How electronic controls boost electric motor performance, efficiency and capabilities
Explore the evolution of industrial electric motors with electronic controllers. Learn improved effectiveness and capabilities in a wide range of applications across industries.
If you have ever been on a guided tour of an Amazon warehouse, you will find yourself inside an operations area of typically around 800,000 square feet – a space equivalent to more than 10 football pitches – distributed over four floors.
And this giant space is dedicated mostly to one activity: moving goods around. Sometimes with conveyors, other times with floor robots that look like animated paving slabs, and occasionally with robot arms for pick and place activities.
All these modes of movement share a common requirement for electric motors: from powerful types for the conveyors, to compact, high-precision products in the robot arms.
While the need for industrial motors is particularly obvious in warehouses like this, they are equally ubiquitous across all types of industrial manufacturing and production sites. A single factory can have hundreds of motors, and an IEA report from 2022 found that 70 percent of industrial power consumed is tied to electric motor and systems use . This means that any improvements in efficiency and reliability can have a significant positive impact on operational expenses and the environment.
When electric motors first appeared in factories during the 19th century, energy efficiency wasn’t a concern, as interest focused more on their ability to replace manual labour and steam engines. However, as industries grew more complex, so did the demand for more efficient and specialised electric motors. Companies that specialised in electric motor manufacturing adapted various motor technologies, such as synchronous and asynchronous motors, to better suit the needs of specific industries .
World War 2 military contracts and the post-war economic boom provided the necessary capital for research and development, resulting in marked improvements in electric motors efficiency. In the years that followed, the focus on energy conservation and sustainability brought further attention to the efficiency of electric motors. Electric motors with reduced heat loss, lower energy consumption, and greater torque became available.
Innovation and development have continued to the present day, and no doubt into the future, to keep pace with the rapidly-evolving demands of multiple and diverse industrial environments. Motors have become highly efficient and specialised machines that are integral to modern industries around the world.
These highly advanced capabilities are based on two key factors – the electrical and mechanical properties of the motors themselves, and the capabilities of the electronics and software used to drive them.
The article below explores the latest state of the art for industrial electric motors by firstly considering the generic capabilities of modern electric drives, and then seeing how these are being applied to the different types of motor technology currently available. We show various manufacturers’ solutions, with product examples, for each of these motor types.
AMD’s Motor Control eBook describes how an electric drive is a collection of systems put together for motion control. These edge devices are made up of the power source, power converter, motor, mechanical load, and controller. Modern electric drives also use industrial Ethernet to exchange command and status data with system-level controllers, like PLCs and motion controllers that govern the system the electric drive is connected to.
They have fieldbus connectivity (the ability to connect multiple machines), positioning control, speed control, torque control, and power staging (modulating the power supply to minimize stress on the motor). In 2010, integrated safety mechanisms were added. This led to the introduction of the IEC 61508 functional safety in manufacturing specification, and the ISO 13849 machine safety standard. Around 2016, the industry introduced cloud connectivity and time-sensitive networking (TSN), and since then, the complexity of electric drives has continued to grow.
Along with the evolution of the drive, there have been constant changes to software and systems over the past few decades. Prior to the 1990s, most applications were programmed in Assembly or C language. By the middle of the decade, C++ had become well-established, Python was gaining in popularity, and Simulink from MATLAB was starting to take hold. Additionally, the Linux operating system had become mainstream for managing drive systems. Since then, these platforms and tools have continued to expand, with Simulink 6 in 2004, for example, and Python 3 in 2008.
In addition to the evolution of software, silicon carbide (SiC) and gallium nitride (GaN) technologies have appeared in the market. Among their advantages, SiC and GaN can sustain higher voltage than silicon alone. They can provide very fast switching mechanisms and operate at very high temperatures and frequencies, making them ideal for use in high-voltage motors for high-power and performance applications.
Motor control is the process of continuously regulating the magnetic fields by measuring current, rotor position, and deviation from the desired setpoint. It determines speed, torque, and position, and protects the motor by keeping all parameters within the motor's operational range. This dynamic process continuously measures currents and the rotor position. When a motor runs slower, the voltage created through motor control will drive the rotor to follow that pace and not run ahead of it. Motor control reads data from the motor and when the rotor is behind or ahead of its expected position, it reacts quickly to synchronise.
