1 phase , 50 Hz, 20 KVA , 2200/220 v , is connected as an auto transformer of step up type . Determine , a. The auto-transformer transformation ratio . b. Auto-transformer primary and secondary currents . c. Full load efficiency at 0.8 power factor . for an iron loss of 150 w and full load cu loss of 275 w . also , calculate the two winding transformer efficiency if the loss remain the same .

This is NOT a forum for college problem solutions. How would you have a 20 KVA transformer and an Atlas Sound AF140... these are different animals... Autotransformer is a more efficient connection when it is possible... the transformer will step the 220 up to 2200+220 volts ignoring the copper loss voltage. For proper designed transformers the primary and secondary copper losses should be close to equal... but in autotransformer connection the efficiency is improved as the added voltage of the supply going to the high voltage winding power does NOT suffer and add to the current required in the primary of this connection. The purpose of this problem is for you to discover that the efficiency of autoformer connection is higher than of a simple step up connection. Now with this carefully work the problem... The ratio I have all but given you... It is unclear what is considered full load here so I would base it on regular connection at 20 KVA at 2200 volts to calculate what the currents would be primary and secondary.in normal connection... calculate resistance of primary and secondary ASSUMING equal losses primary and secondary. What isn't clear is if the loss figures are for the autoformer connection OR just the specs for normal connection. The power factor kink adds to the misery. Approach this problem by making an equivalent circuit of the transformer showing the primary and secondary resistances... again the question is are the loss figures the specs of the transformer or the actual running values for the system....