How many types of contactors are there? This is one of the most frequent questions asked by electrical professionals. To answer this easy question, I listed the types of contactors that are used in the electrical industry. After understanding the types, you will avoid selecting the wrong device for your applications. Because the reason for contactor failure is usually the wrong product selection. Contactors have specific types for specific purposes. Let’s check them one by one.
There are many types of contactors in electrical systems. Below you will find different types of contactors that are used in the industry.
A power contactor is an electrically controlled switch used for switching an electrical power circuit. Power contactors come in many forms with varying capacities and features. Generally, they switch high-capacity loads such as motors, heaters, and transformers.
They are produced from 9A to 2000A. Power contactors are provided in either three or four power pole configurations with a variety of accessories, including auxiliary contacts, connecting links, interlocks, and bus bars. Most of the power contactors belong to the class of air-break. If coil power is removed, an arc is created as the contacts open. Air-break contactors extinguish the arc by separating the contacts by a sufficient distance.
Mini contactors are ideal for general-duty applications where small size and cost are key concerns. They can be used in special modular and compact applications. The small dimensions provide customers with high flexibility in use for applications up to 20 A resistive loads and motor loads up to 5.5 kW. (Generally) They dissipate less heat and some models that have low coil consumption can directly actuate from PLC. A mini contactor can be mounted on din rail or wall. Their accessory options are limited. You can use them on small machines, automatic doors, industrial kitchen appliances, and cleaning machines.
It is always recommended to use a dedicated capacitor contactor for switching capacitor bank, which optimizes the switchgear cost and enhances the equipment life. Capacitor contactor are specially designed to meet the requirements of capacitor switching. When capacitor banks are switched, the voltage associated with a low line impedance may produce high currents on the capacitors. These contactors are fitted with the front-mounted block of 3 early make auxiliary contact in series with quick discharge damping six-resistors-2 per phase to limit peak current to value within contactor making capacity such that normal rated capacitor current is carried by main contacts which, after closing, effectively short out the resistors. You need capacitor contactors for power quality improvement projects. Their utilization category is AC6b.
Bar mounted contactors
The bar contactor is a durable, open-type contactor used for switching very high AC and DC applications. Bar contactors are designed to cut out considerable electric arcs. They are extremely versatile and easily accessible for maintenance. They have a special type of coil and variable number and type of main poles. (N.O., N.C.) Their mechanical durability is around 10 million operating cycles. Bar-mounted contactors are largely used in the iron and steel industry for traction (rolling stock), electrolysis, induction furnaces, and hoisting equipment for applications up to 5000A.
It is also called a silent or modular contactor. Their operation is identical to an industrial contactor but installation contactors operate silently during the operation or control stage. This feature has a high value in building installations where hum-free and silent operations are important for people’s comfort. They are useful in hotels, apartments, hospitals, shopping centers, and warehouses. Mostly they are intended for lighting or heating control but can also control power to motors for air conditioning systems and pumps. Installation contactor includes various ratings from 20 A to 100 A with 2 to 4-pole versions. They significantly reduce space compared to industrial contactors and can also be operated manually.
Solid-state contactors are ideal replacements for electromechanical contactors where fast and demanding switching of loads such as heaters, solenoids, transformers, and motors, is required. Compared to electromechanical contactors, solid-state contactors stand out due to their considerably longer service life. Thanks to the high quality, their switching is extremely precise, reliable, and insusceptible to faults. They have a compact modular design complete with a heatsink. They are available in single-phase, dual-phase, or three-phase versions. If your application demands low maintenance, fast switching, or operation in harsh environmental conditions, consider a solid-state contactor solution.
Safety contactors are designed for machine safety applications. They come with fixed front auxiliary contact blocks, making them ideal for monitoring and controlling circuits. Mechanically linked and mirror contacts help make your system safer. Safety contactors are required to have mirrored contact construction. A mirror contact is a normally closed (NC) auxiliary contact that cannot be closed simultaneously with a normally open (NO) power contact. The N.C. auxiliary contacts will not change state when a power contact welds.
Lighting contactors can be used individually for simple control schemes or as integral components in full-featured lighting control systems. They provide reliable and efficient means of local or remote switching of lighting as well as non-inductive loads. These contactors do not change state and disconnect power from the load during a loss of control power whether momentary or sustained. That is because the operating coil is not required to be continuously energized. Lighting contactors can be used to control a variety of lighting loads including tungsten filament lighting loads (incandescent), iodine lamps, quartz-iodine, infrared lamps, electric discharge lighting loads (ballast), high-intensity discharge (HID), mercury vapor, metal halide, and high-pressure sodium and fluorescent lamps. Parking lots, shopping centers, industrial plants, airports, office buildings, hospitals, stadiums are the typical applications.
Vacuum contactors are applied on low voltage and medium voltage systems up to 15kV on motors, standard and high-efficiency induction, synchronous, wound rotor slip-ring, transformer feeder switching, and capacitor switching. They use the vacuum interrupter to extinguish the arc, which is used to frequently turn on and off the normal working current. Minimal contact bounce, low arc energy, and temperatures minimize the risks of contact welding. Besides, they have a long electrical and mechanical lifetime.
AC contactors are only applicable for use in AC systems. Main contacts should be fed with alternating current. The AC contactor uses the main contact to control the circuit and the auxiliary contact to conduct the control circuit.
DC contactors are only applicable for use in DC systems. Main contacts should be fed with direct current. A special type of connection is needed when you want to control DC loads in the systems.
3 pole contactors
3 pole contactors are typically used in motor starting applications. These contactors utilize three wires to control the electrical current direction.
4 pole contactors
4 pole contactors are typically used in commercial and industrial applications. These contactors utilize four wires to control the electrical current direction. The additional 4th pole for neutral wire connection.