FREQUENCY monitoring relays are offered in the following styles:



FREQUENCY monitoring relays are used in circuits where equipment can be damaged if the voltage exceeds or falls below the normal level. Another common application is generators. The relay won't allow the emergency power to be connected until the correct number of cycles is present thus avoiding possible damage to equipment.

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Type No
Description Under Frequency Relay Over Frequency Relay Under Frequency Relay Over Frequency Relay  
Function Under Frequency Over Frequency Under Frequency Over Frequency
Time Delay (from fault) ≈1S ≈1S ≈200mS ≈200mS
Hysteresis ≈1% ≈1% 0.3-3Hz 0.3-3Hz
Latch No No No No
Output SPDT Relay SPDT Relay DPDT Relay DPDT Relay
Output Rating 8A @ 250VAC 8A @ 250VAC 8A @ 250VAC 8A @ 250VAC
Supply Voltage Un 12, 48VAC/DC, 24VDC 12, 48VAC/DC, 24VDC 110, 230, 400VAC 110, 230, 400VAC
  24, 110, 220/240VAC 24, 110, 220/240VAC - -
Integral Transformer 110, 220/240V only 110, 220/240V only Yes Yes
Monitoring Range 35-70Hz 35-70Hz 40-60, 50-70Hz 40-60, 50-70Hz