Cooling Devices and Systems

Abstract

To provide a cooling device capable of specifying a motor in which an abnormality has occurred, and stopping driving the motor only.SOLUTION: A cooling device includes: a heat exchanger for cooling air; a plurality of fans for blowing air to different parts of the heat exchanger respectively; a plurality of AC motors for driving the plurality of fans respectively; a plurality of blowout temperature sensors provided in correspondence with the plurality of fans for detecting blowout temperature of air passing through the heat exchanger; an energizing path switching part for switching states between a state for applying AC power to all the plurality of AC motors and a state for applying the AC power to each of the plurality of AC motors individually; a current detection part provided on the upstream for detecting a current applied to the AC motors; and a control part for detecting the AC motor that has broken down on the basis of a determination condition using a difference in temperatures detected by the plurality of blowout temperature sensors and the current detected by the current detection part, and stopping only the AC motor that has broken down while controlling the energizing path switching part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a cooling device including multiple fans that blow and circulate cool air through an area to be cooled, and a cooling system including multiple such devices. [Background technology]

[0002] Relatively large-capacity refrigerator / freezer showcases and refrigerators / freezers are equipped with cooling devices that blow and circulate cool air. When a cooling device has multiple fans, AC motors are often used to drive those fans. Furthermore, multiple AC motors are often driven while connected in series to an AC power source without going through a drive circuit such as an inverter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-45172 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when using such an AC motor, the current value when the motor locks is included in the normal operating current fluctuation range, making it difficult to detect the malfunction. Therefore, conventional cooling devices do not have the function to detect the motor in which an abnormality has occurred and stop its operation, and when any motor breaks down, the user who discovered the malfunction has no choice but to stop the operation of all the motors. Therefore, depending on the time it takes for a serviceman to arrive at the site, the quality of the products stored in the storage room, etc., cannot be maintained, and the products may have to be discarded, resulting in economic losses.

[0005] In view of this, a cooling device and a cooling system are provided that can identify a motor in which an abnormality has occurred and stop driving only that motor. [Means for solving the problem]

[0006] The cooling device of the embodiment includes a heat exchanger for cooling air and a cooling fan for blowing air to different portions of the heat exchanger. Two Fans of these Two Each of the fans is driven by Two and the AC motor Two a fan for detecting the temperature of the air blown out from the heat exchanger; Two The blowout temperature sensor and the AC power supply are Two a first state in which all of the AC motors are energized; Two a current detection unit that is provided upstream of the current path switching unit and detects a current flowing through the AC motor; and Two The difference in temperature detected by the outlet temperature sensors It is set according to The current detected by the current detection unit About The control unit detects a faulty AC motor based on a determination condition and controls the current path switching unit to stop only the faulty AC motor.

[0007] In addition, the cooling system of the embodiment includes a heat exchanger that cools air, and a cooling device that blows air to different portions of the heat exchanger. Two Fans of these Two Each of the fans is driven by Two and the AC motor Two a fan for detecting the temperature of the air blown out from the heat exchanger; Two The blowout temperature sensor and the AC power supply are Two a first state in which all of the AC motors are energized; Two a current path switching unit that switches between a first state in which current is applied to each of the AC motors and a second state in which current is applied to each of the AC motors. Two The cooling device and the AC power supply Two a first state in which all of the cooling devices are energized; Twoa current detection unit that is provided upstream of the upper current path switching unit and detects a current supplied to the AC motor; Two The difference in temperature detected by the outlet temperature sensors It is set according to The current detected by the current detection unit About The power supply control unit detects a faulty AC motor based on a judgment condition, and controls the current path switching unit and the upper current path switching unit to stop only the faulty AC motor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a first embodiment of the present invention, and is a schematic diagram showing an electrical configuration of a cooling device. [Diagram 2] A perspective view of the cooling unit from the front [Diagram 3] A perspective view of the cooling unit from the rear [Figure 4] Schematic longitudinal side view of a cooling unit [Diagram 5] Flowchart showing the processing contents of the control circuit [Figure 6] A diagram showing the changes in the temperature sensor inside the cabinet and the two outlet temperature sensors when the fan 7(1) is stopped. [Figure 7] A diagram showing the changes in the temperature sensor inside the cabinet and the two outlet temperature sensors when the fan 7(2) is stopped. [Figure 8] A diagram explaining how the current value of a faulty AC motor increases above normal levels. [Figure 9] A diagram explaining how the current value of the path that current flows through two AC motors increases when one of the AC motors fails. [Figure 10] FIG. 11 is a front view showing a second embodiment, and is a schematic diagram showing a configuration in which a cooling unit is incorporated inside a showcase having an open front. [Figure 11] Schematic longitudinal sectional side view of a showcase [Figure 12]FIG. 13 is a diagram illustrating an electrical configuration of a cooling system according to a third embodiment. [Figure 13] Flowchart showing the processing contents of the control circuit (part 1) [Figure 14] Flowchart showing the processing contents of the control circuit (part 2) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) As shown in Figs. 2 to 4, the cooling unit 1 of this embodiment is installed on the upper part of the inner wall surface of a cold storage warehouse or the like, and is connected to a refrigerator, which is an outdoor unit not shown, by refrigerant piping to form a cooling device 14. The cooling unit 1 can adjust the temperature inside the warehouse over a wide range, such as 5°C to -20°C, according to the optimum storage temperature for the stored items in the warehouse. The cooling unit 1 has a rectangular case 2 that narrows toward the rear in Fig. 2, and the front end surface of the case 2 in Fig. 2 serves as a cold air outlet 3. The outlet 3 has, for example, a plurality of slits formed therein. Outlet temperature sensors 4(1), 4(2) are disposed on the left and right sides of the outlet 3 in Fig. 2, respectively.

