An SSR or a Solid State Relay is a piece of electronic switching equipment which when applied by a small external voltage across its control terminal switches ON and OFF. SSRs have a sensor in them that reacts to a proper control signal (input), a piece of switching equipment that changes power to the load circuit, and a coupling process to empower the control signal to initiate this switch without the help of any mechanical parts. The relay might be made to switch either DC or AC to the load. It offers the same functionality as that of an electromechanical relay but comes with no moving parts.

Packaged Solid State Relay utilizes power semiconductors like transistors and thyristors to change the electrical current approximately to hundred Amperes. The switching speed of solid-state relays is comparatively faster than that of the electromechanical relays. In addition to that, it has no physical contacts to wear out. The devices using the Solid State Relays must take into consideration their higher value of “ON” state resistance as well as their lower capacity to hold out against momentary overload. In contrast to an electrochemical relay, the SSR offers only a limited amount of switching arrangement.

Operation

A Solid State Relay that works based on a particular MOSFET (or multiple ones in a parallel array) works well with DC loads. This MOSFET comes with a substrate diode which helps in the conduction of electricity in the reverse direction. Thus it is not possible for a particular MOSFET to stop the current in both directions. To carry out an AC operation, 2 MOSFET are positioned one after the other with their source pins integrated. The output side is connected with their drain pins. The substrate diodes are reverse biased alternately such that the current can be blocked whenever the relay is OFF. Whenever the relay is ON both the gates are positively biased comparative with the source by the photograph diode.

Parameters

Solid State Relay is governed by several parameters. They are:

• Required activating output current and voltage
• Required activating input current and voltage
• AC or DC
• Resistance or potential drop affecting the output current and thermal resistance.
• SSRs are much less sensitive to operating environment and storage factors like humidity, mechanical shock, external magnetic fields, and vibration.

Advantages of SSR over Mechanical Relays:

• Slimmer and smaller than a mechanical relay.
• It carries out a totally silent operation.
• The switching speed of SSRs is much faster than that of electromechanical relays.
• The output resistance does not vary regardless of the amount it is utilized.
• The operation is bounceless and clean.

Disadvantages:

• For the gate charged circuit an isolated bias supply is needed.
• There is a chance of false switching because of the voltage’s momentary variations.

Hope you liked going through the article on Solid State Relay. Brands that make SSRs are Crydom, Omron and Phoenix Contact. Make sure to follow them using the links as provided here. Thank you for reading.

View all the Solid State Relay – Industrial Mount

A switch that can be operated electrically is known as a relay. It consists of several operating contact terminals as well as a group of input terminals for multiple or single control signals. The switch might come with a different number of contacts in several contact forms, like break contacts, make contacts, etc.

Relays have found its uses at places where several circuits need to be controlled by a particular signal or where it is important to control the circuit by a low power signal which is independent. Firstly relays were utilized as signal repeaters in long-distance telegraph circuits. Here they used to revive the signal rolling in from one circuit by broadcasting it on another circuit. Relays were utilized excessively in early computers as well as telephone exchanges to carry out logical operations.

The basic version of relays takes the help of an electromagnet to open or close the contacts, however, other working standards have been concocted like the solid-state relays which utilize the semiconductor properties for controlling. Relays that comes with multiple operating coils and adjusted working attributes are utilized in protecting electrical circuits from faults and overload. In current electric power frameworks, these capabilities are taken care of by digital instruments known as protective relays.

Types of Industrial Relay

• Coaxial Relay – Whenever a single antenna is shared between a radio receiver and a transmitter, coaxial relays are used. It helps in switching the antenna from the receiver to the transmitter. Thus the receiver is defended from transmitter's high power.

• Contactor – A heavy-duty relay that comes with a high current rating which is utilized for switching lighting loads and electric motors is known as a contactor.

• Force-guided contacts relay - These types of relay come with contacts that are linked together mechanically such that whenever the relay coil gets energized or de-energized, all of them moves together.

• Latching Relay – A latching relay is basically an electromechanical switch that helps in controlling small flow of electrical current with a larger flow of current.

• Machine tool relay - A machine tool relay is a relay that is used mainly for industrial control of transfer machines, machine tools, etc.

• Mercury Relay – The relay that takes the help of mercury as a switching element is known as mercury relay.

• Multi-Voltage relay – These relays are made in such a manner that they can withstand a wide range of frequency (0 to 300 Hz) as well as a wide range of voltage (24 to 240 VAC).

• Polarized relay – This relay positions the armature in between the poles of a permanent magnet only with a motive to increase sensitivity.

• Static Relay – This kind of relay comes with electronic circuitry to imitate each one of those attributes which are accomplished by moving parts in an electromagnetic relay.

This was all we have regarding Industrial Relays. Hope you enjoyed going through it. Brands that manufacture them are Phoenix Contact, TE Connectivity, and Omron. Make sure to visit them from the links as provided.