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EP-4738683-A1 - A REFRIGERATION SYSTEM AND A METHOD OF OPERATING A REFRIGERATION SYSTEM

EP4738683A1EP 4738683 A1EP4738683 A1EP 4738683A1EP-4738683-A1

Abstract

There is described a refrigeration system 10, the refrigeration system 10 comprising an induction motor 18 having a rotor 23, wherein the refrigeration system 10 is configured to: supply 102 an alternating current to the induction motor 18 to induce rotation of the rotor 23, wherein rotation of the rotor 23 powers one or more loads 20, 21 of the refrigeration system 10; identify 104 a predetermined threshold value R t1 of a parameter R of the induction motor 18 and a predetermined relationship associated with the induction motor 18 between the parameter R and a derating amount P 1 , the parameter R being an angular velocity or a slip of the rotor 23 of the induction motor 18; determine 106 the parameter R of the rotor 23 during rotation of the rotor 23; determine 108 whether the determined parameter R meets a first condition, the first condition being the angular velocity R being less than the predetermined threshold value R t1 or the slip being greater than the predetermined threshold value R t1 ; upon determining that the first condition has been met, determine 110 a derating amount P 1 based on the determined parameter R and the predetermined relationship; and derate 112 the one or more loads 20, 21 by the derating amount P 1 . There is also described a method 100, 200, 300, 400, 500 of operating a refrigeration system.

Inventors

  • SMYTH, Ciarán

Assignees

  • Thermo King LLC

Dates

Publication Date
20260506
Application Date
20241029

Claims (15)

