Explore our elite selection of high-efficiency, flameproof, and application-specific three-phase asynchronous motors designed to meet international engineering standards.
The Authorized Global Channel Partner of WOLONG Electric Drive Group Co., Ltd.
Founded in 1984 and listed on the Shanghai Stock Exchange in 2002 (SH600580), Wolong Electric Drive Group has grown over three decades into a preeminent global leader in the design, manufacture, and distribution of industrial electric motors and complex control systems. Shaanxi Nanfang Motor Technology Co., Ltd. serves as the premier authorized distributor for Wolong, delivering advanced drive engineering and explosion-proof solutions to complex industrial facilities globally.
Today, Wolong operates a massive network of 3 key manufacturing bases, 39 advanced factories, and 3 global research and development centers. The group's commitment to technological innovation, process control, and rigorous global brand strategy has established its reputation as a leading power in drive engineering.
Wolong's growth is supported by strategic acquisitions of some of the most respected brands in motor engineering history. This integration has united centuries of technical capability under a unified banner:
Acquired in 2011 (97.94% stake). As one of the top three European motor manufacturers, ATB brings critical design capabilities. The acquisition included renowned brands Morley and Laurence Scott, adding high-specification electrical machinery capacity to the group.
Boasting nearly 130 years of history, Morley is synonymous with quality and power in the underground coal mining market. They produce high-performance, high-specification flameproof mine motors capable of operating in the most hazardous mining conditions.
Famous for developing specialized low-starting-current motors, Laurence Scott has supplied equipment to British nuclear power stations and naval vessels. Following its acquisition by Wolong, Laurence Scott received the Queen's Award for three consecutive years.
With over a century of experience in motor design, Brook Crompton is a leader in energy-efficient motors. They offer a complete range of low, medium, and high-voltage AC motors, including the "W" and "10" series, and adjustable speed drive packages designed for harsh environments.
Schorch has set high standards for high-quality heavy-duty drive systems globally. Collaborating with strategic partners, Schorch serves critical sectors including petrochemicals, power generation, water and waste treatment, shipbuilding, steel processing, and tunnels.
Dating back to 1999, Wolong has partnered with OLI, the world's leading brand in vibration motors (MVE) and Ex vibration sensors, capturing a significant share of the global bulk solids handling and concrete consolidation markets.
In 2018, GE's commercial and industrial motor division partnered with Wolong. As a historic manufacturer of electrical machinery, GE provides technical support to Wolong, serving heavy industries like petrochemicals, metals, water, and cement.
Joining Wolong in 2015, CNE is China's largest research and production base for explosion-proof motors. CNE specializes in low-voltage asynchronous, high-voltage explosion-proof, and custom motors used in oil, coal, chemical, metallurgical, military, and nuclear industries.
By integrating CNE's technology, Wolong has strengthened its capability to build safe, durable explosion-proof motors certified by global authorities including ATEX, IECEx, and CU-TR.
By bringing together engineers from China, Europe (ATB, Schorch, Morley, Laurence Scott), and Japan, Wolong has formed a global collaborative R&D network. The Shanghai Central Research Institute serves as a central hub, developing new technologies in motor science, power electronics, and motor control.
Our production facilities utilize modern precision processes, including digital machining centers, advanced VPI insulation treatment, and comprehensive automated performance testing. These processes ensure that all products, from low-voltage asynchronous machines to large-scale high-voltage positive-pressure motors, deliver reliable, long-term performance.
A Technical Deep Dive into the Design, Operation, and Torque Benefits of Dual-Cage Induction Motors.
Standard squirrel-cage induction motors face a fundamental design trade-off between starting torque and running efficiency. A high-resistance rotor offers high starting torque but exhibits high slip and lower efficiency during normal operation. A low-resistance rotor achieves high efficiency and low slip but generates poor starting torque.
The Double Squirrel Cage Motor solves this challenge by using two separate cages in the rotor core:
During startup, the rotor frequency equals the stator supply frequency (e.g., 50Hz or 60Hz). Due to the *skin effect*, the high reactance of the inner cage directs the rotor current through the high-resistance outer cage, generating high starting torque (up to 200–250% of full-load torque) and keeping starting current low.
As the rotor accelerates toward synchronous speed, the slip frequency drops (typically down to 1.5–3Hz). At this low frequency, the inductive reactance of both cages decreases. The current shifts to the low-resistance inner cage, allowing the motor to operate at high efficiency with minimal slip.
A reliable double squirrel cage motor requires high-quality stator winding and insulation systems, especially when starting high-inertia loads that generate thermal stress.
Our stators are built with premium materials, including polyester film and high-mica-content tapes. The wound stator core undergoes a comprehensive Vacuum Pressure Impregnation (VPI) process:
Double squirrel cage motors generate significant electromagnetic torque forces during startup. To handle these stresses without mechanical deformation, the housing frame must be highly rigid.
Our motor frames are designed using multi-physics structural and fluid dynamic simulations (FEA). Key features include:
Heavy-duty motors can generate significant high-frequency noise from their cooling fans. To meet strict industrial noise limits, our motors feature advanced low-noise ventilation systems:
Providing high-torque, explosion-proof motor systems for challenging global industries.
