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In industrial automation and electrical installations, a decision often has to be made: should a solid state relay (SSR) or a classic electromechanical relay be used?
Both types of relays perform a similar function – they switch signals between different circuits – but they differ radically in terms of design, operating characteristics and intended applications.
Design and operation – SSR relay vs electromechanical relay
An electromechanical relay is a classic mechanical solution. Inside, there is a coil which, when voltage is applied, attracts a shunt and closes the contacts. A distinct click is heard during switching. This mechanical movement causes sparking and, in the long term, wear on the contacts.
In contrast, a solid state relay (SSR) operates entirely electronically, using signals to switch thyristors, thyristors or transistors. The absence of moving parts means quiet, trouble-free operation and the ability to switch even dozens of times per second. Furthermore, SSRs do not generate sparks, and models with a zero voltage switch function reduce electromagnetic interference (EMI).
Comparison of key features – table
| Feature | SSR – Solid State Relay | Electromechanical Contactor |
|---|---|---|
| Construction | Semiconductor (triac, thyristor) | Mechanical (moving contacts) |
| Operating noise | Silent – no mechanical sound | Audible – clicking sound when switching |
| Durability | Very high – no wear | Limited – contact wear over time |
| Switching frequency | High (up to 100/sec) | Limited (a few per minute) |
| EMI interference | Minimal (thanks to zero-crossing feature) | Possible – due to contact arcing |
| Size and mounting | Compact, panel / DIN rail | Typically larger |
| Typical applications | Heaters, HVAC, LED, precision automation | Motors, general lighting |
When to choose an SSR and when to choose a classic electromechanical relay?
SSR relays are best suited for applications where the load is switched frequently and regularly, e.g. in the control of electric heaters, LED lighting, HVAC systems or laboratory equipment. Their silent operation and vibration resistance make them suitable for use in any working environment, even in very demanding conditions.
Electromechanical relays remain a good choice where:
In practice, many systems combine both technologies – e.g. SSRs for heaters and electromechanical relays for main motor power supplies.
What to choose from the ELTRON offer?
The ELTRON online store offers both SSR relays and classic electromechanical relays. Popular models of Carlo Gavazzi SSR relays, such as RM1A48D50, RGS1A60D75KKE and RZ3A60D55, are often chosen for heating and industrial automation.
ELTRON also offers assistance in selecting the right SSR relay for your application – all you need to know are the load parameters and operating environment to find the right model.
🔗 Read also: How to select an SSR relay for a heater?
🔗 See also: The most popular Carlo Gavazzi relays – which one to choose and why?
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