INVT GD5000 Series 4-Quadrant Medium Voltage VFD: Empowering Efficient Energy Saving for Mine Hoists

1. Project Background

Hoists are critical and significant safety apparatus within mines, utilized for elevating minerals, materials, and equipment — serving as the lifeline of mining systems. Traditional hoists predominantly employ an AC speed control system, utilizing a wound rotor asynchronous motor with series resistances in the rotor circuit. This system suffers from discrete speed control, resulting in low torque at low speeds, significant slip power, and large starting and shifting current impacts. Additionally, mid-to-high-speed operations are characterized by substantial vibrations, unsafe and unreliable braking, inadequate handling of regenerative energy, and discontinuous speed adjustments during the inclined hoist operation, which increases the likelihood of derailment and fault occurrences.

2. Client Requirements

A mining company in Shaanxi has an auxiliary hoisting system in a secondary shaft that has been operational for 25 years. The hoist has a length of 1,050 meters and an inclination of 21 degrees, with a designed maximum load of 45 tons, primarily used for transporting coal cars and hydraulic supports. It utilizes a wound asynchronous motor driven by the traditional series resistance speed control method.

The client envisions a transition to a permanent magnet synchronous motor driven by a VFD, aimed at achieving simplified operations, energy savings, and smooth running.

Permanent Magnet Synchronous Motor Parameters:
Motor Model: TYC-800-72P
Rated Power: 800 kW
Rated Voltage: 6,000 V
Speed: 21 r/min
Number of Poles: 72

3. INVT Solution

In response to the client's requirements and the operational characteristics of the permanent magnet synchronous hoist, INVT has developed a bespoke solution utilizing the GD5000 Medium Voltage 4-quadrant VFD, as depicted in the control system diagram below:

Advantages of this Solution:

1. The GD5000 control system employs a multi-core DSP+FPGA+ARM architecture, utilizing advanced closed-loop vector control in conjunction with an encoder, which is well-suited for regulating permanent magnet synchronous motors. This design ensures high control precision, rapid dynamic response, and substantial low-frequency output torque.

2. The VFD is equipped with a buffering resistor circuit, ensuring no impact on the power grid upon initial startup. Throughout operation, whether during constant speed, deceleration, or creeping phases, current surges are minimized.

4. Client Benefits

With the implementation of this solution, the client can achieve:

1. Energy Efficiency and Cost Reduction: The INVT GD5000 4-quadrant VFD enables regenerative braking during the lowering of heavy loads, allowing energy feedback to the grid, thereby achieving notable energy savings. Compared to the previous control method, energy consumption has been greatly reduced, with operational currents halved, yielding annual savings of approximately 300,000 yuan in electricity costs. Furthermore, the simplified operation of the VFD, coupled with remote monitoring capabilities, significantly lowers labor costs.

2. Stability and Reliability: The encoder-based closed-loop vector control provides high precision, ensuring a smooth startup process. The hoist can operate steadily at a minimal speed of 0.1 m/s, allowing for stable heavy load starts without slipping.

3. Reliable After-Sales Service: INVT boasts extensive service coverage and guarantees 24/7 support.

INVT GD5000 4-Quadrant Medium Voltage VFD

Permanent Magnet Synchronous Hoist and Control System in the Field

5. Conclusion

As the safety and energy efficiency requirements for mining hoisting systems continue to evolve, the application of VFD-driven permanent magnet synchronous hoists is likely to expand further. The successful deployment of the INVT GD5000 4-quadrant Medium Voltage VFD in permanent magnet synchronous hoists showcases its formidable technological prowess within the mining sector. Additionally, INVT offers comprehensive solutions across various facets of the mining industry, assisting clients in achieving energy savings and operational efficiency.