17 Motor Control: Permanent Magnet Motor Reversing, DC Motor Control from an AC Source using an SCR, Braking in DC Motors, and Brushless DC Motors
Permanent Magnet Motor Reversing
Permanent magnet motors are widely used in various applications due to their efficiency and reliability. Reversing the direction of rotation in these motors is essential for many industrial processes and automation systems.
Techniques for Reversing: Reversing the direction of rotation in a permanent magnet motor can be achieved through several methods, including:
- Changing the polarity of the voltage applied to the motor terminals.
- Reversing the direction of current flow in the motor windings.
- Using electronic motor controllers with built-in reversing capabilities.
Applications: Permanent magnet motor reversing is crucial in applications such as conveyor systems, robotics, and automotive systems where bidirectional motion is required.
DC Motor Control from an AC Source using an SCR:
Direct current (DC) motors are often preferred for their simplicity and controllability. However, in some applications where only an alternating current (AC) power source is available, it becomes necessary to convert AC to DC for motor control.
SCR (Silicon Controlled Rectifier) Control: An SCR-based circuit can be used to convert AC to DC and control the speed of a DC motor. The SCR acts as a rectifier, converting the AC input into a pulsating DC output, which can then be smoothed using capacitors.
Advantages: SCR-based DC motor control offers simplicity, efficiency, and robustness. It provides a cost-effective solution for applications where precise speed control of DC motors is required but only AC power is available.
Braking in DC Motors:
Braking is an essential aspect of motor control, allowing for the rapid deceleration and stopping of rotating machinery. In DC motors, braking techniques vary depending on the application and the desired braking characteristics.
- Dynamic Braking: In dynamic braking, the motor’s kinetic energy is converted into electrical energy by short-circuiting the motor terminals. This energy is dissipated as heat in resistors or returned to the power supply.
- Regenerative Braking: Regenerative braking is employed in some DC motor systems to recover energy during braking. Instead of dissipating the energy as heat, it is fed back into the power supply or stored in a battery for reuse.
- Applications: Braking in DC motors is crucial in applications such as electric vehicles, elevators, cranes, and machine tools where precise control of acceleration and deceleration is required for safety and efficiency.
Brushless DC Motors:
Brushless DC (BLDC) motors offer numerous advantages over traditional brushed DC motors, including higher efficiency, longer lifespan, and reduced maintenance requirements.
Figure 2: Brushless DC Motor ( “Blaupunkt CR-4500 – drive unit – tape Drive Capstan, brushless DC electric motor-9992” by Raimond Spekking is licensed under CC BY-SA 4.0. and “2-coil 10-blade DC brushless motor” by Materialscientist is licensed under CC BY-SA 4.0.)
- Working Principle: BLDC motors operate using electronic commutation rather than mechanical brushes and commutators. They typically employ sensors or sensorless techniques to detect the rotor position and control the switching of the stator windings.
- Applications: BLDC motors are widely used in applications such as electric vehicles, drones, HVAC systems, and industrial automation due to their superior performance, reliability, and controllability.
- Advancements: Recent advancements in BLDC motor technology include the development of high-efficiency motor designs, advanced control algorithms for improved performance, and integration with smart control systems for enhanced functionality.
By understanding and implementing these advanced motor control techniques, engineers can optimize the performance, efficiency, and reliability of electric motor systems in a wide range of applications. Whether it’s reversing the direction of a permanent magnet motor, converting AC to DC for DC motor control, implementing braking mechanisms, or harnessing the benefits of brushless DC motors, these techniques play a crucial role in modern electromechanical systems.
Deepen your understanding: Watch the accompanying lecture video to delve deeper into the concepts covered in the reading.
References:
[1] A. O. Diab and M. A. Helal, “An investigation on the performance of permanent,” Applied Computational Physics, vol. 2446, no. 1, pp. 100004, Oct. 2021. [Online]. Available: https://pubs.aip.org/aip/acp/article/2446/1/100004/2824533/An-investigation-on-the-performance-of-permanent
[2] J. R. Hendershot and T. J. E. Miller, Permanent Magnet Motor Technology: Design and Applications. CRC Press, 2009. [Online]. Available: https://www.amazon.com/Permanent-Magnet-Motor-Technology-Applications/dp/1420064401
[3] M. Alalayah, “An investigation on the performance of permanent,” Applied Computational Physics, vol. 2446, no. 1, pp. 100004, Oct. 2021. [Online]. Available: https://pubs.aip.org/aip/acp/article/2446/1/100004/2824533/An-investigation-on-the-performance-of-permanent
[4] Bodine Electric Company, “PMDC Motor Speed Control,” Bodine Electric Company Blog. [Online]. Available: https://www.bodine-electric.com/blog/pmdc-motor-speed-control/
[5] Arduino Forum, “Regenerative Braking on BLDC Motor,” Arduino Forum. [Online]. Available: https://forum.arduino.cc/t/regenerative-braking-on-bldc-motor/1185023