What percentage of total transformer capacity is available in an open delta system?
The 3 phase capacity of an open delta system is 87% of the total transformers in the circuit. An example would be: two 50 KVA single phase transformers connected in open delta. The 3 phase capacity would be the sum of the two units multiplied by .87 or 100 KVA x .87 which would equal 87 KVA. In the event the third transformer of 50 KVA was added to this open delta bank to form a closed delta, the 3 phase capacity would then be the sum of the three transformers in the bank or 150 KVA.
