Littelfuse 77C - The 77C single-phase relay provides motor protection with input voltage from 100–240 V ac and motor full load ampere range as follows: 2–25 A (looped conductors required); 26–90 A (direct); 91–800 A (external CTs required).
Littelfuse

77C

Alternate Item Number: 77C

UPC: 079458991192

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Overview

The Littelfuse 77C Series electronic overload relay (SKU: 77C) provides comprehensive single-phase motor protection for applications ranging from 2A to 800A Full Load Amps (FLA). Operating on a 100-240V AC input, this programmable relay safeguards motors against critical conditions including overload, underload, and voltage fluctuations, thereby extending equipment lifespan and minimizing unplanned industrial downtime. Its versatility is demonstrated through three distinct current measurement methods: looped conductors for 2-25A motors, direct connections for 26-90A motors, and external current transformers (CTs) for 91-800A motors. This adaptability ensures compatibility across a broad spectrum of industrial applications such as conveyor systems, HVAC units, industrial saws and grinders, fan motors, and various pumping systems. Key operational features include a built-in 3-digit LED display for real-time monitoring of voltage and current, alongside diagnostic fault codes for efficient troubleshooting. The 77C offers programmable voltage and current settings, along with three selectable restart options (automatic, semi-automatic, manual) and three configurable restart delay timers. These timers are crucial for applications requiring precise cycle control, motor cooldown periods, or dry-well recovery protocols. Enhanced safety and operational efficiency are achieved through remote display compatibility, which allows for real-time data and fault history viewing without opening control cabinets, supporting arc flash compliance. Resetting the relay can be performed locally via a pushbutton or remotely using optional 777-MRSW/OL-RESET kits. For advanced system integration, network communication is supported via optional modules (Modbus, DeviceNet™, Profibus, Ethernet), enabling remote monitoring and control of up to 99 units from PC, PLC, or SCADA systems. Data logging capabilities are available through optional Solutions software. The 77C provides 480VA @ 240VAC output with SPDT relay contacts. For high-voltage systems (340-480V AC), the 777-HVR-SP model is recommended.
  • Comprehensive single-phase motor protection for 2-800A FLA.
  • Overload, underload, and voltage monitoring with programmable settings.
  • Flexible current measurement: looped conductors, direct, or external CTs.
  • Built-in 3-digit LED display for real-time data and fault codes.
  • Supports remote display, flexible reset options, and network communication.

Specifications

Connection Type
looped conductors (2–25 A), direct (26–90 A), external CTs (91–800 A)
Current Rating
2-800 A
Current Rating
2–800 A
Series
77C
Voltage Rating
100–240 V ac
Voltage Rating
100-240 V AC
Package Dimensions (L x W x H)
5.05 IN x 3.85 IN x 3.05 IN
Package Dimensions (L x W x H)
128.3 mm x 97.8 mm x 77.5 mm
The 777-575-P2 three-phase current and voltage monitor provides motor protection with input voltage from 500–600 V ac and motor full load ampere range as follows: 2–20 A (looped conductors required); 20–90 A (direct); 90–800 A (external CTs required).

777-575-P2

The 777-575-P2 three-phase current and voltage monitor provides motor protection with input voltage from 500–600 V ac and motor full load ampere range as follows: 2–20 A (looped conductors required); 20–90 A (direct); 90–800 A (external CTs required).
The 777-HVR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 340–480 V ac and full load ampere range as follows: 2–20 A (looped conductors required); 20–90 A (direct); 90–800 A (external CTs required).

777-HVR-P2

The 777-HVR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 340–480 V ac and full load ampere range as follows: 2–20 A (looped conductors required); 20–90 A (direct); 90–800 A (external CTs required).
The 777-KW/HP-P2 three-phase current and voltage monitor provides protection with input voltage from 200–480 V ac and motor full load ampere range as follows: 2–20 A (looped conductors required); 20–90 A direct; 90–800 A (external CTs required).

777-KW/HP-P2

The 777-KW/HP-P2 three-phase current and voltage monitor provides protection with input voltage from 200–480 V ac and motor full load ampere range as follows: 2–20 A (looped conductors required); 20–90 A direct; 90–800 A (external CTs required).
The 777-P2 three-phase current and voltage monitor provides motor protection with input voltage from 200–480 V ac and motor full load ampere range as follows: 2–20 A (looped conductors required): 20–90 A (direct); 90–800 A (external CTs required).

777-P2

The 777-P2 three-phase current and voltage monitor provides motor protection with input voltage from 200–480 V ac and motor full load ampere range as follows: 2–20 A (looped conductors required): 20–90 A (direct); 90–800 A (external CTs required).
The 777-LR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 200–480 V ac and motor full load ampere range of 1–9 A (direct); 10–800 A (external CTs required).

