Refrigeration system and method of operating refrigeration system

Abstract

Described is a refrigeration system 10 comprising: an induction motor 18 having a rotor 23; a power source 16 connected to the induction motor 18 for supplying 102 alternating current to the induction motor 18 to cause rotation of the rotor 23, where the rotation of the rotor 23 supplies power to one or more loads 20, 21 of the refrigeration system 10; and a controller 12. The controller 12 is configured to: identify 104 a predetermined threshold value Rt1 of a parameter R of the induction machine 18 and a predetermined relationship associated with the induction machine 18 between the parameter R and a derating amount P1, the parameter R being an angular rate or slip of a rotor 23 of the induction machine 18; determining 106 a parameter R of the rotor 23 during rotation of the rotor 23; determining 108 whether the determined parameter R satisfies a first condition that the angular rate R is less than a predetermined threshold Rt1 or the slip is greater than the predetermined threshold Rt1; upon determining that the first condition has been satisfied, determining a 110 derating amount P1 based on the determined parameter R and a predetermined relationship; and derating the one or more loads 20, 21 by a derating amount 112 by a derating amount P1. Methods 100, 200, 300, 400, 500 of operating the refrigeration system are also described.

Description

Refrigeration system and methods for operating the refrigeration system Technical Field

[0001] This invention relates to refrigeration systems and methods for operating refrigeration systems. Background Technology

[0002] An induction motor comprises a stator with multiple stator windings and a rotor with multiple rotor windings. During operation, electricity is supplied to the stator windings, which generates a rotating magnetic field. This 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 applied to the rotor, causing it to rotate in the same direction as the rotating magnetic field. The current flowing through the stator windings causes the temperature of the stator windings to rise, and if the stator windings become too hot, they can be damaged. Therefore, induction motors typically incorporate a control system that includes a temperature sensor embedded in the stator windings that senses the temperature of the stator windings during operation and, if the stator windings become too hot, reduces the load rating on the induction motor, i.e., derating it. However, the sensor may be unreliable, expensive, and may not accurately reflect the true temperature of the stator windings. Therefore, an improved cooling system and a method for operating the cooling system are desired to address these problems. Summary of the Invention

[0003] According to one aspect, a refrigeration system is described, the refrigeration system comprising: an induction motor having a rotor, a power supply, and a controller. The power supply is connected to the induction motor to supply alternating current to the induction motor to cause rotation of the rotor, wherein the rotation of the rotor powers one or more loads of the refrigeration system. The controller is configured to: identify the predetermined threshold 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 rate or slip of the rotor of the induction motor; determine the parameter of the rotor during rotation of the rotor; determine whether the determined parameter satisfies a first condition, the first condition being that the angular rate is less than the predetermined threshold or the slip is greater than the predetermined threshold; when the first condition is determined to be satisfied, determine the derating amount based on the determined parameter and the predetermined relationship; and drate the one or more loads by the derating amount.

[0004] The controller can be configured to: after derated the induction motor by the derated amount, determine updated parameters of the rotor during the rotation of the rotor, wherein the determined updated parameters are an updated angular rate or an updated slip of the rotor of the induction motor; determine whether the determined updated parameters satisfy a second condition, wherein the second condition is that the updated angular rate is greater than a predetermined threshold or the slip is less than the predetermined threshold; and stop derated the induction motor by the derated amount when it is determined that the second condition has been satisfied.

[0005] The controller can be configured to: determine whether the determined updated parameters satisfy the second condition for a predetermined threshold prior time period; when it is determined that the second condition has been continuously satisfied for the predetermined threshold prior time period, stop derate the induction motor by the derate amount; and when it is determined that the second condition has not been satisfied for the predetermined threshold prior time period, continue to derate the induction motor by the derate amount.

[0006] The controller can be configured to: identify another predetermined threshold, the other predetermined threshold being a predetermined threshold of a determined updated parameter, wherein if the parameter is the angular rate of the rotor, the other predetermined threshold is less than the predetermined threshold, and wherein if the parameter is the slip of the rotor, the other predetermined threshold is greater than the predetermined threshold; and determine whether the determined updated parameter satisfies a third condition, the third condition being that the updated angular rate is greater than the other predetermined threshold or the updated slip is less than the other predetermined threshold.

[0007] The controller can be configured to: when it is determined that the third condition has been met, determine an updated derating amount based on the determined updated parameters and the predetermined relationship; determine whether the updated derating amount is greater than the derating amount; and when it is determined that the updated derating amount is greater than the derating amount, derate the induction motor by the updated derating amount.

[0008] The controller can be configured to shut down the induction motor when it is determined that the third condition has not yet been met.

[0009] The cooling system is configured such that the alternating current supplied to the induction motor can have a phase. The predetermined threshold can be predetermined as a first amount of angular velocity or slip of the rotor of the induction motor that causes the temperature of the windings of the induction motor to be lower than a predetermined rated temperature of the windings of the induction motor when the induction motor is supplied with the phase of the alternating current.

[0010] The other predetermined threshold may be defined as a second amount of angular velocity or slip of the rotor of the induction motor that causes the temperature of the windings of the induction motor to be lower than the predetermined rated temperature of the windings of the induction motor when the induction motor is supplied with the phase of alternating current, the second amount being less than the first amount.

[0011] As the determined parameters and / or the determined updated parameters tend toward the other predetermined threshold, the derating amount and / or the updated derating amount may tend toward a predetermined maximum derating amount. The predetermined maximum derating amount may be, or is based on, the maximum amount by which the load on the induction motor needs to be reduced so that the temperature of the winding is less than the temperature of the winding that is a first amount lower than the predetermined rated temperature of the winding.

[0012] As the determined parameters and / or the determined updated parameters approach the predetermined threshold, the derating amount and / or the updated derating amount may approach zero.

[0013] The reduction amount can be proportional to the difference between the determined parameter and the predetermined threshold. The updated reduction amount can be proportional to the difference between the determined updated parameter and the predetermined threshold.

[0014] The induction motor may be selected from a plurality of induction motors. One or more of the predetermined threshold, the other predetermined threshold, the predetermined relationship between the derating amount and the determined parameters associated with the induction motor, the previous time period of the predetermined threshold, the predetermined first amount, the predetermined rated temperature, the predetermined second amount, and the predetermined maximum derating amount of each of the plurality of induction motors may be stored in a memory accessible by the refrigeration system, wherein, optionally, the memory is in the form of a lookup table.

[0015] The determined parameters can be the average angular velocity or average slip of the rotor over a predetermined time period.

[0016] The controller may be configured to: start the refrigeration system; determine whether the refrigeration system is operating in an electric operation mode; when it is determined that the transport refrigeration system is operating in the electric operation mode, perform the steps of any of the preceding claims; and when it is determined that the transport refrigeration system is not operating in the electric operation mode, not perform the steps of any of the preceding claims.

