601575 - 601 Series

Series: 601 Questions? Contact Littelfuse Support
Littelfuse Voltage Monitoring Relays
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 SCADA system.


When a harmful condition is detected, the 601’s output relay is deactivated after the specified trip delay. The output relay reactivates after power line conditions return to an acceptable level for the programmed restart delay (RD2).


Eleven (11) setpoints are viewable with the 3-digit LED display or from a networked device:

    low voltage
      high voltage
        voltage unbalance
          low frequency
            high frequency
              RS485 address
                trip delay for voltage/frequency faults
                  trip delay for single-phase faults
                    rapid-cycle timer (RD1)
                      restart delay after all faults (RD2)
                        type of restart after all faults (manual or automatic)

                        Six (6) parameters are viewable while the motor is running:

                          L1-L2 voltage
                            L2-L3 voltage
                              L1-L3 voltage
                                average voltage
                                  voltage unbalance (%)
                                    voltage frequency (%)


                                    When used with the RS485MS-2W communications module, the 601 can communicate with most Modbus RTU master devices. Voltage conditions can be monitored and setpoints can be changed remotely using Solutions software, an RM-1000, RM-2000 or other device.

Property (Mouseover for details) Value
Input Voltage (V) 500 to 600VAC
Maximum Input Power 5W
Input AC Line Frequency (Hz) 50/60Hz
Output Load Rating (VA) Pilot Duty: 480VA @ 240VAC; General Purpose: 10A @ 240VAC
Timing Accuracy (%) 5% ±1s
Rapid Cycle Timer (s) 0 2 - 500s
Restart Delay Range Restart Delay After All Faults: 2 - 500s
Repeat Accuracy (%) Voltage: ±0.5%
Trip Delay Range Voltage/Unbalance/Frequency Faults/Single-Phase Faults: 1 - 50s
Overvoltage Reset Voltage (%) 97% of HV Setting
Undervoltage Reset Voltage (%) 103% of LV Setting
Voltage Unbalance Reset (%) UB Setting -1%
Voltage Accuracy (%) ±1%
Over/Under Frequency (%) Low: 35Hz - HF setting; High: LF setting - 75Hz
Protection Class IP20 NEMA 1 (finger safe)
Address A01-A99
Termination Type Torque: 7in-lbs
Mounting Method Surface mount (4 - #8 screws) or DIN rail mount
Operating Temperature -20° to 70°C (-4° to 158°F)
Storage Temperature (F/C) -40° to 80°C (-40° to 176°F)
Humidity 95% non-condensing per IEC 68-2-3
Dimensions 3.05 in H x 3.85 in W x 5.05 in D (77.5 x 97.8 x 128.3 mm)
Weight (lbs/g) 1.2 lbs. (19.2 oz. 544.3 g)