System for charging at least one energy storage cell in a controllable energy store which is used to control and supply electrical energy to an n-phase electrical machine, where n ≥ 1, wherein - the controllable energy store has n parallel energy supply branches (3-1, 3-2, 3-3), which ▪ have in each case at least two energy storage modules, which are connected in series and comprise in each case at least one electrical energy storage cell having an associated controllable coupling unit, ▪ can be connected on one side to a reference rail (T-) and ▪ can be connected on the other side to in each case one phase (U, V, W) of the electrical machine, and - the coupling units are configured as full bridges and, depending on control signals, bypass the respectively associated energy storage cells or connect the respectively associated energy storage cells into the respective energy supply branch (3-1, 3-2, 3-3), characterized in that - a star point of the electrical machine at one end and the reference rail (T-) at the other can be connected to a secondary side of a charging transformer, - wherein the coupling units are configured, in a current increase stage in the energy supply branches (3-1, 3-2, 3-3), to set a voltage which is smaller in terms of magnitude than that at the secondary side (9; 9-1'; 9-1''; 9-2'; 9-2''; 9-3'; 9-3'') of the charging transformer (10; 10'; 10'') and, in a current reduction stage following the current increase stage in the energy supply branches (3-1, 3-2, 3-3), to set a voltage which is greater in terms of magnitude than that at the secondary side (9; 9-1'; 9-1''; 9-2'; 9-2''; 9-3'; 9-3'') of the charging transformer (10; 10'; 10''). - the controllable energy store has n parallel energy supply branches (3-1, 3-2, 3-3), which ▪ have in each case at least two energy storage modules, which are connected in series and comprise in each case at least one electrical energy storage cell having an associated controllable coupling unit, ▪ can be connected on one side to a reference rail (T-) and ▪ can be connected on the other side to in each case one phase (U, V, W) of the electrical machine, and ▪ have in each case at least two energy storage modules, which are connected in series and comprise in each case at least one electrical energy storage cell having an associated controllable coupling unit, ▪ can be connected on one side to a reference rail (T-) and ▪ can be connected on the other side to in each case one phase (U, V, W) of the electrical machine, and - the coupling units are configured as full bridges and, depending on control signals, bypass the respectively associated energy storage cells or connect the respectively associated energy storage cells into the respective energy supply branch (3-1, 3-2, 3-3), - a star point of the electrical machine at one end and the reference rail (T-) at the other can be connected to a secondary side of a charging transformer, - wherein the coupling units are configured, in a current increase stage in the energy supply branches (3-1, 3-2, 3-3), to set a voltage which is smaller in terms of magnitude than that at the secondary side (9; 9-1'; 9-1''; 9-2'; 9-2''; 9-3'; 9-3'') of the charging transformer (10; 10'; 10'') and, in a current reduction stage following the current increase stage in the energy supply branches (3-1, 3-2, 3-3), to set a voltage which is greater in terms of magnitude than that at the secondary side (9; 9-1'; 9-1''; 9-2'; 9-2''; 9-3'; 9-3'') of the charging transformer (10; 10'; 10'').