Why Choose the Lovato PMF20A240 Frequency Monitoring Relay?
The Lovato PMF20A240 is a reliable minimum and maximum frequency monitoring relay designed to supervise the frequency of 220–240 V AC electrical supplies. As part of the established Lovato Electric PMF20 monitoring relay range, it helps protect machinery, control systems and electrical equipment against potentially damaging underfrequency and overfrequency conditions.
The relay is self-powered directly from the monitored circuit and supports selectable nominal frequencies of 50 or 60 Hz. Adjustable minimum and maximum frequency thresholds allow engineers to define an acceptable operating window around the selected rated frequency, making the PMF20A240 suitable for generator systems, industrial machinery and power-quality supervision.
Adjustable tripping and resetting times from 0.1 to 20 seconds help prevent nuisance operation during short-duration frequency fluctuations. Its normally energised changeover output, automatic reset and clear LED indication provide dependable fault signalling in compact DIN rail control panels where stable frequency is essential for equipment performance.
Key Advantages
- Monitors both minimum and maximum AC frequency.
- Designed for 220–240 V AC monitored supplies.
- Selectable nominal frequency of 50 or 60 Hz.
- Adjustable underfrequency and overfrequency thresholds.
- Adjustable tripping and resetting delays reduce nuisance operation.
- Self-powered design removes the need for a separate auxiliary supply.
- Normally energised relay output supports fail-safe control circuits.
- Compact two-module DIN rail housing for industrial panels.
Key Features
- Lovato Electric PMF20 series.
- Minimum and maximum frequency monitoring.
- 220–240 V AC rated monitored voltage.
- 50 or 60 Hz selectable rated frequency.
- Minimum frequency threshold adjustable from 90% to 99% of rated frequency.
- Maximum frequency threshold adjustable from 101% to 110% of rated frequency.
- Frequency measurement range from 40 to 70 Hz.
- Tripping delay adjustable from 0.1 to 20 seconds.
- Resetting time adjustable from 0.1 to 20 seconds.
- Automatic reset with 0.5% hysteresis.
- 1 SPDT changeover relay output.
- LED indication for power and minimum or maximum frequency faults.
- Front potentiometers for straightforward adjustment.
- Screw terminals and 35 mm DIN rail mounting.
Reliable Frequency Supervision for Electrical Systems
Abnormal supply frequency can affect motor speed, transformer performance, timing functions and the stability of sensitive electronic equipment. The Lovato PMF20A240 continuously compares the measured frequency with the configured minimum and maximum limits, providing a clear fault response whenever the frequency moves outside the permitted range.
When an abnormal frequency remains present beyond the selected tripping delay, the normally energised relay output de-energises. This output can stop machinery, activate an alarm or send a fault signal to a PLC or control system. Automatic resetting restores the output once the frequency returns within the acceptable range for the configured resetting time.
Typical Applications
- Generator and standby power systems.
- Industrial machinery and control panels.
- Power-quality monitoring circuits.
- Motor and pump control systems.
- Renewable and distributed generation equipment.
- Electrical distribution boards.
- Building automation systems.
- Alarm and equipment interlocking circuits.
