77C-KW Series - Single-Phase Current & Voltage Monitor Series - Littelfuse 77C-KW Current & Voltage Monitor Provides Exceptional Protection

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The 77C-KW single-phase relay is part of the 777/77C product family. The 77C-KW, 77C-KW/HP and 77C-LR-KW/HP are fully programmable pump protection relays that monitor for high or low voltage and overload and underload conditions based on power. These overload relays are designed to protect any motor drawing 2-800 full load A (external CTs are required above 90 A). The 777-HVR-SP and 77C are for single-phase 100-240 V ac applications.

All of the overload relays provide unsurpassed protection by combining overload, underload, and voltage in one unit. 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 network communications 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.

The underpower trip feature is desirable anytime the current vs. load characteristic is non-linear or has little change. In general terms, smaller motors and slow-speed motors have little change in current over the normal load range. Larger motors that are running light loads will also show small current changes over the operating load range. Common uses include pumping applications where motors run slower than 3400 rpm and usually have small current versus load changes, such as slow speed mixers or agitator motors up to 50 hp, mag-drives, or can pumps.

Note: The Littelfuse PumpSaver® relay provides the high sensitivity of a power monitor to protect pump motors from dry run and dead head conditions.

*Compatible with Modbus using optional communications module (RS485MS-2W)


  • Underload protection
  • Built-in display
  • 15 programmable criteria settings
  • Last fault memory
  • Remote display compatibility
  • Flexible reset

Access specifications, certifications, check availability and order parts below

Catalog #Weight (lbs/g)StockSamplesCompare
77C-KW/HP0 KgCheckOrder
77C-LR-KW/HP0 KgCheckOrder
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