[0017] The controller can be configured to determine the parameters and / or the updated parameters based on one or more values ​​output to the controller by one or more sensors of the refrigeration system. The one or more sensors may include angular rate sensors, and the one or more values ​​may indicate the angular rate of the rotor. The one or more sensors may include angular position sensors, and the one or more values ​​may indicate the angular position of the rotor. The one or more sensors may include current sensors, and the one or more values ​​may indicate the current of the rotor or stator of the induction motor. The one or more sensors may include voltage sensors, and the one or more values ​​may indicate the voltage of the rotor or stator of the induction motor. The one or more sensors may include frequency meters, and the one or more values ​​may indicate the frequency of the rotor or stator of the induction motor.

[0018] A method of operating a refrigeration system according to any one of the preceding claims, the method comprising: supplying an alternating current to an induction motor to cause rotation of the rotor, wherein the rotation of the rotor powers one or more loads of the refrigeration system; identifying predetermined thresholds for parameters of the induction motor and predetermined relationships between the parameters and derating amounts associated with the induction motor, the parameters being angular velocity or slip of the rotor of the induction motor; determining parameters of the rotor during rotation of the rotor; determining whether the determined parameters satisfy a first condition, the first condition being that the angular velocity is less than the predetermined threshold or the slip is greater than the predetermined threshold; determining a derating amount based on the determined parameters and the predetermined relationship when the first condition is determined to be satisfied; and derating the one or more loads by the derating amount. Attached Figure Description

[0019] To better understand the invention and to more clearly illustrate how to implement it, reference will now be made by way of example to the accompanying drawings, in which:

[0020] Figure 1 is a perspective view of a vehicle including a refrigeration system;

[0021] Figure 2 schematically illustrates a first example of a refrigeration system;

[0022] Figure 3 is a flowchart of a first method for operating the first example refrigeration system;

[0023] Figure 4 is a flowchart of a second method for operating the first example refrigeration system;

[0024] Figure 5 is a flowchart of the third method for operating the first example refrigeration system;

[0025] Figure 6 is a flowchart of the fourth method for operating the first example refrigeration system;

[0026] Figure 7 schematically illustrates a second example refrigeration system;

[0027] Figure 8 is a flowchart of the method for operating the second example refrigeration system;

[0028] Figure 9 is a graph showing the relationship between slip and torque in an induction motor; and

[0029] Figure 10 is a flowchart of a method for pre-determining the characteristics of an induction motor. Detailed Implementation

[0030] Figure 1 shows a vehicle 2 including a climate-controlled module 4. The climate-controlled module 4 is a refrigerated semi-trailer for road transport with a structure 6 supporting (or forming) a single climate-controlled compartment 8, which is configured to be cooled by a refrigeration system 10 (also referred to as a transport refrigeration unit or TRU). The structure 6 also supports the refrigeration system 10. The vehicle 2 also includes a tractor unit 13, which can be removably coupled to the climate-controlled module 4.

[0031] Figure 2 is a schematic diagram of a refrigeration system 10. The refrigeration system 10 includes a controller 12 and a housing 14. A compressor 20, a condenser 34, an expansion device 36, and an evaporator 38 are disposed within the housing 14 and are connected in series in terms of flow. A power supply 16, an induction motor 18, and a generator 21 are also disposed within the housing 14. The induction motor 18 includes a stator 17; a rotor 23; a plurality of stator windings 24a, 24b, 24c, 24d, 24e, 24f; and a plurality of rotor windings 25a, 25b, 25c, 25d, 25e, 25f. The controller 12 is configured to operate the refrigeration system 10 according to methods 100, 200, 300, and 400 described below.

[0032] The controller 12 is communicatively connected to the power supply 16 via a first wired or wireless connection 28, and the power supply 16 is connected (i.e., electrically connected) to the induction motor 18 via a wired connection 30. The power supply 16 is configured to output alternating current. The power supply 16 may generate only alternating current. Alternatively, the power supply 16 may generate direct current, which is then converted to alternating current by an inverter forming part of the power supply 16, the inverter being configured to supply alternating current to the induction motor 18 to cause rotation of the rotor 23. In such an embodiment, the inverter may be housed together with other components of the power supply 16. Alternatively, the inverter may be positioned separately (e.g., housed) from other components of the power supply 16, but still form part of the power supply 16.

[0033] It should be understood that power source 16 is a power source for induction motor 18 (i.e., the component from which induction motor 18 receives power), but does not need to be the final power source (i.e., the feature that generates power in the first case). For example, power source 16 itself may have power supplied by another power source 27 (shown in dashed lines in Figure 2), and then power source 16 supplies that power to induction motor 18. For example, power source 16 may be a power supply interface module (such as a high-voltage tray) powered by AC power (e.g., the grid, an inverter, or other AC power supply). Such a power supply interface module may be a switch box and includes a set of contactors that can be selectively engaged or disengaged to connect and disconnect induction motor 18 from the AC power received from power source 27.

[0034] Although the power supply 16 has been described as being located within the housing 14, in alternative embodiments, the housing 14 may be omitted. Alternatively, the housing 14 may still be provided, but components of the refrigeration system 10 may be located outside the housing 14. For example, the power supply 16 may be located outside the housing 14. By another example, the compressor 20 and / or the condenser 34 and / or the expander 36 and / or the evaporator 38 may be located outside the housing 14.

[0035] The refrigeration system 10 also includes a sensor 40. The sensor 40 is operatively coupled to the rotor 23 via an operative coupling 42. The sensor 40 can be physically, i.e., physically coupled to the rotor 23, in which case the operative coupling 42 is a physical connection. Alternatively, the operative coupling 42 can be located away from the rotor 23, in which case the operative coupling 42 is a non-physical connection. The sensor 40 is communicatively coupled to the controller 12 via a second wired or wireless connection 44. In the illustrated embodiment, the sensor 40 is an angular rate sensor configured to output one or more values ​​indicating the angular rate of the rotor 23. It should be understood that the controller 12 may include a single controller or multiple controllers located at different locations. For example, although not shown, a portion of the controller 12 may be located within the sensor 40, and a portion of the controller 12 may be located remotely from the sensor 40.

[0036] Induction motor 18 is mechanically coupled to compressor 20 via a first mechanical coupling 32, which is schematically shown in Figure 2 along with other components of refrigeration system 10. Induction motor 18 is connected to generator 21 via a second mechanical coupling 31. Generator 21 is then electrically connected to one or more electrical components of refrigeration system 10, such as one or more fans of refrigeration system 10 and / or one or more batteries of refrigeration system 10. In an alternative embodiment, both compressor 20 and generator 21 may be connected to induction motor 18 via a single mechanical coupling.

