Crompton frequency protectors give continuous surveillance of the monitored circuit. When the frequency moves outside the set point limit the relay will operate giving an alarm, control or tripping signal.
An illuminated LED indicates when the relay is energised. Since speed is proportional to the frequency, this protector can be used to monitor over and under-speed and to protect mains supplies, computer supplies and standby supplies for industrial, hospital or marine use.
Operation
Frequency protectors offer user adjustable frequency trip point (set point) and differential (hysteresis) settings. The set point adjustment range is centred around the nominal 50Hz, 60Hz or 400Hz system frequency. The differential setting adjustment can be used to reduce nuisance tripping if the measured signal is noisy or unstable. When the measured frequency moves outside the set point limit, the relay will operate, giving an alarm or initiation signal. As soon as the monitored frequency moves outside of the set point limit, a trip will occur. The units draw their operating power from the measuring inputs. Combined units offer under and over frequency trips in one compact unit. Single function units are also available.
Over-Frequency Models
When the monitored frequency exceeds the set point, the relay will energise and the red LED will illuminate to indicate the trip condition. The relay will automatically reset once the monitored frequency falls below the set point minus the differential. When
reset, the LED will extinguish and the relay de-energises.
Under-Frequency Models
When the monitored frequency falls below the set point, the relay will de-energise and the red LED will extinguish to indicate the trip condition. The relay will automatically reset once the monitored frequency rises above the set point plus the differential.
When reset, the LED will illuminate and the relay energises.
Options
250 series protector relays offer various customised options to suit individual requirements.
- Adjustment ranges – different adjustment ranges are possible for the set point and differential controls.
- Time delay – internal fixed time delay before a trip occurs.
- Relay operation – standard models are fail safe, but the relays can be customised to energise or de-energise on trip.
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