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Littelfuse 355-600 - 3PH VltMon/475-600V/VUB,TD,RD/480V rel.. 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 and simple user-friendly diagnostics. Applications include pump panels, commercial HVAC, oil rigs and others. The 355 uses microcontroller technology to monitor incoming voltage and de-energize its output relay if power problems exist. The 355 can protect motors from damage caused by single-phasing, high and low voltage, phase reversal and voltage unbalance. It has four diagnostic LEDs that clearly show overvoltage, undervoltage, voltage unbalance, reverse-phase and normal conditions. Equipped with a 470VA @ 600VAC pilot duty SPDT relay. A high voltage (600V) DPDT relay output option is available with the 400V model.

Littelfuse 355-600 3PH VltMon/475-600V/VUB,TD,RD/480V rel.. The 355 is a 3-phase voltage monitor with…

UPC: 079458989823

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Contact for Pricing

Call +1 (262) 252-1600 (toll-free 877-268-3700) or email [email protected] for pricing and availability.

Overview

The Littelfuse 355-600 (SKU: 355-600) is a microcontroller-based 3-phase voltage monitor designed for heavy-duty industrial applications operating between 475-600VAC. This device actively safeguards motors and critical equipment from damaging power line anomalies, including single-phasing, high/low voltage, phase reversal, and voltage unbalance. Its advanced microcontroller-based sensing circuit continuously monitors incoming 3-phase voltages and de-energizes the output relay when harmful conditions are detected, preventing costly equipment damage and downtime. Key features include adjustable trip and restart delay settings for precise system response control, ensuring compatibility with diverse industrial processes. The 355-600 is equipped with a 470VA @ 600VAC pilot duty SPDT relay for reliable switching operations. Four diagnostic LEDs provide clear visual indication of operating states, including overvoltage, undervoltage, voltage unbalance, reverse-phase, and normal conditions—enabling rapid troubleshooting and maintenance. Ideal for demanding environments such as pump panels, commercial HVAC systems, and oil rigs, the Littelfuse 355-600 delivers robust electrical protection with user-friendly diagnostics. Its compact design and straightforward installation make it a practical solution for protecting 3-phase motors across a wide range of industrial applications. The device operates on 24V DC control power and is engineered for continuous duty in harsh industrial settings.
  • Microcontroller-based 3-phase voltage monitoring for 475-600VAC systems
  • Protects against single-phasing, high/low voltage, phase reversal, and unbalance
  • Adjustable trip and restart delay settings for precise system response
  • 470VA @ 600VAC pilot duty SPDT relay for reliable switching
  • Four diagnostic LEDs for overvoltage, undervoltage, unbalance, reverse-phase, and normal conditions

Specifications

Brand Name
Littelfuse
Operating Temperature
-40 to 158
Operating Temperature, Maximum
158
Operating Temperature, Minimum
-40
Poles
3P
Series
355
Special Features
5YR WARR
Standard
UL
Sub Brand
Symcom
Voltage Rating
475-600 V
3PH Lin-Lod VltMon/475-600V/aj.VUB,TD,RD. 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 impending contactor failure. Line side monitoring will also protect the motor from damaging fault conditions that may be present prior to the motor starting. With other line/load side monitors, the motor must be started before a voltage fault is detected. With the 455, your motor is fully protected at all times. The 455 Series are 3-phase, dual range voltage monitors that protect 190-480VAC, 50/60Hz motors, regardless of their size. It automatically selects between the 200V and 400V rangewhen the user selects the nominal voltage setpoint. Other adjustments include a 2-30 second trip delay, a 2-300 second restart delay (and manual restart) and a voltage unbalance trip point of 2-8percent. The voltage monitor’s circuitry is powered through the line side connections, so there is no need for separate control power, making it easy to install. Equipped with an infrared LED, the 455 Series can communicate to the optional hand-held diagnostic tool, Informer-MS to obtain valuable information such as real-time voltage, voltage unbalance on both line and load sides, motor run hours, last 20 faults, last 32 motor starts, high and low voltage trip points, voltage unbalance trip.

455-575

3PH Lin-Lod VltMon/475-600V/aj.VUB,TD,RD. 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 impending contactor failure. Line side monitoring will also protect the motor from damaging fault conditions that may be present prior to the motor starting. With other line/load side monitors, the motor must be started before a voltage fault is detected. With the 455, your motor is fully protected at all times. The 455 Series are 3-phase, dual range voltage monitors that protect 190-480VAC, 50/60Hz motors, regardless of their size. It automatically selects between the 200V and 400V rangewhen the user selects the nominal voltage setpoint. Other adjustments include a 2-30 second trip delay, a 2-300 second restart delay (and manual restart) and a voltage unbalance trip point of 2-8percent. The voltage monitor’s circuitry is powered through the line side connections, so there is no need for separate control power, making it easy to install. Equipped with an infrared LED, the 455 Series can communicate to the optional hand-held diagnostic tool, Informer-MS to obtain valuable information such as real-time voltage, voltage unbalance on both line and load sides, motor run hours, last 20 faults, last 32 motor starts, high and low voltage trip points, voltage unbalance trip.
CM-PVS.31S THREE-PHASE MON.

