Basics Of Solid State Relays

What do you mean by Solid State Relay?

Solid State Relay is a totally electronic device that depends on the magnetic, electrical and optical properties of semiconductors to control the flow of current in a circuit. An alternative to Electro-mechanical relay giving enhanced electrical performance and reliability. A electronic switch that has no moving mechanical parts - Solid State.

Solid State Relays have a long lifespan and superior reliability when exposed to vibration and shock. They are very small-sized, need less control power, and have very short response times. Loads can be switched without any disturbance or no bounce and no switching noise is generated. Neighbouring components cannot be disturbed during the switching process by the electromagnetic radiation typically caused by switching sparks or coil. When comparing with mechanical relays, the solid-state relays experience more power loss on the load circuit. Due to this reason they are often mounted on a heat sink.

Features of Solid State Relay:

1.       Solid State Relays have no internal mechanical elements and full-sealed perfusion in the structure. Therefore, Solid State Relays have advantages such as vibration resistance, corrosion resistance, long life and high reliability.

2.       Low noises and AC Solid State Relays use zero-crossing triggering technology, thus effectively reducing the voltage rise rate dv/dt and current rise rate di/dt on the line, making Solid State Relay minimal interference to the power supply in the long-term working.

3.       Switching time is very short, so Solid State Relays can be used in high frequency applications.

4.       Optoelectronic isolation is used between input and outputs circuits and insulation voltage is more than 2500V.

5.       Solid State Relays are compatible with TTL and COMS circuits and has Low input power consumption.

6.       Protection circuit is set in the output terminal.

7.       It has High load capacity.

Advantage of Solid State Relays:

       (1) High life and High reliability: Solid State Relay has no mechanical parts, complete the contact device features a solid, no moving parts, so in high shock and vibration of the working environment, composed of solid state relays as components inherent characteristics, determine the solid-state relays, long life, high reliability.

       (2) High Sensitivity, small power control, electromagnetic compatibility: solid state relay wide input voltage range, low drive power, compatible with most logic integrated circuits or drive without additional buffers.

       (3) Fast Conversion: With the use of solid during solid-state relay, so the switching speed can be from a few milliseconds to a few subtle.

       (4) Electromagnetic interference laugh: solid state relay does not enter "coil" and did not touch the light arc and rebound, thus reducing electromagnetic interference. Most AC output solid state relay is a zero-voltage switching at turn-on at zero voltage, zero current at turn-off, reducing the sudden interruption of current waveform, thus reducing the switching transients.