Document Type : Original Research Paper

Authors

• Bahram Rashidi
• Leila Golpaiegany

Department of Electrical Engineering, Faculty of Engineering, Ayatollah Boroujerdi University, Boroujerd, 69199-69411, Iran.

Abstract

Background and Objectives: This research presents a circuit design for controlling the speed and direction of high-current Direct Current (DC) motors. The circuit can control DC motors with voltages ranging from 12V to 48V and currents up to 60A. Given that the switching MOSFETs in 48V motors operate at high voltages, the circuit must be capable of handling these conditions. Various techniques are employed in the design of the proposed circuit to control these high-voltage motors effectively.
Methods: The proposed hardware implementation incorporates several well-established techniques in power electronics to enhance reliability, switching performance, and protection under high-current operating conditions. These include: (1) ultra-fast parallel diodes for motor freewheeling current paths, (2) RC snubber networks across each MOSFET to suppress voltage overshoot and oscillations during switching, (3) a series gate resistor combined with a reverse diode to ensure controlled gate charging and provide a fast discharge path, (4) Schottky diodes connected across the MOSFET terminals to improve switching behavior and reduce stress, (5) an opto-isolator to provide electrical isolation between the control and power stages, and (6) the use of four parallel MOSFETs in the switching stage to improve current handling capability and reduce conduction losses. To accommodate different motor characteristics, the output pulse frequency can be adjusted using a variable capacitor. In addition, smooth startup operation is achieved by initially setting the PWM duty cycle to a low value and gradually increasing it, thereby preventing abrupt motor acceleration and reducing mechanical shock during startup.
Results: The pulse width modulation (PWM) pulse frequency generated by the pulse generator is 6.356 kHz, with a duty cycle that can be adjusted from 3% to 99%. Additionally, we have implemented a variable-frequency mode, enhancing the circuit's ability to control a range of motors.
Conclusion: Based on the tests conducted, the proposed circuit can effectively control the speed and direction of high-current DC motors without issues. Considering the components used, the circuit is capable of supplying the necessary power to drive DC motors operating at 12-48 V and currents up to 60 A.

Keywords

• Speed Control
• Opto-isolator
• High-current DC Motors
• Hardware Implementation Snubber Circuit

Main Subjects

• Electronic Circuits

Open Access

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Publisher

Shahid Rajaee Teacher Training University