Refrigerator and method for controlling the same

A refrigerator comprising:

• a storage chamber;
• a cold air supply configured to provide cold air;
• a tray provided in the storage chamber and including at least one cell which forms a space in which a liquid is introduced to be phase-changed into ice, the space having a spherical shape including a top portion, a middle portion, and a bottom portion, wherein a mass of liquid in the space increases from the top portion to the middle portion and decreases from the middle portion to the bottom portion;
• a heater configured to provide heat to the tray;
• and
• a controller configured to control output power of the heater, wherein the controller is configured to control the heater so that when a target temperature of the storage chamber decreases, a heating amount of the heater increases, and when the target temperature of the storage chamber increases, the heating amount of the heater decreases.

A refrigerator, comprising:

• a storage chamber;
• a cold air supply configured to provide cold air;
• a tray provided in the storage chamber and including at least one cell which forms a space in which a liquid is introduced to be phase-changed into ice, the space having a spherical shape including a top portion, a middle portion, and a bottom portion, wherein a mass of liquid in the space increases from the top portion to the middle portion and decreases from the middle portion to the bottom portion;
• a heater configured to provide heat to the tray;
• and
• a controller configured to control output power of the heater to vary the output power as ice is formed from the top portion to the bottom portion,
• wherein the controller is configured to control the heater such that:
• when a heat transfer amount between the cold air within the storage chamber and the liquid in the space increases, a heating amount of the heater increases, and
• when the heat transfer amount between the cold air within the storage chamber and the liquid in the space decreases, the heating amount of the heater decreases so as to maintain an ice making rate of the liquid in the space within a predetermined range that is lower than an ice making rate that occurs if the heater is turned off.