SSR relay with DIN rail heatsink 30A, instantaneous switching, 24V DC control 77.31.9.024.8051

Direct Load Switching in Industrial Installations

This modular solid-state relay (SSR) from FINDER's 77 series is designed for controlling loads with a rated current of up to 30 A in AC circuits. The device features immediate switching, meaning the transition occurs instantly upon the appearance of the control signal, without waiting for the voltage to cross zero. This characteristic is crucial in applications requiring precise timing control or rapid system response, such as short-cycle heating processes or motor control with specific starting requirements.

Thanks to its built-in heatsink and compact DIN-rail construction, this relay fits perfectly into control cabinets, saving space while ensuring effective thermal protection. The control supply voltage is 24 V DC, making it compatible with most standard automation systems and PLC controllers. The wide load voltage range (from 48 to 480 V AC) allows its use in various industrial environments, from simple lighting installations to more complex drive systems.

Key Features and Practical Applications

The device combines the advantages of traditional electromechanical relays with the reliability of semiconductor solutions – the absence of moving parts means no arcing and extended service life even with high numbers of switching cycles. Immediate switching eliminates the delays characteristic of zero-crossing relays, which can be critical when regulating power via phase control or during fast operating cycles.

Main application areas include:

• Heating systems: Control of heating elements (heaters), where rapid response enables precise temperature maintenance.
• Industrial lighting: Management of large lighting loads without the risk of contact arcing.
• Drives and motors: Control of single-phase motors (taking into account inrush current characteristics).
• Building automation: Integration with BMS systems requiring fast response to sensor signals.

It is worth noting that the modular version facilitates installation and replacement in case of failure, while the dedicated heatsink ensures stable operation even under continuous loads close to the rated value.

Operating Conditions and Construction Details

The device operates on a control voltage of 24 V DC (with an operating range of 4–32 V), providing flexibility in connecting to various signal sources. The rated current for resistive loads (AC-1) reaches 30 A, whereas for inductive loads of type AC-3, this value drops to 10.8 A – this should be considered when designing circuits for motors or transformers. The device supports a single-phase AC circuit with a voltage from 48 to 480 V.

The lack of need for additional fans or large external heatsinks simplifies control cabinet design. Thanks to this solution, engineers can rely on predictable system performance even under the challenging environmental conditions typical of production halls or mechanical workshops. The robust housing construction ensures high immunity to electromagnetic interference, while the immediate response to the control signal eliminates the time delays typical of other SSR solutions.