power distribution, a requirement of only three conductors, rather than four, represented a considerable distribution-wire cost savings due to the expense of conductors and installation. While both two-phase and three-phase circuits have a constant combined power for an ideal load, practical devices such as motors can suffer from power pulsations in two-phase systems. These power pulsations tend to cause increased mechanical noise in transformer and motor laminations due to magnetostriction and torsional vibration in generator and motor drive shafts. Two-phase power can be derived from a three-phase source using two transformers in a Scott connection: One transformer primary is connected across two phases of the supply. The second transformer is connected to a center-tap of the first transformer, and is wound for 86.6% of the phase-to-phase voltage on the three-phase system. The secondaries of the transformers will have two phases 90 degrees apart in time, and a balanced two-phase load will be evenly balanced over the three supply phases. See also Polyphase system Rotary converter Single-phase electric power Split-phase electric power Three-phase electric power References Notes Specific references General references Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition, McGraw-Hill, New York, 1978, Edwin J. Houston and Arthur Kennelly, Recent Types of Dynamo-Electric Machinery, copyright American Technical Book Company 1897, published by P. F. Collier and Sons New York, 1902 Electric power AC power