— Overview of the YBBP Series Variable-Frequency Explosion-Proof Motors

The YBBP variable-frequency explosion-proof motor is a new-generation explosion-proof variable-frequency adjustable-speed motor developed to meet market demands, based on the introduction of advanced foreign technologies and the accumulation of years of experience in manufacturing variable-frequency motors. In electromagnetic design, adjustments have been made to the stator and rotor slot configurations, winding types, and connection methods to ensure compatibility with power supplied by variable-frequency drives (VFDs). This design ensures both high-frequency overload capability and constant-torque output at low frequencies. In structural design, except for overall length, the mounting dimensions are identical to those of the YB2 series motors; other external dimensions also match the YB2 series, ensuring strong interchangeability and facilitating user integration. This series employs an independently mounted axial-flow blower for forced ventilation, guaranteeing effective cooling across the entire frequency range and keeping temperature rise within specified limits.

The speed-control system formed by combining YBBP variable-frequency explosion-proof motors with variable-frequency drives delivers significant energy-saving benefits compared to other speed-control methods. It offers excellent speed-control performance, a wide speed-adjustment range, low noise, minimal vibration, and compatibility with various domestic and international variable-frequency drives. It is widely applicable in industries such as light industry, textiles, chemical processing, metallurgy, and machine tools—especially in constant-torque or constant-power speed-control applications—as well as in energy-saving speed control for fans and pumps, supporting automated control of speed-control systems.

Key features of variable-frequency motors primarily manifest in electromagnetic design and structural design.

The explosion-proof performance of this motor series complies with GB3836.1–2000 “Electrical Apparatus for Explosive Gas Atmospheres—Part 1: General Requirements” and GB3836.2–2000 “Electrical Apparatus for Explosive Gas Atmospheres—Part 2: Flameproof Enclosure ‘d’ "d"”, as well as IEC79-1, BS4683, and EN50018. These motors are manufactured as flameproof-type apparatus. Their explosion-proof markings are ExdI, ExdIIAT4, and ExdIIBT4, suitable for locations where explosive gas mixtures may be present.

ExdI is suitable for underground coal mine environments (non-mining faces) where methane or coal dust explosive mixtures may exist.

ExdIIAT4 is suitable for industrial environments classified as Category II, Group A, with temperature classes T1, T2, T3, and T4 for explosive gas mixtures.

ExdIIBT4 is suitable for industrial environments classified as Category II, Group B, with temperature classes T1, T2, T3, and T4 for explosive gas mixtures.

ExdIICT4 is suitable for industrial environments classified as Category II, Group C, with temperature classes T1, T2, T3, and T4 for explosive gas mixtures.

　　II. Electromagnetic Design of the YBBP Series Variable-Frequency Explosion-Proof Motors

For conventional explosion-proof motors, key design considerations include performance parameters such as overload capacity, starting performance, efficiency, and power factor. For variable-frequency explosion-proof motors, however, critical slip ratio is inversely proportional to supply frequency; thus, direct starting is possible even when critical slip ratio approaches 1. Consequently, overload capacity and starting performance require less emphasis, while the primary challenge becomes improving the motor’s adaptability to non-sinusoidal power supplies. Typical approaches include the following:

1) Minimize stator and rotor resistance as much as possible.

Reducing stator resistance lowers fundamental-wave copper losses, thereby compensating for increased copper losses caused by higher-order harmonics.

2) To suppress higher-order harmonic currents, motor inductance must be appropriately increased. However, large rotor-slot leakage reactance intensifies skin effect, increasing higher-order harmonic copper losses. Therefore, motor leakage reactance must be carefully selected to ensure rational impedance matching across the entire speed-control range.

3) The main magnetic circuit of variable-frequency motors is generally designed to operate in an unsaturated state—firstly, to mitigate deep saturation caused by higher-order harmonics, and secondly, to allow appropriate increase of the VFD’s output voltage at low frequencies to enhance output torque.

　　III. Structural Design of the YBBP Series Variable-Frequency Explosion-Proof Motors

During structural design, primary consideration is given to the effects of non-sinusoidal power supply characteristics on the insulation structure, vibration, noise, and cooling methods of variable-frequency motors. Generally, the following issues require attention:

1) Insulation class—typically Class F or higher—to enhance ground insulation and turn-to-turn insulation strength, with special emphasis on the insulation’s ability to withstand impulse voltage.

2) Regarding motor vibration and noise, sufficient attention must be paid to the rigidity of motor components and the overall structure; efforts should be made to increase the natural frequency to avoid resonance with various force-wave harmonics.

3) Cooling method—generally forced ventilation cooling, i.e., the main motor’s cooling fan is driven by a separate motor.

4) Shaft current prevention measures: For motors exceeding 160 kW, bearing insulation measures shall be adopted. Magnetic circuit asymmetry easily arises and may generate shaft current; when combined with high-frequency current components, shaft current increases significantly—potentially causing bearing damage—thus insulation measures are generally required.

5) For constant-power variable-frequency motors, when speed exceeds 3000 r/min, high-temperature-resistant special grease shall be used to compensate for increased bearing temperature.

　　IV. Ordering Instructions for the YBBP Series Variable-Frequency Explosion-Proof Motors

1. Prior to ordering, consult the product catalog to confirm required model numbers, specifications, and other data. If your required type or specification differs from those listed in the catalog, please contact our company immediately. For special requirements, submit specific and clear requests in advance and consult with the relevant department of our company; contracts or trial-manufacturing agreements shall be signed only after mutual agreement.

2. The purchase contract must specify the motor model, power rating, voltage, speed, and structural type.

3. The purchase contract must specify the number of output shafts, terminal box position, and direction of rotation; otherwise, the motor will be supplied with a single output shaft, clockwise rotation (as viewed facing the main drive shaft), and right-side terminal box.

4. For export products requiring 60 Hz motors or English-language instruction manuals, such requirements must be explicitly stated in the contract.

5. If the application environment is special and manufacturing to tropical-humid conditions is required, this must be specified in the contract.

6. To continuously improve product quality and technical-economic performance, ongoing product improvements are implemented; therefore, data, dimensions, and matched motor dimensions listed in this catalog may change over time. Users are advised to contact us for the latest information.

7. Should any part of the above ordering instructions be unclear, please contact our company.

     V. Technical Data Table for the YBBP Series Variable-Frequency Explosion-Proof Motors

YBBP Series Variable-Frequency Speed-Control Explosion-Proof Motors (Technical Parameters)—Xi’an Tefu SIMO Motor