Abstract
The paper presents a closed loop speed control of a separately excited d.c. motor. The d.c. motor is fed from an a.c. supply through a cascade combination of a diode bridge rectifier and a Single-Ended Primary Inductance Converter (SEPIC). This converter offers both step-up and step-down characteristics of the motor terminal voltage as well as an approximately sinusoidal supply current with an improved power factor. A high performance is achieved with a simple control circuit having only one switch for the converter. A Fuzzy Logic speed controller is used to deal with system nonlinearity and parameters change. A wide range of speed and load control tests showed satisfactory performance of the proposed controller. The system is modelled by using its nonlinear differential equations for different modes of operation. An experimental laboratory model is implemented and the controller is investigated using a digital signal processing board (DSP1102). Experimental results are given to verify the simulation results and demonstrate the effectiveness of the controller. The results confirm the relevance of the proposed configuration as a useful rectifier that achieves d.c. motor speed control with sinusoidal supply current and high power factor.