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Series: 777

Littelfuse 777 Current & Voltage Monitor Provides Exceptional Motor Protection
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The 777 unit is a fully-programmable, electronic overload relay designed to protect any motor drawing 2-800 full load A (external CTs are required above 90 A). The 777 (family of products) is used for 3-phase, 200-480 V ac applications, with several specialized units for other voltage ranges and unique applications. Common applications include conveyor systems, HVAC equipment, saws and grinders, fan motors, and almost any pumping application. Some unique applications include use with a Subtrol* equipped Franklin submersible motor to detect high motor temperatures and applications where a fast linear trip is required.

All of the overload relays provide unsurpassed protection by combining overload, voltage, phase loss and reversal, voltage and current unbalance, power monitoring, and underload based on current - all in one package. For standalone applications, the units incorporate a 3-digit LED display that is used for programming, providing real-time operational information, and displaying diagnostic codes to aid in troubleshooting a fault condition. The units also feature a communications network port that can be used with communication modules listed in the 777 accessories section to form a Modbus, DeviceNet*, Profibus, or Ethernet network. Up to 99 units can be remotely monitored and controlled from a PC, PLC, or SCADA system, and data logging through a PC with the optional Solutions software. This capability allows for a simple, cost-effective way to meet new requirements for arc-flash safety.

*Subtrol and DeviceNet are trademarks of their respective owners.

  • Built-in display
  • Programmable voltage and current settings
  • 3 selectable restart options
  • 3 programmable restart delay timers
  • Remote display compatibility
  • Flexible reset
  • Network communications capability
  • Visual indication for programming, viewing real-time voltage or current, and last fault code
  • Allows usage on wide range of systems
  • Choose from automatic, semi-automatic, or manual to best meet individual application needs
  • Program separate restart delay time for rapid cycle protection, motor cool down, and dry-well recovery
  • Aids compliance with arc flash safety regulations and increases safety by displaying real-time data remotely, which eliminates need to open a cabinet
  • Reset can be done through a push button on the relay or remotely with optional 777-MRSW or OL-Reset remote reset kit
  • Compatible with Modbus, DeviceNet*, Profibus, or Ethernet using optional communications module

777 Parts

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777 Applications

Highlights Section

  • Conveyor systems
  • HVAC equipment
  • Saws and grinders
  • Fan motors

Series: 777 Resources