Three-phase relays are applicable for three-phase receiver protection against untolerable variations in mains voltage, against phase loss and phase imbalance, phase coincidence and incorrect phase sequence. They are efficiently adapted for protection of refrigerating and air-conditioning installations, compressor plants and other equipment with an electric motor load. They are also used in the devices that call for continuous monitoring of mains voltage existence / quality and all-the phases-presence, e. G. In the automatic throw-over circuit breakers.
Hysteresis is about 5v in all the relays. The operational capability range is 30 -150% of a nominal voltage. Deep under voltage ( when one or more phase voltage value drops by 30 v below the user-preset minimum voltage threshold ) and / or abrupt over voltage ( when one or more phase voltage exceeds by 30v the user-preset maximum voltage threshold ) entail the automatic relay tripping with acceleration. The relay will reset automatically (i. E. Will activate a load ) with user- preset time delay on return to normal operating conditions when voltage values regenerated, reaching the level set by hysteresis. The relays are compact, rugged and have a small weight. All the relays are mounted on the standard din rail.
The relays are connected in parallel to load and they energise a magnetic starter coil, therefore the relay operation is practically independent on load power. Two groups of independent contacts ( one pair is n. C. Contacts, another pair is n. O. Contacts ) at the relay output terminals switch the load up to 5a power.