Finder 77.H1.9.024.8650 – 77 Series Modular solid state relays

Why Choose the Finder 77.H1.9.024.8650 Solid State Relay?

The Finder 77.H1.9.024.8650 is a high-current 125 A single-phase solid state relay (SSR) designed for reliable, silent and contactless switching of industrial AC loads. Part of the Finder Series 77, this hockey puck-style relay combines semiconductor switching technology with zero-crossing operation, making it particularly suitable for electric heating, industrial automation and machinery control applications.

Featuring a 24–660 V AC switching voltage range and a 600 V AC rated output voltage, the Finder 77.H1.9.024.8650 provides a rated output current of 125 A when installed with suitable thermal management. Its 24 V DC nominal control input, with an operating range of 3–32 V DC, supports integration with compatible PLC outputs, electronic controllers and industrial control equipment.

The relay incorporates one normally open semiconductor output (1 NO / SPST-NO) and uses zero-crossing switching to activate the connected load near the AC voltage waveform's zero crossing. Its compact 45 × 59 × 29.4 mm housing, screw terminals and folding protective covers provide a practical solution for professional industrial electrical installations.

Key Advantages

• 125 A rated output current: Provides substantial switching capacity for compatible industrial AC loads.
• 24–660 V AC switching range: Supports a wide range of industrial AC operating voltages.
• 24 V DC nominal control input: Suitable for compatible low-voltage automation and control circuits.
• 3–32 V DC control range: Offers flexibility when interfacing with electronic control equipment.
• Zero-crossing switching: Helps reduce switching transients and electromagnetic interference in suitable AC applications.
• 2250 A peak surge current capability: Accommodates short-duration current peaks of up to 2250 A for 10 ms within specified limits.
• Silent semiconductor operation: Eliminates the mechanical clicking associated with electromechanical relays.
• Contact bounce-free switching: Avoids mechanical contact movement and associated wear.
• High switching endurance: Well suited to applications requiring frequent switching cycles.
• 4 kV input-to-output dielectric withstand: Provides electrical separation between the control and load circuits.
• LED status indication: Allows convenient visual monitoring of the control input.
• Panel or heat sink mounting: Supports thermal management in demanding industrial installations.
• Compact hockey puck housing: Provides a robust mounting arrangement for control cabinets and machinery panels.

Key Features

• Finder Series 77 industrial solid state relay.
• Type 77.H1 single-phase configuration.
• One normally open semiconductor output.
• SPST-NO switching arrangement.
• 125 A rated output current.
• 600 V AC rated output voltage.
• 24–660 V AC switching voltage range.
• 24 V DC nominal control voltage.
• 3–32 V DC control input operating range.
• Zero-crossing turn-on operation.
• 47–400 Hz operating frequency range.
• 2250 A maximum peak current for 10 ms.
• 1600 V repetitive peak OFF-state voltage.
• 100 mA minimum switching current at 250 V AC.
• 0.1 mA OFF-state leakage current at rated voltage.
• 4 kV input-to-output dielectric withstand.
• LED input status indication.
• Silent and contact bounce-free switching.
• High electrical endurance without mechanical contact wear.
• Hockey puck-style housing with folding protective screw covers.
• Panel or heat sink mounting.
• Screw-type electrical terminals.
• IP20 protection rating.

High-Current Zero-Crossing Switching for Industrial AC Loads

The Finder 77.H1.9.024.8650 uses semiconductor switching technology to control AC electrical loads without the moving contacts found in conventional electromechanical relays. When a suitable DC control signal is applied, the electronic output switches on and supplies the connected AC load.

Its zero-crossing turn-on characteristic initiates conduction close to the point where the AC voltage waveform crosses zero. This can reduce switching disturbances and electromagnetic interference in suitable resistive loads, particularly industrial electric heating equipment.

The relay's 125 A rated output current provides substantial capacity for high-power AC load switching. Its 24–660 V AC switching range allows integration into a variety of industrial electrical systems, provided the connected load and supply remain within the specified operating limits.

The device also offers a 2250 A maximum peak current rating for 10 ms, providing short-duration surge capability under the manufacturer's specified conditions. This peak rating must not be confused with the permissible continuous output current.

With an operating frequency range of 47–400 Hz, the relay can support compatible AC applications operating outside conventional 50/60 Hz mains frequencies. Suitability must be assessed against the complete electrical and thermal requirements of the installation.

The 3–32 V DC control input enables the relay to be operated by compatible industrial controllers, including appropriately rated PLC outputs. Its LED indicator provides a convenient visual indication of the control input state during commissioning and maintenance.

Thermal Management and Installation Requirements

The Finder 77.H1.9.024.8650 is designed for mounting on a suitable panel surface or dedicated heat sink. Because semiconductor switching devices generate heat during conduction, correct thermal management is essential when operating at high load currents.

At its rated current, the relay has a specified 150 W power dissipation. The heat sink, thermal interface, mounting arrangement, ambient temperature and enclosure ventilation must therefore be considered when designing the installation.

The full 125 A output rating must not be assumed without verifying the manufacturer's thermal derating requirements. Actual permissible continuous current depends on the operating conditions and the heat sink's ability to dissipate the generated heat.

The relay provides 4 kV input-to-output dielectric withstand, supporting electrical separation between the control circuit and switched load. Its hockey puck-style enclosure features screw terminals with folding protective covers and a relay-style arrangement with control and load connections on opposite sides.

Unlike a mechanical isolator, a solid state relay may permit a small leakage current when switched off. The Finder 77.H1.9.024.8650 therefore must not be relied upon for safe electrical isolation. Appropriate overcurrent protection and a separate means of disconnection must be provided where required.

Typical Applications

• Industrial electric heating systems.
• High-current resistive heating element control.
• Industrial ovens and furnaces.
• Temperature-controlled manufacturing processes.
• Industrial machinery and production equipment.
• High-power AC load switching.
• Commercial and industrial lighting control.
• Compatible AC solenoid and contactor driver circuits.
• PLC-controlled industrial load switching.
• Industrial process automation.
• Electrical control cabinets and machinery panels.
• Equipment requiring frequent and silent switching.
• OEM industrial electrical and automation assemblies.