Air conditioning systems and methods for operating the same

Abstract

Air conditioning systems ( 1 ) may include an air conditioning circuit ( 2 ) and an electrically driven compressor (C). The compressor may have a motor (M) that includes a rotor ( 12 ) and a stator ( 14 ). The rotor may be rotated by a magnetic force generated when current is supplied to the stator. A temperature sensor ( 22 ) may detect the temperature of the rotor or the ambient temperature when the rotor is started to be rotated. A current calculator ( 26 ) may calculate a demagnetization limit current of the rotor at the detected temperature. The calculated demagnetization limit current may be used for determining a current that will be supplied to the stator for a predetermined period. In the alternative, the supplied current may increase as the rotor temperature increases during the initial operation. Preferably, the current may be less than the demagnetization limit current and may be greater than a minimum current that is required to rotate the rotor.

1 . An apparatus comprising: 
 a compressor arranged and constructed to compress a cooling medium,    an electrically driven motor driving the compressor, the motor having a stator and a rotor, the stator producing a magnetic force that causes the rotor to rotate when sufficient current is supplied to the stator,    a temperature sensor arranged and constructed to detect a temperature that is representative of the rotor temperature, and    a controller arranged and constructed to control the supply of current to the stator in response to the temperature detected by the temperature sensor, wherein the controller is further arranged and constructed to supply current to the stator during an initial operation, in which the rotor temperature is relatively low, the supplied current being greater than or equal to a minimum current required to rotate the rotor and less than or equal to a demagnetization limit current.    
     
     
         2 . An apparatus as in  claim 1 , wherein the controller is further arranged and constructed to determine the demagnetization limit current based upon the detected rotor temperature.  
     
     
         3 . An apparatus as in  claim 2 , wherein the controller is further arranged and constructed to determine an initial stator current based upon the detected rotor temperature at the initiation of compressor operation and to supply the initial stator current until the rotor temperature substantially reaches a predetermined temperature.  
     
     
         4 . An apparatus as in  claim 3 , wherein the initial stator current is slightly less than the demagnetization limit current at the time when current is initially supplied to the stator.  
     
     
         5 . An apparatus as in  claim 3 , wherein the controller is further arranged and constructed to increase the stator current as the rotor temperature increases, wherein the current supplied to the stator is less than, but nearly equal to, the demagnetization limit current.  
     
     
         6 . An apparatus as in  claim 5 , wherein the controller is further arranged and constructed to supply current to the stator until the detected rotor temperature reaches a demagnetization limit temperature that is determined for a normal stator current.  
     
     
         7 . A method for supplying current to a compressor motor that includes a rotor and a stator, the rotor being rotated by a magnetic force generated by supplying current the stator, the method comprising: 
 detecting a temperature representative of a rotor temperature when compressor operation is initiated,    calculating a demagnetization limit current of the rotor at the detected temperature, and    supplying current to the stator, the current being less than or equal to the demagnetization limit current and greater than or equal to a minimum current that is required to rotate the rotor.    
     
     
         8 . A method as in  claim 7 , further comprising: 
 calculating a demagnetization limit temperature of the rotor for normal operation; and    calculating a period of time that is necessary for the rotor to reach the demagnetization limit temperature while the current is supplied to the stator;    supplying the current to the stator for at least the calculated period of time.    
     
     
         9 . A method as in  claim 7 , further comprising: 
 calculating a demagnetization limit temperature of the rotor for normal operation,    periodically detecting the temperature representative of the rotor temperature and    supplying current to the stator at least until the temperature of the rotor reaches the demagnetization limit temperature, the amount of current supplied to the stator being increased as the detected temperature increases.    
     
     
         10 . An apparatus for supplying current to a compressor motor that includes a rotor and a stator, the rotor being rotated by a magnetic force generated by supplying current the stator, the apparatus comprising: 
 means for detecting a temperature representative of a rotor temperature when compressor operation is initiated,    means for calculating a demagnetization limit current of the rotor at the detected temperature, and    means for supplying current to the stator, the current being less than or equal to the demagnetization limit current and greater than or equal to a minimum current that is required to rotate the rotor.    
     
     
         11 . An apparatus as in  claim 10 , further comprising: 
 means for calculating a demagnetization limit temperature of the rotor for normal operation; and    means for calculating a period of time that is necessary for the rotor to reach the demagnetization limit temperature while the current is supplied to the stator;    means for supplying the current to the stator for at least the calculated period of time.    
     
     
         12 . An apparatus as in  claim 10 , further comprising: 
 means for calculating a demagnetization limit temperature for normal operation,    means for periodically detecting the temperature representative of the rotor temperature and    means for supplying current to the stator at least until the temperature of the rotor reaches the demagnetization limit temperature, the amount of current supplied to the stator being increased as the detected temperature increases.    
     
     
         13 . An apparatus comprising: 
 a compressor arranged and constructed to compress a cooling medium,    a motor coupled to the compressor for driving the compressor, the motor having a stator and a rotor, the stator producing a magnetic force to rotate the rotor when current is supplied to the stator,    a temperature sensor arranged and constructed to detect a temperature that represents the temperature of the rotor, and    a controller arranged and constructed to control the supply of current to the stator based upon output signals from the temperature sensor, wherein the rotor rotates without being demagnetized, the controller storing a chart or function for correlating the detected rotor temperature to a demagnetization limit current, which correlation chart or function determines an upper limit for the current supplied to the stator and the controller being further arranged and constructed to supply an initial stator current that is less than or equal to the demagnetization limit current, but greater than or equal to a minimum current required to rotate the rotor.    
     
