Economic Advantages: How Drives and Servos Deliver Savings

Jakarta, INTI - For decades, manufacturers and their equipment suppliers have relied on tried-and-true hydraulic and pneumatic actuators in their automated equipment. However, due to fluid leaks, inaccuracies, and related inefficiencies, many machine builders and manufacturers are replacing fluid power systems with electric drives in practical applications.

For example, all-electric injection molding machines (IMMs) consume less energy than hydraulically operated molding machines. In such machines, electric cables, motors, and drives replace hydraulic components like fittings, lines, and oil coolers. The design is cleaner and more environmentally friendly. However, there's more to this story than just energy efficiency.

In addition to improved energy efficiency, the increased speed, accuracy, and repeatability of electric drives can result in faster changeovers, higher quality manufactured parts, and higher output volumes. This enhanced production efficiency is achieved through reduced scrap rates, with less material wasted, rework time, and waste.

Improving Energy Efficiency

Replacing fluid power systems is just one approach to reducing global energy consumption with electric drive technology. The push for efficiency has spurred the development of new clean electric drive technologies. The use of these technologies continues to increase as advancements in permanent magnet motors and silicon carbide (SiC) semiconductors improve the performance of insulated gate bipolar transistors (IGBTs) and make drive technology more efficient.

Next-generation IGBTs make modern inverters, where all the fast switching occurs, more energy-efficient. Drives also enable the digital transformation of machines and equipment, leading to advancements in simulation and data analysis, resulting in increased efficiency, according to Craig Nelson, senior product manager at Siemens Industry, Inc.

Other improvements, such as battery-less encoder technology, reduce the number of components while enhancing axis performance, according to Ben Strong, servo product marketing manager at Mitsubishi Electric Automation. Strong explains, "Enhanced simulation techniques allow us to increase motor torque density, reducing motor size on our new MR-J5 series servo drives and motors by 10–20% compared to previous servo drive and motor series."

Digital Transformation in Industrial Equipment

Xudong Tao, deputy director of the R&D center at VEICHI Electric Co., Ltd., agrees that vector frequency converters and servo drives will be key components of the digital transformation of industrial equipment. He notes that digital transformation will significantly impact the industrial economy by integrating data, improving production efficiency, and optimizing operations.

"Most manufacturers are just beginning to understand where they are using energy," Nelson explains. "The latest drive technology can help them better understand where and when they are using most of their energy by collecting all the information from running all their machines. They can then use simulation and data analytics to model various energy-saving scenarios."

Choosing the Right Motor

Selecting the right motor depends on factors such as application load and inertia, as well as dynamic positioning and motor inductance requirements. High inductance windings can kill performance when trying to ramp up from 0 to 1,000 rpm in 25 ms, for example. Servo motors and drives are generally used in low-inertia, high-dynamic applications. Other factors need to be considered on a case-by-case basis.

Most motor selections for specific applications come down to power and speed requirements, according to Nelson. He says, "Stepper motors are economical but typically used in applications under 1,000 rpm and below 1 kW. Permanent magnet servo motors are more expensive but highly dynamic and typically applied up to 6,000 rpm and 25 kW." For less dynamic, high-power needs, induction motors with encoders are an economical alternative.

Vector Drives vs. Servo Drives

Once the motor is chosen, the next step in designing an electrically driven system is selecting a vector or servo drive. In industrial settings, vector drives and servos are used in different applications with varying requirements for accuracy, dynamic performance, and load variation.

Chloe Wei, an overseas technical support engineer at VEICHI, says that vector drives are better suited for speed control applications, while servo drives are better suited for positioning applications, such as in CNC machines, printers, and robotics.

Vector drives are used to control the speed of AC motors to enhance system efficiency, reduce energy consumption, and achieve accurate motor control on equipment. In manufacturing and industrial facilities, vector drives are typically used to power fans, pumps, compressors, rollers, and other equipment requiring speed control. The output frequency and voltage to the motor can be adjusted using internal components like rectifiers, filters, inverters, and control circuits.

Achieving Peak Performance

Voltage and current measurements (sensorless vector control) or encoder feedback (vector control) can be used to determine rotor position. These values are used to calculate optimal output for peak motor performance. Vector drives control the position, speed, or torque output of the motor. Variable frequency drives (VFDs) with vector control functionality are used to operate induction motors and permanent magnet motors (PMMs). Vector drives offer better speed and torque control, especially at lower speeds.

