Zijin Mining Tibet Julong Copper Mine Phase II Expansion Project

Case Study — 2×90 MW Dual-Drive Mill Motors (Domestic Demonstration of Large-Scale Mill Drive Systems)

Project Overview

With the accelerated development of low-grade ore mines and the explosive demand for ultra-large grinding mills, Shanghai Electric Group Shanghai Electric Motor Factory successfully developed and delivered the 2×90 MW dual-drive mill motor solution for large-scale mine mills. This solution matches international advanced products in both structural design and technical parameters, showing significant differences from traditional domestic motors. It provides a new technical pathway and engineering practice for domestically-produced, ultra-high-power, low-speed electric drive systems.

This type of motor has been deployed in multiple major domestic and international mining projects:

• Zijin Mining Tibet Julong Copper Mine Phase II Expansion

• Zijin Tibet Xianglong (Juno) Copper Mine Project

• Zijin Bor Copper Renovation Project, Serbia

It is specifically designed to meet the drive requirements of extra-large grinding mills.

Application Background and Requirements

• Ultra-high mill capacity and rotational inertia (extra-large ball/rod mills), requiring long-term continuous, high-inertia, low-speed drive

• Low starting current multiple, smooth startup, and stable parallel operation to minimize impact on plant power grid

• High reliability, easy maintenance, and restricted site repair conditions (high-altitude or overseas mines) require a high level of domestic manufacturing and rapid service response

• High compatibility with mill gearboxes, couplings, hydraulic couplings, or direct-drive systems, with support for intelligent monitoring and maintenance

2×90 MW Dual-Drive Solution Overview

The dual-drive design adopts the concept of “two motors driving one mill in parallel” (two motors of equal power connected via coaxial gearboxes or parallel couplers to the mill shaft). The core idea is torque sharing, redundancy, and improved startup/operation conditions:

• Each motor rated at 90 MW, allowing a peak drive capability of 180 MW in parallel operation (depending on mill design)

• Integrated VFD / torque controller and excitation system for coordinated control, enabling soft start, torque sharing, and symmetrical parallel operation

• Supports “primary/backup” or “shared load” modes for enhanced flexibility and reliability

• Equipped with advanced monitoring and diagnostic systems, providing real-time monitoring of windings, bearings, vibration, axial force, and torque distribution

Key Technical Innovations (Compared to Traditional Domestic Products)

• Ultra-high-power low-speed motor design: Optimized magnetic circuit, shallow slot ratio, and large conductor cross-section for 90 MW class, balancing efficiency and electromagnetic vibration control

• Modular and serviceable structure: Modular key components (end covers, cooling modules, bearing housings) reduce onsite maintenance difficulty, ideal for high-altitude and overseas sites

• Enhanced cooling system: High heat flux management via composite cooling (full water cooling / water-air hybrid / partial oil cooling), redundant cooling loops, and online flow/temperature monitoring

• Dual-drive parallel control: High-precision torque distribution and synchronization algorithms ensure smooth load sharing and switching without torque shocks

• Starting current and grid impact control: VFD soft-start, constant torque ramp, and mill inertia management achieve low-multiple starts and significantly reduce electrical impact on the plant grid

• High-reliability bearings and lubrication: Large oil-lubricated / oil-circulation bearings or water-lubricated bearings with online temperature, oil quality, and bearing condition monitoring

Typical Technical Parameters (Illustrative)

Manufacturing and Factory Test Highlights

• Critical materials and supply chain control: Large conductors, large silicon steel sheets, bearings, and cooling components strictly supplier-approved and inspected

• Assembly process control: Stator/rotor assembly, VPI vacuum impregnation, rotor assembly, and multi-stage dynamic balancing under controlled procedures

• Cooling loop and sealing inspection: Pressure test, flow distribution verification, corrosion resistance test

• Factory acceptance testing (FAT): No-load, temperature rise, dynamic balance, parallel operation test (two motors simulating mill load), short-circuit/overload test, and protection logic verification

• Third-party and client witness: Key tests witnessed by client and third parties with documented reports

Transportation, Installation, and Parallel Commissioning

• Specialized heavy transport and onsite segmented hoisting plan, with detailed positioning procedures

• Foundations and machine bases designed for high rigidity and verified by modal analysis

• Parallel operation commissioning focuses on torque distribution, synchronization, and interlock protection

• Coordinated debugging with mill gearbox/coupling/hydraulic coupling; record no-load/load temperature rise and vibration trends

Engineering Challenges and Solutions

• Thermal management: CFD and thermal simulation optimize cooling paths; redundant loops and online emergency switching strategies

• Parallel control complexity: High-precision torque sharing and synchronization algorithms ensure smooth switching and load sharing

• High-inertia startup and grid impact: VFD soft start and inertia management reduce starting current and grid influence

• Transportation and onsite risk: Segmented handling, protective measures, specialized lifting equipment, and online verification to ensure first-time successful installation

Operational Performance and Client Value

The 2×90 MW dual-drive motor solution provides the following benefits in mining mill applications:

• Reliability and redundancy: Dual-drive structure increases system availability and fault tolerance

• Smooth startup and grid friendliness: VFD and parallel control reduce startup current peaks and grid impact

• Domestic production and supply assurance: Key large-power components are domestically produced, resolving long import cycles, high costs, and spare part challenges

• Controllable O&M: Modular design and online diagnostics reduce maintenance complexity and downtime, offering long-term TCO advantages

• Replicable engineering: Provides a replicable electric drive solution for other ultra-large mills, facilitating scalable adoption

Recommended Monitoring and KPI Metrics

• Unit Availability: target ≥ 98%

• Starting Current Multiple (Inrush Ratio): target ≤ 2.5–3.0× depending on grid conditions

• Torque Share Accuracy: target ±2%

• Winding and bearing temperature rise: within design margin

• Vibration and axial displacement: compliant with mechanical specifications and foundation response

• Cooling system reliability and backup switching response time

The 2×90 MW dual-drive mill motors for projects including Zijin Tibet Julong Phase II, Juno Copper Mine, and Serbia Bor Renovation represent a major breakthrough in domestically-produced ultra-high-power, low-speed electric drive systems. Through innovations in electromagnetic design, cooling technology, parallel control, and modular manufacturing, this solution rivals international advanced products in performance, reliability, and engineering implementation, while offering clear advantages in delivery time, cost, and localized service. It provides a replicable technical pathway for domestic ultra-large mill drives.