Motor contactors serve a crucial role in the electrical sector, functioning as switches to manage the connection or disconnection of electric motors and various load devices to power supplies. Designed with normally open contacts, these devices ensure that the load is disconnected once the contactor coil loses power.
Given their duty to interrupt significant motor currents, motor contactors incorporate arc extinguishing devices to control and suppress arcing alongside their electromagnetic and control systems. For those questioning, "How does a motor contactor work?" this setup explains how these components come together to efficiently and securely connect electric motors.
Components of Motor Contactors
Key components include the coil or electromagnet, which provides the necessary force to close contacts
Key components include the coil or electromagnet, which provides the necessary force to close contacts, and the contacts themselves, which manage current flow. Contacts come in three types: contact springs, power contacts, and auxiliary contacts, each fulfilling a specific role in directing current through the contactor to the load.
The frame is another critical component, housing, protecting, and insulating the contacts and coil. These frames are made from durable materials such as polyester, polycarbonate, Nylon 6, and Bakelite. Open-frame motor contactors often require additional enclosures to shield against environmental hazards like dust, weather, and oil.
Types of Contactors
To meet diverse electrical application needs, several types of contactors are available. Definite-purpose contactors are often used in HVAC systems to control various loads. Safety contactors are designed with mechanically linked contacts that ensure proper operation and fail-safe mechanisms.
Other variants include non-reversing (FLNR) contactors such as NOARK’s Ex9C Series, suitable for single and three-phase applications, and reversing contactors (FLR), like NOARK’s Ex9CR Series, which feature interlocks preventing simultaneous closure of multiple contactors.
Difference Between a Contactor and a Motor Starter
Typically designed with normally open contacts, contactors cut the load’s main circuits when de-energized
A motor starter differs from a contactor by combining the functions of starting a motor and providing protection against overcurrents. While contactors connect power to the load without offering circuit protection, they integrate three main components: an electromagnetic system, a contact system, and an arc extinguishing device.
Typically designed with normally open contacts, contactors cut the load’s main circuits when de-energized. Their designs offer compact, durable solutions for handling a wide range of currents, along with numerous operational cycles.
Contactors can also be equipped with accessories like different coils, auxiliary contacts, mechanical interlocks, surge suppression blocks, and time delay relays. However, they are not suitable for interrupting short-circuit currents, a task better suited to motor starters, which provide protection and can utilize contactors for remote control.
NOARK’s Advanced Motor Contactors
NOARK’s motor contactors operate by managing circuits to connect or disconnect loads based on coil energy. The energizing of the coil closes power contacts to supply power, and de-energization opens the contacts, disconnecting supply.
This allows safer control of motors and high-load devices, emphasizing the importance of motor contactors in various motor load applications. Despite their association with motor starters for remote operations, contactors and starters are distinct in their functions and constructions.
Motor contactors are electrical switches used as means of control, connecting or disconnecting electric motors and other load devices to the power supply. They’re typically designed for normally open contacts, which ensures the load disconnects whenever the coil of the contactor de-energizes.
Because this interrupts heavy motor currents, arcing must be suppressed and controlled with an arc extinguishing device, which functions alongside the contactor’s electromagnetic and control systems. For those wondering, “How does a motor contactor work?” this explains how these components function together to connect electric motors safely and efficiently.
Components of Motor Contactors
- Coil or Electromagnet: The electromagnetic coil provides the force needed to close the contacts.
- Contacts: Contacts perform the current carrying function in a contactor. There are three contact types: contact springs, power contacts, and auxiliary contacts. Each plays a unique role in how a current passes through the contactor to the load.
- Frame: the frame houses, protects, and insulates the contacts, coil and other components. They can be made of a wide range of materials, including polyester, polycarbonate, Nylon 6, thermosetting plastics, and Bakelite. Open-frame motor contactors normally have a secondary enclosure to protect them from weather, dust, oil, or other explosive hazards.
Types of Contactors
To accommodate different electrical applications, there are several types of contactor, which include the following:
- Definite-purpose contactors, used in the HVAC equipment to control single- and three-phase loads (mostly for low duty-cycle applications).
- Safety contactors, where the contacts are mechanically linked, ensuring all three poles simultaneously close and that the contactor fails in an open state.
- Non-reversing (FLNR) contactors (such as NOARK’s Ex9C Series 9A to 1,000A Standard IEC Contactor), which use a single contactor for single one phase or three phase motor applications.
- Reversing contactors (FLR), such as NOARK’s Ex9CR Series 9-500A, are multi-contactor assembly connected by an electrical and mechanical interlock that ensures only one contactor closes at a time.
Difference Between a Contactor and A Motor Starter
A motor starter combines a means of starting a motor (connect/disconnect), as well as providing branch circuit protection and overcurrent protection for the motor. A Contactor, on the other hand, is an electrical switch that connects power to the load. A motor contactor on its own has the following attributes:
- Three components: (1) an electromagnetic system, (2) a contact system, and (3) an arc extinguishing device.
- Contactors work with normally open contacts (in most cases), cutting the load’s AC and DC main circuits once the coil is de-energized.
- Compact for easy field mounting or handheld use (sometimes metered).
- Designed to mitigate electrical arcing.
- A wide range current carrying capacity, from several to thousands of amperes.
- Durable with several tens of thousands of open and closed operations.
There are also several additional accessories possible, including:
- Different coils.
- Auxiliary contacts.
- Mechanical interlocks.
- Surge suppression block.
- Time delay relay.
- As durable as contactors are, be aware that they aren’t intended to interrupt short-circuit currents.
Motor starters are able to offer protection to motors and may use contactors for remote operation, but the starter itself have a very different construction.
NOARK’s Advanced Motor Contactors
Motor contactors work by controlling the circuit to connect or disconnect the load from the supply. This is done by energizing the coil which in turn closes the power contacts to supply power to the load or de-energizing the coil which opens the contact and disconnects the power to the load.
This allows users to control motors and other high-load devices with less risk, making motor contactors essential components in any motor load application. Although the contactor is used in a motor starter for remote operation, the two are different devices with distinct functions.
