Performance prediction of D.C motor controlled by thyristor chopper

The D.C motor is a widely used device in the field of speed control because it has variable speed and load characteristics. The object of this work is to indicate the main factors governing the operation of the D.C. motor fed from the thyristor chopper. A criterion was adopted in the closed-form solution of the system to determine the factors governing the discontinuous operation of the motor. The duty ratio, the chopping frequency, and the motor speed are the main factors governing the discontinuous operation of the motor system. The discontinuous operation of the motor leads to a speed variation that must be avoided during the motor operation. The analytical results were implemented with MATLAB Simulink results to prove the validity of the analysis. A computer program is developed to calculate the motor performance during a transient as well as steady-state operation. The motor voltage and current waveforms are obtained, for continuous and discontinuous conduction modes. From the Matlab/Simulink results, the condition of unstable operation of the D.C. motor at steady-state has appeared at low duty ratio, low chopping frequency, and light load.