Motor control creates accurate input/output parameters, repeatedly—the faster, the better. The more calculations you can assign exclusively to the motor, the more precise your results will be. If you can accurately calculate what the next voltage will be, you’ll have a better chance at precisely controlling the motor’s angle of force. A motor should always build a magnetic field that is in the best alignment to move the rotor. The moving field should always be precisely angled and optimised to match the torque or speed you want to create. This can help to ensure that the energy is transformed into torque to the rotor and not wasted. When you can very precisely manage a motor with a controller, you can reduce acoustic noise and vibration and minimise electromagnetic emissions.
As mentioned earlier, the operation of an electric motor relies on producing and controlling magnetic fields. This means that an imperfect magnet may require adjustments through motor control at every rotor revolution. Every magnet has its own special pattern of behaviour, so the better you can measure magnetic force, the better performance you will be able to achieve out of your motor. Correcting inconsistencies in every rotor revolution can give you better efficiency, and have a direct impact on the motor’s service life.
Electromagnetic interference (EMI): Motors can use intelligent pulse width modulation to avoid peaks and improve noise distribution.
Torque: Motor control can adjust power or force, or influence efficiency by adjusting the rotor angle.
Synchronisation of motors: You can distribute the load across multiple motors when you can control them with the same chip. All motors can run at the same speed and at the same rotor angles. In many cases, four smaller, synchronised motors can provide a more durable and reliable solution than one larger motor.
Safety: Safe drive is normally a motor control unit with an extra area that monitors if the motor is running within an expected range. There is a safety-limited position or speed with extra circuitry or area on the chip that monitors whether the motor is running at the speed you are expecting. When a motor runs too slow, you can switch it off as a safety feature.
Predictive maintenance and extension of service life: You can extend motor service life with predictive maintenance driven by motor control. You can view feedback from the motor and monitor it for changes. The currents you supply to the motor may not be the same on all connecting wires. You can be notified when a loose or broken cable changes a feedback signal interval - and with predictive maintenance, you can take action to fix it before it results in a failure.
Intelligent motor control systems can monitor motor performance and collect real-time data, enabling predictive maintenance practices. By analysing motor behaviour and detecting early signs of malfunction or wear, maintenance activities can be scheduled proactively. This prevents unexpected downtime, extends motor life, and reduces repair costs.
Energy efficiency: One of the most-promising uses cases for industrial motor control is driving energy efficiency. Intelligent motor control systems often incorporate advanced algorithms and technologies to optimise energy consumption. By reducing power wastage and improving motor efficiency, these features can lead to substantial energy savings, resulting in lower utility bills and reduced operating cost.
Our article: “Multiple ways to improve manufacturing energy efficiency” discusses how energy-efficient motors and drives can contribute towards overall industrial manufacturing power efficiency.
Acoustic noise control: Torque ripple, magnetic interference, and vibration are often the cause of acoustic noise in motors. Motor control techniques can be used to mitigate both noise and vibration in various applications where this is an issue.
Many intelligent motor controls enable continuous monitoring of motor conditions, including temperature, vibration, and load fluctuations. By detecting anomalies or abnormal patterns, these systems can alert operators to potential issues before they escalate. This allows for timely corrective actions, minimising the risk of motor failures, and avoiding costly production interruptions.
Advanced motor control systems employ diagnostic algorithms to analyse motor performance data. They can identify specific faults or deviations from optimal operating conditions, pinpointing the root causes of motor problems. This facilitates faster troubleshooting and reduces the time and resources required for fault diagnosis, leading to cost savings.
Intelligent motor control features often offer enhanced precision and accuracy in motor control, allowing for better speed and torque regulation. This can result in improved process control, higher product quality, and reduced scrap rates. By minimising variations and errors, these features can enhance overall operational efficiency and reduce costs associated with rework or rejected products.