1SVR730794R1300

CM-PVS.31S THREE-PHASE MON.
Three Phase Monitor Relay; DIN-Mount; 190-500V; 10A DPDT; Phase Loss; Reversal; Unbalance; Under/Over Voltage

PMDU

Three Phase Monitor Relay; DIN-Mount; 190-500V; 10A DPDT; Phase Loss; Reversal; Unbalance; Under/Over Voltage
Relay 460V 3 Phase Monitor

18883000015

Relay 460V 3 Phase Monitor
520CP/display NC=no Cur when c=0 4 sec. The 520CS and 520CP are fully-programmable, microcontroller-based, current-sensing devices designed to monitor 3-phase pumps. The 520CP is designed to work with motors that have ramp-up times of 4 seconds or less. The 520CS has a programmable motor acceleration time that can be set from 0-50 seconds. Both current monitors protect 3-phase motors from: Overcurrent. Undercurrent. Current Unbalance. Rapid Cycling. Single Phasing. Phase Reversal.

520CP115RX56

520CP/display NC=no Cur when c=0 4 sec. The 520CS and 520CP are fully-programmable, microcontroller-based, current-sensing devices designed to monitor 3-phase pumps. The 520CP is designed to work with motors that have ramp-up times of 4 seconds or less. The 520CS has a programmable motor acceleration time that can be set from 0-50 seconds. Both current monitors protect 3-phase motors from: Overcurrent. Undercurrent. Current Unbalance. Rapid Cycling. Single Phasing. Phase Reversal.
The 777-MV-P2 three-phase current and voltage monitor provides motor protection with input voltage from 100–240 V ac and motor full load ampere range of 10–800 A (external CTs required).

777-MV-P2

The 777-MV-P2 three-phase current and voltage monitor provides motor protection with input voltage from 100–240 V ac and motor full load ampere range of 10–800 A (external CTs required).
3PH VOLT mntr/380-480V/adj.RD/480V Rly. 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 heavy-duty relays, it comes in fixed voltage range models rather than a dual autoranging version like the Model 250. The 350-200 has a 15A general purpose contact. The 350-400 provides a SPDT (Form C) relay rated to switch up to 600V, allowing the use of 480V controls, eliminating the need for a control power transformer to step the voltage down to 120-240V. Several DPDT (two Form C contacts) relay models are also available. The 350 microcontroller-based family of products are low cost yet highly advanced solutions to heavy-duty problems. The 350 includes advanced single LED diagnostics. Five different light patterns distinguish faults and normal operating conditions. Other options such as high voltage trip and adjustable restart delay are available.

350-400-2

3PH VOLT mntr/380-480V/adj.RD/480V Rly. 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 heavy-duty relays, it comes in fixed voltage range models rather than a dual autoranging version like the Model 250. The 350-200 has a 15A general purpose contact. The 350-400 provides a SPDT (Form C) relay rated to switch up to 600V, allowing the use of 480V controls, eliminating the need for a control power transformer to step the voltage down to 120-240V. Several DPDT (two Form C contacts) relay models are also available. The 350 microcontroller-based family of products are low cost yet highly advanced solutions to heavy-duty problems. The 350 includes advanced single LED diagnostics. Five different light patterns distinguish faults and normal operating conditions. Other options such as high voltage trip and adjustable restart delay are available.
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 automatically selects between the 200V and 400V range. A unique microcontroller-based voltage and phase-sensing circuit constantly monitors the 3-phase voltages to detect harmful power line conditions. When a harmful condition is detected, the output relay is deactivated after a specified trip delay. The output relay reactivates after power line conditions return to acceptable levels. The Model 102A includes advanced single LED diagnostics. Five different light patterns distinguish between faults and normal conditions.

102A-9

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 automatically selects between the 200V and 400V range. A unique microcontroller-based voltage and phase-sensing circuit constantly monitors the 3-phase voltages to detect harmful power line conditions. When a harmful condition is detected, the output relay is deactivated after a specified trip delay. The output relay reactivates after power line conditions return to acceptable levels. The Model 102A includes advanced single LED diagnostics. Five different light patterns distinguish between faults and normal conditions.

Frequently Asked Questions

What types of fuses does Littelfuse offer for industrial applications?

Littelfuse offers UL Class fuses, high-speed fuses, medium voltage fuses, 10 x 38 mm fuses, and solar fuses for industrial applications.

What protection do Littelfuse voltage monitors offer?

Voltage monitors provide protection against both supply line and load side faults when the motor is running.

What functions do Littelfuse timers and flashers control?

Timers and flashers delay starting and stopping loads, and control cycling and sequencing of motors, pumps, compressors, heaters, and lighting.

How do Littelfuse arc-flash protection relays enhance safety?

Arc-flash relays detect a developing arc-flash incident and send a trip signal to interrupt power before significant damage occurs.

What types of motor protection does Littelfuse provide?

Littelfuse offers voltage monitors, current monitors, and Bluetooth enhanced overload relays for low and medium voltage motor protection applications.

What do Littelfuse pump controllers protect against?

Pump controllers protect and disable a pump if a hazardous condition arises, with options for single-phase and three-phase applications.

What is the benefit of Littelfuse ground-fault protection relays?

Sensitive ground-fault relays with advanced filtering quickly and reliably detect insulation resistance breakdown caused by moisture, vibration, chemicals, or dust.

What does the Littelfuse trailing-cable protection relay monitor?

Trailing-cable protection relays continuously monitor the integrity of the ground conductor in portable cables to protect equipment from hazardous voltages.

What are Littelfuse fuse blocks and holders designed for?

Littelfuse fuse blocks and holders are selected by OEMs and designers for their compact designs, indication features, and DIN-rail mounting flexibility.

What do POWR-BLOKS power distribution blocks provide?

POWR-BLOKS power distribution blocks offer a safe and convenient way to splice cables and manage power distribution requirements within panels and systems.

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.