Finder 77.C2.9.024.8671 – 77 Series Modular solid state relays

Why Choose the Finder 77.C2.9.024.8671 Solid State Relay?

The Finder 77.C2.9.024.8671 is a high-performance 50 A dual-channel solid state relay (SSR) designed for fast, silent and reliable switching of AC electrical loads. Part of the Finder 77 Series, this industrial semiconductor relay features two independently controlled output channels, making it an excellent choice for industrial heating, motor control, electrical automation and machinery applications.

Featuring a 24–660 V AC load switching range and 4–32 V DC control inputs, the Finder 77.C2.9.024.8671 enables low-power electronic control signals to switch high-power AC circuits. Its random turn-on switching technology provides rapid output activation without waiting for the AC waveform to cross zero, making it particularly suitable for applications requiring precise switching control and fast response times.

The relay uses a robust hockey puck-style housing with screw terminals, protective folding terminal covers and a contactor-style terminal arrangement. Designed for mounting directly onto a suitable heatsink or metal control cabinet mounting surface, it provides a compact alternative to conventional electromagnetic contactors where silent operation, high switching frequency and freedom from mechanical contact wear are important.

Key Advantages

• Two independent solid state switching channels provide flexible control of two AC circuits.
• 50 A rated load current per channel, subject to appropriate heatsinking and thermal conditions.
• 24–660 V AC switching range for industrial electrical loads.
• 4–32 V DC control input range for integration with compatible electronic controllers.
• Random turn-on switching enables fast activation without waiting for a voltage zero crossing.
• Silent semiconductor switching eliminates the mechanical clicking associated with conventional contactors.
• No mechanical switching contacts means no contact bounce or mechanical contact wear.
• High switching endurance makes the relay suitable for frequent switching applications.
• Independent control inputs allow separate operation of the two output channels.
• Hockey puck-style construction provides a compact and robust industrial switching solution.
• Folding screw terminal covers help protect the connection points.
• Panel or heatsink mounting supports effective thermal management in industrial enclosures.
• IP20 protection rating for installation within appropriately protected equipment.
• Suitable for industrial heater control, motor switching and automated machinery.

Key Features

• Finder 77 Series industrial solid state relay.
• Type 77.C2 dual-channel semiconductor switching device.
• Two independent normally open equivalent output channels.
• 2 NO / DPST-NO equivalent output configuration.
• 50 A rated output current per channel.
• 600 V AC nominal output voltage class.
• 24–660 V AC operating load voltage range.
• 4–32 V DC input control voltage range.
• Random turn-on switching mode.
• Two independent DC control inputs.
• 47–400 Hz load operating frequency range.
• 500 A maximum non-repetitive peak current for 10 ms, subject to the manufacturer's specified conditions.
• Silent, spark-free and contact bounce-free operation.
• Hockey puck-style industrial housing.
• Screw terminals with plate clamp connections.
• Contactor-style terminal arrangement with inputs and outputs on adjacent sides.
• Folding protective terminal covers.
• Panel or heatsink mounting.
• IP20 protection rating.
• Operating ambient temperature range of −30 to +80 °C, subject to output current derating.

Reliable Dual-Channel Solid State Switching for Industrial Automation

The Finder 77.C2.9.024.8671 uses semiconductor switching technology instead of mechanical contacts to control AC electrical loads. When a compatible DC control signal is applied to an input, the corresponding output channel conducts, allowing current to flow through the connected load. Removing the control signal causes the channel to stop conducting according to the electrical characteristics of the AC circuit.

Unlike a conventional electromagnetic contactor, the relay has no moving switching contacts. This eliminates mechanical contact bounce and audible switching noise, making the device particularly suitable for machinery and automation systems where frequent switching would otherwise increase mechanical wear.

A major advantage of this model is its dual-channel construction. The relay provides two independently controlled AC outputs, each with its own low-power DC control input. This enables a single compact device to switch two separate circuits or provide two-phase switching in a suitably designed industrial electrical installation.

The 4–32 V DC control voltage range supports integration with compatible PLC transistor outputs, industrial electronic controllers and other suitably rated DC switching devices. Input current requirements and output compatibility must be checked when connecting the relay to a PLC or other automation equipment.

The random turn-on switching function enables the semiconductor output to begin conducting when the input signal is applied, rather than deliberately waiting for the next AC voltage zero crossing. This makes the relay useful in applications where fast response and precise timing are important, including selected heater control and industrial motor switching systems.

Random turn-on operation should not be confused with zero-cross switching. Zero-cross SSRs deliberately delay turn-on until the AC voltage approaches zero, whereas this model is designed for random or instantaneous turn-on. The most appropriate switching method depends on the electrical load, control strategy and electromagnetic compatibility requirements.

With a 50 A rated current per output channel and a 24–660 V AC operating load range, the Finder 77.C2.9.024.8671 can control appropriately rated industrial electrical loads. The continuous current capability depends on the operating temperature, heatsink thermal resistance, installation conditions and the current carried by both channels.

Effective heatsinking is essential. Solid state relays generate heat while conducting, and inadequate thermal management can significantly reduce their permissible load current or cause device failure. Finder provides current-versus-temperature derating information for this model, including reference conditions using a 0.45 K/W heatsink. The final heatsink selection should be based on the actual load and enclosure conditions.

The relay also has an off-state leakage current, which is normal for semiconductor switching devices. Unlike a mechanically opened contact, a solid state output should not be treated as providing complete electrical isolation for maintenance. Suitable isolation devices, circuit protection and load-specific protective arrangements must be included in the electrical design.

Typical Applications

• Industrial electric heater control systems.
• Two-channel resistive load switching.
• Industrial ovens and heating equipment.
• Temperature control panels and process heating machinery.
• Industrial motor switching within the manufacturer's applicable ratings.
• PLC-controlled electrical switching circuits.
• High-frequency industrial switching applications.
• Manufacturing and automated production equipment.
• Packaging and processing machinery.
• Industrial control cabinets and electrical panels.
• Semiconductor-based switching systems requiring silent operation.
• Two-phase AC load control applications.
• OEM machinery and industrial automation equipment.
• Applications requiring independently controlled AC output channels.