Industrial drives play a crucial role in powering machinery in every sector of industry and human endeavor - manufacturing, transport, mining, oil and gas extraction/refining, farming, entertainment, food production, and water treatment and supply.

There's a variety of drives, typically induction motors with variable frequency drives (VFDs), or DC motors with proportional-integral-differential (PID) controllers. They convert electrical into kinetic energy (motion), driving pumps, compressors, conveyors, wheels, fans, gears and propellers - most equipment. Industrial drives account for a significant portion of net electrical energy consumption, sometimes suggested as making up more than 70% of total energy use. Industrial air movement (fans) alone amounts to 7% to 9% of all electricity demand.

Industrial drives are often multi-kilowatt power users with huge financial implications and large opportunities for efficiency savings in their operation. Source: nordroden/Adobe Stock

As industries become more conscious of sustainability issues and seek to reduce operational costs, improving the energy efficiency of industrial drives is an area of relatively easy wins, when the right systemic changes are made. There are various effective strategies, technologies and best practices that can serve in enhancing energy efficiency in industrial drives.

Why energy efficiency in industrial drives matters

Energy efficiency in industrial drives is vital for several reasons:

Cost savings resulting from reducing energy consumption directly lowers operational costs, with a direct impact on a company’s bottom line, particularly in energy-intensive industries.

Environmental impacts result from improved efficiency, reducing greenhouse gas emissions and helping industries meet sustainability goals and comply with environmental regulations.

Equipment longevity is improved with efficient drive systems, as they typically operate more smoothly, reducing wear and shock loading, extending the lifespan of motors, bearings and other components.

Operational performance in energy-efficient drives can enable improved overall system performance, reducing downtime and increasing productivity.

Key factors influencing energy efficiency in industrial drives

Prior to proposing and evaluating specific strategies for improving energy efficiency, it’s valuable to illustrate the pertinent factors that influence the performance of industrial drive systems:

Electric motor efficiency, typically measured as a percentage that describes effectiveness of the motor in converting electrical power into mechanical output. More efficient motors waste less energy in the form of heat.

Motors operate with optimal efficiency when operating close to (but definitely below) their rated capacity under all typical running conditions. Underloading or overloading typically results in energy waste, as most motors have efficiency curves that peak at 75% of maximum rated power.

In many applications, motor speed can be varied to match the needs of the process. Using VFDs allows motors to operate more efficiently by adjusting their speed, while still allowing them to operate at 75% of their rated capacity when powered.

Power quality fluctuations occur when the voltage, or frequency vary, or harmonics are introduced by noisy loads, allowing power quality issues to reduce the efficiency of drive systems and increase energy consumption.

Well-maintained motors and drive systems are more energy-efficient. Poor maintenance can lead to increased mechanical loading, electrical losses, and greatly reduced overall efficiency.

Strategies to improve energy efficiency in industrial drives

There are various strategies by which energy efficiency in industrial drives can be improved. The most effective strategies that are generally applicable:

Use high-efficiency motors

The simplest and most obvious way to improve energy efficiency is to use high-efficiency motors. Up-to-date devices meeting the IE3 or IE4 energy efficiency standards (International Efficiency classifications) will deliver higher efficiency use of electrical power. Compliant devices are designed for minimal electrical, thermal and mechanical losses, making more effective use of electrical energy.

IE3, or premium efficiency motors, offer significantly better performance compared to IE1 (standard efficiency) and IE2 (high efficiency) motors. They are interchangeable in most industrial applications where circuit details, wiring formats and mountings are identical and offer a good balance between cost and efficiency.

IE4, or super-premium efficiency motors, are even higher efficiency than IE3. While they incur considerably higher CAPEX, they can provide substantial energy savings which, over an operational life, deliver beneficial return on investment.

Implement VFDs

VFDs use a method that controls the speed of electric motors by varying the frequency and voltage supplied to them. In most AC motor systems, the free or unloaded speed relates directly to SC frequency. VFDs improve energy efficiency in systems where the motor doesn’t need to run at full speed, such as pumps, fans, and compressors, where varying the motor speed to match demand can deliver considerable energy savings.

For example, reducing the speed of a pump motor by just 20% can moderate energy demand by as much as 50%, according to the affinity laws that define the behavior of pumps and fans.

VFDs also facilitate soft start and stop, which reduces the mechanical stress resulting from bang-bang switching, modestly improving energy efficiency but greatly reducing impulsive loading/stress.

Optimize load matching

Motors are most efficient when they operate slightly below their rated capacity. Operating a motor significantly underloaded can over-consume energy in copper and iron losses in the motor. Overloading a motor tends to cause it to overheat, reducing efficiency.

Ensuring that motors are appropriate power (right sized) for their load is key. Oversized motors waste energy, while undersized motors can be both inefficient and prone to stress/thermal failure.

