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
Products & Services
Motor contactors are relays with large current capacity for connecting and disconnecting a motor from the power supply. Typically, motor contractors are multi-pole for control of all current carrying conductors.
DC Motor Starters
DC motor starters combine a controller (most often a contactor) with overload protection, allowing a motor or motor-controlled equipment to be turned on and off.
Motor Starters and Contactors
Motor starters and contactors are motor-starting devices. They combine a contactor with overload protection and are designed for starting AC or DC motors.
AC Motor Starters
AC motor starters are used to turn-on and turn-off electric motors and motor-controlled equipment. They use solid-state or electromechanical technologies, and are designed for single-phase or three-phase motors.
Engine starters provide the initial rotation for internal combustion engines. They cause the pistons to move before ignition, enabling the engine to turn over so that it can then operate under its own power.
Topics of Interest
Protection and Ratings
The typical method of starting a three-phase induction motor is by connecting the motor directly across the power line. Line starting a motor is done with a...
3.3 SHORT-CIRCUIT CALCULATIONS
Several sections of the NEC relate to proper overcurrent protection. Safe and reliable application of overcurrent-protective devices based on these...
3.5 COMPONENT SHORT-CIRCUIT PROTECTION
This section analyzes the protection of electrical system components from fault currents. It gives the specifier the necessary information...
Single-speed squirrel-cage motors have starters that fall into two categories: full-voltage or across-the-line starters; and reduced-voltage starters.
Full-voltage starters (manual and magnetic) apply...
Overcurrents in an electrical network may be caused by a short-circuit or an overload. The switching devices used to clear these overcurrents are circuit-breakers and fuses.
In this chapter we will...