Laundry treatment machine

A laundry treatment machine comprising:

• a washing tub;
• a washing tub motor to rotate the washing tub;
• a driver to drive the washing tub;
• a drain pump;
• a drain motor to operate the drain pump;
• a converter to output direct current (DC) voltage;
• an inverter to convert the DC voltage from the converter into alternating current (AC) voltage by a switching operation and to output the converted AC voltage to the drain motor;
• and
• a controller configured to control the drain motor,
• wherein while the washing tub motor is rotating at a constant speed, the controller is configured to control the drain motor to operate in a first period during which a speed of the drain motor increases, in a second period including a period in which the speed of the drain motor decreases after the first period, and in a third period during which the speed of the drain motor decreases after the second period,
• wherein when the washing tub performs dewatering, the controller is configured to control the washing tub to rotate at a constant speed, and to control the drain motor to repeat an on period and an off period, the on period of the drain motor comprises the first period, the second period, and the third period, and
• the controller is configured to control the drain motor such that during repetition of the on period and the off period of the drain motor, a length of the on period of the drain motor is longer than a length of the off period of the drain motor, and
• the controller is configured to control the drain motor such that a magnitude of a rising slope of a speed waveform in the second period is less than a magnitude of a falling slope of the speed waveform in the third period.