SPEED AND TORQUE CONTROL OF A DC SHUNT MOTOR Jessica Cabiles-Magsino Elmer R. Magsino Abstract – This paper discusses the speed and torque control of a shunt DC motor through MATLAB Simulink simulations. The DC shunt motor is 120Vdc with rated speed of 1800 revolutions per minute. Blocks pertinent to the control of the DC motor are modeled using basic blocks found in the Simulink library. INTRODUCTION DC motors have been in long use for quite a number of years now. Its application has been widely prevalent in automotives, manufacturing and industrial application, automation, stepper drives etc. Types of motors are classified with respect to the field excitation of the machine. The excitation of the field is dependent upon the connections of the field winding relative to the armature winding. For shunt field DC motor, the field is in parallel to the armature winding. Shunt DC motors find very wide use in constant speed requirements since the drop in the speed from its no-load speed is relatively small. However, it is not recommended for variable-speed application. Speed control techniques for a DC motor are available in two types. The two techniques are: first, the armature control technique and the second one being the field control. For this paper design the armature control is employed. In armature control the field current is maintained as a constant parameter. The speed of the motor is a function of the applied voltage. A reversal in the applied voltage changes the direction of the motor. In reality however, constant voltage – DC supplies are utilized. Thus there is a need for the fixed voltage to be converted to a variable voltage source. Choppers are often employed in such required function. [1] A two-quadrant chopper is utilized in the speed control of the motor. Given the rated speed of the machine, the DC chopper is designed in such a way that the output voltage of the chopper would be sufficient enough to deliver the required speed and torque rating. Mathematical modeling of the DC chopper and the shunt motor are done in Matlab-Simulink© environment. Design of the speed and current controllers will be done using Matlab’s SISO Tool under the Control Toolbox. The expected output performance of the motor speed is taken from the simulation results. SYSTEM MODEL The general system model for the speed and torque control of a DC shunt motor is shown Figure 1. The desired speed of operation is 0 – 100 rpm both in the clockwise and counterclockwise direction. Figure 1 Speed- and Torque-controlled DC Shunt Motor [1] From the system model, there are two loops from which the speed is dependent upon. The inner loop being the current loop, where the armature current, i a , is being fed back to the current controller/compensator. The outer loop is composed of the sampled operating speed, ω m , Current Controller Chopper Circuit Motor Armature c H ω ω sT H + 1 Tacho- generator ω m ω mr i a i a ω s Speed Controller - -