     
         14 . An apparatus as in  claim 13 , wherein the controller is further arranged and constructed to set the initial stator current to nearly the demagnetization limit current at the time when the current is supplied to the motor.  
     
     
         15 . An apparatus as in  claim 13 , wherein the controller is arranged and constructed to vary the initial stator current as the rotor temperature changes, wherein the initial stator current is selected to be less than, but nearly equal to, the demagnetization limit current at that time.  
     
     
         16 . An apparatus as in  claim 15 , wherein the controller is arranged and constructed to supply the initial stator current to the stator until the detected rotor temperature reaches a demagnetization limit temperature for a predetermined demagnetization limit current, which demagnetization limit temperature is found by the correlation chart or function.  
     
     
         17 . An apparatus comprising: 
 a compressor arranged and constructed to compress a cooling medium,    a motor coupled to the compressor for driving the compressor, the motor having a stator and a rotor, the stator producing a magnetic force to rotate the rotor when current is supplied to the stator,    a temperature sensor arranged and constructed to detect a temperature that represents the temperature of the rotor, and    a processor arranged and constructed to control the supply of current to the stator based upon output signals from the temperature sensor, wherein the rotor rotates without being demagnetized,    the processor comprising instructions to: 
 calculate a demagnetization limit current based upon the detected rotor temperature when the motor is started;  
 calculate a demagnetization limit temperature for a normal stator current; and  
 calculate a time period of time that is necessary to supply a current to the stator, wherein the current supplied to the stator is less than or equal to the calculated demagnetization limit current.  
   
     
     
         18 . An apparatus comprising: 
 a compressor arranged and constructed to compress a cooling medium,    a motor coupled to the compressor for driving the compressor, the motor having a stator and a rotor, the stator producing a magnetic force to rotate the rotor when current is supplied to the stator,    a temperature sensor arranged and constructed to detect a temperature that represents the temperature of the rotor, and    a processor arranged and constructed to control the supply of current to the stator based upon output signals from the temperature sensor, wherein the rotor rotates without being demagnetized,    the processor comprising instructions to: 
 calculate a demagnetization limit current based upon the rotor temperature detected by the temperature sensor,  
 calculate a demagnetization limit temperature for a normal stator current, and  
 supply current to the stator during an initial period until the detected rotor temperature reaches the calculated demagnetization limit temperature.  
   
     
     
         19 . An apparatus comprising: 
 a compressor having a motor that includes a rotor and a stator, the rotor being rotated by a magnetic force generated by supplying current the stator, whereby a cooling medium is circulated within an air conditioning circuit,    means for detecting the temperature of the rotor or an ambient temperature when the rotor starts to rotate,    means for calculating a demagnetization limit current of the rotor at the detected temperature, and    means for supplying current to the stator for a predetermined time period, the current being less than or equal to the demagnetization limit current and greater than or equal to a minimum current that is required to rotate the rotor.    
     
     
         20 . An apparatus as in  claim 19 , further comprising: 
 means for calculating a demagnetization limit temperature of the rotor for normal operation,    means for calculating a period of time that is necessary for the rotor to reach the demagnetization limit temperature while the current is supplied to the stator, and    means for supplying the current to the stator for at least the calculated period of time.    
     
     
         21 . An apparatus comprising: 
 a compressor having a motor that comprises a rotor and a stator, the rotor being rotated by magnetic force generated by supplying current to the stator, whereby a cooling medium is circulated within an air conditioning circuit,    means for detecting the temperature of the rotor,    means for calculating a demagnetization limit temperature for normal operation,    means for calculating a demagnetization limit current from the detected temperature, and    means for supplying current to the stator at least until the temperature of the rotor reaches the demagnetization limit temperature, the current being less than or equal to the demagnetization limit current and being greater than or equal to a minimum current that is required to rotate the rotor.    
     
     
         22 . An air conditioning system comprising: 
 a compressor having a motor, the motor including a rotor and a stator, the rotor being rotated by a magnetic force generated by supplying current to the stator, whereby a cooling medium is circulated within an air conditioning circuit,    a temperature sensor arranged and constructed to detect either the rotor temperature or an ambient temperature,    a current calculator arranged and constructed to calculate a demagnetization limit current for the rotor at a temperature detected when current is initially supplied to the stator, and    means for supplying current to the stator for a predetermined period, which current is less than or equal to the calculated demagnetization limit current and is greater than or equal to a minimum current that is required to rotate the rotor.    
     
     
         23 . An air conditioning system as in  claim 22 , further including: 
 a temperature calculator arranged and constructed to calculate a demagnetization limit temperature for the rotor during normal operation, and    a time calculator arranged and constructed to calculate a period of time that is necessary for the rotor to reach the calculated demagnetization limit temperature while the current is being supplied to the stator, wherein the current supplying means supplies the current to the stator at least during the period of time that is calculated by the time calculator.    
     
     
         24 . An air conditioning system comprising: 
 a compressor having a motor, the motor including a rotor and a stator, the rotor being rotated by a magnetic force generated by supplying current the stator, whereby a cooling medium is circulated within a air conditioning circuit,    a temperature sensor arranged and constructed to detect the temperature of the rotor; and    a temperature calculator arranged and constructed to calculate a demagnetization limit temperature of the rotor during normal operation;    a current calculator arranged and constructed to calculate a demagnetization limit current from the temperature detected by the temperature sensor; and    means for supplying current to the stator at least until the detected temperature of the rotor reaches the demagnetization limit temperature, wherein the supplied current is less than or equal to the demagnetization limit current and is greater than or equal to a minimum current that is required to rotate the rotor.