Overview of SIMO YB2/YBX2 Series High-Voltage Explosion-Proof Motors
SIMO’s YB2 and YBX2 series high-voltage explosion-proof motors are high-voltage flameproof three-phase induction motors (frame sizes 355–560), developed as premium products by integrating advanced foreign technologies with the company’s long-standing expertise in manufacturing high-voltage medium-sized motors, and leveraging state-of-the-art design methodologies and cutting-edge materials.
These motors comply with GB 755-2008 “Rotating Electrical Machines – Ratings and Performance”, GB 3836.1-2010 “Explosive Atmospheres – Part 1: General Requirements”, and GB 3836.2-2010 “Explosive Gas Atmospheres – Part 2: Equipment Protection by Flameproof Enclosure ‘d’”. Their explosion-protection marking is ExdIIBT4 Gb, suitable for Class II, Group B industrial environments, temperature class T4, and equipment protection level Gb; they can replace ExdIIAT4 Gb products.
This series offers outstanding flameproof performance, high reliability, compact structure, high efficiency and energy savings, safety and environmental friendliness, low vibration, low noise, and convenient installation and maintenance.
This series represents a new generation of high-voltage flameproof three-phase induction motors, serving as a replacement for the YB560–710 series (IC511 tubular-cooled structure) high-voltage flameproof three-phase induction motors.
Xi’an Tefu SIMO YB2/YBX2 series high-voltage explosion-proof motors are ideal drive units for various general-purpose machinery—including compressors, pumps, crushers, hoists, centrifuges, machine tools, and material handling equipment—whether installed indoors or outdoors, in plateau climates or humid-hot climates. The YB2 and YBX2 series high-voltage flameproof three-phase induction motors consistently deliver exceptional driving performance, earning strong user trust and acclaim.

Basic Technical Parameters of YB2/YBX2 Series High-Voltage Explosion-Proof Motors
Center Height: H355–H560
Rated Voltage: 6 kV, 10 kV
Rated Frequency: 50 Hz
Power Range: 185 kW–1600 kW
Number of Poles: 2P–8P
Protection Class: IP54, IP55
Insulation Class: 155 (F)
Temperature Rise Class: Class B (maximum power rating tested per Class F)
Mounting Type: IMB3
Cooling Method: IC411
Explosion-Protection Rating: ExdⅡBT4 Gb

Technical Features of YB2/YBX2 Series High-Voltage Explosion-Proof Motors
High Reliability and Long Service Life
To ensure motor frames meet the 1.5 MPa hydrostatic pressure requirement specified in GB 3836-2010, ANSYS advanced design software was employed to model and analyze frames and end shields. Frames are fabricated from high-strength gray cast iron; end shields use either reinforced high-strength gray cast iron or steel plates.
To extend service life, components such as frames and fans incorporate advanced aerodynamic design, and an innovative dual-circuit cooling concept ensures uniform internal temperature distribution. Gray cast iron frames and end shields, combined with high-quality corrosion-resistant coatings and surface painting, protect the motor against climatic effects over extended periods, effectively prolonging service life.
High Efficiency and Energy Savings
The YB2 and YBX2 series high-voltage flameproof three-phase induction motors achieve high efficiency and energy savings through refined design and manufacturing. Compared with same-power, same-pole-count YB560–710 series high-voltage flameproof motors, average efficiency improves by 0.8 percentage points, delivering significant energy savings and substantially reducing operational costs.
Compact Structure
All users seek reliable drive systems that conserve valuable installation space. For years, Xi’an Tefu SIMO Motor Co., Ltd. has focused on minimizing motor footprint while enhancing performance and reliability—and achieved notable success. The YB2 and YBX2 series high-voltage flameproof three-phase induction motors perfectly fulfill these requirements.

Low Vibration
Comprehensive rotor dynamics design, innovative manufacturing processes, and high-precision dynamic balancing collectively ensure exceptionally low vibration levels. The YB2 and YBX2 series high-voltage flameproof three-phase induction motors not only meet the vibration requirements stipulated in GB 10068 but often exceed them in most applications.
Low Noise
Lower noise and optimized airflow design depend critically on appropriate fan selection. Since IC411-cooled motors feature relatively low external airflow resistance, air between frame cooling ribs flows predominantly axially; thus, fans and fan guards are designed with optimal streamlined geometry—enhancing fan efficiency while significantly reducing fan noise.
Internal fans are die-cast from aluminum alloy ZL101 and support bidirectional rotation. All 2-pole motors employ axial-flow external fans, compatible with one direction of rotation only. External fans for 4-pole and higher motors adopt bowl-type centrifugal designs, fabricated from welded steel plates and supporting bidirectional rotation.
High-strength frame and end shield construction, along with optimized stator/rotor slot matching, further contribute to lower overall noise levels.
Effective Cooling System
The YB2 and YBX2 series high-voltage flameproof three-phase induction motors feature two independent cooling circuits (see Fig. 1): an internal circuit and an external circuit. Most heat generated by losses transfers from the stator core to the frame and is removed by external cooling air; the remainder transfers via the internal cooling circuit to the frame and is likewise dissipated by external cooling air.
External airflow passes over cooling ribs. Due to the frame’s waist-shaped profile, external air flows axially from the non-drive end to the drive end, achieving high heat-dissipation velocity. The terminal box is mounted away from cooling ribs to avoid interference with airflow. Internal cooling ribs are provided on the inner side of the frame surrounding the stator winding ends.
Xi’an Tefu SIMO YB2/YBX2 series high-voltage explosion-proof motors feature identical drive-end and non-drive-end end shields. For frame sizes H450 and below, both inner and outer surfaces of end shields incorporate cooling ribs—significantly enhancing heat dissipation.
Internal cooling is achieved by the internal fan at the non-drive end, which forces air through rotor ventilation ducts. Airflow becomes highly turbulent over internal cooling ribs on the frame and end shields, ensuring thorough secondary cooling. The frame acts as a heat exchanger between internal and external airflows. Cooled air returns toward the drive end via four internal ventilation ducts—flowing in the same direction as external cooling air—to ensure uniform motor heat dissipation and realize optimal internal/external airflow design.