[0037] During operation, the cooling system 10 is started by the controller 12. The controller 12 instructs the power supply 16 to supply power to the induction motor 18 via the wired connection 30. Specifically, three-phase power is supplied to the stator windings 24a-24f via the power supply 16 (e.g., via the inverter of the power supply 16), which, as described above, can then be supplied with power from another power source 27 (e.g., grid power). The current flowing through the stator windings 24a-24f generates a rotating magnetic field and causes the temperature of the stator windings 24a-24f to rise. The rotational speed of the rotating magnetic field is called the synchronous speed. The rotating magnetic field induces a current in the rotor windings 25a-f of the induction motor 18. The current in the rotor windings 25a-f interacts with the rotating magnetic field generated by the stator windings 24a-f, which in turn generates a force on the rotor 23, causing the rotor 23 to rotate in the same direction as the rotating magnetic field.

[0038] Rotation of rotor 23 causes rotation of the first mechanical coupling 32, which in turn provides mechanical power to compressor 20 to allow compressor 20 to operate. Compressor 20, condenser 34, expander 36, and evaporator 38 operate to provide cooling to compartment 8 (not shown in FIG. 2). Furthermore, rotation of rotor 23 causes rotation of the second mechanical coupling 31, which in turn provides mechanical power to generator 21 to allow generator 21 to generate electricity for additional electrical components of refrigeration system 10 (e.g., fans and / or batteries). In this way, compressor 20 and generator 21 are loads on induction motor 18.

[0039] Figure 3 shows a flowchart of a first method 100 for operating the refrigeration system 10.

[0040] In step 102 of method 100, alternating current is supplied to the induction motor 18, thereby causing the rotor 23 to rotate as described above. Specifically, the controller 12 signals the power supply 16 via a wired or wireless connection 28, and the power supply 16 (e.g., the inverter of the power supply 16) then supplies power to the stator windings 24a-f via a wired connection 30. The alternating current supplied to the induction motor 18 can be three-phase power with a frequency of 50 Hz or 60 Hz. Method 100 then proceeds to step 104.

[0041] In step 104 of method 100, controller 12 is configured to identify a predetermined threshold R of parameter R of induction motor 18. t1 And the predetermined relationship between parameter R and derating amount P1 associated with induction motor 18.

[0042] The parameter R can be the angular velocity of rotor 23. Therefore, the predetermined threshold R t1This can be a predetermined threshold angular velocity of the rotor 23 installed in the refrigeration system 10. The predetermined threshold R t1 This can be referred to as the slip limit. The predetermined relationship between parameter R and derating P1 associated with induction motor 18 can be based on the determined parameters of the rotor 23 of induction motor 18 installed in refrigeration system 10, to limit the amount by which the load rating on induction motor 18 should be reduced.

[0043] Predetermined threshold R t1 The predetermined relationship can be stored in the memory of the controller 12 itself, or in a memory remote from the controller 12 but accessible by the controller 12. Therefore, the predetermined threshold R for identifying the induction motor 18... t1 Alternatively, the predetermined relationship may include: the controller 12 accessing a predetermined threshold R stored in memory corresponding to the induction motor 18 installed in the cooling system 10. t1 Or a predetermined relationship, to identify a predetermined threshold R t1 Alternatively, a predetermined relationship may exist. A predetermined relationship can be in the form of an equation that establishes the relationship between parameter R and derating P1. Alternatively, a predetermined relationship can be in the form of a mapping that sets specific, pre-calculated derating P1 for different determined parameters R of the induction motor 18 installed in the refrigeration system 10.

[0044] The induction motor 18 installed in the refrigeration system 10 can be selected from a plurality of induction motors 18, one or more of which have characteristics different from those of the induction motor 18 installed in the refrigeration system. Therefore, the memory can store a predetermined threshold R for each of the plurality of induction motors 18. t1 And a predetermined relationship. The memory can be a representation where a predetermined threshold R is stored. t1 The lookup table is in the form of a predefined relationship. Method 100 then proceeds to step 106.

[0045] In step 106 of method 100, controller 12 determines parameter R of rotor 23. Sensor 40 outputs a value indicating the angular rate of rotor 23. Controller 12 determines parameter R based on these values. Parameter R can be, for example, a rolling average of the speed of rotor 23 over a predetermined number of previously sensed values ​​of the speed of rotor 23 (e.g., 30 sensed values ​​of the speed of rotor 23). However, it should be understood that any other averaging measurement using a different number of data points can also be used. It should also be understood that parameter R can be a rolling average of the speed of rotor 23 over a predetermined time period (e.g., 5 seconds). Alternatively, parameter R can be an instantaneous (i.e., non-average) value of the rotational speed of rotor 23. Method 100 then proceeds to step 108.

[0046] In step 108 of method 100, controller 12 determines whether parameter R satisfies a first condition. Specifically, controller 12 compares the determined angular velocity R with a predetermined threshold value R of the angular velocity. t1 The comparison is performed, and it is determined whether the determined angular velocity R is less than a predetermined threshold R of the angular velocity. t1 If it is determined in step 108 that the first condition has been met, then method 100 proceeds to step 110. If it is determined in step 108 that the first condition has not been met, then method 100 returns to step 106.

[0047] In step 110 of method 100, controller 12 determines derating amount P1 based on parameter R and a predetermined relationship. As described above, the predetermined relationship can be in the form of an equation relating parameter R to derating amount P1. For example, the predetermined relationship can be in the form of the following equation, where the values ​​of a and b are constants predetermined for the specific induction motor 18 being operated:

[0048]

[0049] In such an embodiment, determining the derating amount based on the relationship between parameter R and derating amount P1 may involve: (i) accessing the above equation from memory; (ii) accessing predetermined values ​​of a and b for the induction motor 18 being operated from memory; and (iii) inserting the predetermined values ​​of a and b and the determined parameter R into the above equation to determine the derating amount P1. Alternatively, determining the derating amount based on the relationship between parameter R and derating amount P1 may involve: (i) accessing the above equation from memory, wherein predetermined values ​​of a and b for the induction motor 18 being operated have been inserted into the equation; and (iii) inserting the determined parameter R into the equation to determine the derating amount P1.

[0050] As described above, the predetermined relationship can be in the form of a mapping that sets specific, pre-calculated derating amounts P1 for different determined parameters R of the induction motor 18 installed in the refrigeration system 10. In such an embodiment, determining the derating amount based on the relationship between the parameter R and the derating amount P1 may involve identifying a specific, pre-calculated derating amount P1 of the induction motor 18 installed in the refrigeration system 10, mapped to the determined parameter R. Method 100 then proceeds to step 112.

[0051] In step 112 of method 100, controller 12 derates one or more loads by the derating amount P1. Controller 12 is configured to communicate with one or more loads and adjust the operation of the one or more loads to implement derating. If the load is compressor 20, the derating of the load by controller 12 may include: controller 12 adjusting a valve (e.g., an electronic throttle valve) of compressor 20 to reduce the electrical power withdrawn by compressor 20 from induction motor 18 during operation by the derating amount P1. If the load is generator 21, the derating of the load by controller 12 may involve: controller 12 adjusting how much power generator 21 withdraws from induction motor 18 during operation by the derating amount P1, for example by reducing fan speed or reducing the charging current to the battery. If multiple loads, rather than a single load, are derated, it should be understood that the derating amount P1 is the combined amount of derating on all loads being powered by rotor 23. The derating 112 of one or more loads 20, 21 powered by the induction motor 18 reduces the temperature of the stator windings 24a-24f, thereby reducing the likelihood of damage to the stator windings 24a-24f. The cooling system 10 and the associated method 100 allow for accurate control of the cooling system without the need for sensors. This improves the reliability and accuracy of control, and reduces costs.

