Solid-state relays, i.e., SSR (from English Solid State Relay), have been steadily gaining popularity for decades, mainly due to their broad electrical parameters, fast response time, and the absence of mechanical parts. These features increase the lifetime of this type of relays and resistance to mechanical shocks caused by impacts or vibrations. The absence of arcing on the contacts and elimination of interference in the control circuit are other advantages of solid-state relays resulting from their design. In some cases, silent operation should also be considered a significant benefit.
Due to high demand (especially from customers involved in automation systems), many manufacturers offer SSR relay models, but not all feature proper quality. Ensuring stable and long-lasting operation of such an element requires the use of suitable components and thoughtful design. Specialists from companies like Relpol, possessing many years of experience in the industry, are best aware of these challenges. Therefore, below we present the offer of SSR relays from this very manufacturer – these are solutions providing not only optimal parameters – they have also been tested on international markets.
Relpol SSR Relays
In this article, we cover topics such as:
- SSR components in PCB mounting formats and on TH35 rail
- Solid-state relays for three-phase circuits
Single-phase solid-state relays
SSR relays for single-phase current handling are available in several popular formats. The first is narrow-profile housings of the RSR30 series for direct PCB mounting (or in a socket). For mounting outside the printed circuit board, RSR52 versions are available with screw terminals and holes for screwing – typical for industrial applications, panel-mounted. This format is used, among other things, in plastic processing machines (e.g., injection molding machines), in food industry devices, HVAC systems (heating, ventilation, air conditioning), and also lighting. To ensure optimal heat dissipation, the manufacturer provides heatsinks compatible with these modules. In RSR72 models, the heatsinks are integrated with the relay body. A mount for fastening on a DIN rail (TH35) is placed on its rear part.
Relpol modules have a range of protections and practical functions simplifying their installation and adapting them to various applications. RSR72 versions have an integrated resistor, capacitor, and varistor together creating an MOV protection, which suppresses overvoltages generated when switching off inductive loads (motors), limits pulses coming from the network, and overall extends the relay’s lifetime. Special versions of components feature functionality for zero-crossing or random switching. Both RSR52 and RSR72 models include LED indicators signaling operation. Thanks to optical isolation, the relays provide protection even at 4000V (RMS).
In terms of electrical parameters, relays support voltages up to 280V AC (RSR30), 660V AC (RSR52/72). Additionally, PCB-mounted models come in versions for switching DC circuits (up to 180V DC). An important advantage of SSR relays is the wide range of control voltages, which in Relpol products may be within DC ranges: 3…10V, 4…32V, or 18..32V; and 90…280V for alternating current. Supported currents range from 1A to 80A. Another advantage of solid-state modules is the short switching time, which can reach as little as 50µs.
Single-phase relays
Three-phase solid-state relays
Relays for handling three-phase currents belong to the RSR62 series and are realized in module format with screw terminals. Similar to the models described above, they come in versions controlled by DC (4…32V) or AC (90…280V) voltages. They are used to switch circuits operating at voltages from 24V to 660V with currents up to 80A. Such a range allows for handling many demanding loads, especially motors and furnaces.
The three-phase models include many of the solutions already described: RC/MOV protections, optical isolation enhancing control circuit safety, signaling LEDs indicating the element’s operation, and the possibility of mounting on a heatsink.
It should also be emphasized that all Relpol products are manufactured in compliance with numerous international standards and regulations (RoHS, REACH, CE, CUL, EAC).
Three-phase relays