Many intelligent motor control systems can be accessed and controlled remotely through network connectivity. This enables real-time monitoring and adjustments without requiring physical presence, saving time and travel expenses. Additionally, remote access facilitates centralised control and coordination of multiple motors across different locations, optimising resource allocation and minimising operational costs.
Intelligent motor control systems are often designed to integrate seamlessly with other automation systems and industrial protocols. This compatibility enables streamlined communication and coordination among various components, such as programmable logic controllers (PLCs) or supervisory control and data acquisition (SCADA) systems. This integration reduces implementation costs and promotes interoperability in industrial environments.
Many intelligent motor control solutions offer scalability, allowing for the expansion or modification of motor control systems to meet evolving needs. This flexibility reduces the cost of system upgrades or replacements in the future, ensuring long-term cost-effectiveness and adaptability to changing operational requirements.
The different types of AC and DC motors, and their variants, add up to a large number. Fig. 1 simplifies the issue by showing a hierarchy with a reduced number of variants. The variants shown have been included because they are well covered by electronic controller solutions from various semiconductor manufacturers. However, many more variants and sub-variants exist.
Figure 1: Simplified electric motor hierarchy
3AC motors are powered by either single-phase or three-phase alternating current. The stator winding generates a rotating magnetic field (RMF) when an AC current is passed through it. The rotor, which has its own electric field, follows the RMF and starts rotation.
3AC synchronous motors have a speed that changes only if the supply current frequency varies; it remains constant for varying loads. Such motors are used for constant speed and precision control applications.
3Permanent magnet synchronous motors (PMSMs) are variants in which the rotor windings are replaced by a permanent magnet. PMSMs, known for their high reliability and efficiency, low noise, and dynamic performance, are used in a variety of applications, including industrial machinery and robotics. Their permanent magnet rotor also means that they deliver higher torque from a smaller frame.
3The stator windings need sinusoidal waveforms for good performance, which require sophisticated control algorithms. Accordingly, Microchip offers solutions based on their higher-performance controllers such as the dsPIC33 Digital Signal Controllers (DSCs), 32-bit PIC32MK or Arm® Cortex-M® based SAM microcontrollers (MCUs) .
3The dsPIC33 family of DSCs offers Digital Signal Processing (DSP) performance and advanced motor control peripherals to generate the waveforms for advanced PMSM control algorithms like Field-Oriented Control (FOC), flux weakening, sensorless control and stall detection. The 32-bit PIC32MK and SAM MCUs feature high-performance peripherals tailored for high-speed, closed-loop motor control.
3Microchip offers a comprehensive ecosystem to help you develop advanced PMSM control solutions like sensorless Field-Oriented Control (FOC). Their solutions also support Surface Mounted Permanent Magnet Synchronous Motors (SPMSMs) and Interior Permanent Magnet Synchronous Motors (IPMSMs).
Figure 2: Microchip PMSM motor control solutions
The induction motor’s most important advantage is its simple construction, relatively low capital and maintenance costs, and robust, mechanically strong and environmentally resilient construction. It has a high starting torque, good speed regulation, and reasonable overload capacity. It is highly efficient, with full load efficiency ranging from 85 to 97 percent .
Asynchronous induction motors are widely used in many industries and applications; probably the most popular AC motor used in industry today . Variants include squirrel cage motors, wound rotor motors, and single-phase industrial motors.
Onsemi’s FNA22512A intelligent power module integrates drive, protection, and control functions, and supports a wide range of control algorithms. It improves inductor motor performance by providing a highly efficient inverter output stage with optimised gate drive for its built-in IGBTs, and multiple on-module protection features such as under-voltage lockouts, overcurrent protection, thermal shutdown and fault reporting. These help to minimise EMI and losses, and improve the motor’s overall efficiency.
Figure 3: Onsemi FNA22512A intelligent power supply module
A DC motor uses direct current (DC) to produce mechanical force. The most common types rely on magnetic forces produced by currents in the coils. Nearly all DC motor types have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current in part of the motor.
DC motors were the first form of motors widely used, as they could be powered from existing direct-current lighting power distribution systems. A DC motor's speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings.
Larger DC motors are currently used in propulsion of electric vehicles, elevators, and hoists, and in drives for steel rolling mills. The advent of power electronics has made replacement of DC motors with AC motors possible in many applications.
