




































































Did you experience overload problems on your single phase reclosers this summer? Do you have recloser locations where the Peak Load Current exceeds 35% of the Minimum Fault Current you wish to detect? How can you provide uncompromising protection for larger Load Currents?








































































For example, consider the following single phase recloser location requirements:






























































System Voltage = 7200 / 12470 V








































Peak Load Current = 60 Amps





























Minimum Fault Current @ 40 ohms = 130 Amps















Maximum Fault Current = 3000 Amps










































The following application rules apply:



















1. The practical thermal limitation on the coil requires that the Peak Load Current not exceed 70% of the nominal coil size.


































2. The Minimum Pickup Current equals 200% plus or minus 20% of the nominal coil size.





























































A type 'L' is an easy choice at this voltage and fault duty. But selecting the appropriate size presents some compromises. The table lists your choices.
























































Minimum Pickup 220% x Coil

Thermal Limit 70% x Coil

Short Circuit Rating 60 x Coil or 4000amps















Coil Size 















50 amps 70 amps 100 amps 

110 amps 154 amps 220 amps 





35 amps 49 amps 70 amps 



3000 amps 4000 amps 4000 amps 














If you are concerned about detecting the Minimum Fault Current, then select the 50 amp coil with 110 amp Minimum Pickup but the compromise is that the 60 amp Peak Load Current exceeds the Thermal Limit of 35 amps. Overheating will definately occur.
































