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SOLID STATE RELAY(SSR)-Three (3) Phase Solid State Relay

A three-phase SSR is fundamentally 3 distinct single-phase SSRs parceled in a single housing with a mutual input so that each SSR is energized instantaneously. In fact, it is not infrequent for engineers to use 3 individual SSRs to change power to a three-phase load.

Since soon after the introduction of Single Phase SSRs in 1970 three Phase Solid State Relays (SSRs) have been accessible. The first of these relays were nothing more than 3 individual SSRs with a common input connection bundled in a single frame. For the most part, this basic design concept remains unchanged today.

Nevertheless, even though the purpose of single-phase and three-phase relays are relatively alike, their applications can differ suggestively. This is primarily due to the features of three-phase power circuits and the characteristics/demands of three-phase loads

DC Solid State Relay

These relays are intended to change DC loads, e.g. solenoid valves, brakes, LEDs, motors (possibly on AC mains under specific conditions). Geya Electrical offers a complete range of DC solid state relays up to 1700DC, 0 to 150A.

For DC-to-DC Solid State Relays, transistors are used as converting elements. The type of transistor used could be Mosfet (for Metal Oxide Semiconductor Field Effect transistor), or IGBT (for Insulated Gate Bipolar Transistor) Bipolar. The choice of the suitable technology will depend on your application.

Solid State Relay Types

There are three (3) rudimentary groups of SSRs that electricians recognize: Photo Coupled, Transformer Coupled, and Reed Relay Coupled. The Reed Relay Coupled SSR has a regulator indicator applied straightly to the coil of a reed relay. As soon as the reed switch closes it stimulates the circuitry which will trigger the thyristor switch.

Solid State Relay Working

A solid-state relay (SSR) is an electrical converting device that changes on or off when an external voltage (AC or DC) is functional across its regulator terminals. Packaged solid-state relays use power semiconductor devices such as transistors and thyristors, to change currents up to about a hundred amperes.

Solid State Relay Problems

Due to the high inrush current of loads such as lamps and motors, SSR output elements are spoiled, if an inrush current exceeds the rated making current of the SSR.

  1. Installation environments: If an ambient temperature surpasses the esteemed value, the SSR output elements may be destroyed.
  2. Malfunction caused by external surge: An exterior surge may suddenly destroy or output elements. A load short circuit may also cause malfunction.
  3. The reverse voltage of the load: High reverse voltage produced by inductive loads such as solenoids and valves may have the SSR output elements destroyed.

Solid State Relay VS Relay

The key difference between solid-state relays and general relays is that there are no movable contacts in the solid-state relay (SSR). Overall, solids state relays are quite similar to the mechanical relays that have movable contacts. SSR provides high-frequency, high-speed switching operations.

Solid State Relay Vs Mechanical Relay

Solid-state relay changes voltages, currents, signals, or electronically by the operation of these electronic circuits. A mechanical relay has contacts and uses electromagnetic force to mechanically change the contacts.

How to test a Solid State Relay?

Connect a load and power supply, and examine the voltage of the load terminals with the input ON and OFF. The output voltage will be close to the load power supply voltage with the SSR turned OFF. The voltage will fall to approximately 1 V with the SSR turned ON.

How does a Solid State Relay Work?

You may be marveling – what kind of switch enables the control signal to power hundreds of amperes? The actual attractiveness of solid-state relays versus electromechanical relays lies finally in the difference between the changing mechanisms. Solid-state relays use what the industry calls optocouplers or optoisolators. In the human state, that means a “light-separator.” That’s right – the switch inside a solid-state relay is just a beam of light! Usually, there is a very low-power LED that shines a beam of light on a photodiode, which approximately suddenly allows power to be transmitted through it or “switched” on.

In a solid-state relay, the photodiode is what makes the connection within the load circuit complete. So, what in the world is a photodiode? It is a very particular transistor that uses photons to power the gate, rather than a distinctive electrical signal. How in the world does that work? It uses a highly particular silicon P-N junction.

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I am William, Electrical Engineering Author. Dedicated to writing technical articles on Timer Relay, Monitoring Relay, Surge Protection Device and other electrical devices. With 7 years of writing experience, I am committed to providing accurate and in-depth expertise to my readers.

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