The brushed DC electric motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary magnets (permanent or electromagnets), and rotating electromagnets.
Advantages of a brushed DC motor include low initial cost, high reliability, and simple control of motor speed. They are ideal for harsh operating environments, and offer a high ratio of torque to inertia. Disadvantages are high maintenance and low life-span for high intensity uses. Maintenance involves regularly replacing the carbon brushes and springs which carry the electric current, as well as cleaning or replacing the commutator. These components are necessary for transferring electrical power from outside the motor to the spinning wire windings of the rotor within .
Brushed DC motors are commonly used in industrial and automotive applications such as robots, valves and healthcare equipment. When only one direction of rotation is required, a single switch topology with PWM modulation can be used to vary the voltage applied to the motor, and thus to control its speed. When positioning is required or when both directions of rotation are needed, a full H-bridge with PWM control is used.
STMicroelectronics’ lineup of STSPIN motor drivers embeds all the functions needed to drive motors efficiently and with the highest accuracy, and include an advanced motion profile generator to relieve the host microcontroller, while ensuring robustness and reliability thanks to a comprehensive set of protection and diagnostic features.
The STSPIN motor drivers for brushed DC motors integrate a dual current control core and a dual full-bridge power stage to drive two brushed DC motors.
Available in a large selection of space-saving, thermally-enhanced packages, STSPIN brushed DC motor driver ICs provide a ready-to-use, optimised solution for motor and motion control systems in a wide range of voltage and current ratings .
Figure 4: STMicroelectronics STSPIN250 motor driver/controller, DC brush
Brushless DC motors operate on the same principle of magnetic attraction and repulsion as brush motors, but they are constructed somewhat differently. Instead of a mechanical commutator and brushes, the magnetic field of the stator is rotated by using electronic commutation. This requires the use of active control electronics.
Compared to brushed motors, brushless types have longer lifetimes with no brushes to wear, high speed and acceleration, high efficiency, and low electrical noise. Their acoustic noise and torque ripple is somewhat better for trapezoidal waveforms, and considerably better for sinusoidal waveforms.
Since brushless motors require more sophisticated electronics, the overall cost of a brushless drive is higher than that of a brush motor. This is changing as brushless motors become more popular, especially in high volume applications like automotive motors. Also, the cost of electronics such as microcontrollers continues to decline, making brushless motors more attractive .
The AMD Kria™ K24 SOM offers whole application acceleration at the edge and is optimised for power-efficient motor control, including brushless DC (BLDC) types. It is highly adaptable from both a hardware and software standpoint and enables future proofing against evolving standards, algorithms, and sensor requirements. The K24 SOM is connector compatible with the K26 SOM, which makes migration easier and allows customers to tune for the right power, cost, and performance without modifying their PCB.
Based on the AMD Zynq™ UltraScale+™ MPSoC architecture, the K24 SOM offers lower latency and is highly deterministic. With 132 I/Os available to users, it can connect up to three medium sized BLDC motors with encoders and provides TSN-enabled networking through 4x 1G Ethernet (2x PS GEM, 2x PL GEM). The resulting platform is highly scalable with many possible end applications and is expandable for evolving system requirements. It also offers enhanced security features through the Zynq UltraScale+ MPSoC’s hardware root of trust and a discrete TPM 2.0 device .
Figure 5: AMD Kria K24 SOM data sheet
A servomotor (or servo motor or simply servo) is a rotary or linear actuator that allows for precise control of angular or linear position, velocity, and acceleration in a mechanical system. It constitutes part of a servomechanism, and consists of a suitable motor coupled to a sensor for position feedback. It also requires a relatively sophisticated controller, often a dedicated module designed specifically for use with servomotors .
Servomotors are not a specific class of motor, although the term servomotor is often used to refer to a motor suitable for use in a closed-loop control system. Servomotors are used in applications such as robotics, CNC machinery, and automated manufacturing.
Demand for servomotors has been increasing as industry becomes steadily more automated. They are perfect solutions for automation and robotics through their ability to combine precise motion control with high torque levels.
