Solid-state relays are often seen as a textbook example of the semiconductor industry. They make use of the electrical and optical properties of semiconductors, such as a silicon-controlled rectifiers, triode that can switch current in both directions and transistor outputs that are faster and more reliable and can therefore handle higher frequencies.

In the world of electronic circuits, there are two prominent players: solid-state relays and electromechanical relays. Each has its own unique characteristics and applications. Below, we’ll dive deeper into the benefits of solid-state relays and how they differ from their electromechanical counterparts.

• Long life: Since there are no moving parts in a solid state relay, they are not subject to contact wear, mechanical stress or corrosion. Solid state relays can operate for millions of cycles without a reduction in performance. Their lifespan is 50-100 times longer than electromechanical relays. Solid state relays are therefore ideal for repetitive applications and where low maintenance is desired.

• Fast Switching : Because there are no moving parts, solid state relays have a very fast response time. This means that power to a load can be added and removed very quickly and accurately. This is especially important in applications that require fast switching on and off.

• Shock and vibration resistant: Solid state relays are well suited for harsh environments with high vibrations. They do not receive electrical or mechanical shocks, because there are no moving parts.

  The Harmony solid-state relays for panel mounting meet, among others, the international standard IEC 61373 for railways and similar guided vehicles. This makes this series extremely suitable for shock and vibration testing.

The long life, fast response time and shock resistance make solid state relays very suitable for applications in heating control, motor control, lighting control, medical devices and automotive. Some important industry segments are HVAC, rail and transportation, packaging and food & beverage.

But rest assured, there are also specific solutions and functionalities to overcome these with Schneider Electric's Harmony solid-state relays.

• Thermal Management: It is important to understand that semiconductors are never fully on or fully off. When in the “on” state, the resistance inside the solid state relay can generate significant heat as current flows through it. This heat can significantly shorten the life of the solid state relay. Therefore, it is essential to protect these relays from overheating.

  Schneider Electric’s Harmony solid state relays offer a solution to this. They have DIN rail mounting options that are integrated with a heatsink. This helps dissipate the heat generated. They also offer panel mounting options with a range of heatsinks to choose from. When selecting a heatsink, you should consider the ambient temperature and current of your application. This will ensure effective thermal management and extend the life of your solid state relay.

• Extra slim design : In general, solid state relays are larger than electromechanical relays due to the fact that they have a carbon body (heatsink). This is a problem for many panel builders during installation, as control panels and cabinets are becoming more and more compact. Schneider Electric has specific ranges that provide a solution to this challenge.

  For example , the SSL range : Save panel space with selected products from the Harmony solid-state relay range. The SSL range has a slim design that is only 6.2mm wide. The SSM2 range offers two inputs and two outputs in a single relay that is only 18mm wide. The SSD range is packaged in 22.5mm wide (up to 35A) and 45mm wide (up to 60A) models and comes with a high power density.

• Quiet Operation: Solid-state relays produce no noise, making them ideal for commercial and medical applications where quiet operation is desired. However, the “clicking” sound of contacts switching can sometimes be useful, especially to warn of a fault. Because solid-state relays operate silently, it is challenging to identify faults or damage unless manually tested.

To facilitate troubleshooting and avoid reactive maintenance, Schneider Electric has developed a smart diagnostic solid-state relay with built-in visual LEDs and a debugging test button to monitor the operation of the solid-state relays and to react immediately to abnormalities.