A tall inrush-current spike rises at switch-on and decays to the steady running current as the motor accelerates. The spike height changes with the selected method. The bar at the right compares the peak currents of the three methods.
$$I_{rated}=\frac{P}{\sqrt{3}\,V\,\eta\,\cos\varphi},\qquad I_{start,DOL}=k_{LR}\cdot I_{rated}$$
Rated (full-load) line current I_rated and the direct-on-line starting current I_start,DOL. P: rated power, V: rated voltage, η: efficiency, cosφ: power factor, k_LR: locked-rotor ratio.
$$I_{start}=\frac{I_{start,DOL}}{3}\;(\text{star-delta}),\qquad I_{start}=0.5\,I_{start,DOL}\;(\text{50% voltage})$$
Star-delta starting applies 1/√3 of the line voltage to each winding, so the starting current and torque both fall to one third. With reduced voltage, current scales with voltage while torque scales with the square of the voltage.