Since their introduction to the market, solid-state relay has found acceptance in a wide number of applications. Although the solid state relay made available the advantages of semiconductor switching in a convenient form, it has been realized that it has certain characteristics which require ensuring reliable operation. In selecting the proper solid-state relay for the project, consideration should be given to its advantages and disadvantages.
Advantages of Solid State Relay
When used correctly in the application, the solid-state relay provides many benefits for the systems.
- It does not have any mechanical contact or moving parts.
- It has a long electrical and mechanical life expectancy and high reliability: Almost limitless. Up to 10⁹ operations.
- It has a very good shock and vibration resistance.
- It does not bounce or generate an electrical arc.
- It has a high input-output isolation voltage.
- It can be directly controlled by logic circuits like PLCs.
- It operates rapidly. The response time between energization and switching is extremely fast. (in microseconds)
- It does not generate an electrical noise
- It is not affected by electromagnetic interference.
- It needs very little power to energize. The operation voltage is low.
- It is compact and does not need so much space.
- It has various types. It can be classified by appearances, such as panel-mounting models, socket models, PCB models, or by applications.
- It has been used in the market since 1972.
- Its contact does not wear like a mechanical relay.
- It does not dissipate heat during work.
- It does not need any maintenance.
- It can operate in very low and very high temperatures.
- From the low-level signal demands, power loads up to 43,000 watts can be controlled with solid state relay.
- It is microprocessor compatible.
Disadvantages of solid state relay
The drawbacks of the solid-state relay are listed below:
- It has high output resistance and voltage.
- Multiple switch configurations are difficult. (Only SPST easily.)
- It is expensive.
- Off-state leakage can affect the load or be hazardous.
- It can only be used in demanding applications. The market size is not huge.
- It is generally designed for AC or DC loads. Not for both.
- It cannot switch very low signals such as audio.
- The specifications for solid-state relays are complex because of their semiconductor parameters.
- Condensation can cause failures such as insulation deterioration.
In conclusion, solid-state relays have been widely accepted in various applications due to their numerous advantages, including high reliability, fast response time, compact size and low power consumption. However, it is important to consider their drawbacks, such as high output resistance, limited switch configurations and high cost. To ensure reliable operation, proper consideration should be given to selecting the appropriate solid-state relay for the specific application. Despite its limitations, solid-state relays have proved to be an excellent alternative to mechanical relays and have been used in the market for more than 50 years.