The question of maintaining plasma equilibrium in a three-turn stellarator by means of an external transverse field H⊥ is investigated in an ideal magnetohydrodynamic model as a first approximation with respect to β, where β is the ratio of the gas-kinetic pressure of the plasma to the magnetic pressure. An "island" structure of the paraxial magnetic surfaces is observed under conditions of precise compensation and slight undercompensation of the homogeneous component of the plasma magnetic field by the field H⊥. The optimum conditions are found for controlling the position of the magnetic axis with an external transverse field. Relations are obtained for estimating the maximum equilibrium pressure of the plasma in a three turn stellarator in the presence of an external transverse magnetic field.