The characteristics of these devices are adjusted during operation with an on-load tap changer. Lamination is introduced into these devices to minimize eddy current losses. The open-circuit and short-circuit tests are used to determine losses in these (15[1])devices and model them as a cantilever or T-circuit after referring impedances to one side. Non-ideal versions of these devices have losses due to (*) hysteresis and non-infinite permeability, as well as (-5[1])copper wiring and leakage (10[1])flux. Since they rely on a conserved flow of magnetic flux, the (10[1])emf ratio of these devices equals the ratio between the number of windings the (-5[1])primary and secondary coils have around the magnetic (-5[1])core. For 10 points, name these devices used in power grids to step up or step down voltages. (0[3])■END■