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 Control Basics

Motor control allows operational control of electrical motors in various environments. 

Motor control circuits provide a safe way to operate electrical motors. Back when motor control circuits were in their infancy, it would have been common to see a simple disconnect switch that would be used to turn on and off a motor. Depending on the size of the motor and how much voltage was required, operating this disconnect would have been dangerous, with a very high possibility of arcing or electrocution. Not to mention that when the disconnect was actuated, the large amount of inrush current would have damaged the motor over time.

In today's motor control circuits, there are a few common pieces of hardware. 

A circuit breaker is used to protect the motor and any hardware downstream. A contactor and an overload relay are connected together and function in tandem to allow for remote and safe operation of the motor. The contactor functions much like a relay, allowing for a smaller electrical circuit to remotely close the motor contacts, starting the motor. The overload relay is designed to protect the motor in the case of a prolonged overcurrent event. These two devices are wired in series, so that if the overload relay detects an overcurrent event, the contactor will open the motor contacts, shutting off power to the motor.

The other two most common types of motor control hardware are a soft starter and a Variable Frequency Drive (VFD). 

Both of these devices function in a similar way to the motor circuit with some added functions. The soft starter is designed to reduce large inrush current to the motor upon startup. This “soft starting” of the motor will prolong its life and allow for safer operation. The VFD performs the soft start functions, but also allows for speed control of the motor. This speed control is critical in many different environments and has made VFDs one of the most common and safe to use motor control circuits today.