Refrigeration apparatus and method of operation

Abstract

A refrigeration apparatus (10) has one or more chambers (12′, 12″) in which items to be cooled can be located. A compressor (20 driven by an electric motor (22) compresses vaporised refrigerant as part of a refrigeration cycle. The refrigeration apparatus (10) has an ambient temperature sensor (34) for measuring ambient temperature and at least one inner temperature sensor (36, 38) for measuring a temperature of the interior of the refrigeration apparatus (10). A controller (40) receives outputs from temperature sensors (34, 36, 38). The controller (40) obtains measures of a motor current of the electric motor (22) at time intervals which are based on the ambient temperature and the inner temperature. Based on the measures of the motor current at the time intervals, the controller (40) at least one of (ii) controls operation of the electric motor (22) and (ii) initiates defrost procedure for the refrigeration apparatus (10).

1 . Refrigeration apparatus, the refrigeration apparatus comprising:
 a chamber in which items to be cooled can be located;   a compressor for compressing vaporised refrigerant;   an electric motor for driving operation of the compressor;   an ambient temperature sensor for measuring ambient temperature in the neighbourhood of the refrigeration apparatus;   at least one inner temperature sensor for measuring a temperature of the interior of the refrigeration apparatus; and   a controller constructed and arranged to receive outputs from the ambient temperature sensor and the inner temperature sensor;   the controller being constructed and arranged to obtain measures of a motor current of the electric motor at time intervals which are based on the ambient temperature and the inner temperature;   the controller being constructed and arranged, based on the measures of the motor current of the electric motor at the time intervals, to at least one of (ii) control operation of the electric motor and (ii) initiate a defrost procedure for the refrigeration apparatus.   
     
     
         2 . Refrigeration apparatus according to  claim 1 , wherein the controller is arranged such that the time intervals at which the measures of the motor current of the electric motor are obtained are based on the difference between the ambient temperature and the temperature of the interior of the refrigeration apparatus. 
     
     
         3 . Refrigeration apparatus according to  claim 2 , wherein the controller is arranged such that the time intervals in units of time are proportional to the magnitude of the difference between the ambient temperature and the temperature of the interior of the refrigeration apparatus. 
     
     
         4 . Refrigeration apparatus according to  claim 1 , wherein the controller is arranged to at least one of (ii) control operation of the electric motor and (ii) initiate a defrost procedure for the refrigeration apparatus based on comparing the values of the motor current as measured at adjacent time intervals. 
     
     
         5 . Refrigeration apparatus according to  claim 4 , wherein the values of the motor current as measured at adjacent time intervals are compared by, for each adjacent pair of time intervals, taking a difference of the motor currents as measured in the adjacent time intervals, and comparing the number of said difference of the motor currents that are less than a predetermined percentage threshold with the number of said difference of the motor currents that are more than the percentage threshold. 
     
     
         6 . Refrigeration apparatus according to  claim 5 , wherein in the case that, over a time period, the number of said difference of the motor currents that are less than the predetermined percentage threshold is substantially the same as the number of said difference of the motor currents that are more than the percentage threshold, then the controller is arranged to command the electric motor to run at a lower speed and to initiate a defrost procedure for the refrigeration apparatus. 
     
     
         7 . Refrigeration apparatus according to  claim 5 , wherein in the case that, over a time period, the number of said difference of the motor currents that are less than the predetermined percentage threshold is more than around twice the number of said difference of the motor currents that are more than the percentage threshold, then the controller is arranged to command the electric motor to stop and to initiate a defrost procedure for the refrigeration apparatus. 
     
     
         8 . Refrigeration apparatus according to  claim 1 , comprising:
 an evaporator in which refrigerant vaporises in use to absorb heat from the chamber;   pipes for respectively carrying refrigerant from the evaporator to the compressor and for carrying refrigerant from the compressor to the evaporator;   one or more fans for circulating air within the refrigeration apparatus; and   one or more air channels through which cold air passes in use to circulate cold air within the refrigeration apparatus.   
     
     
         9 . A method of operating a refrigeration apparatus, the refrigeration apparatus comprising:
 a chamber in which items to be cooled can be located;   a compressor for compressing vaporised refrigerant;   an electric motor for driving operation of the compressor;   an ambient temperature sensor for measuring ambient temperature in the neighbourhood of the refrigeration apparatus; and   at least one inner temperature sensor for measuring a temperature of the interior of the refrigeration apparatus;   the method comprising:   a controller receiving outputs from the ambient temperature sensor and the inner temperature sensor;   the controller obtaining measures of a motor current of the electric motor at time intervals which are based on the ambient temperature and the inner temperature; and   based on the measures of the motor current of the electric motor at the time intervals, the controller at least one of (ii) controlling operation of the electric motor and (ii) initiating a defrost procedure for the refrigeration apparatus.   
     
     
         10 . A method according to  claim 9 , wherein the time intervals at which the measures of the motor current of the electric motor are obtained are based on the difference between the ambient temperature and the temperature of the interior of the refrigeration apparatus. 
     
     
         11 . A method according to  claim 10 , wherein the time intervals in units of time are proportional to the magnitude of the difference between the ambient temperature and the temperature of the interior of the refrigeration apparatus. 
     
     
         12 . A method according to  claim 9 , wherein the controller at least one of (ii) controls operation of the electric motor and (ii) initiates a defrost procedure for the refrigeration apparatus based on comparing the values of the motor current as measured at adjacent time intervals. 
     
     
         13 . A method apparatus according to  claim 12 , wherein the values of the motor current as measured at adjacent time intervals are compared by, for each adjacent pair of time intervals, taking a difference of the motor currents as measured in the adjacent time intervals, and comparing the number of said difference of the motor currents that are less than a predetermined percentage threshold with the number of said difference of the motor currents that are more than the percentage threshold. 
     
     
         14 . A method according to  claim 13 , wherein in the case that, over a time period, the number of said difference of the motor currents that are less than the predetermined percentage threshold is substantially the same as the number of said difference of the motor currents that are more than the percentage threshold, then the controller commands the electric motor to run at a lower speed and initiates a defrost procedure for the refrigeration apparatus. 
     
     
         15 . A method according to  claim 13 , wherein in the case that, over a time period, the number of said difference of the motor currents that are less than the predetermined percentage threshold is more than around twice the number of said difference of the motor currents that are more than the percentage threshold, then the controller commands the electric motor to stop and initiates a defrost procedure for the refrigeration apparatus.