What to Expect in Solid-State Industrial Drive Systems

Solid-state control has rapidly replaced conventional electromechanical devices and vacuum tube electronics in its first decade of industrial usage. The growth of solid-state applications has been evolutionary and based on a practical approach to utilizing the optimum available solution, both economically and technologically, to achieve improved control system reliability and performance. The application of solid-state electronic devices is discussed from the input of the operator's commands through a typical industrial control system to the power conversion equipment that supplies the drive motor. Frequency of failures in solid-state devices is so low that maintenance men do not retain familiarity with circuits and device theory. This has necessitated the need for low-level maintainability through the use of functional plug-in printed circuit cards, full-time instrumentation, light-emitting diode logic status indicators, and system engineered diagnostic test circuits built into the system. The future looks promising for further technological developments in solid-state devices. A continued growth in solid-state industrial drive systems is assured with expected trends toward further development of adjustable frequency power conversion systems, and hybrid logic/control systems.