[0010] As shown in Figs. 1 and 4, a heat exchanger 5 and AC motors 6(1) and 6(2) are arranged inside the case 2. One of the heat exchangers 5 is arranged horizontally toward the side where the air outlet 3 is located, and has an inlet and an outlet so that the refrigerant of the refrigeration cycle flows through the inside. The above-mentioned outlet temperature sensors 4(1), 4(2) are arranged to correspond to the AC motors 6(1) and 6(2), respectively. The AC motor 6 is, for example, a single-phase capacitor motor equipped with a running capacitor. The AC motor 6 is fixed so that its rotating shaft faces downward and is slightly tilted backward in Fig. 4. Fans 7(1,2) are attached to the tip of the rotating shaft. An intake port 8 is formed at a portion of the lower surface of the case 2 corresponding to the fan 7.

[0011] Cooling unit 1 is disposed inside, for example, a refrigerated warehouse. When AC motor 6 is driven to rotate fan 7, outside air is drawn into case 2 through intake port 8. The drawn-in air is cooled by heat exchanger 5, and then blown out as cold air from outlet 3 to cool the interior of the warehouse. An internal temperature sensor 9 for detecting the temperature inside the warehouse is disposed on the underside of case 2. Outlet temperature sensors 4(1), 4(2) are disposed so as to detect the temperatures of the cold air blown out by fans 7(1), 7(2), respectively.

[0012] As shown in FIG. 1, AC motors 6(1) and 6(2) of the cooling unit 1 are driven by power supplied from a single-phase AC power source 10. A current detection circuit 11, which is a current detection unit, a first relay 12(1), and a second relay 12(2) are connected to one end of the AC power source 10, and the cooling unit 1 is connected between the first relay 12(1) and the second relay 12(2) and the other end of the AC power source 10. The first relay 12(1) is connected to one end of a winding terminal of the AC motor 6(1), and the second relay 12(2) is connected to one end of a winding terminal of the AC motor 6(2). The other ends of the winding terminals of the AC motors 6(1) and 6(2) are commonly connected to the other end of the AC power source 10. Note that the temperature sensors are not shown in FIG. 1. The relay 12 is an example of a current path switching unit.

[0013] The opening and closing of the relay 12 is controlled by a control circuit 13. The temperatures detected by the temperature sensors 4 and 9 and the current detected by the current detection circuit 11 are input to the control circuit 13. The above components excluding the AC power supply 10 constitute a cooling device 14.

[0014] The control circuit 13 is installed at a position where a user can easily operate it, such as on the wall of the entrance to the cold storage warehouse, and is incorporated in a controller (not shown) which is an operating part of the cooling device 14 that sets the temperature inside the cold storage, or is incorporated in the refrigerator which is an outdoor unit. When the cooling device 14 is normally operated, both the first relay 12(1) and the second relay 12(2) are closed, and the AC motors 6(1) and 6(2) are connected in parallel to the AC power source 10. This causes both the fans 7(1) and 7(2) of the cooling unit 1 to rotate. This corresponds to the first state. Also, a state in which only one of the first relay 12(1) and the second relay 12(2) is closed, and only one of the AC motors 6(1), 6(2) is connected to the AC power source 10 corresponds to the second state.

