The difference between solid state relays and mechanical relays

The difference between solid state relays and mechanical relays

What is a solid state relay

Everyone thinks that solid state relays are similar to mechanical relays. Because they both use a control circuit and a separate circuit to switch the load. But there are a lot of differences between the two devices. I compared the two devices for you. here we go! Solid State Relays vs Mechanical Relays!

The difference between solid state relays and mechanical relays is:

1. Definition

A solid state relay is a special switching device without any moving contacts. It is not much different in operation from a mechanical relay, but it employs semiconductor switching elements such as thyristors, diodes and transistors. A mechanical relay is a special device used to switch small currents through its moving contacts. The contacts of a mechanical relay change position as the coil is energized and de-energized.

2. Movement part

The main difference between solid state relays and mechanical relays is the contact movement.

Solid state relays do not have any moving parts that mechanical relays have. It consists of semiconductors and electronic parts. Solid state relays electronically switch signals, currents or voltages through the operation of these electronic circuits.

Mechanical relays have contacts and use electromagnetic force to switch the contacts mechanically.

Solid State Relays vs Electromechanical Relays

2. Dimensions

In today's design environment, size is more important than ever. Using a compact product is important to reduce the overall size of the device. Solid state relays are more compact than mechanical relays when controlling the same load capacity.

4. Lifetime

Compared to mechanical relays, solid state relays have longer electrical and mechanical life. The reliability of the SSR depends on the runtime, not the number of switching cycles. When used within published specifications, the SSR has a lifespan of over 19 million hours. Mechanical relays typically have an electrical life of 100,000 to 500,000 operations.

5. Speed and frequency

Solid State Relays enable high speed and high frequency switching. It has a fast response time and an almost unlimited number of switching operations. Instant-on solid state relays respond to control signals in less than 100 µs.

6. Electrical noise

Mechanical relays generate electrical and audible noise that can be disruptive in automation applications. Solid State Relays, on the other hand, do not make noise when the output contacts change state. This is highly desirable in many commercial and medical applications.

7. Shock and Vibration

Mechanical relays are more susceptible to physical shock and vibration than solid state relays. In addition, the orientation of the mechanical relay with respect to shock or vibration must be considered in the design that anticipates physical motion.

What is the role of solid state relay

8. Power consumption

Mechanical relays consume more power than solid state relays. A mechanical relay must energize the coil before it can switch. Coil energy must be maintained to hold the contacts in the desired position. Typically, a mechanical relay consumes 80 mW of power to energize the coil. Solid state relays require very little input power (in the 3mW range) to switch large loads.

9. Heat dissipation

Solid state relays can be packed more densely than mechanical relays while generating less heat. Lower power consumption means less heat to deal with, which is an additional and often hidden saving for designers.

10. Contact wear

Solid State Relays do not use switch contacts that physically wear out. This is why solid state relays do not experience any contact wear. However, the contacts of mechanical relays are prone to wear due to high current, temperature or environmental conditions.

11. Isolation

Features high I/O isolation, which is critical for isolating sensitive equipment from loads. For applications requiring high input to output isolation, solid state relays provide a better solution. For mechanical relays, the isolation from input to output is often referred to as insulation resistance. This term defines the resistance value between all isolated conductive parts of a relay. This value will include isolation between the coil and contacts, between open contacts, and between contacts of any core or frame that are at ground potential. Mechanical relays are typically only rated for 1000 Vrms due to physical construction limitations (such as contact gaps) and materials used.

Solid State Relay Appliances

 Dedicated solid state relays are available with short circuit protection, overload protection and overheat protection. Through the combination logic curing package, users can realize intelligent modules. It is used directly in the control system.

Solid state relays have been widely used in computer peripheral interface equipment, constant temperature systems, temperature adjustment, electric furnace heating control, motor control, CNC machine tools, remote control systems, industrial automation devices, signal lights, dimming, scintillators, lighting stage lighting control systems, instruments, Medical equipment, copiers, automatic laundry. Machinery, automatic fire protection, security systems, power capacitor switching switches are used as power factor compensation for power grids, etc., in addition to chemical industry, coal mines, explosion-proof, anti-corrosion, anti-corrosion, etc. The logic curing package can realize the intelligent module required by the user, which can be directly used in the control system.

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