Definite Purpose Contactors

More Information about Definite Purpose Contactors

A definite purpose contactor comes with specific features and specifications that make it suitable for its intended purposes. It may have different terminal styles for easy installation and wiring, such as screw terminals or quick-connect terminals. Some DP contactors have specific mounting plates or brackets for convenient installation in equipment or panels.

A DP contactor is generally designed for switching motor loads, controlling compressors, or operating specific devices in the industry it is intended for. It has multiple poles to handle the necessary electrical connections and provide effective motor control or load switching.

DP contactors may have specific industry certifications or meet certain standards, such as NEMA (National Electrical Manufacturers Association) standards or IEC (International Electrotechnical Commission) standards. These certifications ensure that the contactors meet the required safety and performance criteria.

Depending on the manufacturer and the specific application, DP contactors may have additional features or variations. Some DP contactors may be designed for specific applications like reversing motor control, pump control, or panel-mounted applications.

It's important to note that DP contactors are specifically designed and selected to meet the unique requirements of their intended applications. They are not interchangeable with general-purpose contactors or starters. Manufacturers provide detailed specifications and application guidelines for their DP contactors to assist customers in choosing the appropriate contactor for their specific needs.

Definite purpose contactors, or DP contactors, are contactors designed for specific applications and industries. They have features, ratings, and certifications tailored to the requirements of those applications, such as air conditioning, refrigeration, HVAC, and industrial plants. DP contactors play a crucial role in controlling motors, switches, and devices in their intended applications, providing reliable and efficient operation.

FAQs

Are definite purpose contactors used for pumps in HVAC applications?

Yes, definite purpose contactors are commonly used for pumps in HVAC (heating, ventilation, and air conditioning) applications. Pumps are an essential component of HVAC systems, and definite purpose contactors are specifically designed to control and switch motor loads like pumps.

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.