[0015] Next, the operation of this embodiment will be described with reference to Figures 5 to 8. During normal operation of cooling device 14, control circuit 13 monitors the temperature values ​​detected by internal temperature sensor 9 and outlet temperature sensors 4(1) and 4(2) at intervals of, for example, one minute. In addition, current values ​​Ic passing through AC motors 6(1) and 6(2) from AC power source 10 are also sampled 10 times at one minute intervals to determine their average value Iv.

[0016] As shown in FIG. 5, the control circuit 13 obtains the difference between the temperature values ​​Tf1 and Tf2 detected by the discharge temperature sensors 4(1) and 4(2), and compares the absolute value of the difference with a threshold value of 4K (S1).

[0017] Now, reference will be made to Figures 6 and 7. For example, suppose that the cooling temperature inside the refrigerator by cooling unit 1 is set to 2°C. At this time, the temperature values ​​detected by discharge temperature sensors 4(1) and 4(2) are approximately equal, and both are, for example, -1°C. From this state, as shown in Figure 6, if a malfunction occurs in AC motor 6(1) and rotation of fan 7(1) stops, the temperature detected by inside temperature sensor 9 will rise by 1K. Then, while the temperature detected by discharge temperature sensor 4(1) will decrease, the temperature detected by discharge temperature sensor 4(2) will increase. As a result, the difference between the two temperatures will increase to about 4K.

[0018] 7, when a failure occurs in AC motor 6(2) and fan 7(2) stops rotating, the temperature detected by outlet temperature sensor 4(2) drops and the temperature detected by outlet temperature sensor 4(1) rises, so the temperature difference between the two also increases to about 4 K. Therefore, in step S1, it is determined whether the absolute value of the difference between temperature values ​​Tf1, Tf2 is equal to or greater than a predetermined value of 4 K, and if it is less than 4 K (NO), the process proceeds to step S8, and if it is equal to or greater than 4 K (YES), the process proceeds to step S2.

[0019] In step S2, relays 12(1), 12(2) are opened, respectively, and current values ​​I2, I1 flowing through AC motors 6(2), 6(1) are detected and monitored by current detection circuit 11. Next, temperature values ​​Tf1, Tf2 are compared (S3), and if (Tf1>Tf2) (YES), it is determined whether current value I2 is equal to or greater than twice current value I1 (S4).

[0020] As shown in Fig. 8, when the current flowing through AC motor 6 is about 3.0 A under normal conditions, if AC motor 6 fails, the current flowing therethrough will rise to about 6.0 A. If (I2 ≥ I1 × 2) (S4; YES), relay 12(2) is opened to stop AC motor 6(2) and fan 7(2). Then, only AC motor 6(1) and fan 7(1) are operated, and a display (not shown) is caused to display that an abnormality has occurred in fan 7(2) (S5).

[0021] On the other hand, if (Tf1≦Tf2) (S3; NO), it is determined whether or not the current value I1 is equal to or greater than twice the current value I2 (S6), and if (I1≧I2×2) (YES), relay 12(1) is opened to stop AC motor 6(1) and fan 7(1). Note that "I1×2" and "I2×2" are examples of second state predetermined values. Then, only AC motor 6(2) and fan 7(2) are operated, and an indication that an abnormality has occurred in fan 7(1) is displayed on a display (not shown) (S7). If "NO" is determined in step S6, the process returns to step S1.

[0022] In step S8, it is determined whether the absolute value |Ic-Iv| of the difference between the latest sampled current value Ic and the latest average value Iv is 20% or more of the average value Iv. Incidentally, "20% of the average value Iv" is an example of the first state predetermined value. As shown in Fig. 9, when the average value in the state where AC motors 6(1) and 6(2) are driven in parallel is, for example, about 6 A, if one of the AC motors 6 stops due to a failure, the current value detected by current detection circuit 11 becomes about 9 A, which is an increase of 120% or more from the average value.

[0023] If |Ic-Iv| is 20% or more of the average value Iv (YES), the same process as in step S2 is performed (S9), and then a similar decision is made to step S4 (S10). If |Ic-Iv| is less than 20% of the average value Iv (NO), the process returns to step S1. If the decision in step S10 is "YES," the process proceeds to step S5, and if the decision is "NO," the process proceeds to step S11, where a decision is made to the same as step S6. If the decision in step S11 is "YES," the process proceeds to step S7, and if the decision is "NO," the process returns to step S1.

[0024] As described above, according to this embodiment, in the cooling unit 1 constituting the cooling device 14, the fans 7(1) and 7(2) that blow air to different parts of the heat exchanger 5 that cools the air are driven by the AC motors 6(1) and 6(2), respectively. The blowout temperature sensors 4(1) and 4(2) are provided corresponding to the fans 7(1) and 7(2) to detect the blowout temperatures Tf1, Tf2 of the air that has passed through the heat exchanger 5. The relays 12(1) and 12(2) switch between a first state in which the AC power source 10 simultaneously energizes the AC motors 6(1) and 6(2) and a second state in which the AC motors 6(1) and 6(2) are individually energized.

