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 and 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. 261-993
Mfr. Part No.84874320
BrandCrouzet
£121.19
Each
Units
Speed 24 → 240 V ac/dc SP-NO/NC - - - - - - - 15 ms - - -
RS Stock No. 146-187
Mfr. Part No.RM35UA13MW
£95.00
Each
Units
Voltage 24 → 240 V ac/dc DPDT Overvoltage, Undervoltage - 15 → 600 V - - - - 0.3 → 30 s - - -
RS Stock No. 850-5392
Mfr. Part No.LMCCR-10A 24-230VAC/DC
£82.70
Each
Units
Current 24 → 230 V ac/dc SPDT - - - Overcurrent, Undercurrent 0.2A 10A - 0.1 → 30 s - - -
RS Stock No. 397-9139
Mfr. Part No.45TCR 24/230VAC
£111.05
Each
Units
Temperature 24/230 V ac - - - - - - - - 200 ms - -50 → +300°C 0 → 100 °C, 0 → 50 °C, 100 → 200 °C, 200 → 300 °C, -50 → 50 °C
RS Stock No. 850-5405
Mfr. Part No.LMCVR-500V 24-230VAC/DC
£83.54
Each
Units
Voltage 24 → 230 V ac/dc SPDT Overvoltage, Undervoltage - 10 → 100 V, 2 → 20 V, 20 → 200 V, 5 → 50 V, 50 → 500 V - - - - 0.1 → 30 s - - -
RS Stock No. 850-5382
Mfr. Part No.LXPRF 280-520VAC
£49.70
Each
Units
Phase, Voltage 280 → 520 V ac SPDT Undervoltage - Maximum of 520 V - - - Phase Failure 100 ms - - -
RS Stock No. 776-3648
Mfr. Part No.A9E16065
£128.47
Each
Units
Time Delay 24 V dc, 24 → 240 V ac SPDT - - 24 → 240 V ac - - - - - - - -
RS Stock No. 876-5023
Mfr. Part No.1SVR730712R1400
BrandABB
£114.90
Each
Units
Temperature 24 → 240 V ac/dc SPDT - - - - - - - <100 ms Overtemperature, Winding Temperature - -
RS Stock No. 298-9416
Mfr. Part No.45175 230VAC
£72.89
Each
Units
Speed 230 V ac SPDT - - - - - - - 0.5 → 30 min, 0.5 → 30 s - - -
RS Stock No. 794-3960
Mfr. Part No.MJA3BK
BrandGIC
£46.36
Each
Units
Thermistor 24 V ac/dc DPDT - - - - - 6A - 100 ms, 500 ms - - -
RS Stock No. 417-9914
Mfr. Part No.3RN1013-1BW10
BrandSiemens
£152.00
Each
Units
Thermistor motor protection relay 24 → 240 V ac/dc DPDT - - - - - - - - Overtemperature, Undertemperature +60 → +180°C -
RS Stock No. 794-3941
Mfr. Part No.MG21DH
BrandGIC
£32.39
Each
Units
Voltage 208 → 480 V ac SPDT Overvoltage, Undervoltage 3 - - - 5A - 0.5 → 15 s, 5 s - - -
RS Stock No. 397-9202
Mfr. Part No.45PUVR-4W 400VAC
£76.05
Each
Units
Phase, Voltage 400 V ac DPDT Undervoltage 3 Maximum of 400 V ac - - - Neutral Loss, Phase Loss 200 ms - - -
RS Stock No. 850-5389
Mfr. Part No.LXPRT-4W 230V (400V)
£55.57
Each
Units
Phase, Voltage 230 V ac SPDT Undervoltage - Maximum of 300 V - - - Phase Failure, Phase Sequence 0.2 → 10 s - - -
RS Stock No. 445-9052
Mfr. Part No.IL5881.12/100 DC12-280V 5-200kOHM
BrandDold
£165.04
Each
Units
Voltage 12 → 280 V dc DPDT - - - - - - - 0.5 → 20 s - - -
RS Stock No. 261-915
Mfr. Part No.84873022
BrandCrouzet
£72.26
Each
Units
Phase 208 → 480 V ac SPDT - 3 - - - - Phase Failure, Phase Sequence 0.1 → 10 s - - -
RS Stock No. 124-0191
Mfr. Part No.RM35JA32MR
£121.00
Each
Units
Current 20.4 → 264 V ac/dc DPDT - 1 - Overcurrent, Undercurrent 150mA 15A - 0.1 → 30 s - - -
RS Stock No. 794-3935
Mfr. Part No.MA51BC
BrandGIC
£29.52
Each
Units
Voltage 415 V ac SPDT - 3 - - - 5A - 2 s, 7 s - - -
RS Stock No. 819-3245
Mfr. Part No.K8AK-LS1 100-240VAC
BrandOmron
£50.95
Each
Units
Level Control 100 → 240 V ac SPDT - - - - - - - - - - -
RS Stock No. 794-3957
Mfr. Part No.MJ83BK
BrandGIC
£45.42
Each
Units
Thermistor 110 → 240 V ac DPDT - 1 - - - 6A - 100 ms, 500 ms - - -
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