Definite Purpose Starters

More Information about Definite Purpose Starters

These starters are typically designed and manufactured according to industry standards, such as NEMA (National Electrical Manufacturers Association) or IEC (International Electrotechnical Commission) standards. Compliance with these standards ensures that the starters meet specific safety and performance requirements.

When selecting a definite purpose starter, it is essential to consider the application's requirements, including the motor's voltage, current rating, and duty cycle. The manufacturer's specifications provide guidance on which starter is suitable for a particular application. Proper selection ensures reliable and efficient operation while protecting the motor and other components.

Definite purpose starters are typically open or closed devices, meaning they can be manually operated to either close or open the electrical circuit. They provide reliable motor control and switching, and they are designed to withstand the demands of the specific application they are intended for.

In summary, definite purpose starters are specialized electrical devices used in specific industries and applications. They are designed to meet the unique requirements of these applications, providing reliable motor control and switching while ensuring the safety and efficiency of the system.

FAQs

What is the difference between a definite purpose starter and a definite purpose contactor?

While both definite purpose starters and definite purpose contactors serve specific purposes in controlling motors, the key difference lies in the fact that a definite purpose starter is a complete motor control package that includes both a contactor and an overload relay, whereas a definite purpose contactor refers to the standalone switching device used for controlling the motor.

Motor Starters, Soft Starters and VFDs

Motor Starters

Motor starters safely start and stop a motor in industrial applications. They are designed with a contactor, overload and circuit protection. They are used when basic motor control is required, where torque on the motor is not a concern and speed control is not needed. The advantages of motor starters include: lower cost, allows for remote operation, allows for monitoring of motor state (with the use of auxiliary contacts) and they are safe and efficient. The disadvantages include: high inrush current that can cause fuses to blow and breakers to trip if the inrush is too high, and the starter will allow a full torque to start the motor which can cause the motor to ramp up to full speed very quickly potentially causing the motor to wear and degrade prematurely.

Soft Starters

Soft starters protect motors from inrush current by gently ramping up the motor to full speed. They provide all of the same functions as a traditional motor starter. The advantages of soft starters include: they are less expensive than a VFD when only startup control is needed, they are a smaller system than a VFD where space is a concern and they prevent unwanted torque upon startup, prolonging the life of the motor. The disadvantages include: they are more expensive than a traditional motor starter and they do not allow for full speed control. 

VFDs

Variable Frequency Drives (VFDs) allow for the slow ramp up of a motor during startup and the slowing down of the motor during shutdown. They also allow for full speed control during the entire run cycle of the motor. VFDs provide the same functions as both the traditional motor starters and soft starters. The advantages of VFDs include: full speed control (start, stop and in-between), more custom control and monitoring, energy savings due to efficient motor usage and less wear and tear on the motors. The disadvantages include: they are more expensive and larger than other motor control options and they generate heat that may require fans or AC units.