1.Introduction

As the key core equipment of the mine transportation system, the mine hoist is responsible for lifting and lowering personnel, ores, materials, etc.The safety, reliability and efficiency of its operation are directly related to the production efficiency of the mine and the safety of life and property of personnel.With the continuous development of modern science and technology, the application of permanent magnet technology in the field of mine hoists has gradually become a research hotspot.

Permanent magnet motors have many advantages such as high power density, high efficiency, and low noise. Applying them to mine hoists is expected to significantly improve equipment performance, while also bringing new opportunities and challenges in terms of safety assurance.

2. Application of permanent magnet technology in mine hoist drive system

(1).Permanent magnet synchronous motor working principle

Permanent magnet synchronous motors operate based on the law of electromagnetic induction. The core principle is that when three-phase alternating current is passed through the stator winding, a rotating magnetic field is generated, which interacts with the magnetic field of the permanent magnet on the rotor, thereby generating electromagnetic torque to drive the motor to rotate.The permanent magnets on the rotor provide a stable magnetic field source without the need for additional excitation current, which makes the motor structure relatively simple and improves the energy conversion efficiency.In mine hoist application scenarios, the motor needs to frequently switch between different operating conditions such as heavy load, low speed and light load, high speed. The permanent magnet synchronous motor can respond quickly with its excellent torque characteristics to ensure the smooth operation of the hoist.

(2). Technological advancement compared with traditional drive systems

1. Efficiency comparison analysis

Traditional mine hoists are mostly driven by wound-rotor asynchronous motors, which have relatively low efficiency.The losses of asynchronous motors mainly include stator copper loss, rotor copper loss, iron loss, mechanical loss and stray loss.Since there is no excitation current in the permanent magnet synchronous motor, its rotor copper loss is almost zero, and the iron loss is also reduced due to the relatively stable magnetic field characteristics.Through the comparison of actual test data (as shown in Figure 1), under different load rates, the efficiency of the permanent magnet synchronous motor is significantly higher than that of the wound-rotor asynchronous motor.In the load rate range of 50% – 100%, the efficiency of permanent magnet synchronous motor can be about 10% – 20% higher than that of wound-rotor asynchronous motor, which can significantly reduce energy consumption costs for long-term operation of mine hoists.

Figure 1: Efficiency comparison curve of permanent magnet synchronous motor and wound rotor asynchronous motor

2. Power factor improvement

When a wound-rotor asynchronous motor is running, its power factor is usually between 0.7 and 0.85, and additional reactive power compensation devices are required to meet grid requirements.The power factor of a permanent magnet synchronous motor can be as high as 0.96 or above, close to 1.This is because the magnetic field generated by the permanent magnet greatly reduces the demand for reactive power during the operation of the motor. High power factor not only reduces the reactive power burden of the power grid and improves the power quality of the power grid, but also reduces the electricity cost of mining enterprises and reduces the investment and maintenance costs of reactive compensation equipment.

(3). Impact on safe operation of mine hoists

1.Starting and braking characteristics

The starting torque of permanent magnet synchronous motors is smooth and precisely controllable.At the moment of mine hoist startup, it can avoid problems such as wire rope shaking and increased wear of the sheave caused by excessive torque impact when traditional motors are started. Its starting current is small and will not cause large voltage fluctuations in the power grid, ensuring the normal operation of other electrical equipment in the mine.

In terms of braking, permanent magnet synchronous motors can be combined with advanced vector control technology to achieve precise braking torque regulation.For example, during the deceleration stage of the hoist, by controlling the magnitude and phase of the stator current, the motor enters the power generation braking state, converting the kinetic energy of the hoist into electrical energy and feeding it back to the power grid, thus achieving energy-saving braking. Compared with traditional braking methods, this braking method reduces the wear of mechanical brake components, prolongs the service life of the braking system, reduces the risk of brake failure due to brake overheating, and improves the safety and reliability of hoist braking.

2.Fault redundancy and fault tolerance

Some permanent magnet synchronous motors use a multi-phase winding design, such as a six-phase permanent magnet synchronous motor.When a phase winding of a motor fails, the remaining phase windings can still maintain the basic operation of the motor, but the output power will be reduced accordingly.This fault redundancy design enables the mine hoist to safely lift the hoisting container to the wellhead or well bottom even in the event of a partial motor failure, avoiding the hoist from hovering in the middle of the shaft due to motor failure, thus ensuring the safety of personnel and equipment.Taking a six-phase permanent magnet synchronous motor as an example, assuming that one of the phase windings is open, according to the torque distribution theory of the motor, the remaining five-phase windings can still provide about 80% of the rated torque (the specific value is related to the motor parameters), which is enough to maintain the slow operation of the elevator and ensure safety.

3. Actual case analysis

(1). Application cases in metal mines

A large metal mine uses a permanent magnet synchronous motor to drive the permanent magnet synchronous motor with a rated power of P=3000kw. After using this motor, compared with the original wound asynchronous motor, under the same lifting task, the annual power consumption is reduced by about 18%

Through monitoring and analysis of motor operating data, the efficiency of permanent magnet synchronous motors remains at a high level under different operating conditions, especially at medium and high load rates, where the efficiency advantage is more obvious.