[0052] Figure 4 shows a flowchart of a second method 200 for operating the refrigeration system 10. The second method 200 generally corresponds to the first method 100 described above, wherein the same reference numerals indicate common or similar features. In the second method 200, after step 112, method 200 proceeds to step 216.

[0053] In step 216 of method 200, controller 12 determines the updated parameter R' of rotor 23. Sensor 40 outputs an updated value indicating the angular rate of rotor 23. Controller 12 determines the updated parameter R' based on these values. The updated parameter R' can be calculated in the same manner as the parameter R determined in step 106, but using data received after controller 12 has derated one or more loads 20, 21 by the derated amount P1 in step 112. Method 200 then proceeds to step 218.

[0054] In step 218 of method 200, controller 12 determines whether the updated parameter R' satisfies the second condition. Specifically, controller 12 compares the determined updated angular rate R' with a predetermined threshold value R of the angular rate. t1 The values ​​are compared, and it is determined whether the updated angular rate R' is greater than a predetermined threshold R of the angular rate. t1If it is determined in step 218 that the second condition has been met, then method 200 proceeds to step 220. If it is determined in step 218 that the second condition has not been met, then method 200 returns to step 112.

[0055] In step 220 of method 200, controller 12 removes the derating constraint imposed in step 112, thereby stopping one or more loads 20, 21 from being drated by the derating amount P1. This involves controller 12 sending a command to one or more loads 20, 21 to terminate the derating. Method 200 then returns to step 106.

[0056] Figure 5 shows a flowchart of a third method 300 for operating the refrigeration system 10. The third method 300 generally corresponds to the second method 200 described above, wherein the same reference numerals indicate common or similar features.

[0057] The third method 300 differs from the second method 200 in that step 104 additionally includes: controller 12 determining another predetermined threshold R. t2 Another predetermined threshold R t2 This is a predetermined threshold value for the updated parameter R' of the induction motor 18. Another predetermined threshold value R... t2 It can be another predetermined threshold angular velocity of the rotor 23 installed in the refrigeration system 10, wherein the other predetermined threshold R of the angular velocity t2 It is less than the predetermined threshold R of angular velocity t1 Angular velocity. Another predetermined threshold R t2 This can be referred to as the slip lower limit. Another predetermined threshold R t2 It can be stored in the memory of the controller 12 itself, or in a memory located away from the controller 12 but accessible by the controller 12. Therefore, another predetermined threshold R is identified. t2 This may include: the controller 12 accessing another predetermined threshold R stored in memory corresponding to the induction motor 18 installed in the cooling system 10. t2 To identify the other predetermined threshold R t2 The memory can store another predetermined threshold R for each of the multiple induction motors 18. t2 .

[0058] The difference between the third method 300 and the second method 200 is that if it is determined in step 218 that the second condition has not yet been met, then method 300 proceeds to step 320.

[0059] In step 320 of method 300, controller 12 determines whether the updated parameter R' satisfies the third condition. Specifically, controller 12 compares the determined updated angular rate R' with another predetermined threshold R of the angular rate.t2 The values ​​are compared, and it is determined whether the updated angular rate R' is greater than another predetermined threshold R of the angular rate. t2 If it is determined in step 320 that the third condition has been met, then method 300 proceeds to step 324. If it is determined in step 320 that the third condition has not been met, then method 300 proceeds to step 322.

[0060] In step 322 of method 300, controller 12 shuts down the induction motor 18 of refrigeration system 10. This involves controller 12 sending a command to power supply 16 to terminate the supply of alternating current to induction motor 18. For example, controller 12 may instruct power supply 16 to stop supplying power to induction motor 18 via wired connection 30, such that no three-phase power is supplied to stator windings 24a-24f, rotor 23 does not rotate, and no mechanical power is supplied to compressor 20. Step 322 may also involve controller 12 reporting an over-temperature fault in induction motor 18.

[0061] In step 324 of method 300, controller 12 determines the updated derating amount P2 based on the updated parameter R' and the predetermined relationship. The predetermined relationship can be the same as the predetermined relationship described above. The updated derating amount P2 can be determined in the same manner as the derating amount P1, but using the updated parameter R' instead of parameter R as input. For example, the predetermined relationship can be of the following form:

[0062]

[0063] For a specific induction motor 18, the values ​​of a and b can be the same in each of the equations above. Then, method 300 proceeds to step 326.

[0064] In step 326 of method 300, controller 12 determines whether the updated derating amount P2 calculated in step 324 is greater than the derating amount P1 calculated in step 110. If it is determined in step 326 that the updated derating amount P2 is greater than the derating amount P1, then method 300 proceeds to step 328. If it is determined in step 326 that the updated derating amount P2 is not greater than the derating amount P1, then method 300 returns to step 112.

[0065] In step 328 of method 300, controller 12 rewrites the derating amount P1 calculated in step 110 with the updated derating amount P2 calculated in step 324. Then, in step 112, controller 12 derating one or more loads 20, 21 with the updated derating amount P2. Conversely, if it is determined in step 326 that the updated derating amount P2 is not greater than the derating amount P1, then the derating amount P1 is not overwritten, controller 12 discards the updated derating amount P2, and in step 112, one or more loads 20, 21 derating with the original derating amount P1. This derating action involves controller 12 sending a command to one or more loads 20, 21 to adjust the operation of those loads 20, 21.

[0066] Figure 6 shows a flowchart of a fourth method 400 for operating the refrigeration system 10. The fourth method 400 generally corresponds to the third method 300 described above, wherein the same reference numerals indicate common or similar features. In the fourth method 400, if it is determined in step 218 that the second condition has been met, the method proceeds to step 402.

[0067] In step 402 of method 400, controller 12 determines whether the updated parameter R' continuously satisfies the second condition for a predetermined threshold for the previous time period t. t For example, a predetermined threshold is set for a previous time period t. t It can be 15 minutes. However, it should be understood that any other suitable time can be chosen. If it is determined in step 402 that the updated parameter R' has continuously satisfied the second condition for a predetermined threshold for the previous time period t, then... t Then method 400 proceeds to step 220. If it is determined in step 402 that the updated parameter R' has not continuously satisfied the second condition for a predetermined threshold for the previous time period t, then... t If so, the controller 12 proceeds to step 112, in which the induction motor 18 continues to derate one or more loads 20, 21 by the derating amount P1 or the updated derating amount P2.

