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 to ensure 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 and 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 from 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, or 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 working.
- 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 relay are complex because of its semiconductor parameters.
- Condensation can cause failures such as insulation deterioration.
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