Improvement of Performance of a Chopper Fed DC Separately Excited Motor Using LC Output Filter

In this paper a frequency domain method has been proposed for the design of LC output filter for a chopper fed dc separately excited motor. The design is based on reducing the dominant harmonic in the armature voltage and armature current of motor, below a specified level, and thereby controlling the ripples in armature voltage and current. The performance of motor with LC output filter is compared with that of without filter during steady and transient states. The effect of commutation time of chopper on the performance of the motor has been included. The concept of binary variables is used for simulating the switching devices for automatic formulation of network equations at mode change over points. It is found that the LC output filter improves the performance by eliminating the discontinuous current zone. The settling time of the transient response of the motor with filter is slightly larger than that of without filter in continuous current region. The computed results are compared with those obtained experimentally and found in close agreement. The efficiency of motor with and without filter has also been compared.