If the stator voltage of a wound rotor motor is reduced by 50%,by how much the starting current will reduce?

The starting current and the current at low speed during acceleration will be 50% of the full-voltage value. At rated torque near full speed, the current will be higher than it would be at full voltage. Therefore, the current vs. speed curve for 50% voltage will be below the current vs. speed curve for full-voltage at low speeds, but the two curves will cross as the motor approaches full speed.