Self-Protecting Starters

Self-protecting starters (SPSs) were first introduced to the U.S. in 1987. However, SPSs have been used internationally for several years. Recently, several manufacturers and private labelers have introduced new products worldwide. These starters are expected to be widely used in the U.S. during the next two years. Several features make the SPS preferred over traditional motor controls. A self-protected starter combines contactor, overload, and short-circuit protection in one package. It is sized according to motor load current and horsepower. Generally, a small interchangeable module protects against both thermal and magnetic overload. The self-protected starter can be used in single or multiple installations and satisfy Article 430 of the National Electric Code (NEC) which addresses the safe installation of motors, circuits, and controllers. Power-control equipment comprises motor control, overload and short-circuit protection, and isolation. Before SPSs, no one device could perform all these functions. They were handled by a motor starter (contactor plus overload relay) wired to either fuses or circuit breakers. Depending on the use, location, and control sophistication required, three options were available for group or multiple motor installations. The first choice was a NEMA-rated starter. It was selected by a particular size classification that was suitable for switching motors and other kinds of loads such as capacitor banks. The second was an IEC (International Electrotechnical Commission -- European Standard) starter rated by horsepower. The third choice was a horsepower-rated definite-purpose starter. To add to the complexity, there are over six different classifications available for fuses including H, J, K, RK, RK-1, and 5. Furthermore, short-circuit protection must be coordinated with the overload relay and the contactor to protect personnel and equipment. To ensure coordinated protection, an engineer must determine the available fault current, the corresponding fuse class, and the need for a single or dual-element device. Choices for circuit