[0025] Current detection circuit 11 is disposed between AC power supply 10 and relays 12(1) and 12(2). Control circuit 13 detects a faulty AC motor 6 based on a judgment condition using a difference |Tf1-Tf2| in temperatures detected by discharge temperature sensors 4(1) and 4(2), respectively, and a current detected by current detection circuit 11, and controls relays 12(1) and 12(2) to stop only the faulty AC motor 6.

[0026] Specifically, as a judgment condition, the control circuit 13 detects the values ​​of currents I1, I2 passed through each of the AC motors 6(1) and 6(2) after the temperature difference |Tf1-Tf2| becomes equal to or greater than 4K, compares the detected current values, and judges that the AC motor 6 whose current value difference is equal to or greater than the second state predetermined value is faulty.

[0027] The cooling unit 1 of the cooling device 14 is required to cool a very wide range of low temperatures. Since frost accumulates on the heat exchanger 5 through which air is circulated by the fans 7(1) and 7(2), a defrosting operation is performed as appropriate to remove the frost. When the frost grows on the heat exchanger 5 and freezes, it causes clogging, and the amount of air circulated by the fans 7(1) and 7(2) is significantly reduced. If the amount of air circulated is reduced, the current flowing through the AC motors 6(1) and 6(2) that drive the fans 7(1) and 7(2) is significantly reduced.

[0028] Frost on heat exchanger 5 rarely grows uniformly, and tends to freeze easily on the refrigerant inlet side, which is either the left or right side of heat exchanger 5. For this reason, the frozen state of heat exchanger 5 can differ greatly between the left and right sides of heat exchanger 5, i.e., the positions facing fans 7(1) and 7(2). Under such operating conditions with large load fluctuations on fans 7(1) and 7(2), it is very difficult to detect faults in AC motors 6(1) and 6(2).

[0029] Therefore, in this embodiment, by adding not only the current detected by the current detection circuit 11 but also the temperature difference |Tf1-Tf2| detected by the discharge temperature sensors 4(1) and 4(2) to the judgment conditions, it is possible to reliably detect a failure of the AC motor 6 while suppressing erroneous detections even under operating conditions with large load changes, such as in the cooling unit 1.

[0030] The control circuit 13 also obtains an average value Iv of the current Ic detected in the first state, and as a judgment condition, judges whether or not the difference |Ic-Iv| between the detected current Ic value and the average value Iv after the temperature difference |Tf1-Tf2| becomes less than the threshold value, and if the difference in the current values ​​|Ic-Iv| is Iv×20% or more, detects the current values ​​I1 and I2 supplied to each of the AC motors 6(1) and 6(2) in the second state, compares the current values ​​I1 and I2, and judges the AC motor 6 whose difference in the current values ​​is (I2≧I1×2) or (I1≧I2×2) or more to be faulty. This makes it possible to reliably detect a faulty AC motor 6 even when the temperature difference |Tf1-Tf2| is less than the threshold value.

[0031] Second embodiment Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted, and only the different parts will be described. As shown in Fig. 10 and Fig. 11, in the second embodiment, a cooling unit 22 is incorporated inside a showcase 21 whose front is open to form a cooling device 23. The components of the cooling unit 22 are the same as those of the cooling unit 1.

[0032] A heat exchanger 5 is disposed below the space formed between an outer wall 24 and an inner wall 25 of the showcase 21, and an AC motor 6 and a fan 7 are disposed in front of the heat exchanger 5 on the left side in Fig. 11. When the AC motor 6 and the fan 7 rotate, outside air is taken in from the lower front of the showcase 21, and the air cooled by the heat exchanger 5 is blown upward and blown into the interior of the showcase 21 from an outlet 26 on the upper front side. A blowout temperature sensor 4 is disposed above the heat exchanger 5.

[0033] A plurality of shelves 27 are attached to the inner wall 25, and an in-storage temperature sensor 9 is disposed on the inner wall 25 at a position where the lowest shelf 27 is located. As shown in Fig. 10, the fans 7(1), 7(2) and the blowout temperature sensors 4(1), 4(2) are disposed at positions separated on the left and right sides when viewed from the front of the showcase 21.