  1. A refrigeration system (10), the refrigeration system (10) comprising an induction motor (18) having a rotor (23), wherein the refrigeration system (10) is configured to: supply (102) an alternating current to the induction motor (18) to induce rotation of the rotor (23), wherein rotation of the rotor (23) powers one or more loads (20, 21) of the refrigeration system (10); identify (104) a predetermined threshold value (R t1 ) of a parameter (R) of the induction motor (18) and a predetermined relationship associated with the induction motor (18) between the parameter (R) and a derating amount (P 1 ), the parameter (R) being an angular velocity or a slip of the rotor (23) of the induction motor (18); determine (106) the parameter (R) of the rotor (23) during rotation of the rotor (23); determine (108) whether the determined parameter (R) meets a first condition, the first condition being the angular velocity (R) being less than the predetermined threshold value (R t1 ) or the slip being greater than the predetermined threshold value (R t1 ); upon determining that the first condition has been met, determine (110) a derating amount (P 1 ) based on the determined parameter (R) and the predetermined relationship; and derate (112) the one or more loads (20, 21) by the derating amount (P 1 ).
  2. A refrigeration system (10) as claimed in claim 1, wherein the refrigeration system (10) is configured to: determine (216) an updated parameter (R') of the rotor (23) during rotation of the rotor (23) following derating (112) the induction motor (18) by the derating amount (P 1 ), the determined updated parameter (R') being an updated angular velocity or an updated slip of the rotor (23) of the induction motor (18); determine (218) whether the determined updated parameter (R') meets a second condition, the second condition being the updated angular velocity (R) being greater than the predetermined threshold value (R t1 ) or the slip being less than the predetermined threshold value (R t1 ); and stop derating (220) the induction motor (18) by the derating amount (P 1 ) upon determining that the second condition has been met.
  3. A refrigeration system (10) as claimed in claim 2, wherein the refrigeration system (10) is configured to: determine (218) whether the determined updated parameter (R') meets the second condition for a predetermined threshold period of preceding time (t t ); stop derating (220) the induction motor (18) by the derating amount (P 1 ) upon determining that the second condition has continuously been met for the predetermined threshold period of preceding time (t t ); and continue derating (112) the induction motor (18) by the derating amount (P 1 ) upon determining that the second condition has not been met for the predetermined threshold period of preceding time (t t ).
  4. A refrigeration system (10) as claimed in claim 2 or 3, wherein the refrigeration system (10) is configured to: identify (104) a predetermined further threshold value (R t2 ), the predetermined further threshold value (R t2 ) being a predetermined threshold value of the determined updated parameter (R'), wherein the predetermined further threshold value (R t2 ) is less than the predetermined threshold value (R t1 ) if the parameter (R) is the angular velocity of the rotor (23), and wherein the predetermined further threshold value (R t2 ) is greater than the predetermined threshold value (R t1 ) if the parameter (R) is the slip of the rotor (23); and determine (320) whether the determined updated parameter (R') meets a third condition, the third condition being the updated angular velocity (R') being greater than the predetermined further threshold value (R t2 ) or the updated slip being less than the predetermined further threshold value (R t2 ).
  5. A refrigeration system (10) as claimed in claim 4, wherein the refrigeration system (10) is configured to: determine (324) an updated derating amount (P 2 ) based on the determined updated parameter (R') and the predetermined relationship upon determining that the third condition has been met; determine (326) whether the updated derating amount (P 2 ) is greater than the derating amount (P 1 ); and derate (328) the induction motor (18) by the updated derating amount (P 2 ) upon determining (326) that the updated derating amount (P 2 ) is greater than the derating amount (P 1 ).
  6. A refrigeration system (10) as claimed in claim 4 or 5, wherein the refrigeration system (10) is configured to: shut down (322) the induction motor (18) upon determining that the third condition has not been met.
  7. A refrigeration system (10) as claimed in any preceding claim, wherein the alternating current that the refrigeration system (10) is configured to supply to the induction motor (18) has a phase, wherein the predetermined threshold value (R t1 ) is predetermined as being the angular velocity or slip of the rotor (23) of the induction motor (18) that results in a temperature (T lt ) of the winding (24a-24f, 25a-25f) of the induction motor (18) being a predetermined first amount lower than a predetermined rated temperature (T rated ) of the winding (24a-24f, 25a-25f) of the induction motor (18) when the induction motor (18) is supplied with the phase of alternating current.
  8. A refrigeration system (10) as claimed in claim 7 when appended to any of claims 4 to 6, wherein the predetermined further threshold value (R t2 ) is predetermined as being the angular velocity or slip of the rotor (23) of the induction motor (18) that results in a temperature (T ut ) of the winding (24a-24f, 25a-25f) of the induction motor (18) being a predetermined second amount lower than the predetermined rated temperature (T rated ) of the winding (24a-24f, 25a-25f) of the induction motor when the induction motor (18) is supplied with the phase of alternating current, the second amount being less than the first amount.
  9. A refrigeration system (10) as claimed in claim 7 or 8, wherein the derating amount (P 1 ) and/or the updated derating amount (P 2 ) tend to a predetermined maximum derating amount (P max ) as the determined parameter (R) and/or the determined updated parameter (R') tend to the predetermined further threshold value (R t2 ), wherein the predetermined maximum derating amount (P max ) is or is based on the maximum amount the load on the induction motor (18) needs to be reduced by for the temperature of the winding (24a-24f, 25a-25f) to be less than the temperature (T lt ) of the winding (24a-24f, 25a-25f) that is the first amount lower than the predetermined rated temperature (T rated ) of the winding (24a-24f, 25a-25f).
  10. A refrigeration system (10) as claimed in any preceding claim, wherein the derating amount (P 1 ) and/or the updated derating amount (P 2 ) tend to zero as the determined parameter (R) and/or the determined updated parameter (R') tend to the predetermined threshold value (R t1 ).
  11. A refrigeration system (10) as claimed in any preceding claim, wherein the derating amount (P 1 ) is directly proportional to the difference between the determined parameter (R) and the predetermined threshold value (R t1 ) and/or wherein the updated derating amount (P 2 ) is directly proportional to the difference between the determined updated parameter (R') and the predetermined threshold value (R t1 ).
  12. A refrigeration system (10) as claimed in any preceding claim, wherein the induction motor (18) is selected from a plurality of induction motors (18), wherein one or more of the predetermined threshold value (R t1 ), the predetermined further threshold value (R t2 ), the predetermined relationship associated with the induction motor (18) between the derating amount (P 1 ) and the determined parameter (R), the predetermined threshold period of preceding time (t t ), the predetermined first amount, the predetermined rated temperature (T rated ), the predetermined second amount and the predetermined maximum derating amount of each of the plurality of induction motors (18) are stored in a memory that is accessible by the refrigeration system (10), wherein optionally the memory is in the form of a lookup table.
  13. A refrigeration system (10) as claimed in any preceding claim, wherein the determined parameter (R) and/or the determined updated parameter (R') is an average angular velocity or an average slip of the rotor (23) over a predetermined period of time.
  14. A refrigeration system (10) as claimed in any preceding claim, wherein the refrigeration system (10) is configured to: start up (502) the refrigeration system (10); determine (502) whether the refrigeration system (10) is operating in an electric mode of operation; carry out the steps of any preceding claim upon determining that the transportation refrigeration system (10) is operating in the electric mode of operation; and not carry out the steps of any preceding claim upon determining that the transportation refrigeration system (10) is not operating in the electric mode of operation.
  15. A method (100, 200, 300, 400, 500) of operating a refrigeration system (10) as claimed in any preceding claim, the method (100, 200, 300, 400, 500) comprising: supplying (102) an alternating current to the induction motor (18) to induce rotation of the rotor (23), wherein rotation of the rotor (23) powers the one or more loads (20, 21) of the refrigeration system (10); identifying (104) a predetermined threshold value (R t1 ) of a parameter (R) of the induction motor (18) and a predetermined relationship associated with the induction motor (18) between the parameter (R) and a derating amount (P 1 ), the parameter (R) being an angular velocity or a slip of the rotor (23) of the induction motor (18); determining (106) the parameter of the rotor (23) during rotation of the rotor (23); determining (108) whether the determined parameter (R) meets a first condition, the first condition being the angular velocity (R) being less than the predetermined threshold value (R t1 ) or the slip being greater than the predetermined threshold value (R t1 ); upon determining that the first condition has been met, determining (110) a derating amount (P 1 ) based on the determined parameter (R) and the predetermined relationship; and derating (112) the one or more loads (20, 21) by the derating amount (P 1 ).