(2). Coal Mine Application Cases

A coal mine installed a mine hoist using permanent magnet technology. Its permanent magnet synchronous motor has a power of 800kw and is mainly used for lifting and transporting personnel and coal. Due to the limited capacity of the coal mine power grid, the high power factor of the permanent magnet synchronous motor effectively reduces the burden on the power grid. During operation, there was no significant fluctuation in the power grid voltage due to the start-up or operation of the hoist, which ensured the normal operation of other electrical equipment in the coal mine.

4.Future development trend of permanent magnet motor for mine hoist

(1). Research and development and application of high-performance permanent magnetic materials

With the continuous advancement of materials science, the research and development of new high-performance permanent magnetic materials has become an important direction for the development of permanent magnetic technology for mine hoists.For example, the new generation of rare earth permanent magnet materials is expected to achieve breakthroughs in magnetic energy product, coercive force, temperature stability, etc.Higher magnetic energy product will enable permanent magnet motors to output greater power with smaller volume and weight, further improving the power density of mine hoists; better temperature stability will enable permanent magnet motors to adapt to harsher mine environments, such as high-temperature deep mines; stronger coercive force will enhance the permanent magnet’s anti-demagnetization ability and improve the motor’s reliability and service life.

(2). Integration of intelligent control technology

In the future, the permanent magnet technology of mine hoists will be deeply integrated with intelligent control technology. With the help of artificial intelligence, big data, Internet of Things and other advanced technologies, the intelligent operation and maintenance of hoists will be realized.For example, by installing a large number of sensors on key components of permanent magnet motors and hoists, operating data can be collected in real time, and the data can be analyzed and processed using artificial intelligence algorithms to achieve early prediction and diagnosis of equipment failures, arrange maintenance plans in advance, reduce equipment failure rates, and improve operational reliability.At the same time, the intelligent control system can automatically optimize the operating parameters of the motor, such as speed, torque, etc., according to the actual production needs of the mine and the operating status of the hoist, so as to achieve the goal of energy saving and efficiency improvement and improve the production efficiency and economic benefits of the mine.

(3). System integration and modular design

In order to improve the convenience and maintainability of the application of permanent magnet technology in mine hoists, system integration and modular design will become the development trend.The various subsystems such as permanent magnet motors, braking systems, and safety monitoring systems are highly integrated to form standardized functional modules.When constructing a mine or renovating equipment, you only need to select the appropriate modules for assembly and installation according to actual needs, which greatly shortens the equipment installation and commissioning cycle and reduces engineering construction costs. In addition, the modular design facilitates equipment maintenance and upgrades. When a module fails, it can be quickly replaced, reducing downtime and improving the production continuity of the mine.

5.Technical advantages of Anhui Mingteng permanent magnet motor

Anhui Mingteng Permanent-Magnetic Machinery & Electrical Equipment Co., Ltd（https://www.mingtengmotor.com/）.was established in 2007. Mingteng currently has more than 280 employees, including more than 50 professional and technical personnel. It specializes in the research and development, production and sales of ultra-high-efficiency permanent magnet synchronous motors. Its products cover a full range of high-voltage, low-voltage, constant frequency, variable frequency, conventional, explosion-proof, direct drive, electric rollers, all-in-one machines, etc. After 17 years of technical accumulation, it has the ability to develop a full range of permanent magnet motors. Its products involve various industries such as steel, cement, and mining, and can meet the needs of various working conditions and equipment.

Ming Teng uses modern motor design theory, professional design software and self-developed permanent magnet motor design program to simulate the electromagnetic field, fluid field, temperature field, stress field, etc. of the permanent magnet motor, optimize the magnetic circuit structure, improve the energy efficiency of the motor, and solve the difficulties in on-site bearing replacement of large permanent magnet motors and the problem of permanent magnet demagnetization, fundamentally ensuring the reliable use of permanent magnet motors.

6. Conclusion

The application of permanent magnet motors in mine hoists has demonstrated excellent performance in terms of safety and technological advancement. In the drive system, the high efficiency, high power factor and good torque characteristics of permanent magnet synchronous motors provide a solid foundation for the safe and stable operation of the hoist.

Through actual case analysis, it can be seen that permanent magnet motors have achieved remarkable results in the application of mine hoists in different types of mines, whether in reducing energy consumption, reducing maintenance costs, or ensuring the safety of personnel and equipment. Looking to the future, with the development of high-performance permanent magnet materials, the integration of intelligent control technology, and the advancement of system integration and modular design, permanent magnet motors for mine hoists will usher in a broader development prospect, injecting strong impetus into the safe production and efficient operation of the mining industry. When considering upgrading hoist technology or purchasing new equipment, mining customers should fully realize the huge potential of permanent magnet motors, and reasonably apply permanent magnet motors in combination with the actual working conditions, production needs, and economic strength of their own mines to achieve sustainable development of mining enterprises.

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https://mp.weixin.qq.com/s/18QZOHOqmQI0tDnZCW_hRQ

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