[0068] In step 220 of method 400, the derating constraint is removed, such that one or more loads 20, 21 are stopped from being drated by the derating amount P1 or the updated derating amount P2.

[0069] Figure 7 schematically illustrates a second example refrigeration system 11. The second example refrigeration system 11 generally corresponds to the first example refrigeration system 10 described with reference to Figure 3, wherein the same reference numerals indicate common or similar features. However, the second example refrigeration system 11 additionally includes a diesel motor 19, a third wired or wireless connection 29, and a third mechanical coupling 33. Although the diesel motor 19 is shown as being housed within the housing 14 of the refrigeration system 10, the diesel motor 19 may alternatively be located outside the housing 14. For example, the diesel motor 19 may be an electric motor used to supply power to the tractor unit 13. The controller 12 is communicatively connected to the diesel motor 19 via the third wired or wireless connection 29. The diesel motor 19 is mechanically coupled to the compressor 20 via the third mechanical coupling 33.

[0070] The second example refrigeration system 11 can operate in either electric or diesel mode. In electric mode, the compressor 20 is powered by an induction motor 18 via a first mechanical coupling 32. In diesel mode, the compressor 20 is powered by a diesel motor 19. When operating in electric mode, the second example refrigeration system 11 can operate according to any of the methods 100, 200, 300, and 400 described above. When operating in diesel mode, the controller 12 provides a control signal to the diesel motor 19 via a third wired or wireless connection 29 and controls the diesel motor 19 to power the compressor 20 via the third mechanical coupling 33.

[0071] Figure 8 shows a flowchart of a method 500 for operating the second example refrigeration system 11. Method 500 generally corresponds to the fourth method 400 described above, wherein the same reference numerals indicate common or similar features.

[0072] In step 502 of method 500, controller 12 starts the second example refrigeration system 11. Method 500 then proceeds to step 504. In step 504 of method 500, controller 12 determines whether refrigeration system 10 is operating in electric mode. If controller 12 determines in step 504 that refrigeration system 10 is operating in electric mode, method 500 proceeds to step 102. If controller 12 determines in step 504 that refrigeration system 10 is not operating in electric mode, method 500 proceeds to step 506. In step 506 of method 500, controller 12 classifies refrigeration system 10 as operating in diesel mode. Method 500 then proceeds to step 508. In step 508 of method 500, controller 12 does not implement any of the methods described in 100, 200, 300, and 400. The process then ends at step 510.

[0073] Figure 9 is a graph showing the relationship between slip and torque in an induction motor (such as induction motor 18 described herein). As shown, in the stable region of operation of induction motor 18, as slip increases from zero to the threshold slip level S... threshold The torque applied by the induction motor 18 increases from zero to the maximum torque T in a substantially proportional manner. max Conversely, in the unstable region of operation of the induction motor 18, as the slip continues to decrease from the threshold slip level S... threshold As the value of 1 increases, the torque decreases. At a predetermined threshold R... t1 The amount of slip occurring at point and at another predetermined threshold R t2 The slip amounts occurring at points are represented by S1 and S2 in Figure 9, and the corresponding torque values ​​are represented by T1 and T2, respectively. From Figure 9, it can be inferred that when parameter R is within a predetermined threshold... t1 and another predetermined threshold R t2 During this period, the induction motor 18 is operating within its stable operating region. Therefore, when the induction motor 18 is operating at a predetermined threshold R... t1 and another predetermined threshold R t2 During operation, the torque applied by the induction motor 18 is substantially proportional to the speed parameter R.

[0074] Figure 10 shows a flowchart of a method 600 for determining predetermined motor characteristics. Before performing methods 100, 200, 300, 400, and 500, method 600 can be repeated under test conditions for a range of different induction motors 18. The induction motors 18 being tested can each have different operating characteristics, and therefore, method 600 can be used to characterize their performance. The induction motors 18 being tested can differ from the induction motors 18 incorporated into the cooling system 10 because at least one of their stator windings 24a, 24b, 24c, 24d, 24e, and 24f is equipped with a temperature sensor to sense the temperature of that stator winding 24a, 24b, 24c, 24d, 24e, and 24f.

[0075] In step 602 of method 600, the maximum rated temperature value T of stator windings 24a-24f is identified. rated Maximum rated temperature T rated This could be the temperature at which stator windings 24a-24f are damaged. For example, the maximum rated temperature T of stator windings 24a-24f. rated This can be determined through testing or obtained from the instruction manual for stator windings 24a-24f. Method 600 then proceeds to step 604.

[0076] In step 604, based on the maximum rated temperature value T ratedTo determine the lower threshold temperature value T of the stator windings 24a-24f. lt The lower limit threshold temperature T of stator windings 24a-24f lt It can be limited to a value greater than the maximum rated temperature T. rated The temperature of the first predetermined amount. For example, the lower limit threshold temperature value T. lt It can be limited to the maximum rated temperature T of the stator windings 24a-24f. rated 10°C lower. However, it should be understood that the predetermined initial amount can be greater or less than 10°C. Method 600 then proceeds to step 606.

[0077] In step 606, based on the maximum rated temperature value T rated To determine the upper threshold temperature value T of the stator windings 24a-24f. ut The upper limit threshold temperature T of stator windings 24a-24f ut It can be limited to a value greater than the maximum rated temperature T. rated The temperature of the lower predetermined second quantity, wherein the predetermined second quantity is less than the temperature value T used to determine the lower threshold temperature. lt The predetermined first quantity. For example, the upper limit threshold temperature value T. ut It can be limited to the maximum rated temperature T of the stator windings 24a-24f. rated 5°C lower. However, it should be understood that the predetermined second amount can be greater or less than 5°C. Method 600 then proceeds to step 608.

[0078] In step 608, the induction motor 18 is started. Initially, a relatively small load is applied to the induction motor 18. Method 600 then proceeds to step 610.

[0079] In step 610, the load on the induction motor 18 is increased. Simultaneously, the temperature T of the stator windings 24a-24f and the R of the rotor 23 are measured. Method 600 then proceeds to step 612.

[0080] In step 612, the controller 12 compares the temperature T of the stator windings 24a-24f with the lower limit threshold temperature value T. lt A comparison is made. If, in step 612, the temperature T of the stator windings 24a-24f is determined to be equal to the lower threshold temperature value T... lt Or at the lower threshold temperature value T lt If the temperature T of the stator windings 24a-24f is within a predetermined range (e.g., 1°C), then method 600 proceeds to step 612. If, in step 612, it is determined that the temperature T of the stator windings 24a-24f is not equal to the lower threshold temperature value T, then... lt Or not below the lower limit threshold temperature value T lt If the value falls within the predetermined range, then method 600 returns to step 610.

[0081] In step 614, the speed of the induction motor 18 (i.e., the temperature T of the stator windings 24a-24f) is equal to the lower threshold temperature value T. lt Or the lower limit threshold temperature value T lt The current value of the speed of the induction motor 18 within the predetermined range is recorded as the predetermined threshold R. t1 Method 600 then proceeds to step 616. The current load P on the induction motor 18 is recorded as the lower limit threshold temperature load P. lt .

