Littelfuse, Inc. Datasheets for Protective Relays and Monitoring Relays

Protective relays and monitoring relays detect or monitor for abnormal power system conditions.
Protective Relays and Monitoring Relays: Learn more

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Product Name Notes
Obsolete: 08/11/2020 The FlexMod electronic voltage sensing relay & timer monitors both battery voltage and ignition status. shutting down non-critical loads when the cutoff voltage is reached. or at the...
Operates on AC resistance grounded systems and DC grounded systems.The EL731 is a microprocessor-based AC/DC Sensitive Earth-Leakage Relay that offers complete coverage for all frequencies from 0-6,000 Hz. Two CT’s...
Specialized OptoMOS® single-pole, normally open Solid State Relays (1-Form-A) with an integrated active current limit and thermal shutdown feature that can replace electromechanical relays while enhancing the robustness of wireline...
The 102A is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-400VAC, 50/60Hz motors regardless of size. The product provides a user selectable nominal voltage setpoint and the voltage monitor...
The 102A is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-600VAC, 50/60Hz motors regardless of size. The product provides a user selectable nominal voltage setpoint and the voltage monitor...
The 201-xxx-DPDT is an 11-pin octal base plug-in voltage monitor designed to protect 3-phase motors regardless of size. The 201-100-DPDT is used on 95-120VAC, 50/60Hz motors and the 201-200-DPDT is...
The 201-xxx-SP is an 8-pin octal-base, plug-in voltage monitor designed to protect single-phase motors regardless of size. The 201-100-SP is used on 95-120VAC, 50/60Hz motors to prevent damage caused by...
The 201-xxx-SP-DPDT is an 8-pin octal-base, plug-in voltage monitor designed to protect single-phase motors regardless of size. The 201-100-SP-DPDT is used on 95-120VAC, 50/60Hz motors to prevent damage caused by...
The 201A is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-480VAC, 50/60Hz motors regardless of size. The product provides a user selectable nominal voltage setpoint and the voltage monitor...
The 201A-AU is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-480VAC, 50/60Hz motors regardless of size. Has user adjustable 1-30 second trip delay, manual or 1-500 second restart delay,...
The 202 series is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-600VAC, 50/60Hz motors regardless of size. The 202-RP monitors the phase rotation of 3-phase systems and trips on...
The 202-200-SP voltage monitor is designed to protect single-phase motors regardless of size. It can be used with 190V-240VAC, 50/60Hz motors to prevent damage caused by incoming power problems. A...
The 233P is a single-phase pump monitor designed to protect single-phase pumps from dry-well, dead-head, jammed impeller, rapid cycle, overvoltage and undervoltage conditions. The 233P protects 230 volt, 2 or...
The 250A is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-480VAC, 50*/60Hz motors regardless of size from low and high voltage, unbalance/single-pha se, and reverse-phase. The product provides a...
The 250A is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-480VAC, 50/60Hz motors regardless of size from low and high voltage, unbalance/single-pha se, and reverse-phase. The product provides a...
The 350 is a heavy-duty voltage monitor. This product should be used when high current relays or dual contacts are required, or 480V controls are used. Since the 350 uses...
The 355 is a 3-phase voltage monitor with adjustable trip and restart delay, adjustable voltage unbalance and multiple diagnostic lights. It is perfect for heavy-duty applications that need both protection...
The 455 Series are 3-phase voltage monitors that combine load and line side monitoring to offer complete protection. Monitoring the load side will alert the user of contactor failure or...
The 460 is a 3-phase voltage monitor that protects 190-480VAC or 475-600V, 50/60Hz motors regardless of size. The product provides a user selectable nominal voltage set point and the voltage...
The 460-100-SP is used on 95-120VAC, 50*/60Hz single-phase motors and the 190-240VAC, 50*/60Hz single-phase motors to protect them from damaging high and low voltage conditions. An adjustment knob allows the...
The 50R single-phase voltage monitor has a voltage-sensing circuit which constantly monitors the single-phase power for a low voltage condition. Single-phase motors on fans, compressors, air conditioners, heat pumps, well...
The 50R-400-ALT alternating relays are used to alternate between two loads, most commonly in duplex pumping and compressor applications to balance the runtime of both loads. When used in single...
The 601-CS-D-P1 3-phase power monitor is a fully programmable electronic power monitor designed to monitor 3-phase systems. The 601-CS-D-P1 has a single relay that can be configured as a general...
The 777 is a fully programmable electronic overload relay designed to protect any motor drawing 2-800 full load amps (external CTs are required above 90 amps). The 777 (family of...
The 777 Manual Remote Reset Kit allows the 777 line of motor and pump protection products to be manually reset without opening the panel door. Simply connect the 9-pin adapter...
The 777-AccuPower is a fully-programmable 3-phase motor and pump protection relay. It allows motor hp rating, full load amps, efficiency and power factor to be entered and will accurately calculate...
