In the metals and mining industries, efficiency, reduced costs, and sustainability are crucial concerns. At a time when margins are tight, businesses need to find technological innovations to optimise operations and reduce energy consumption while maintaining productivity. One such example is the variable speed drive (VSD), a technology that significantly enhances the performance of electric motors by adjusting their speed to match the required load. A key factor in achieving the best results is ensuring the software is tailored to the application, which requires expert industry knowledge.

Jose Giacomoni, Senior Commercial Product Manager at Nidec, explains the role of VSDs and how they can optimise performance.

Traditional motors operate at a constant speed, often leading to wasted energy when full power is not required. A VSD, also known as a variable frequency drive (VFD) is a power electronic device that controls the speed and torque of an electric motor by varying the frequency and voltage of its power supply. This allows motors to be operated at optimal speeds, reducing energy consumption and wear and tear on equipment.

Conveyors and pumps

Mining and metal processing facilities rely heavily on conveyor systems to transport materials. VSDs allow for precise speed control, optimising material flow and reducing energy consumption. By adjusting conveyor speeds based on load conditions, VSDs help prevent material spillage, belt wear, and excessive energy use.

Mining operations also require extensive use of pumps for dewatering, slurry transport, and cooling systems. Older pumps often run at full capacity, leading to energy wastage. VSDs enable dynamic speed control, adjusting pump performance to match demand, reducing both energy consumption and equipment wear. Similarly, ventilation fans in underground mines benefit from VSDs by optimising air circulation via speed regulation, thus reducing power usage based on the principals of the “Square-cube” law.

Crushing and grinding operations are among the most energy-intensive processes in mining and metal refining. By employing VSDs, operators can adjust the torque of crushers and grinding mills to accommodate varying ore hardness and feed rates, greatly improving efficiency and reducing unnecessary power consumption, boosting productivity while cutting costs.

Precise control and functionality

VSDs can also provide enhanced control for hoisting systems, ensuring smooth lifting operations with reduced mechanical stress. This is especially important in deep mining applications where hoists transport heavy loads over long distances. Controlled acceleration and deceleration improve safety and prevent sudden movements that could damage equipment. Regenerative drive systems, also known as active front end (AFE), are well used in this type of application taking advantage of excess energy during braking, returning it back to the mains or reusing it in other parts of the integrated system.

During smelting and refining, various electrically driven assets, such as mixers, blowers, and casting equipment, can benefit from VSDs. These applications require precise speed control to maintain product quality, reduce energy costs, and ensure optimal process conditions. Each operation has its own requirements and while the hardware within a range of VSDs will be similar, it is the software that provides the detailed control and functionality.

Having selected a solution depending on the motor type, AC, DC or servo, the next step is to ensure the required features and controls are built-in. Modern drives, such as those from Nidec, are tailored to applications to ensure they deliver the required inputs, outputs, communications, motor protection, and integration with connected hardware to achieve optimum performance.

Key benefits 

The ancillary field hardware installation cost comparison between a conventional fixed speed application (direct on-line (DOL), star delta, reactor starter, etc.), to that of a VSD is beneficial due to the intelligent motor fluxing optimisation during the initial start cycle. This reduces the excessive peak inrush currents, resulting in smaller power cables at a reduced cost. In addition to this, the maximum peak electrical power demand during the start cycle is dramatically lower, thus the electrical billing base rate is at a lower tariff.

By optimising motor speeds based on demand, VSDs can reduce energy consumption by 20% to 50%. Providing precise control over motor speeds on equipment that operates under fluctuating loads such as conveyors, crushers, pumps, and fans, VSDs offer improved process control and consistency.

The savings achieved by introducing VSDs are not just financial. The reduction in energy consumption is directly proportional to the drop in associated carbon emissions, which contributes to the sustainability goals of the business. Increasingly, legislation is being introduced to reinforce the need to reduce global emissions and industrial consumers are responsible for consuming 37% of the world’s total produced energy.