Improve power quality

Poor power quality, including voltage imbalances, harmonics and current/voltage phase shifts will influence the power efficiency of industrial drive systems, pushing up energy consumption and increasing device stress/wear/overheating. Power quality issues often result in wasted energy in multiple systems, but they can disproportionately affect induction type motors

Harmonics are cyclic distortions in the Sine wave of the electrical supply that tend to reduce motor efficiency and increase overheating and vibration. Large inductive loads that are hard-switched are commonly the cause of these issues. Installing harmonic filters or using low-harmonic VFDs can moderate these issues.

Voltage swell and sag, particularly when imbalanced between the three phases of the supply, can lead to inefficient motor operation. Voltage regulation and uninterruptible power supplies (UPS) or battery energy storage systems (BESS) can stabilize the power supply, improving motor efficiency.

Regular maintenance

Routine maintenance of motors and drive systems is essential in maintaining optimized system efficiency. Regular inspections, cleaning, and lubrication can reduce the issues that degrade motor performance - increased friction, electrical losses or mechanical wear.

Effectively maintained and appropriate lubrication of motor bearings is one of the simplest maintenance tasks yet it can significantly reduce friction and energy losses. Over time, worn or dry bearings make motors work harder, wasting power and reducing effective output.

Misalignment between motors and driven equipment leads to increased friction and drive stress, reducing system efficiency. Ensuring proper alignment through regular checks or installing tolerant couplings such as dog clutches can help sustain optimal performance.

Regular testing of motor insulation can prevent electrical losses due to breakdowns and internal arcing. Insulation failure can lead to voltage leakage and potential motor damage through erosion and overheating.

Energy monitoring and performance analytics

Energy monitoring systems that log power consumption, power quality, on-time, that feed data analytics can play a crucial role in evaluating, improving and maintaining energy efficiency. By monitoring energy consumption in real time, system operators can identify inefficiencies and areas for improvement.

Carrying out regular energy audits can help identify motors/drives that are consuming the most energy and where improvements can potentially be made. Audits can also reveal inefficiencies caused by load mismatches, maintenance needs, system performance degradation, and power quality issues. Driving deep analysis can result in enhancement/maintenance opportunities becoming evident.

Machine learning combined with these data analytics can enable optimization of motor operation, resulting from holistic analysis of long-cycle energy usage patterns.

Energy-efficient operating practices

Adopting generalized energy-efficient operating practices can also help reduce energy consumption in industrial drive systems and raise operator awareness of the efficiency opportunities that present. This can include scheduling non-essential processes during off-peak hours, minimizing idle time, and powering-down equipment in slack periods.

In too many industrial processes, motors run at capacity irrespective of process needs. Optimizing operations by matching motor output to actual demand can reduce energy wastage. Implementing automated systems to turn off or reduce the speed of motors during idle periods can save energy.

Energy-efficient system design

Designing systems with energy efficiency as a central goal can deliver surprising long-term savings. Examples abound in industrial processes. Typical fan efficiencies vary by over 30% for nominally identical equivalent devices. Selecting for long term efficiency over CAPEX savings can pay back handsomely.

In drive systems that require mechanical power transmission and reduction gearing, selecting high-efficiency gearboxes and couplings can greatly reduce energy dissipation.

Integrated drive systems that use smart controls, with localized intelligence for dynamic and fast-optimized direct control can better synchronize multiple components and moderate energy use in connected islands of energy saving throughout an entire production facility.

Emerging technologies for energy efficiency in industrial drives

Increasingly, industrial operations must focus on energy efficiency and recognize/implement novel technologies and approaches as they emerge to continuously improve the performance of industrial drive systems:

Permanent magnet motors use high field strength permanent magnets to produce torque rather than energized coins. This reduces energy losses compared to induction motors, delivering higher efficiency, especially at low speeds. These are increasingly being used in applications where energy savings compensate for higher CAPEX.

Advanced VFDs with localized capacity for intelligent and responsive parameter adjustment can self-monitor motor performance in real-time and adjust for efficiency. These smart drives can also provide ML based condition-monitoring and AI based predictive maintenance insights.

Wireless IoT (internet of things) sensors and control systems enable more flexible monitoring of energy consumption in drives. This approach can provide real-time data and analytics, enabling more precise control and optimization of motor performance.

Conclusion

Improving energy efficiency across industrial drive systems is an essential tool in moderating operating costs, environmental impact, and system performance deficits/deterioration. By integrating high-efficiency motors, implementing VFDs, optimizing load matching, and ideal power quality, plant operators can achieve significant energy savings.

Additionally, incorporating regular improved and even predictive maintenance programs, operational monitoring, IoT integration and deep analytics can further enhance efficiency and drive long-term sustainability.

With the right strategies and technologies implemented and optimized, system operators can reap extensive and long-term benefits.