Using its manufacturing expertise and long experience, Infineon has developed a SiC trench technology that offers higher performance than the IGBT but with comparable robustness, e.g., short-circuit times of 2 µs or even 3 µs. Infineon's CoolSiC™ MOSFETs also address potential problems inherent in SiC devices, such as unwanted capacitive turn-on.
The 1200 V CoolSiC™ MOSFET offers up to 80 percent lower switching losses than the corresponding IGBT alternative, with the additional advantage of the losses being independent of temperature.
As a result, a drive solution using CoolSiC™ MOSFET technology can achieve as much as a 50 percent reduction in losses (assuming similar dv/dt), based on lower recovery, turn-on, turn-off, and on-state losses. The CoolSiC™ MOSFET also has lower conduction losses than an IGBT, especially under light-load conditions.
In addition to the overall higher efficiency and lower losses, the higher switching frequencies enabled by SiC technology directly benefit both external and integrated servo drives in more dynamic control environments. This is possible due to the faster response of the motor current under changing motor load conditions.
Figure 6: Infineon CoolSiC GenVI Trenchstop IGBT, 274W
A stepper motor is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can be commanded to move and hold at one of these steps without any position sensor for feedback (an open-loop controller), as long as the motor is correctly sized to the application in respect to torque and speed.
Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated.
Stepper motor controllers and drives are used primarily in motion control applications in manufacturing and construction environments, among others, and used to control motor speeds, torques, and position. They are used in many applications including machine tools, micro-positioning, and robotics, among many other types of machinery, such as conveyors or OEM equipment.
In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems.
The controller, commonly integrated with the drive circuits, supplies the control signals to the drive. Stepper drives are also known as pulse drives and step amplifiers. Stepper controllers are also known as motor indexers .
Renesas has collaborated with a stepper motor manufacturer to produce a new type of resolver-based stepping motor which they say allows precision motor control even in harsh environments, providing more opportunities for stepper motors. The motors are aimed at applications such as robotics, office and medical equipment, that need compact motors with precision controls, and resistance to environmental influences such as heat, dust and vibration .
Renesas has also developed driver software for controlling the resolver-to-digital converter (RDC) with a 32-bit RX microcontroller. To help application developers, a resolver-based stepping motor control kit has been produced that includes development tools, a 42mm square motor with resolver, and an evaluation board incorporating the RDC.
This technology can be implemented with Renesas RAA3064002GFP and RAA3064003GFP ICs. These are resolver-to-digital converters which are intended for use with single-phase excitation, two-phase output type resolver sensors (angle sensors). The resolver sensor outputs analogue signals (electrical angle information) which are proportional to the angle of the mechanical rotation of the resolver. This IC converts these analogue signals to digital signals .
Figure 7: Renesas evaluation system for stepper motor with resolver
This article has shown that, irrespective of the motor type, electronic solutions are constantly evolving to improve their functionality, efficiency, diagnostics, communications, controllability, security and more. In general, as electronic control solutions become more capable yet smaller, more rugged, and lower cost, they allow new approaches like replacing DC motors with AC types. The Renesas resolver to digital ICs are particularly interesting, as they essentially create a new motor variant.
Yet the electronics manufacturers are not just facilitating motor industry growth by developing ever more powerful chips; most if not all of them also help design engineers by providing comprehensive development kits and evaluation boards, as well as complete lineups of complementary products; these mitigate the risk, cost, delay, and resource load of integrating new solutions and bringing them to market.
Analog devices, Inc. (ADI)’s Trinamic motor and motion control product portfolio is a good example of this. It allows users to transform digital information into precise physical motion, enabling Industry 4.0 performance in applications such as advanced robotics, automation, medical prosthetics, 3D printing, and more. The ADI Trinamic™ portfolio includes motors, encoders, and motor control ICs and modules. These complete, efficient, small footprint solutions can help reduce complexity and time to market for intelligent motion systems while supporting potential space and performance efficiency improvements .
NXP follows this approach too; Their motor control design resources include a brushless DC and permanent magnet synchronous motor control development kit, a model-based design environment for motor control algorithm development, motor control reference designs, motor control development boards, and others .
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