Solid State Relays & Accessories
How do Solid State Relays work?
Solid state relays for PCB mounting are partially pin-compatible with electromagnetic relays. As a result, they can often serve as no-fuss replacements in existing designs, thus letting users quickly benefit from the advantages that solid state relays offer.
Solid state relays (SSR) are not actually relays in the traditional sense, even if they are generally categorized as such. Instead, SSRs are electronic components made with transistors or thyristors. Because they operate without moving parts, solid state relays offer a long operating life. In addition, they are suited for high switching cycles and adverse environments. Solid state relays are capable of switching AC voltages at the zero crossing point, thus enabling the avoidance of noise impulses. They also support the integration of optocouplers on the IC to achieve galvanic separation. Compared to mechanical relays, SSRs experience higher losses in the load current path and must therefore often be mounted on a heat sink.
CODICO offers 1- and 3-phase solid state relays for DIN rail and PCB mounting.
Subcategories of Solid State Relays & Accessories:
Solid State Relays vs PhotoMOS-Relays
So-called PhotoMOS relays are special SSR variants whose design is similar to an optocoupler. On the control side, these relays operate like an optocoupler with an IR LED. At the same time, they are not equipped with thyristors on the load side – as the previously described SSRs are – but instead with MOSFETs. This enables the on-off switching of an AC voltage circuit connected between the two drain terminals or of two DC circuits, one each connected between the source terminal and the two drain terminals. PhotoMOS relays do not require cooling, and they characteristically experience a lower voltage drop at low load currents than other types of solid state relays. However, they do typically have a higher contact resistance than mechanical relays. PhotoMOS relays also operate reliable, without bounce and at high switching speeds, while special versions are able to achieve switching frequencies of up to 100kHz.