Description

FIELD OF THE INVENTION The invention relates to a refrigeration system and a method of operating a refrigeration system. BACKGROUND OF THE INVENTION Induction motors comprise a stator having a plurality of stator windings and a rotor having a plurality of rotor windings. During operation, power is provided to the stator windings, which generates a rotating magnetic field. The rotating magnetic field induces a current in the rotor windings that interacts with the rotating magnetic field generated by the stator windings. This interaction results in a force being imparted on the rotor that causes it to rotate in the same direction as the rotating magnetic field. The electrical current flowing through the stator windings causes the temperature of the stator windings to increase and become damaged if they get too hot. Accordingly, induction motors commonly incorporate control systems comprising temperature sensors embedded in the stator windings that sense the temperature of the stator windings during operation and derate the load on the induction motor if the stator windings become too hot. However, the sensors may be unreliable, expensive and not accurately reflect the true temperature of the stator windings. It is therefore desirable to provide an improved refrigeration system and method of operating a refrigeration system that addresses these issues. STATEMENTS OF INVENTION According to an aspect there is described a refrigeration system, the refrigeration system comprising an induction motor having a rotor. The refrigeration system is configured to: supply an alternating current to the induction motor to induce rotation of the rotor, wherein rotation of the rotor powers one or more loads of the refrigeration system; identify a predetermined threshold value of a parameter of the induction motor and a predetermined relationship associated with the induction motor between the parameter and a derating amount, the parameter being an angular velocity or a slip of the rotor of the induction motor; determine the parameter of the rotor during rotation of the rotor; determine whether the determined parameter meets a first condition, the first condition being the angular velocity being less than the predetermined threshold value or the slip being greater than the predetermined threshold value; upon determining that the first condition has been met, determine a derating amount based on the determined parameter and the predetermined relationship; and derate the one or more loads by the derating amount. The refrigeration system may be configured to: determine an updated parameter of the rotor during rotation of the rotor following derating the induction motor by the derating amount, the determined updated parameter being an updated angular velocity or an updated slip of the rotor of the induction motor; determine whether the determined updated parameter meets a second condition, the second condition being the updated angular velocity being greater than the predetermined threshold value or the slip being less than the predetermined threshold value; and stop derating the induction motor by the derating amount upon determining that the second condition has been met. The refrigeration system may be configured to: determine whether the determined updated parameter meets the second condition for a predetermined threshold period of preceding time; stop derating the induction motor by the derating amount upon determining that the second condition has continuously been met for the predetermined threshold period of preceding time; and continue derating the induction motor by the derating amount upon determining that the second condition has not been met for the predetermined threshold period of preceding time. The refrigeration system may be configured to: identify a predetermined further threshold value, the predetermined further threshold value being a predetermined threshold value of the determined updated parameter, wherein the predetermined further threshold value is less than the predetermined threshold value if the parameter is the angular velocity of the rotor, and wherein the predetermined further threshold value is greater than the predetermined threshold value if the parameter is the slip of the rotor; and determine whether the determined updated parameter meets a third condition, the third condition being the updated angular velocity being greater than the predetermined further threshold value or the updated slip being less than the predetermined further threshold value. The refrigeration system may be configured to: determine an updated derating amount based on the determined updated parameter and the predetermined relationship upon determining that the third condition has been met; determine whether the updated derating amount is greater than the derating amount; and derate the induction motor by the updated derating amount upon determining that the updated derating amount is greater than the derating amount. The ref