Monitoring Relays

Monitoring relays are a type of relay that trips a circuit breaker when a fault is detected. A relay is an electrically controlled switch that is used to turn the power on or off in a circuit. 


Monitoring relays are more sophisticated than regular relays, as they have adjustable operating conditions, whereas normal relays switch according to a fixed threshold. They measure a given parameter, such as voltage or temperature, and will trip a circuit breaker when the parameter gets too high or low. 


What are monitoring relays used for?

Monitoring relays have a wide range of uses, depending largely on the factor being monitored. For example, they can protect against overcurrent if measuring current, or they can detect an abnormally low frequency if frequency is being measured.


Types of monitoring relay

The main way in which monitoring relays differ is the function that they measure. This can be a number of things, including:

  • voltage
  • current
  • temperature
  • frequency

The factor that you need to measure will decide which monitoring relay you choose.


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Description Price Monitoring Application Supply Voltage Contact Configuration Voltage Sensitivity Electrical Phase Voltage Sensing Range Current Sensitivity Minimum Current Sensed Maximum Current Sensed Phase Sensitivity Time Delay Temperature Sensitivity Temperature Sensing Range Frequency Sensing Range
RS Stock No. 102-6130
BrandRS PRO
$102.14
Each
units
Voltage 12 → 24 V dc SPDT Undervoltage 1 12 → 24 V dc - - - - 0 → 30 s - - -
RS Stock No. 102-6137
BrandRS PRO
$155.44
Each
units
Phase, Voltage 400 V ac SPDT Overvoltage, Undervoltage 3 300 → 380 (Undervoltage) V, 420 → 500 (Overvoltage) V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6135
BrandRS PRO
$104.31
Each
units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage 3 Maximum of 280 V - - - Phase Failure, Phase Sequence 100 ms - - 48 → 63 Hz
RS Stock No. 102-6136
BrandRS PRO
$97.58
Each
units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage 3 300 → 500 (Undervoltage) V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6134
BrandRS PRO
$105.96
Each
units
Current 24 → 230 V ac/dc SPDT - 1 - Overcurrent, Undercurrent 1A 10A - 0.1 → 30 s - - 48 → 63 Hz
RS Stock No. 102-6131
BrandRS PRO
$80.66
Each
units
Voltage 230 V ac SPDT Overvoltage, Undervoltage 1 173 → 218 (Undervoltage) V, 242 → 288 (Overvoltage) V - - - - 0.2 → 10 s - - 48 → 63 Hz
RS Stock No. 102-6133
BrandRS PRO
$172.73
Each
units
Voltage 24 → 230 V ac/dc SPDT Overvoltage, Undervoltage 1 50 → 500 V - - - - 0.1 → 30 s - - 48 → 63 Hz
RS Stock No. 261-993
Mfr. Part No.84874320
BrandCrouzet
$319.28
Each
units
Speed 24 → 240 V ac/dc SP-NO/NC - - - - - - - 15 ms - - -
RS Stock No. 417-9891
Mfr. Part No.3RN1000-1AM00
BrandSiemens
$107.12
Each
units
Thermistor motor protection relay 230 V ac SPDT - - - - - - - - Overtemperature, Undertemperature +60 → +180°C -
RS Stock No. 261-959
Mfr. Part No.84871122
BrandCrouzet
$227.55
Each
units
Current 24 → 240 V ac/dc SP-NO/NC - - - Overcurrent, Undercurrent 2A 20A - 500 ms - - -
RS Stock No. 145-976
Mfr. Part No.RM35JA32MW
$300.53
Each
units
Current 24 → 240 V ac/dc DPDT - - - Overcurrent, Undercurrent 0.15A 15A - 0.3 → 30 s - - -
RS Stock No. 857-7696
Mfr. Part No.DPB01CM48
$551.16
Each
units
Phase, Voltage 380 → 480 V ac SPDT Overvoltage, Undervoltage 3, 3+N 323 → 550 V ac - - - Phase Loss, Phase Sequence 1 s, 6 s - - -
RS Stock No. 417-9914
Mfr. Part No.3RN1013-1BW10
BrandSiemens
$349.25
Each
units
Thermistor motor protection relay 24 → 240 V ac/dc DPDT - - - - - - - - Overtemperature, Undertemperature +60 → +180°C -
RS Stock No. 518-7180
Mfr. Part No.3UG4617-1CR20
BrandSiemens
$383.73
Each
units
Phase, Voltage 160 → 690 V ac DPDT Overvoltage, Undervoltage 3 160 → 690 V ac - - - Phase Failure, Phase Imbalance, Phase Sequence 0.1 → 20 s - - -
RS Stock No. 776-3657
Mfr. Part No.A9E16066
$342.93
Each
units
Time Delay 24 V dc, 24 → 240 V ac SPDT - - 24 → 240 V ac - - - - - - - -
RS Stock No. 146-070
Mfr. Part No.RM35S0MW
$372.67
Each
units
Speed 24 → 240 V ac/dc SPDT - - - - - - - 0.6 → 60 s - - -
RS Stock No. 876-5023
Mfr. Part No.1SVR730712R1400
BrandABB
$272.48
Each
units
Temperature 24 → 240 V ac/dc SPDT - - - - - - - <100 ms Overtemperature, Winding Temperature - -
RS Stock No. 656-6247
Mfr. Part No.IK9055.11 50-50000IPM UH=DC24V Hyst.1-20%
BrandDold
$190.53
Each
units
Speed 24 V dc SPDT - - - - - - - 0.1 → 20 s - - -
RS Stock No. 146-480
Mfr. Part No.RM35TF30
$533.60
Each
units
Phase, Voltage 220 → 480 V ac DPDT Overvoltage, Undervoltage 3 194 → 528 V ac - - - Phase Asymmetry, Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS Stock No. 321-6826
Mfr. Part No.45200 110VAC
$132.53
Each
units
Temperature 110 V ac SPDT - - - - - - - 50 ms Overtemperature - -
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