[0082] In step 616, the load on the induction motor 18 is further increased, while the temperature T of the stator windings 24a-24f and the speed of the induction motor 18 are continued to be measured. Method 600 then proceeds to step 618.

[0083] In step 618, the controller 12 compares the temperature T of the stator windings 24a-24f with the upper limit threshold temperature value T. ut A comparison is made. If, in step 618, it is determined that the temperature T of the stator windings 24a-24f is equal to the upper threshold temperature value Tmax. ut Or the upper limit threshold temperature value T ut If the temperature T of the stator windings 24a-24f is within the predetermined range, then method 600 proceeds to step 620. If it is determined in step 618 that the temperature T of the stator windings 24a-24f is not equal to the upper limit threshold temperature value T, then... ut Or the upper limit threshold temperature value T ut If the value falls within the predetermined range, then method 600 returns to step 616.

[0084] In step 620, the speed of the induction motor 18 (i.e., the temperature T of the stator windings 24a-24f is equal to the upper limit threshold temperature value T) ut Or the upper limit threshold temperature value T ut The current value of the speed of the induction motor 18 within the predetermined range is recorded as another predetermined threshold R. t2 Method 600 then proceeds to step 622.

[0085] In step 622, the maximum reduction amount P is determined. max and minimum reduction amount P min Minimum reduction amount P min It can be set to zero.

[0086] Maximum reduction amount P max One or more loads on the induction motor 18 (e.g., compressor 20 and / or generator 21) may need to be reduced (i.e., derated) to lower the temperature T of the stator windings 24a-24f below the lower threshold temperature value T. lt The maximum amount. Maximum reduction amount P maxIt can be determined by the following equation, where P rated This indicates the rated load of induction motor 18, and the lower limit threshold temperature load P. lt This indicates that the temperature T on the induction motor 18 that causes the stator windings 24a-f to be equal to the lower threshold temperature value T lt Load:

[0087]

[0088] Rated load P of induction motor 18 rated This could be a load on the induction motor 18 that would damage the stator windings 24a-24f if the load exceeded this value. For example, the rated load P of the induction motor 18. rated This can be determined through testing or obtained from the instruction manual of the induction motor 18 or stator windings 24a-24f.

[0089] Alternatively, the maximum reduction amount P max The temperature T of the stator windings 24a-24f may be reduced below a lower threshold temperature value T based on the need to reduce (i.e., reduce the rating) of one or more loads on the induction motor 18 (e.g., compressor 20 and / or generator 21). lt The maximum amount. For example, the maximum reduction amount P. max It can be determined by the following equation, where n represents the safety factor:

[0090]

[0091] The safety factor n can be set to a value greater than 1, such that the maximum depreciation amount P max The value of n is greater than the maximum derating that would otherwise exist without applying a safety factor. For example, to apply a 10% safety factor, the value of n can be set to 1.1. However, it should be understood that the safety factor can be greater than or less than 10%. In reality, due to manufacturing tolerances of the induction motor 18 (e.g., manufacturing tolerances of windings 24a-24f, 25a-25f of the induction motor 18) and variations in the amount of AC current supplied to the induction motor 18 during operation, the temperature of the stator windings 24a-24f under set conditions may differ from their nominal expected values, and therefore, in some cases, exceed their nominal expected values. Therefore, using a safety factor in the manner described above ensures that the loads 20, 21 are adequately derated, and that the actual temperature of the stator windings 24a-24f does not exceed the expected value. Method 600 then proceeds to step 624.

[0092] In step 624, a specific derating equation is determined for the induction motor 18 under test. If the temperature T of the stator windings 24a-24f meets certain criteria, the specific derating equation defines a predetermined relationship, and therefore, the amount of load on the induction motor 18 under test should be reduced based on parameter R. The specific derating equation is based on the following general derating equation:

[0093]

[0094] The general reduction formula is based on linear interpolation between two known points, and sets a condition when parameter R equals another predetermined threshold R. t2 Apply maximum depreciation amount P at time max And when parameter R equals a predetermined threshold R t1 Apply minimum depreciation amount P at time min The general derating equation also specifies that, in response to changes in parameter R, the applied derating P1 is at the maximum derating P. max and minimum reduction amount P min They decrease and increase proportionally.

[0095] To determine the specific derating equation for the induction motor 18 under test, a specific value for the derating determined for the induction motor 18 under test is inserted into the general derating equation. By way of example, if a minimum derating P is determined... min The maximum reduction amount P is 0. max For 1000 watts, the predetermined threshold R t1 The value is 1433 RPM, and another predetermined threshold R t2 If the value is 1418 RPM, then the equation for a specific reduction amount can be determined as follows:

[0096]

[0097] By way of example, for this induction motor 18, the predetermined maximum rated temperature value T of the stator windings 24a-24f. rated It can be 155℃, the lower limit threshold temperature T of stator winding 24a-24f. lt It can be 145℃, and the upper limit threshold temperature T of stator windings 24a-24f. ut It can be 150℃.

[0098] The specific derating equation for the induction motor 18 being tested can be recorded in a memory as described above (e.g., in a lookup table) along with any predetermined values ​​described herein. The specific derating equation used to determine the updated derating P2 is the same as the specific derating equation used to determine the derating P1.

[0099] If the predetermined relationship is changed to the form of a mapping graph, the derating amount P1 or P2 can be pre-calculated using the above equations, and the derating amount P1 or P2 can be associated with a potentially determined parameter R for later retrieval from memory.

[0100] As described above, method 600 can be repeated for a range of different induction motors 18. It should be understood that each induction motor 18 can have different characteristics. For example, the maximum rated temperature T of the stator windings 24a-24f of different induction motors 18 may vary. rated The stator windings 24a-24f of different induction motors 18 can be different, and can respond differently to increases in load on the induction motor 18. However, for the purpose of providing a direct comparison, the predetermined first and second quantities are the same and are independent of the induction motor 18 being tested.

[0101] The characteristics exhibited by the induction motor 18 can vary depending on the phase of the power being supplied to it. For example, in the example above, when the induction motor 18 is being supplied with 50 Hz power, the predetermined relationship between parameter R and derating P1 associated with the induction motor 18 can be as follows:

[0102]

[0103] However, when the induction motor 18 is being supplied with 60 Hz power, the predetermined relationship between parameter R and derating P1 associated with the induction motor 18 can instead be as follows:

[0104]

[0105] Therefore, the methods 100, 200, 300, 400, and 500 described herein may further include: identifying the phase of the power being supplied to the induction motor 18; and identifying a predetermined relationship between the parameter R and the derating amount P1 associated with the induction motor 18 for the identified phase of the power. It should be understood that method 600 may correspondingly involve: pre-determining the characteristics of the induction motor 18 at multiple phases of the power supply.

