SCR Drives---AC Line Disturbance, Isolation, and Short-Circuit Protection

In just eleven years, 1962-1973, adjustable-speed drives based on the SCR have progressed from zero to perhaps 80 percent of the market. Their real advantages are incontestable, high performance, efficiency, and reliability versus low cost, weight, size, and maintenance. But compatibility of the SCR drives with the ac line has become a live subject, to be covered in three parts in this paper. 1) AC line disturbance discusses the effects of the SCR drives on the ac line. 2) Short-circuit protection describes the adverse effects large power systems can have on SCR drives unless proper precautions are taken. 3) Isolation by means of a transformer is sometimes desirable to minimize these effects.