9 Types of Contactors and Protection Relays
This article explains the various types of relays, such as mercury wetted relay, Buchholz relay, solid-state contactor relay, solid-state relay, and more that are used in industries. Let’s start with the fundamental relay circuits, which include voltage suppression relays.
What Are Voltage Suppression Relays?
In industries, relays are controlled by computers, and for this purpose, they are fitted with semiconductors such as transistors. This can result in voltage spikes. Therefore, voltage suppression gadgets are needed; otherwise, the spikes will damage the transistors.
The voltage suppression is performed by either the relay or the computer. If relays are used, they are termed voltage-suppression relays. In these relays, voltage is suppressed with the aid of high-value resistors and capacitors and diodes. Among these, resistors and diodes are commonly utilized.
Other types of basic relay circuits are de-spiking diode relays and de-spiking resistor relays.
Types of Contactors And Protection Relays
Let’s look at the various types of contactors and protection relays in detail:
Contactor relays have heavy loads. They are chiefly utilized to switch electric motors. Contactor relays have an array of current ratings ranging from a few to hundreds of amps. These relays’ contacts are typically built with alloys with a small amount of silver to avoid the damaging impact of arcing.
Contactor relays are utilized for rough use, and they generate loud sounds while working and, therefore, cannot be utilized in places that need some amount of quietness and silence.
Solid State Relay (SSR)
As their name suggests, these types of contactors and protection relays are built with solid-state elements. They are designed without any moving components, and so are highly reliable.
Solid State Contactor Relay
Solid-state contactor relays combine the features of both contactor and solid-state relays. This gives them many advantages. They can be built for the right on-off cycles and have an excellent heat sink. Microcontrollers, microprocessors, or PLC control solid-state contactor relays.
Machine Tool Relay
Machine tool contactors and relays are commonly used in industries to control all types of machines. They have multiple contacts with replaceable coils. As a result, these relays can be effortlessly transformed from NO to NC contact. You can easily set up several kinds of these relays in a control panel. However, in many industries, machine tool relays are being replaced by PLCs.
Mercury Wetted Relay
Mercury wetted relays are similar to reed relays. The major difference is in these relays is that mercury is used to wet the contacts and not inert gases. This means these relays are more expensive and position sensitive.
They need to be mounted vertically for functioning. Mercury wetted relays have limited contact resistance and therefore are ideal for timing applications. For these reasons, these relays are not frequently used.
Overload Protection Relay
As their name suggests, these relays are utilized to protect electric motors from getting damaged by short circuits or over current. For this purpose, these relays have their heating element in series with the motor. When there is overheat, the bi-metallic strip linked to the motors gets heated and discharges a spring to work the relay’s contacts.
These relays are used as safety devices. They help to detect the gas amount present in big oil-filled transformers. Buchholz relays generate a warning when they sense either fast or slow gas production in the transformer oil.
These relays are sensitive and have been utilized since the telephone was invented. They played vital roles in older telephone exchanges and in identifying telegraphic distortion. The relay’s sensitivity is simple to adjust as their armature is positioned between the permanent magnet’s poles.
These relays are essential for their contacts. To protect them from the atmosphere, they are securely placed in an inert or vacuum gas. This relay has very low voltage ratings and switching current but is noted for its switching speeds.
The Way Forward
Now that you know about the different types of contactors and relays, consult with a licensed electrical professional to determine your requirements and find the best contactors and relays. Hiring a professional helps ensure that all electrical proceedings are absolutely safe and have been performed as per industry specifications.