From Motor to System Trimming Motor Controls for Energy Efficiency

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Motors consume a lot of energy worldwide. Efficient control is therefore crucial. The article highlights motor design, frequency converters and solutions for motor control applications.

Motors have become an integral part of our everyday lives and can be found in household appliances such as washing machines, dryers, dishwashers and garden pumps. They are also indispensable in the automotive sector: modern cars contain between 40 and 100 motors, depending on the model and equipment variant. In industrial applications, motors are particularly needed in robotics and factory automation.

Key Trends in Motor Efficiency

Energy-efficient motors:One of the most important trends in motor efficiency is the transition from conventional motors, such as AC induction motors, to more efficient types such as brushless DC motors (BLDC), permanent magnet synchronous motors (PMSM) and permanent magnet motors with an internal magnet (IPM). These motors offer higher efficiency and improved performance. In addition, advances in materials, such as the use of amorphous metals and rare earth magnets, have further improved motor efficiency.

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Engine Design And Materials

In the field of engine technology, advances in materials and design have significantly improved the efficiency and performance of engines over the last century. Only by analyzing the components and their further developments is it possible to understand how the increases in efficiency were achieved.

A motor consists of end caps, a rotor, bearings and a stator with windings. Over the years, the materials used in these components have evolved. For example, the transition from aluminum to copper in the rotor and stator windings has improved conductivity and efficiency. In addition, advances in manufacturing tolerances have led to less noise and even greater efficiency.

A notable trend in motor technology is the use of amorphous materials in rotors and stators. Traditionally, silicon steels were used, but these had high eddy current and hysteresis losses. These are now being replaced by amorphous materials such as metallic glasses, which have lower losses and therefore higher efficiency. There have also been significant improvements in the field of permanent magnet motors. Stronger magnets, e.g. made of rare earth metals such as neodymium, iron and boron, offer higher torque and efficiency. However, for reasons of sustainability, alternatives such as magnets based on aluminum, nickel, chromium and ferrite are being researched. They exhibit good properties over a wide temperature range and in strong magnetic fields.

The transition from plain bearings to ball bearings has significantly reduced friction and improved tolerances, thereby increasing the efficiency of motors. Over the last century, motors have become considerably smaller with the same power output. For example, a modern 5 hp three-phase induction motor with a squirrel cage rotor is considerably smaller and weighs only around 20 percent of what a motor with the same rated output weighed in 1910. This reduction in size is due to lighter and more efficient materials as well as more advanced thermal and electrical insulation. Lighter motors are particularly beneficial for automotive applications, where lower weight leads to greater efficiency and the ability to integrate motors into more compact spaces. The impact of these advances is profound, leading to more efficient motor systems.

Continuous improvements in motor materials and designs have led to significant advances in efficiency and performance. From the use of amorphous materials and stronger magnets to the advancement of bearings and miniaturization of motors, these innovations are driving the future of motor technology. As we continue to explore new materials and designs, the potential for even greater efficiency and performance in motor systems remains promising.

Use of Frequency Inverters (VFD)

Variable frequency drives (VFDs) are increasingly being used for motor speed control and greater efficiency. VFDs adapt the speed of the motor to the load requirements and thus reduce energy consumption. The transition from insulated gate bipolar transistors (IGBTs) to silicon carbide/SiC technology in VFDs has also contributed to higher efficiency and faster switching times.

VFDs have revolutionized engine control by enabling precise control of engine speed and torque. They optimize motor performance and significantly improve system efficiency. A VFD adjusts the frequency and voltage supplied to the motor so that it can operate at maximum efficiency for a given load. Conventional motor systems (e.g. pump motors) often operate at full load, with the flow rate controlled by throttle valves, resulting in significant energy losses. In contrast, VFDs eliminate the need for throttling by matching the motor speed to the required flow rate, reducing energy consumption and increasing the overall efficiency of the system. Studies have shown that switching to a VFD can more than double the efficiency of a motor system from around 31 to 72 percent.

Solutions And Hardware Support

Microchip provides components for motor control applications. These include microcontrollers, gate drivers, power electronics and sensors. Hardware support and algorithms for motor control are also offered. Microchip's hardware accelerates the development of motor control systems and optimizes performance and efficiency. For VFD, the company offers AC/DC converters and inverters with high-efficiency SiC MOSFETs and advanced gate drivers for precise switching. The inverters, which are controlled by the dsPIC digital signal controller (DSC), convert DC to AC at variable frequency for efficient motor operation. Integrated sensors provide real-time feedback on current, voltage and temperature, increasing system reliability. Microchip also offers evaluation and development boards, reference designs, software libraries and development tools to support development work and incorporate complex motor control algorithms.

Advanced Control Algorithms

Algorithms are fundamental to the optimization of motor control systems. Conventional methods, such as V/f control for AC induction motors, are inexpensive and straightforward, but do not offer the highest efficiency. More advanced algorithms, such as six-stage commutation for BLDC and PMSM motors, offer better torque control and can be sensor-based or sensorless. The most efficient algorithm is field-oriented control (FOC), which offers high efficiency, low noise and excellent torque and speed performance. FOC can be implemented with or without sensors, depending on the motor type and application requirements. Microchip's motor control solutions incorporate advanced algorithms such as FOC, maximum torque per ampere (MTPA) and field weakening to maximize efficiency and performance. These algorithms are supported by tools such as the MPLAB motorBench Development Suite, which facilitates the implementation and optimization of control algorithms. In addition, Microchip offers machine learning capabilities for predictive maintenance. This ensures optimal motor operation with maximum efficiency and reduces the risk of unexpected failures. The Zero Speed/Maximum Torque (ZS/MT) control algorithm is a new variant of the sensorless FOC algorithm. It enables sensorless control techniques in high torque or low speed applications. ZS/MT eliminates the need for Hall effect sensors by using a reliable Initial Position Detection (IPD) method based on High Frequency Injection (HFI) to determine the exact rotor position at zero and low speeds.

Integration With IoT And AI/ML

IoT and AI technologies have revolutionized engine control. Sensors play a crucial role in this. They are essential for recording current, torque and rotor position. These sensors supply data to microcontrollers that process this information. By integrating machine learning algorithms, these systems can perform predictive maintenance by analyzing sensor data to predict potential motor failures or maintenance needs. This capability is particularly beneficial in industrial environments where unexpected motor failures can lead to significant downtime and financial loss. Predictive maintenance ensures that motors operate at maximum efficiency and performance, reducing the likelihood of unexpected failures.

Predictive maintenance uses sensors and machine learning algorithms to monitor the condition of the motor and detect potential problems before they lead to failure. By continuously analyzing parameters such as current, torque and vibration, it ensures efficient motor operation and minimizes downtime. This approach is particularly beneficial in industrial environments where unexpected motor failures can lead to significant production downtime. Microchip's demo application illustrates predictive maintenance for motors using the MPLAB Machine Learning Development Suite in conjunction with the dsPIC LVMC Motor Control Board. The system uses a classification model to determine the operating condition of a motor and, by monitoring the I_q current, determine whether the motor is operating normally or has anomalies such as an unbalanced load or a faulty bearing.

Conclusion

Optimized motor control in terms of energy efficiency is crucial to reduce global energy consumption and improve the performance of various applications. Efficient motors, frequency converters, advanced control algorithms as well as IoT and AI technologies provide significant energy savings. Development kits offer a range of solutions to support these efforts. Hardware, software and know-how are available to ensure the development of efficient motor controls. As the demand for energy-efficient solutions continues to grow, advances in motor control will play a crucial role. (mr)

Pramit Nandy is Product Marketing Manager at Microchip Technology.

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