | Ignition point of gas (°C)
T1 | 200 | T | 450 | 450
T2 | 200 | T | 300 | 300
T3 | 135 | T | 200 | 200
T4 | 100 | T | 135 | 135
T5 | 85 | T | 100 | 100
T6 | T | 85 | 85
III. Explosion Properties of Some Common Substances
Name | Ignition point (°C) | Temperature class | Explosion group number
—— | —— | —— | ——
Propane | 540 | T1 | IIA
Acetylene | 305 | T2 | IIC
Acetic anhydride | 330 | T2 | IIA
Benzene | 555 | T1 | IIA
Butane | 365 | T2 | IIA
n-Butanol | 340 | T2 | IIA
Benzenochloride | 590 | T1 | IIA
Ethanol | 425 | T2 | IIA
Ethyl acetate | 460 | T1 | IIA
Methanol | 455 | T1 | IIA
*** | 430 | T1 | IIA
n-Pentane | 285 | T3 | IIA
Propane | 470 | T1 | IIA
Toluene | 535 | T1 | IIA
Hydrogen | 560 | T1 | IIC
Hydrogen sulfide | 270 | T3 | IIB
Carbon disulfide | 102 | T5 | IIC
IV. Power Supply Restrictions for Intrinsic Safety Sensor Circuits
Power supply restrictions are mainly reflected in the following three aspects:
1. Isolating the power supply from electronic components. 2. Take measures to prevent external interference from coupling electromagnetic fields into electronic components via the relay or current output terminals. 3. Limiting the operating power supply and voltage of the sensing circuit. Intrinsic safety circuits can be divided into two categories: ia and ib. Ib intrinsically safe circuits must ensure that the circuit components do not catch fire or explode, both when the circuit is operating normally and in the event of a fault within the system. Intrinsic safety circuits require that components do not catch fire or explode under normal operating conditions as well as in the presence of two faults. V. Main explosion-proof standards followed by EH instruments: 1. IEC / CENELEC / EUROPE and NORTH AMERICA / FM standards are commonly used, whereas the CANADA / CSA standard is hardly used in China. Example: CENELEC: Eex de/Eex d ib IIC T2-T6 FM: NI/I/Z/ABCD DIP/II, III/1/EFG XP/I/1/ABCD DIP/II, III/1/EFG CSA: Class I, Div 2, ABCD. The new European explosion-proof standard ATEX100a will replace the previous CENELEC standards (as of 2003). ATEX 100a: II IG Ee*a IIB T6 I II 1G Zone 0 1D, 2D, 3D – dust explosions; Mining, other applications. 2G Zone 1 – Industrial applications. 3G Zone 2. VI. Classification of protection levels for instrument enclosures: For instruments used in explosive hazard areas, it is also necessary to specify the protection level of their enclosures, which is represented by a certain code, namely the IP rating. The enclosure protection rating specified by IEC144 is represented by a code that corresponds to its resistance to impact and penetration by external objects as well as its waterproofing capability. For example, the measurement circuit board of an intrinsically safe instrument should not be removed from its enclosure, as this would violate the minimum requirements specified by IP40. The protection rating consists of two digits, preceded by the word IP. IP1 2 First digit Second digit Resistance to impact by external objects Waterproofing capacity 0: No resistance to penetration 0: No waterproofing capability 1: External object size greater than 50 mm (very large) 1: Water droplets falling vertically 2: External object size greater than 120 mm (medium) 2: Water droplets at an angle of -15° 3: External object size greater than 2.5 mm (small) 3: Water sprayed at a 60° angle 4: Granular external objects with particle sizes greater than 1 mm 4: Spraying from all directions 5: Hazardous dust 5: Water jet of 50 liters per minute 6: Penetrating dust (applicable only to special enclosures) 6: Water jet of 100 liters per minute 7: Immersion in water at a speed of 1 meter per minute 8: Immersion in water in a pre-agreed manner 1: Category, grade, and temperature group of explosion-proof electrical equipment 1.1 Classification of hazardous areas in explosive gas environments Zone 0: An environment where explosive gas mixtures are present continuously or for extended periods of time. Zone 1: An environment where explosive gas mixtures may occur during normal operation. Zone 2: An environment in which explosive gas mixtures cannot occur under normal operating conditions, or in which such mixtures exist only for a short period of time. Zone 0 generally exists only within the gas-filled spaces inside enclosed containers, storage tanks, etc. In actual design, Zone 1 is also rare; in most cases, it falls under Zone 2. 1.2 Explosion-proof electrical equipment is divided into two categories: Category I – electrical equipment used in coal mines; Category II – electrical equipment used in locations other than mines. 1.3 Electrical equipment of Category II is further divided into three subcategories, IIA, IIB, and IIC, based on their maximum allowable safety gap or minimum ignition current when exposed to explosive gas mixtures ； And they are divided into six groups, T1 to T6, according to their highest surface temperature. 1.4 Explosive gas mixtures are classified by ignition temperature, as shown in Table 1. 2. Noun predicates 2.1 Flameproof electrical equipment: Electrical equipment whose enclosure is capable of withstanding the explosive pressure of internal explosive gas mixtures and preventing the spread of an internal explosion to the explosive mixtures surrounding the enclosure; such equipment is marked with “d”. 2.2 Increased safety electrical equipment does not generate arcs, sparks, or high temperatures that could ignite explosive mixtures under normal operating conditions; structural measures are taken to increase safety margins in order to prevent the occurrence of arcs, sparks, or high temperatures under normal and permitted overload conditions. Such equipment is marked with the symbol “e”. 3. Explosion prevention principle: There are two reasons why electrical equipment can ignite a flammable gas mixture: one is the sparks and arcs generated by the electrical equipment, and the other is the heating of the surface of the electrical equipment (i.e., the surface in contact with the flammable gas mixture). To achieve explosion protection, the components of the equipment that can generate arcs or sparks during normal operation should be placed within an explosion-proof enclosure, or other explosion-proof designs such as encapsulation, sand filling, oil filling, or positive pressure systems can be employed. Safety-enhanced electrical equipment refers to devices that do not generate arcs, sparks, or dangerous high temperatures during normal operation. By implementing additional protective measures in their design, it is possible to ensure that such devices do not experience arcs, sparks, or overheating under normal operating conditions or under approved overload conditions, thereby further enhancing their safety and reliability. Therefore, such equipment has no ignition source when operating normally, and can be used in explosive hazardous environments. 4. Examples of explosion-proof markings 4.1 If the electrical equipment is of IIB category, explosion-proof type T3, the marking will be Exd II BT3. 4.2 If the electrical equipment is of Category II increased safety type, with temperature group T2, the marking is Exe II T2. 4.3 If an electrical device adopts more than one composite protection type, the main explosion protection type shall be indicated first, followed by the other protection types. For example, if the main type is enhanced safety with internal IIC classification explosion-proof components and the temperature group is T4, the marking will be Exed II CT4. 4.4 If the electrical equipment is of dust-proof and explosion-proof type, Group T11. The identifier is: DIPDPT11.