Choosing variable-frequency drive systems for the mining process units
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | E3S Web of Conferences |
| Authors | Наталья Николаевна Кугушева, А С Семенов, Ilya Yakushev, Svetlana Pavlova, Ayaal Egorov |
| Institutions | Nizhny Novgorod State Technical University, North-Eastern Federal University |
| Citations | 9 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”The research analyzes the selection and implementation of Variable-Frequency Drive (VFD) systems, specifically Frequency Converters (FCs), for energy-intensive process units in diamond mining operations.
- Core Value Proposition: VFD implementation provides a multiplicative economic effect through power savings, reduced maintenance costs (due to smoother transient processes), and extended service life of electric motors and actuators.
- Operational Classification: Mining mechanisms using VFDs are categorized into two groups: (1) energy-saving units (pumps, fans) controlled by process parameters, and (2) process-critical units (hoists) requiring precise speed and torque control.
- Selection Pitfalls: A negative case study involving dredge hoists demonstrated that inadequate technical specifications (failing to specify the need for vector control/torque control) led to a year of unreasonable operational costs.
- Economic Comparison (315 kW Unit): A comparative analysis showed that implementing a Low-Voltage (LV) FC system pays off faster (5 years) than a High-Voltage (HV) FC system (6 years), primarily due to significantly lower annual operating and maintenance costs for the LV option.
- Technical Requirements: For mechanisms requiring high torque at low speed (e.g., hoists), vector control is technically justified, despite the increased converter cost, as it maintains required motor torque across the speed range.
- Future Guidelines: The study concludes that formalized guidelines are necessary, based on classifying equipment by process requirements and failure criticality, to ensure the correct and cost-effective selection of FC technology.
Technical Specifications
Section titled “Technical Specifications”The following table summarizes key technical and economic data extracted from the comparison of low-voltage FCs and the economic modeling of 315 kW VFD systems.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Unit Capacity | 5 | MW | Capacity of single technological units |
| Low-Voltage VFD Power (Tested) | 200 - 220 | kW | Commercial low-voltage FC comparison |
| High-Voltage VFD Power (Tested) | 315 | kW | Pumping unit modernization case study |
| Input Voltage (LV FCs) | 380 | V | Standard low-voltage supply |
| Voltage Tolerance | +10, -15 | % | Typical tolerance range for tested FCs |
| Speed Maintaining Accuracy (Feedback) | ± 0.1 to ± 0.2 | % | Performance metric for LV FCs |
| Torque Maintaining Accuracy (Feedback) | ± 2 to ± 5 | % | Performance metric for LV FCs |
| Overload Margin (1 min rated output) | 120 - 160 | % | Overload capacity of tested LV FCs |
| LV VFD Capital Cost (315 kW) | 6,247.5 | KRUB | Includes new motor, substation, and cable |
| HV VFD Capital Cost (315 kW) | 5,705.5 | KRUB | Converter only (retains existing HV motor) |
| LV VFD Annual Operating Costs | 1,176.8 | KRUB | Maintenance, spare parts, tools |
| HV VFD Annual Operating Costs | 2,235.7 | KRUB | Maintenance, spare parts, tools |
| Payback Period (LV VFD) | 5 | years | Calculated using Net Present Value (NPV) |
| Payback Period (HV VFD) | 6 | years | Calculated using Net Present Value (NPV) |
| Discount Factor (i) | 0.15 | - | Used for NPV calculation |
Key Methodologies
Section titled “Key Methodologies”The research employed a mixed-methods approach combining case study analysis, technical comparison, and economic modeling using the Net Present Value (NPV) technique.
- Process Unit Categorization: Mechanisms were divided into two groups based on control requirements: (1) energy-saving units (speed control based on process parameters like pressure or level) and (2) process-critical units (requiring precise torque control for specific operating modes).
- Technical Comparison of Low-Voltage FCs: Four commercial low-voltage frequency converters (VESPER, ABB, DANFOSS) in the 200-220 kW range were compared based on control method (Scalar vs. Vector), accuracy, overload margin, and total cost (capital, spare parts, and annual maintenance).
- High-Voltage Converter Classification: HV converters were classified by power conversion type (direct, cascade, and multilevel) to understand cost drivers, noting that multilevel converters (using low-voltage H-bridges/IGBTs) are generally cheaper.
- Economic Modeling (315 kW Pumping Unit): Detailed cost calculations were performed for two modernization options for a 315 kW pumping unit:
- Option 1: High-Voltage VFD implementation.
- Option 2: Low-Voltage VFD implementation (requiring a new LV motor, substation, and power cable).
- NPV and Payback Analysis: The Net Present Value (NPV) technique was applied to the economic data over a 7-year planning horizon, considering a 0.15 discount factor and a 10% maximum annual increase in electricity cost, to determine the precise payback period for both HV and LV options.
Commercial Applications
Section titled “Commercial Applications”The findings directly support the optimization of electric drive systems in energy-intensive industrial environments, particularly those requiring high reliability and precise control.
- Diamond and Ore Mining: Primary focus, optimizing large technological units (up to 5 MW) like crushers, conveyors, and processing plant equipment.
- Slurry and Fluid Pumping: Implementing VFDs to achieve energy savings and reduce maintenance costs by eliminating fluid hammer and smoothing transient processes in pipelines.
- Industrial Ventilation Systems: Using VFDs for automatic speed control of main fans based on air depression, leading to significant power savings.
- Heavy Hoisting and Lifting Equipment: Application in mine hoists and dredge trip spotting hoists, where vector control is essential for maintaining precise rope tension and torque at low speeds.
- Industrial Power Management: Utilizing VFDs to improve overall energy transformation and transmission quality, contributing to increased productivity across various industrial actuators.
View Original Abstract
Mining enterprises are energy intensive facilities. The capacity of single technological units can reach 5 MW. Variable-frequency drive systems are often used to set them in motion. The paper analyzes the features of choosing and using variable-frequency drives under diamond mining conditions. The study objective is to formulate and formalize the problems of introducing and operating variable-frequency drives at diamond-mining enterprises to further develop and implement guidelines for improving the performance of this drive type. To achieve this objective, the use of variable frequency drives in various process units of diamond mining should be studied and analyzed. The units are considered, for which in recent years, electric drive systems have been groundlessly (according to the authors) chosen by the engineering staff of enterprises. A technical and economic comparison of low-voltage frequency converters with the same power but different control modes is performed. The economic indicators of introducing high-voltage and low-voltage frequency converters into an existing electric drive system are calculated and represented as a comparative table. Conclusions are made on the need to proceed with the research and develop guidelines for implementing frequency converters at diamond-mining enterprises.