[0106] Although sensor 40 has been described as an angular rate sensor configured to output one or more values ​​indicating the angular rate of rotor 23, sensor 40 may alternatively be an angular position sensor configured to output one or more values ​​indicating the angular position of rotor 23. In such an embodiment, controller 12 determines the speed of rotor 23 based on the value indicating the angular position of rotor 23 by determining the rate of change of the angular position of rotor 23 over time.

[0107] Although the parameter R has been described as the angular rate of the induction motor 18, in an alternative embodiment, the parameter R may instead be the slip of the induction motor 18. In such an embodiment, sensor 40 includes one or more sensors configured to output a value indicating the slip of the induction motor 18. That is, sensor 40 is configured to output a value that can be used by controller 12 to determine the slip of the induction motor 18. Controller 12 can determine the slip of the induction motor 18 in any known manner. For example, sensor 40 may output a value indicating the angular rate of rotor 23, and controller 12 may determine the synchronous speed N by using the following equation to determine the supply frequency f and the number of poles P in the induction motor 18. s :

[0108]

[0109] Then, the controller 12 can determine the slip of the induction motor 18 based on the following equation, where N s It is the synchronization speed, and N r The speed of rotor 23:

[0110]

[0111] It should be understood that various methods for determining the slip of an induction motor are known to those skilled in the art, and in alternative embodiments, one or more sensors 40 configured to output a value indicating the slip of the induction motor 18 may include one or more of the following sensors: an angular rate sensor configured to output a value indicating the angular rate of the rotor 23; an angular position sensor configured to output a value indicating the angular position of the rotor 23; a current sensor configured to output a value indicating the current of the rotor 23 or the stator 17; a voltage sensor configured to output a value indicating the voltage of the rotor 23 or the stator 17; or a frequency meter configured to output a value indicating the frequency of the rotor 23 or the stator 17.

[0112] In such an embodiment: when the slip is greater than a predetermined threshold R, which is a threshold for slip. t1 When the first condition of step 108 is met; the updated parameter R' determined in step 216 is the updated slip of the rotor 23 of the induction motor 18; when the slip is less than a predetermined threshold R t1 When the updated slip is less than another predetermined threshold R, which is another threshold of slip, the second condition of step 218 is met. t2 When the third condition of step 302 is met; the predetermined threshold R t1 The temperature T of the stator windings 24a-24f, which is intended to be caused by the rotor 23, is... ltThe predetermined rated temperature T of stator windings 24a-24f rated The first predetermined amount of slip; another predetermined threshold R t2 The temperature T of the stator windings 24a-24f, which is intended to be caused by the rotor 23, is... ut The predetermined rated temperature T of stator windings 24a-24f rated A lower predetermined second amount of slip; and the determined parameter and / or the determined updated parameter is the average slip of rotor 23 over a predetermined time period. In such an embodiment, another predetermined threshold R of slip. t2 (For example, expressed as a percentage) is greater than a predetermined threshold R of slip. t1 The slip value.

[0113] It should be understood that features of each of methods 100, 200, 300, 400, and 500 described above can be incorporated into other aspects of methods 100, 200, 300, 400, and 500. For example, additional features of the fifth method 500 can be incorporated into the first through third methods 100, 200, and 300. By way of example, additional features of the fourth method 400 can be incorporated into the second method 200. It should also be understood that the order of the steps in methods 100, 200, 300, 400, 500, and 600 is merely exemplary, and alternative orders may be used where appropriate.

[0114] Although methods 100, 200, 300, 400, 500, and 600 have been described with respect to stator windings 24a-24f, methods 100, 200, 300, 400, 500, and 600 may alternatively be performed with respect to rotor windings 25a-25f.

[0115] It should be understood that if the first value is determined to be greater than the second value, and it is uncertain whether the condition has been met, then if the second value is not determined to be less than the first value, the condition can be met alternatively. Similarly, it should be understood that if the first value is determined to be less than the second value, and it is uncertain whether the condition has been met, then if the second value is not determined to be greater than the first value, the condition can be met alternatively.

[0116] It should be understood that controller 12 may include a single controller or multiple controllers located at different locations. For example, a portion of controller 12 may be located remotely from sensor 40, and another portion of controller may be located within sensor 40.

Claims

1. A refrigeration system (10), the refrigeration system (10) comprising: An induction motor (18) having a rotor (23); A power supply (16), which is connected to the induction motor (18) to supply (102) alternating current to the induction motor (18) to cause rotation of the rotor (23), wherein the rotation of the rotor (23) supplies power to one or more loads (20, 21) of the refrigeration system (10); and a controller (12), which is configured to: identify (104) a predetermined threshold (R) of a parameter (R) of the induction motor (18). t1 ) and a predetermined relationship between the parameter (R) and the derating amount (P1) associated with the induction motor (18), wherein the parameter (R) is the angular rate or 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 parameter (R) determined satisfies a first condition, wherein the first condition is that the angular rate (R) is less than the predetermined threshold (R). t1 ) or the slip is greater than the predetermined threshold (R) t1 When it is determined that the first condition has been met, the derating amount (P1) is determined based on the determined parameter (R) and the predetermined relationship; and the one or more loads (20, 21) are drated (112) by the derating amount (P1).

2. The refrigeration system (10) according to claim 1, wherein, The controller (12) is configured to: after derated (112) the induction motor (18) by the derated amount (P1), determine (216) an updated parameter (R') of the rotor (23) during rotation of the rotor (23), wherein the determined updated parameter (R') is an updated angular rate or an updated slip of the rotor (23) of the induction motor (18); determine whether the updated parameter (R') determined (218) satisfies a second condition, wherein the second condition is that the updated angular rate (R) is greater than a predetermined threshold (R). t1 ) or the slip is less than the predetermined threshold (R) t1 ); and when it is determined that the second condition has been met, stop (220) derated the induction motor (18) by the derated amount (P1).

3. The refrigeration system (10) according to claim 2, wherein, The controller (12) is configured to: determine whether the updated parameter (R') determined by (218) satisfies the second condition for a predetermined threshold period of time (t). t ); after determining that the second condition has been continuously met for a previous time period (t) prior to the predetermined threshold. t When the second condition has not been met, stop (220) derated the induction motor (18) by the derated amount (P1); and continue for a period of time prior to the predetermined threshold (t) until the second condition is determined to be met. t When ), the induction motor (18) is derated (112) by the derated amount (P1).

4. The refrigeration system (10) according to claim 2 or 3, wherein, The controller (12) is configured to: identify (104) another predetermined threshold (R) t2 ), the other predetermined threshold (R) t2 ) is a predetermined threshold of the determined updated parameter (R'), wherein if the parameter (R) is the angular rate of the rotor (23), then the other predetermined threshold (R) is... t2 The value is less than the predetermined threshold (R). t1 ), and wherein if the parameter (R) is the slip of the rotor (23), then the other predetermined threshold (R) t2 ) is greater than the predetermined threshold (R) t1 ); and determine whether the updated parameter (R') determined by (320) satisfies a third condition, the third condition being that the updated angular velocity (R') is greater than the other predetermined threshold (R). t2 ) or the updated slip is less than the other predetermined threshold (R) t2 ).