Underground coal conveyors and cutting machinery require high starting torque under full load. Wolong YBC coal shearer motors and YBSD series flameproof conveyor motors utilize double squirrel cage technology to start reliably under heavy loads. Morley mining motors provide robust explosion protection for these deep-mine operations.
Large-scale fans and compressors in petrochemical facilities require continuous operation in hazardous environments. Our YBXKK and YBBPX high-voltage explosion-proof motors are certified to ATEX/IECEx standards. They deliver stable power while preventing gas ignition, ensuring safety in Class I Div 1 & Zone 1 environments.
Municipal water networks and wastewater plants require motors that can handle high hydraulic inertia and pump start-up loads. Our YKS/YKK high-voltage AC motors and YBRB flameproof water pump motors are designed for high starting torque and long service life under continuous operation.
Our motors are certified to major international standards, facilitating integration into global industrial projects.
Wolong Group maintains strict quality management processes, earning core electrical and explosion-proof certifications required for global markets:
Nemko/Atex
CSA
CE
CCC
SABS
TESTSAFE
Aligning with Industry 4.0, IE5 Ultra-Efficiency, and Smart Thermal Analytics.
The industrial motor sector is undergoing a major transition driven by carbon neutrality goals and digital transformation. Double squirrel cage motors are evolving to offer higher efficiency and intelligent diagnostics. Shaanxi Nanfang Motor and Wolong are leading this change through three key initiatives:
Traditional dual-cage induction motors face rotor resistive losses during starting sequences. By optimizing cage geometry using finite element analysis (FEA) and utilizing high-conductivity copper formulations, our engineers are raising motor efficiency to IE4 and IE5 levels, helping operators lower energy costs and carbon footprints.
Operating double squirrel cage motors on VFDs requires careful engineering to manage harmonic heating. Wolong's YBBPX and TBVF series use specialized insulation and reinforced bearing designs to prevent high-frequency damage, ensuring reliable variable speed performance.
Modern plants are adopting IoT-based monitoring. Our future motors feature integrated sensors that track vibration, stator temperature, and rotor slip in real time. This data is processed by local or cloud analytics to predict maintenance needs and prevent unscheduled downtime.
A direct performance comparison across key industrial parameters.
| Performance Parameter | Single Cage Squirrel Motor (Class B/C) | Double Squirrel Cage Motor (Class D/High Torque) | Wound Rotor (Slip Ring) Motor |
|---|---|---|---|
| Starting Torque ($T_{start}$) | Low to Medium (100% - 150% rated) | High (200% - 280% rated) | Extremely High (Adjustable via external resistance) |
| Starting Current ($I_{start}$) | High (6 - 8x rated) | Low to Medium (4.5 - 5.5x rated) | Low (Typically < 2.5x rated) |
| Running Efficiency | Excellent (IE3 / IE4 compliant) | Very Good (Slightly lower slip losses than Class B) | Moderate (Brush contact friction losses) |
| Maintenance Requirements | Low (Brushless, standard bearings) | Low (Robust, brushless rotor design) | High (Regular brush inspection and slip ring replacement) |
| Hazardous Area (Ex) Compatibility | Excellent (Simple design, easy to seal) | Excellent (Easy to seal for Ex d / Ex p protection) | Difficult (Slip rings present sparking risks, requires heavy enclosures) |
| Ideal Application Profile | Fans, light pumps, low-inertia systems | Heavy conveyors, high-inertia crushers, coal shearers | Heavy mills, cranes, weak-grid systems requiring long starts |
Answering key technical and purchasing questions for industrial project managers.
A1: During starting, the high-resistance outer cage carries most of the rotor current and absorbs the initial thermal energy. The outer bars are designed with larger thermal margins and materials that can withstand high temperatures. Once the motor reaches operating speed, current shifts to the low-resistance inner cage, allowing the outer cage to cool. Proper ventilation design is essential to dissipate this heat during frequent startups.
A2: Yes, in many applications. Wound rotor motors are often chosen for their high starting torque and low starting current. However, they require regular maintenance of brushes and slip rings. A double squirrel cage motor provides similar torque performance with a simpler, brushless rotor design, reducing maintenance costs. This is particularly beneficial in dusty environments like coal mines or cement plants.
A3: ATEX and IECEx standards define specific construction requirements to prevent ignition in explosive atmospheres. For flameproof (Ex d) motors, the housing is designed to contain any internal explosion and cool escaping gases below ignition temperatures. Positive pressure (Ex p) motors maintain a clean air or inert gas pressure inside the frame to exclude external gases. These designs require high-strength castings, precise joints, and tested sealing components.
A4: For smaller capacities, we use centrifugal die-casting of pure aluminum directly into the rotor slots, which integrates the rotor bars and end rings into a solid structure. For larger motors, copper bars are inserted and welded to the end rings under tight control. High-speed rotors also include retaining rings to prevent radial displacement under centrifugal forces.
A5: Yes, but with some design considerations. When powered by a VFD, the motor's rotor frequency matches the slip frequency, which remains low. Consequently, the current flows primarily through the inner cage, maintaining high efficiency. The stator insulation must also be designed to resist high voltage spikes ($dv/dt$) from the VFD inverter, and insulated bearings may be needed to prevent electrical erosion.
High-voltage, flameproof, and increased-safety asynchronous motors for oil & gas, mining, and heavy process industries.
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