Application Considerations for SCR DC Drives and Associated Power Systems

A rapid growth of silicon controlled rectifier (SCR or Thyristor) dc drive applications has resulted from the many benefits derived by these equipments where adjustable speed of drive is required. These are areas normally served by conventional Ward Leonard M-G sets as well as eddy-current couplings. However, SCR drives are not exact equivalents of M-G sets and special considerations requiring some fundamental knowledge of this conversion technology must be made. This paper presents some of the application considerations regarding successful utilization of SCR drives. The paper will be divided into two parts: The first deals with the static power conversion equipment itself, its characteristics and benefits, as well as its effect on the dc drive motor. The second part deals with the effects of the SCR power conversion equipment on the power distribution system, with suggested approaches to certain problems that may arise, particularly as related to kilovar supply.