5. The refrigeration system (10) according to claim 4, wherein, The controller (12) is configured to: when it is determined that the third condition has been met, determine (324) the updated derating amount (P2) based on the determined updated parameter (R') and the predetermined relationship; determine (326) whether the updated derating amount (P2) is greater than the derating amount (P1); and when it is determined that (326) the updated derating amount (P2) is greater than the derating amount (P1), derate (328) the induction motor (18) by the updated derating amount (P2).

6. The refrigeration system (10) according to claim 4 or 5, wherein, The controller (12) is configured to shut down (322) the induction motor (18) when it is determined that the third condition has not been met.

7. The refrigeration system (10) according to any one of the preceding claims, wherein, The cooling system (10) is configured such that the alternating current supplied to the induction motor (18) has a phase, wherein the predetermined threshold (R) t1 The temperature (T) of the rotor (23) of the induction motor (18) that causes the windings (24a-24f, 25a-25f) of the induction motor (18) to be at the phase of the alternating current supplied to the induction motor (18) is predetermined to be the temperature (T) of the rotor (23) of the induction motor (18) that causes the windings (24a-24f, 25a-25f) of the induction motor (18). lt The temperature (T) of the windings (24a-24f, 25a-25f) of the induction motor (18) is higher than the predetermined rated temperature (T). rated The first predetermined amount of angular velocity or slip.

8. The refrigeration system (10) according to claim 7 when it is dependent on any one of claims 4 to 6, wherein, The other predetermined threshold (R) t2 The temperature (T) of the rotor (23) of the induction motor (18) that causes the windings (24a-24f, 25a-25f) of the induction motor (18) to be at the phase of the alternating current supplied to the induction motor (18) is predetermined to be the temperature (T) of the rotor (23) of the induction motor (18) that causes the windings (24a-24f, 25a-25f) of the induction motor (18). ut The predetermined rated temperature (T) of the windings (24a-24f, 25a-25f) of the induction motor is higher than that of the induction motor. rated The second predetermined amount of angular velocity or slip is less than the first amount.

9. The refrigeration system (10) according to claim 7 or 8, wherein, As the determined parameter (R) and / or the determined updated parameter (R') tends towards the other predetermined threshold (R'), t2 The derating amount (P1) and / or the updated derating amount (P2) tend to the predetermined maximum derating amount (P). max ), wherein the predetermined maximum derating amount (P) max The load on the induction motor (18) needs to be reduced by the maximum amount required to reduce the load on the induction motor (18) so that the temperature of the windings (24a-24f, 25a-25f) is less than the predetermined rated temperature (T) of the windings (24a-24f, 25a-25f). rated ) lower than the first amount of temperature (T) lt ).

10. The refrigeration system (10) according to any one of the preceding claims, wherein, As the determined parameter (R) and / or the determined updated parameter (R') tend towards the predetermined threshold (R'), t1 The derating amount (P1) and / or the updated derating amount (P2) tend to zero.

11. The refrigeration system (10) according to any one of the preceding claims, wherein, The reduction amount (P1) is determined in relation to the determined parameter (R) and the predetermined threshold (R). t1 The difference between the updated derating amount (P2) and the predetermined threshold (R') is proportional, and / or, wherein the updated derating amount (P2) is proportional to the determined updated parameter (R') and the predetermined threshold (R'). t1 The difference between them is directly proportional.

12. The refrigeration system (10) according to any one of the preceding claims, wherein, The induction motor (18) is selected from a plurality of induction motors (18), wherein the predetermined threshold (R) of each of the plurality of induction motors (18) t1 ), the other predetermined threshold (R) t2 The predetermined relationship between the derating amount (P1) and the determined parameter (R) associated with the induction motor (18), and the predetermined threshold prior time period (t) t The predetermined first quantity, the predetermined rated temperature (T) rated One or more of the predetermined second amount and the predetermined maximum derating amount are stored in a memory accessible by the refrigeration system (10), wherein, optionally, the memory is in the form of a lookup table.

13. The refrigeration system (10) according to any one of the preceding claims, wherein, The determined parameter (R) and / or the determined updated parameter (R') is the average angular rate or average slip of the rotor (23) over a predetermined time period.

14. The refrigeration system (10) according to any one of the preceding claims, wherein, The controller (12) is configured to: start (502) the refrigeration system (10); determine (504) whether the refrigeration system (10) is operating in an electric operation mode; when it is determined that the transport refrigeration system (10) is operating in the electric operation mode, perform the steps of any one of the preceding claims; and when it is determined that the transport refrigeration system (10) is not operating in the electric operation mode, not perform the steps of any one of the preceding claims.

15. The refrigeration system (10) according to any one of the preceding claims, wherein, The controller (12) is configured to determine (106) the parameter (R) and / or the updated parameter (R') based on one or more values ​​output to the controller (12) by one or more sensors (40) of the refrigeration system (10), wherein one or more of the following conditions are met: the one or more sensors (40) include angular rate sensors, and the one or more values ​​indicate the angular rate of the rotor (23); the one or more sensors (40) include angular position sensors, and the one or more values ​​indicate the angular position of the rotor (23). Location; the one or more sensors (40) include current sensors, and the one or more values ​​indicate the current of the rotor (23) or stator (17) of the induction motor (18); the one or more sensors (40) include voltage sensors, and the one or more values ​​indicate the voltage of the rotor (23) or stator (17) of the induction motor (18); and the one or more sensors (40) include frequency meters, and the one or more values ​​indicate the frequency of the rotor (23) or stator (17) of the induction motor (18).

16. A method (100, 200, 300, 400, 500) of operating a refrigeration system (10) according to any one of the preceding claims, said method (100, 200, 300, 400, 500) comprising: An alternating current is supplied (102) to the induction motor (18) to cause the rotor (23) to rotate, wherein the rotation of the rotor (23) supplies power to one or more loads (20, 21) of the refrigeration system (10); a predetermined threshold (R) of the parameter (R) of the induction motor (18) is identified (104). t1 ) and a predetermined relationship between the parameter (R) and the derating amount (P1) associated with the induction motor (18), wherein the parameter (R) is the angular rate or slip of the rotor (23) of the induction motor (18); determine (106) the parameter of the rotor (23) during rotation of the rotor (23); determine (108) whether the parameter (R) determined satisfies a first condition, wherein the first condition is that the angular rate (R) is less than the predetermined threshold (R). t1 ) or the slip is greater than the predetermined threshold (R) t1 When it is determined that the first condition has been met, the derating amount (P1) is determined based on the determined parameter (R) and the predetermined relationship; and the one or more loads (20, 21) are drated (112) by the derating amount (P1).

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