Sustainability

In mining and metals processing, VSDs allow for smoother adjustments to process requirements. This helps prevent bottlenecks, enhances throughput, and minimises operational disruptions. This results in lower operating expenditure (OPEX) and a reduced carbon footprint, making operations more sustainable.
 
One example of the processes using a significant amount of energy is the cooling system, which is crucial to maintaining a comfortable working environment in underground mining sites. Energy audits frequently highlight the feasibility of installing VSD technology on the pumps and fans, and this is supported by pilot schemes that demonstrate real-world savings. 

In fact, VSDs double-up on this. Motors running at lower currents not only consume less energy, they also generate less heat, which reduces the demand on the cooling systems. In addition, VSDs contribute to a quieter working environment by minimizing motor noise, further improving workplace conditions.

Operating electric motors at constant high speeds can lead to excessive mechanical stress, shortening the lifespan of equipment and increasing maintenance costs as well as the demand for replacement parts. VSDs mitigate this by reducing the strain on mechanical components, extending their service life and reducing the need to consume additional materials in the form of spares.

Comparing technologies

Some of the benefits derived from VSDs can be achieved by soft starters, but it is important to understand the differences between the two technologies before any decisions are made. A step up from DOL or star-delta arrangements, soft starters ramp up the supply voltage to the motor, providing speed and torque control only during start-up.

They are often used when the mechanical system the motor is driving requires a gentle start to relieve torque spikes and tension associated with normal start-up, for example conveyors, belt-driven fans, and geared drives. Soft starters are widely used because of their simplicity and small footprint, but there are many applications that would benefit from the more advanced features of the VSD.

Variable speed drives offer fully adjustable speed, ideal for pumps, conveyors, and fans, and can control starting, stopping, and acceleration. The speed control that a VSD offers can be used to reduce the pressure surges caused in pumping systems, optimising performance and extending service life. They also have dynamic torque control and provide smooth motion for applications such as elevators and cranes.

However, the overarching benefits come from the continuous control of peak energy demand and reducing power when it is not required, minimising energy costs. The ability to maintain speed while torque requirements vary is important for many applications including conveyors, mixers, grinders and crushers.

Environmental considerations

If there is one common factor between mining and metals processing, it is the harsh working environment, which can involve abrasive dust, corrosive salt air as well as extremes of temperature. Operating machinery, and its control apparatus, is a challenging task. Equipment needs to be carefully specified, not just for its suitability to perform the task in hand, but also withstand the local environmental conditions.

This is where the choice of equipment supplier becomes so important. Working with a manufacturer that has experience in the industry, as well as expertise in the specific applications under discussion, is vital to a successful outcome. Ideally, multiple examples in the field, supported by positive operator feedback, can be used to exemplify the reliable and robust design.

For mining applications, a brand that delivers durability in this market will often perform well in all other sectors. With such challenging conditions and operational requirements, tailored solutions for variable speed drives will deliver the best solutions, ensuring operators maximise the benefits and achieve peace of mind for their application.

Looking to the future

The key to achieving these benefits is not just installing the VSD, it is the way in which the VSD delivers the control, how it is configured, and how the hardware interacts with the software. Operators should certainly engage with a leading drive manufacturer, such as Nidec, to apply their industrial expertise to optimise the application. 

As the metals and mining industries continue to prioritise sustainability and operational efficiency, the adoption of  VSDs will likely increase. Advances in digitisation, automation, and remote monitoring further enhance the capabilities of VSD technology. Many modern VSDs come equipped with smart sensors and connectivity features, allowing for real-time performance monitoring and predictive maintenance. This reduces downtime and further optimises energy consumption.

Variable speed drives are transforming the metals and mining industries by improving energy efficiency, enhancing process control, reducing maintenance costs, and contributing to a safer working environment. From conveyor systems to crushers and hoists, VSDs offer unparalleled benefits that lead to cost savings and improved operational performance. As companies strive to meet environmental regulations and sustainability goals, the integration of VSDs will play a vital role in shaping the future of the industry.