Finder 77.D3.9.024.8671 – 77 Series Modular solid state relays

Why Choose the Finder 77.D3.9.024.8671 Three-Phase Solid State Relay?

The Finder 77.D3.9.024.8671 is a high-current 60 A three-phase solid state relay (SSR) designed for contactless switching of industrial AC electrical loads. Part of the Finder Series 77, this relay provides electronic switching for applications such as industrial heating, machinery control and automated production equipment.

Featuring a 600 V AC rated output voltage and a 24–660 V AC switching range, the Finder 77.D3.9.024.8671 incorporates three normally open semiconductor outputs (3 NO / 3PST-NO). Its 60 A rated current makes it suitable for demanding three-phase applications when correctly installed with suitable thermal management and protective equipment.

The relay operates from a 4–32 V DC control input and features random turn-on switching, also described as instantaneous switching. Its hockey puck-style construction, screw terminals and panel or heat sink mounting arrangement support integration into professional industrial control systems.

Key Advantages

• Three-phase switching: Three normally open semiconductor outputs provide coordinated switching of three-phase AC loads.
• 60 A rated output current: Suitable for higher-current industrial applications with appropriate heat sinking.
• 24–660 V AC switching range: Supports a broad range of industrial AC operating voltages.
• 4–32 V DC control input: Compatible with appropriately rated electronic controllers and PLC outputs.
• Random turn-on switching: Provides instantaneous semiconductor switching rather than waiting for the next voltage zero crossing.
• Silent operation: No mechanical contact movement or audible contactor operation.
• Contact bounce-free switching: Eliminates the mechanical bounce associated with conventional electromechanical contacts.
• High electrical endurance: Semiconductor switching avoids mechanical contact wear.
• 700 A maximum peak current for 10 ms: Provides short-duration surge capability within specified operating limits.
• Hockey puck construction: Designed for installation on a suitable mounting surface or heat sink.
• Contactor-style terminal arrangement: Facilitates organised control and load wiring.
• IP20 protection: Suitable for installation within appropriately designed electrical enclosures.

Key Features

• Finder Series 77 industrial solid state relay.
• Type 77.D3 three-phase configuration.
• Three normally open electronic outputs.
• 3PST-NO output arrangement.
• 60 A rated output current.
• 600 V AC rated output voltage.
• 24–660 V AC switching voltage range.
• 4–32 V DC control voltage range.
• Random or instantaneous turn-on switching.
• 47–400 Hz operating frequency range.
• 1600 V repetitive peak OFF-state voltage.
• 700 A maximum peak current for 10 ms.
• 12 A AC-53 rated load current.
• 10 mA typical OFF-state leakage current at 600 V AC.
• 1.6 V maximum ON-state voltage drop at rated current and 25 °C.
• Contactless, silent semiconductor switching.
• Hockey puck-style enclosure.
• Panel or heat sink mounting.
• Screw-type terminals.
• IP20 degree of protection.

High-Current Three-Phase Switching for Industrial Automation

The Finder 77.D3.9.024.8671 is designed to switch three-phase AC loads electronically, avoiding the mechanical contacts used in conventional three-pole contactors. Its three normally open semiconductor outputs allow the relay to control all three phases of a compatible load.

The random turn-on switching characteristic allows the semiconductor outputs to activate when a valid control signal is applied, without deliberately delaying turn-on until an AC voltage zero crossing. This characteristic distinguishes the model from zero-crossing solid state relays and should be considered when selecting a relay for a particular load.

With a 600 V AC rated output and a switching range extending to 660 V AC, the relay can be used in appropriately designed industrial AC systems. Its 47–400 Hz operating frequency range also supports applications operating outside conventional 50/60 Hz mains frequency, provided all relevant load specifications are met.

The 60 A output rating is subject to adequate heat dissipation. As semiconductor devices generate heat during conduction, the relay must be mounted using suitable thermal coupling and heat sinking. The permissible load current depends on ambient temperature, heat sink performance, installation arrangement and duty cycle.

For inductive or motor-related applications, the applicable utilisation rating must be considered separately from the general output current rating. The Series 77.D3 has a specified 12 A AC-53 load rating, demonstrating why the full 60 A figure should not be applied indiscriminately to every type of load.

The relay offers silent switching and avoids contact bounce, making it useful where frequent operation or reduced mechanical maintenance is desirable. However, it does not provide mechanical contact separation and may allow leakage current when switched off. A separate isolating device and appropriately rated protective equipment must be included where required.

Typical Applications

• Three-phase industrial electric heating systems.
• Industrial ovens and heating machinery.
• Three-phase resistive load switching.
• Industrial process heating control.
• Manufacturing and production equipment.
• Automated machinery and production lines.
• PLC-controlled three-phase load switching.
• Industrial temperature control systems.
• Electrical control panels and machine cabinets.
• Industrial automation requiring random turn-on switching.
• Compatible three-phase inductive loads within the applicable utilisation ratings.
• OEM industrial machinery and electrical assemblies.