The 777-KW/HP-P2 Series has the overload, voltage, phase loss and reversal, voltage and current unbalance, current and power monitoring*, and underload trip based on power in one package. The underpower...
The 777/ 77C is a fully programmable electronic overload relay designed to protect any motor drawing 2-800 full load amps (external CTs are required above 90 amps). The 777-HVR-SP and...
The AF0100 Series arc-flash relay is a cost-effective solution that reduces arc-fault damage by detecting the light from an arc flash and rapidly tripping. Two remote light sensors can be...
The AF0500 is a microprocessor-based arc-flash protection relay that limits arc-fault damage by detecting the light from an arc flash and rapidly tripping the feeder breaker. The unit is well...
The ALT alternating relays are used to alternate between two loads. The ALT is commonly used in duplex pumping applications to balance the runtime of both pumps. The ALT-S is...
The ALT-xxx-1-SW and ALT-xxx-3-SW are used to alternate between two loads and are commonly used in duplex pump-up and pump-down applications to balance the runtime of both pumps. The ALT-xxx-1-SW...
The ARP Series is used in systems where equal run time for two motors is desirable. The selector switch allows selection of alternation of either load for continuous operation. LED’s...
The ASQU and ASTU Series of 17.5 mm, knob adjustable, universal solid-state timers offer multiple functions, voltages, and time delay ranges. Choose one of 5 functions and 4 time delay...
The CP-5 is an undercurrent monitor designed to monitor one leg of a 3-phase system. It is commonly used as a tower monitor on center pivot irrigation systems to detect...
The CT Series combines a delay-on-make and delay-on-break time delay into one unit and may be used to control fan delays in heating and/or cooling equipment. The CT includes bypass...
The D0920 Arc Detection Unit is a high-speed arc-detection device for electrical power-distribution systems. The D0920 supports up to three point sensors (A0220) mounted in a switchboard, and requires a...
The DLMU Series is a universal voltage, 3-phase voltage monitor. It continuously measures the voltage of each of the three phases with microcontroller accuracy and compares the value to preset...
The DSQU and DSTU Series of 17.5 mm, switch adjustable, universal solid-state timers offer multiple functions, voltages, and time delay ranges. Choose one of 5 functions and 4 time delay...
The EL3100 is a self-powered ground-fault and phasevoltage indication system for 3-phase systems. The EL3100 meets the National Electrical Code (NEC) and the Canadian Electrical Code (CEC) requirements for ground...
The EL731 is a microprocessor-based AC/DC Sensitive Earth-Leakage Relay that offers complete coverage for all frequencies from 0-6,000 Hz. Two CT’s are required for the entire frequency range, or one...
The ERD Series is a combination of digital electronics and an electromechanical relay. DPDT relay output for relay logic circuits, and isolation of input to output voltages. For applications, such...
The ERD3425A is a combination of digital electronics and a reliable electromechanical relay. DPDT relay output for relay logic circuits, and isolation of input to output voltages. Cost effective for...
The ERDM Series are a combination of digital electronics and a reliable electromechanical relay. These devices offer a DPDT relay output for relay logic circuits, and isolation of input to...
The FlexMod electronic voltage sensing relay & timer monitors both battery voltage and ignition status. shutting down non-critical loads when the cutoff voltage is reached, or at the set time...
The Littelfuse 111-Insider-P single-phase products fit inside 1/3 and 1/2 115V control boxes and are designed to protect single-phase pumps from dry-well, dead-head, jammed impeller, rapid-cycle, overvoltage, and undervoltage conditions.
The Littelfuse 231-Insider-P fits inside 1/3, 1/2, 3/4, and 1 hp, 230V control boxes and are designed to protect single-phase pumps from dry-well, dead-head, jammed impeller, rapid-cycle, overvoltage, and undervoltage...
The Littelfuse 235P is designed to protect 5-15 hp, 230V, single-phase pumps from dry-well, dead-head, jammed impeller and overvoltage and undervoltage conditions. A calibration adjustment allows the 235P to be...
The Littelfuse Models 111P (115 volt, ¹?³ to 1hp); 233P-1.5 (230 volt, ¹?³ to 1.5hp); and 233P (230 volt, ¹?³ to 3hp) protect pumps from dry-well, dead-head, jammed impeller, overvoltage/...
The Model 232-Insider single-phase PumpSaver® fits inside 1/3, 1/2, 3/4, and 1hp, 230V Grundfos control boxes. The PumpSaver® Model 232-Insider is a current monitor designed to protect single-phase pumps from...
The Model 601 is a fully-programmable voltage monitor designed to protect 3-phase motors. It can be used as a stand-alone product or networked with an RM-1000, RM-2000, PLC, computer or...
The OptoMOS® line of solid state relays uses discrete semiconductor components and the patented OptoMOS® architecture to deliver fast, reliable, bounce-free switching in a compact design. From one of the...
The OptoMOS® line of solid-state relays uses discrete semiconductor components and the patented OptoMOS® architecture to deliver fast, reliable, bounce-free switching in a compact design. From one of the world's...
The PumpSaver® Model 234-P protects singlephase pumps from dry-well, dead-head, rapid-cycle, jammed-impeller, and over/undervoltage conditions. Typical applications include residential waterwells, commercial waterwells, irrigation wells, and golf course and other sprinkler...

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