250 series ac current protectors provide continuous surveillance of the monitored circuit. When the current moves outside the set point limit the relay operates. The protector can be used to monitor over and undercurrent conditions, load detection and for monitoring electric heating systems. An illuminated LED indicates when the relay is energised. For three-phase systems, the sequence of connection is not important.
Operation
AC current protectors provide continuous surveillance of the monitored circuit. These products offer user adjustable trip point (set point) and time delay settings. The set point adjustment range is between 40% and 120% of the nominal current. Input currents can be via current transformers or direct up to 10A. An internal differential setting of 1% reduces nuisance tripping if the measured signal is noisy or unstable. When the measured current moves outside the set point limit the relay will operate, giving an alarm or initiation signal. An adjustable time delay is provided to prevent the relay from tripping for a predetermined period to prevent nuisance tripping. The units draw their operating power from a separate auxiliary supply input. Single-phase and three-phase products are available. Three-phase products monitor the current level for each phase and are not phase sequence sensitive. Combined units offer under and over-current trips in one compact unit. Single function units are also available.
Over-Current Models
When the monitored current 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 current falls below the set point minus the differential. When reset, the LED will extinguish and the relay de-energises.
Under-Current Models
When the monitored current 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 current 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. Please call for options.
- Adjustment ranges – different adjustment ranges are possible for the set point and differential controls.
- Relay operation – standard models are fail safe, but the relays can be customised to energise or de-energise on trip.
|
