Method for operating a household refrigeration appliance which has a heat-insulated carcass with a coolable inner container , which delimits a coolable interior space provided to store food, a refrigerant circuit provided to cool the coolable interior space with a coolant and a compressor , and a regulated electric drive , wherein the regulated electric drive has a three-phase AC synchronous motor and a control element, which is configured in particular as an inverter , for activating the three-phase AC synchronous motor and the compressor has a compressor chamber with an inlet and an outlet , a piston mounted in a displaceable manner within the compressor chamber , a crankshaft and the three-phase AC synchronous motor of the regulated electric drive , wherein the regulated electric drive has a measuring apparatus , which is used to measure electric phase currents ( i 1,2,3 ) of the three-phase AC synchronous motor , and an actual speed of the three-phase AC synchronous motor is determined by the measuring apparatus preprocessing the determined actual speed and the measured electric phase currents ( i 1,2,3 ) of the three-phase AC synchronous motor , so that the determined actual speed and the measured electric phase currents ( i 1,2,3 ) of the three-phase AC synchronous motor are processed by a regulator of the electric drive in a suitable form, wherein the three-phase AC synchronous motor comprises a number P of pole pairs greater than 1, a stator and a rotor that is coupled to the piston by way of the crankshaft and mounted in such a manner that it can rotate in relation to the stator , so that when the compressor operates, the piston is able to reduce a volume enclosed by the compressor chamber and piston by means of the three-phase AC synchronous motor , in order to compress the coolant, having the following method steps for determining the position of the piston relative to the compressor chamber during operation of the compressor in the intended manner: - Determining the greatest sum of at least one instantaneous value of at least one of the electric phase currents ( i 1,2,3 ) of the three-phase AC synchronous motor , for at least one full rotation of the rotor relative to the stator , - Determining the angular position of the rotor relative to the stator assigned to the determined instantaneous value , wherein to this end the three-phase AC synchronous motor generates a torque (M) as a function of the position of the piston , which is at a maximum close to or at the top dead centre, and at least one of the phase currents ( i 1,2,3 ), the current strengths of which are a function of the torque (M), in order to identify the top dead centre, and - Determining the position of the piston relative to the compressor chamber based on the speed of the three-phase AC synchronous motor and the angular position of the rotor assigned to the determined instantaneous value . - Determining the greatest sum of at least one instantaneous value of at least one of the electric phase currents ( i 1,2,3 ) of the three-phase AC synchronous motor , for at least one full rotation of the rotor relative to the stator , - Determining the angular position of the rotor relative to the stator assigned to the determined instantaneous value , wherein to this end the three-phase AC synchronous motor generates a torque (M) as a function of the position of the piston , which is at a maximum close to or at the top dead centre, and at least one of the phase currents ( i 1,2,3 ), the current strengths of which are a function of the torque (M), in order to identify the top dead centre, and - Determining the position of the piston relative to the compressor chamber based on the speed of the three-phase AC synchronous motor and the angular position of the rotor assigned to the determined instantaneous value . <EOS>