Washing machine and spin-drying control method for washing machine

A washing machine comprising:

• an outer tub configured to receive water;
• an inner tub rotatably disposed with respect to a vertical axis of the outer tub, defining an opening at a lower portion, and in fluid communication with the outer tub;
• a drain pump configured to be driven by an electric current to thereby drain the water from the outer tub;
• a motor configured to provide a rotational force to the inner tub;
• and
• a control unit including a processor and configured to control the drain pump and the motor to perform a spin-drying cycle including a sub spin-drying cycle and a main spin-drying cycle,
• wherein the control unit is configured to:
• rotate the motor to increase a rotation speed of the inner tub to a preset first target speed during the sub spin-drying cycle to remove moisture from laundry received in the inner tub,
• measure the current of the drain pump to measure an amount of water dehydrated from the laundry while the inner tub is rotated,
• measure, based on the current of the drain pump being increased and then decreased to or below a preset reference current, the rotation speed of the inner tub, and
• change a preset rotation time of the inner tub in the main spin-drying cycle according to the measured rotation speed of the inner tub.