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 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 copper wiring and leakage flux. Since they rely on a conserved (-5[1])flow of magnetic flux, the emf ratio of these devices equals the ratio between the number of windings the (10[1])primary and secondary coils have around the magnetic core. For 10 points, (-5[1])name these devices used in power grids to step up or step down (10[1])voltages. (0[1])■END■