Explosion Proof Motor Classifications: A Selection Guide


During industrial operations, internal motor parts become very hot and induce blasts. Therefore, explosion-proof motors are designed to prevent hazardous incidents in the workplace. Understanding explosion proof motor classifications is an integral part of the motor selection as it is a serious safety concern. Explosion proof motor certification is necessary to consider while selecting the right explosion-proof motor for the hazardous zone. Xinnuomotor manufactures high-quality explosion-proof electric motors with customizable voltage, junction box, and frequency.  

Figure 1 Explosion Proof Motor

Figure 1: Explosion proof motor

In this article, we will discuss the classification, identification of name-plate, and explosion proof motor certification. 

Explosion proof motor classifications:

Explosion-proof motors are classified into two major classes based on their applications, material exposure, and optimal performance. Nameplate of the motor identifies the class, division, and group of the explosion-proof motor. 

Class I:

Class I locations include combustible gases and vapors. These motors are mainly designed to prevent malfunction caused by any vapors or gases. The temperature of Class I motors remains below the auto-ignition condition of vapors and gases.

Figure 2 Explosion Proof Motor Classifications

Figure 2: Explosion proof motor classifications

 The Class I location motors have an enclosure that avoids blasts and internal damage. Class I is categorized into further two-divisions;

Division I:

According to explosion proof motor classifications, division I assume the presence of flammable gas or vapors during normal equipment operation. 

Division II: 

Division II includes flammable gas or vapor only during machinery malfunction. It does not presume explosion gas or vapor’s presence during normal operation.

Class I Groups: 

On the basis of combustion temperature and pressure, Class I material is classified into two groups;

  • Group C: Diethyl ether, isoprene, ethylene, acetaldehyde, cyclopropane.
  • Group D: Ammonia, ethanol, gasoline, acetone, butane, benzene. 

Class II: 

Class II location involves combustible dust particles; therefore, these explosion-proof motors are controlled differently than Class I. These motors prevent contact between combustion source and solid dust particles. The motor enclosure is designed to restrict exceeding the optimal temperature to ensure safety at hazardous locations

Class II Group:

The materials for class II are classified as;

  • Group F: Coal 
  • Group G: Nylon particle, sugar, wheat, flour, and corn. 

How to identify the model meaning of explosion proof motors?

You must identify the model meaning according to explosion proof motor classifications in order to select the right fit for your operation. Understanding different models will help you ensure the working mechanism and right applications of the 3 phase explosion-proof motor for your hazardous location. 

Figure 3 YBX3 3 phase Explosion-proof Motor

Figure 3: YBX3 3 phase Explosion-proof Motor

Let’s uncover the codes mentioned on the number plate of YBX3-315L1-2 explosion-proof motors; 

  • Y: Y mentioned on the number plate represents that the explosion-proof motor is an induction motor. 
  • B: B indicates flameproof or explosion-proof motor. 
  • X: X explains that the motor has high working efficiency. 
  • 3: It represents the design code of the motor. 
  • 315: The supplementary code indicates the cabinet seat number of the explosion-proof motors.
  • L: It signifies the frame length code of the product.
  • 1: This number demonstrates the core length code of the motor. 
  • 2: The number at the end represents the “numbers of poles.”

Basic parameters to consider while choosing explosion proof motors: 

It is very crucial to closely analyze the basic parameters and explosion proof motor certifications while selecting the best flame-proof motor. Explosion proof motor classifications based on fundamental parameters are discussed below;

Rated Voltage:



Rated Frequency:


Average Frame Size:

The center of frame size ranges between 63-355mm for different flame-proof motors. 

Protection Class:

The protection class used in the most famous explosion-proof motor is IP55. 

Insulation Classification: 

The insulation class of explosion-proof motor is 155 (F)

Cooling Type:

These motors have a reliable IC411 cooling method. 

Connection Type:

  • Star-connection is used under 3kw power.
  • Delta-connection is used for motors above 3kw power output.

Power Range: 

The power range of various explosion-proof motors ranges from 0.12 kW to 315 kW.

Ambient Temperature:

It ranges from 4 °F/-20 °C to +104 °F/+40 °C

Rated Torque: 

The rated torque of the YBX3 series explosion proof motors varies from 1.3 to 2.0. 

Explosion proof motor classifications based on signs: 

Signs represented on the explosion proof motor specify necessary information about the flame-proof motor type. The explosion-proof sign consists of the following marks;

  • Ex—Ex is a general sign that shows that the motor is explosion-proof.
  • D—it represents the flame-proof type of explosion-proof equipment.
  • II—it indicates the class level (Class II).
  • B—it displays the explosion-proof level (Group B).
  • T4—T4 mark the temperature class of the motor. T4 shows that the highest surface temperature is below ≤135 ℃.
  • Gb—it shows the protection class of the equipment.


Understanding the explosion proof motor classifications helps a user to select the perfect equipment for the hazardous zone. Knowing the class, signs, and explosion proof motor certifications of different explosion-proof equipment reduces the risks of explosions at locations. If you have any queries regarding explosion-proof motors, contact us

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