777-LR-P2

The 777-LR-P2 three-phase current and voltage monitor provides motor protection with input voltage from 200–480 V ac and motor full load ampere range of 1–9 A (direct); 10–800 A (external CTs required).
777-LR-KW/HP-P2 three-phase current and voltage monitor provides protection with input voltage from 200–480 V ac and motor full load ampere range as follows: 1–2 A (looped conductors required); 2.1–9.0 A direct; 10–800 A (external CTs required).

777-LR-KW/HP-P2

777-LR-KW/HP-P2 three-phase current and voltage monitor provides protection with input voltage from 200–480 V ac and motor full load ampere range as follows: 1–2 A (looped conductors required); 2.1–9.0 A direct; 10–800 A (external CTs required).

Frequently Asked Questions about Littelfuse

What certifications and standards do Littelfuse products comply with?

Littelfuse products are certified to multiple international standards, including UL (Underwriters Laboratories), CSA (Canadian Standards Association), CCC (China Compulsory Certification), and EAC (Eurasian Conformity). Customers can verify specific product certifications by consulting individual product datasheets on Littelfuse.com, which provide comprehensive details about standards compliance for each component.

What industries and applications are Littelfuse products used for?

Littelfuse products are critical for electrical protection and safety across multiple industrial sectors, including manufacturing, automation, power distribution, and electrical control systems. Their comprehensive product portfolio serves industries that require robust electrical protection, including motor and pump applications, solar installations, programmable logic controllers (PLCs), electrical switch panels, and critical infrastructure environments. Key product lines protect against overcurrent, voltage transients, ground faults, and temperature-related electrical risks, ensuring equipment safety and operational reliability.

What technical support does Littelfuse offer?

Littelfuse offers comprehensive technical support through multiple channels. Their Technical Hotline (800-TEC-FUSE) provides direct access to engineers who can help identify issues and recommend solutions. Additionally, Littelfuse offers extensive online Technical Resources at Littelfuse.com, including datasheets, product manuals, whitepapers, application guides, and online design tools. Their experienced product and application engineers also provide step-by-step support from design to installation.

What are the main product lines offered by Littelfuse?

Littelfuse offers comprehensive industrial protection and control product lines, including fuses, fuse holders, protection relays, temperature sensors, and electrical safety components. Their key product categories span surge protective devices, custom OEM products, electrical switch panels, medium voltage fuses, ground-fault protection relays, motor and pump protection devices, and temperature sensors. These products are designed to minimize electrical safety hazards, limit equipment damage, improve productivity, and safeguard personnel from electrical faults.

What are the key features of Littelfuse products?

Littelfuse products feature exceptional circuit protection technologies with key characteristics including UL/IEC safety standard compliance, low internal resistance, and advanced protective capabilities across multiple product lines. Their components provide critical protection for industrial systems, offering features like overcurrent protection, voltage transient suppression, and resettable protection devices with ultra-low resistance and compact designs. Key product lines include fuses, metal oxide varistors (MOVs), TVS diodes, PolySwitch devices, and specialized electronic protection components that enhance system reliability and safety.

What environmental ratings do Littelfuse products have?

Littelfuse products feature comprehensive environmental ratings, including NEMA Type 1, 2, 3, 3R, 4/4X, 12, and 13 certifications, as well as IP65 protection. These ratings ensure superior protection in diverse industrial environments, with an operating temperature range of -40°F to +131°F (-40°C to +55°C). Many products also include UV-stabilized materials and neoprene gaskets for enhanced durability in outdoor and challenging conditions.

What accessories are available for Littelfuse products?

Littelfuse offers several key accessories across their product lines, including fuse holders, voltage monitoring modules, and terminal connectors. Specific accessories include the LPSM003ZXID (indicating) and LPSM003Z (non-indicating) POWR-SAFE Dead Front fuse holders for Class CC and Midget-Style fuses, the VRM6048 voltage monitor accessory module, and female quick connect terminals (P1015 series) in various wire gauge sizes. These accessories are designed to enhance protection, monitoring, and connectivity for Littelfuse electrical components.

What is Littelfuse's warranty policy?

Littelfuse provides comprehensive warranty details on their official website at www.littelfuse.com/warranty. Customers should visit this page to review the specific warranty terms and conditions for their specific product lines. For direct warranty support or questions, customers can contact Littelfuse Technical Support at 1-800-TEC-FUSE or email [email protected].

What communication protocols do Littelfuse products support?

Littelfuse supports a comprehensive range of industrial communication protocols, including PROFIBUS, PROFINET, EtherNet/IP, DeviceNet, Modbus RTU, and CANopen. Our products provide flexible connectivity solutions across multiple industrial automation platforms, enabling seamless integration with various control systems and network architectures.

How are Littelfuse products typically installed?

Littelfuse products are typically installed using specialized mounting hardware like fuse holders, blocks, and panels designed for specific industrial applications. The POWR-SAFE Dead Front holders, for example, provide optimum protection for Class CC and Midget-Style fuses, supporting installations up to 600 VAC/DC. Installation often involves using precision terminals with strain relief, such as 0.25 in. female quick connect terminals, to ensure secure and safe electrical connections in industrial control systems.