In pump control systems, common in industrial production, vector drives use PID algorithms to adjust the running speed of the pump according to demand. VEICHI overseas technical support engineer Liam Wang says, "Vector control can achieve pump sleep and external wake-up functions to avoid excessive operation."

Similarly, HVAC fan control systems use vector drives to adjust fan speed according to demand and ensure the system operates at optimal working conditions to avoid excessive airflow and energy waste. Vector drives are also commonly used in compressor control systems. Vector drives can help accurate compressor control, adjusting compressor speed based on air demand and preventing unnecessary energy consumption, especially during light loads.

Energy-Efficient Technology

The new generation of electronics and heat dissipation technology allows modern vector drives to deliver higher power density in smaller physical packages, suitable for applications in confined spaces. Some vector drives now feature energy feedback technology, feeding energy generated during braking back into the grid, thus reducing energy waste and improving system energy efficiency.

New high-efficiency motors, such as synchronous reluctance motors and additional magnet motors, require better drive algorithms to support higher efficiency.

By controlling current and speed, vector drives can help prevent unnecessary energy consumption on AC motors while maintaining their optimal working conditions. For example, if the load is lighter, the vector drive will detect the change and adjust the output current for less electricity consumption by the motor.

Soft Starters

Soft starters are mainly used to start motors smoothly and to reduce current and mechanical shock. Compared to vector and servo drives, the most significant difference is that soft starters rarely provide a dynamic reaction to changes in the operating motor.

"Soft starters offer only a fraction of what vector drives can achieve," Wang explains. "They are simple devices primarily used to minimize mechanical shock during the start and stop processes for some high-power motors. Conversely, vector and servo drives typically have high dynamic responsiveness and can quickly adapt to load changes for more flexible system responses."

While the initial cost of soft starters is usually lower, during the operation phase, soft starters may not be as energy-efficient as vector inverters and servo drives in many applications. Vector inverters and servo drives reduce operational costs more by enhancing energy efficiency during operation, yielding better cost-effectiveness in the long run, according to Wang.

If the application requires precise control, high performance, and flexibility, and users can afford the high initial investment cost, vector inverters and servos may be a better choice. If the primary concern is reducing mechanical impact during start-up and the initial investment cost, and the need for dynamic control is not high, soft starters may be an economical and practical choice.

Energy Feedback

Vector and servo drives can capture and reuse regenerative energy caused by deceleration or external torque acting on the motor. This can be achieved using a common DC bus solution, active front-end technology, or a combination of both. The energy generated by the motor can be utilized by other axes in a common DC bus setup or returned to the AC power line for use by other AC loads.

"When regenerating energy from the motor, it's cheaper to share it across the DC bus than to design a system that brings motor energy back to the incoming power supply," Nelson explains. "We do both all the time, but the upfront cost for regenerating energy back to the line is much higher."

Investing in Efficiency

Vector inverters and servo drives will be increasingly adopted as core components of automation systems. As the demand for energy efficiency, environmental protection, and sustainability grows, the high-performance characteristics of vector inverters and servo drives will become more important. The global carbon footprint can be significantly reduced by greater adoption of technology designed to exceed recent energy regulations and standards.

As automation levels in factories and production lines increase, the demand for servo drives will also rise. Vector and servo drive technology is essential for realizing Industry 4.0 and smart manufacturing. By marrying the Internet of Things (IoT) and cloud computing technology, vector and servo drives can help manufacturers achieve remote monitoring, diagnostics, and optimization, providing greater intelligence and flexibility for industrial production.

When determining the economic benefits of using vector and servo drives, it's important to think long-term. Although the initial investment may be higher, there are significant energy savings over the operational lifetime of these systems, especially in systems requiring high precision or frequent load changes. By adjusting output frequency and voltage in real-time based on demand changes, motors and other system components also tend to last longer.

Other benefits from greater efficiency and improved performance include reduced labor, decreased downtime, faster changeovers, lower material costs, and enhanced product yields. As a result, deploying vector and servo drives in industrial applications can be seen as a strategic investment to ensure profitable and sustainable operations.

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