601-CS-D-P1 Series – Three-Phase Power Monitor Series - Littelfuse 601-CS-D-P1 Voltage Monitoring Relays Provide Superior Protection

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Littelfuse products are not designed for, and shall not be used for, any purpose (including, without limitation, automotive, military, aerospace, medical, life-saving, life-sustaining or nuclear facility applications, devices intended for surgical implant into the body, or any other application in which the failure or lack of desired operation of the product may result in personal injury, death, or property damage) other than those expressly set forth in applicable Littelfuse product documentation. Warranties granted by Littelfuse shall be deemed void for products used for any purpose not expressly set forth in applicable Littelfuse documentation. Littelfuse shall not be liable for any claims or damages arising out of products used in applications not expressly intended by Littelfuse as set forth in applicable Littelfuse documentation. The sale and use of Littelfuse products is subject to Littelfuse Terms and Conditions of Sale, unless otherwise agreed by Littelfuse. "Littelfuse" includes Littelfuse, Inc., and all of its affiliate entities.

The 601-CS-D-P1 series is a fully programmable, electronic, three-phase, power monitor designed to monitor three-phase systems. This unit has a single relay that can be configured as a general purpose network output or to trip on ground faults. The 601-CS-D-P1 monitors ground-fault current, phase currents, phase voltages, power factor, and frequency. The RS485MS-2W communications module allows the 601-CS-D-P1 to communicate using the Modbus RTU protocol. The Modbus connection can be used to monitor power parameters, set up the device or control the fault relay. A DeviceNet™ communications I/O module (CIO-601CS-DN-P1) is also available. This CIO module only works with the 601-CS-D-P1 unit. It is used for sending the information from the 601-CS-D-P1 over a DeviceNet™ network. It also provides I/O capabilities and the ability to set the parameters of the 601-CS-D-P1.

The 601-CS-D-P1 includes a built-in display that offers a visual indication for programming and viewing real-time parameters for nominal voltage, voltage unbalance, current, current unbalance, ground-fault warning, ground-fault trip, and ground-fault motor acceleration.

Note: This product must be used with an external zero-sequence CT (not included) for proper operation.


  • Built-in display
  • 15 programmable parameters to control operations
  • Two programmable trip delay timers
  • Network communications capability

Access specifications, certifications, check availability and order parts below

Catalog #Input
Voltage (V)
Termination TypeMounting MethodFull Load Amp Range (A)DimensionsWeight (lbs/g)Communications ProtocolCurrent Accuracy (%)Ground Fault Accuracy (%)HumidityInput AC Line Frequency (Hz)Maximum Input PowerOutput Load Rating (VA)Pollution DegreeStockSamples
601-CS-D-P1200 - 480 VacSPDTTorque: 7 in-lbsSurface mount (4 - #8 screws) or DIN rail mount0.5 - 175 (direct); 176 - 800 (external CTs required)3.05 H x 3.85 W x 5.05 D in. (77.5 x 97.8 x 128.3 mm)0 KgModbus RTU±3% (<100 A direct)±3%10 - 95% non-condensing per IEC 68-2-350 / 6010Pilot Duty: 480 VA @ 240 Vac; General Purpose: 10 A @ 240 Vac3CheckOrder
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