[0034] Third embodiment 12, the cooling system 31 of the third embodiment includes two cooling units 1. The cooling units 1(1) and 1(2) of the third embodiment correspond to cooling devices. For the cooling unit 1(2), the reference numerals of the two components are given (3) and (4) instead of (1) and (2) of the cooling unit 1(1).

[0035] One end of relays 12(5) and 12(6) is connected to current detection circuit 11 of AC power supply 10, the other end of relay 12(5) is connected to one end of relays 12(1) and 12(2), and the other end of relay 12(6) is connected to one end of relays 12(3) and 12(4). A control circuit 32 replacing control circuit 13 controls the opening and closing of all relays 12. Note that discharge temperature sensors 4(1)-4(4) are not shown in the figure. Relays 12(5) and 12(6) are an example of an upper current path switching unit.

[0036] Next, the operation of the third embodiment will be described. In the initial state, both relays 12(5) and 12(6) are closed to operate both cooling units 1(1) and 1(2). In FIG. 13, when the control circuit 32 determines "YES" in step S1, the process is basically the same as steps S2 to S7 in the first embodiment. In step S12, which replaces step S2, the relay 12(6) is opened to stop the cooling unit 1(2). Then, by opening the relays 12(1) and 12(2), respectively, the current detection circuit 11 detects the current values ​​I2 and I1 flowing through the AC motors 6(2) and 6(1).

[0037] If the determination is "YES" in steps S3 and S4, then in step S13, which replaces step S5, the relay 12(6) is closed to operate the cooling unit 1(2). Then, the same process as in step S5 is performed. If the determination is "YES" in step S6, then in step S14, which replaces step S7, the relay 12(6) is similarly closed to operate the cooling unit 1(2). Then, the same process as in step S7 is performed.

[0038] If step S1 is determined to be (NO), in the following steps S15 to S21, processing corresponding to steps S1 to S14 is performed for cooling unit 1(2). In step S15, control circuit 32 obtains the difference between temperature values ​​Tf3, Tf4 detected by discharge temperature sensors 4(3) and 4(4), and compares the absolute value of the difference with a threshold value of 4K. In step S16, relay 12(5) is opened to stop cooling unit 1(1). Then, relays 12(3) and 12(4) are opened, respectively, to allow current detection circuit 11 to detect current values ​​I4, I3 flowing through AC motors 6(4), 6(3).

[0039] In step S17, temperature values ​​Tf3 and Tf4 are compared, and in steps S18 and S20, current values ​​I1 and I2 are replaced with current values ​​I3 and I4 for comparison. In step S19, relay 12(5) is closed to operate cooling unit 1(1). Then, the same process as in step S5 is performed for relays 12(3) and 12(4) and fans 7(3) and 7(4). In step S20, the same process as in step S14 is performed for relay 12(5), relays 12(3) and 12(4), and fans 7(3) and 7(4).

[0040] If the answer in step S15 is "NO," the process proceeds to step S22 shown in FIG. 14. In step S22, it is determined whether the absolute value |Ic4-Iv4| of the difference between the latest current value Ic4 sampled while both cooling units 1(1) and 1(2) are operating and the latest average value Iv4 of the current value Ic4 is 20% or more of the average value Iv4. If |Ic4-Iv4| is 20% or more of the average value Iv4 (YES), relays 12(5) and 12(6) are opened one by one to stop cooling units 1(1) and 1(2). Then, average values ​​Ia1 and Ia2 of the operating currents while cooling units 1(1) and 1(2) are operating are calculated (S23).

[0041] Then, it is determined whether the average value Ia1 is 120% or more of the average value Ia2 (S24), and if (Ia1≧Ia2×120%) (YES), the same processing and determination as in steps S12 and S4 are performed (S25, S26). If the determination in step S26 is "YES", the same processing as in step S13 is performed (S27). If the determination in step S26 is "NO", the same determination and processing as in steps S6 and S14 are performed (S28, S29).

[0042] If the answer is "NO" in step S24, it is determined whether the average value Ia2 is equal to or greater than 120% of the average value Ia1 (S30), and if (Ia2≧Ia1×120%) (YES), the same process as in step S16 is performed (S31). In the following steps S32 to S35, the processes of steps S26 to S29 are performed for the cooling unit 1 (2). Steps S32 and S33 are the same judgment and process as steps S18 and S19, and steps S34 and S35 are the same judgment and process as steps S20 and S21. However, if the answer is "NO" in step S32, the process proceeds to step S34.

[0043] As described above, according to the third embodiment, cooling system 31 includes cooling units 1(1) and 1(2), and control circuit 32 controls relays 12(5) and 12(6) to switch between a first state in which AC power supply 10 supplies current to cooling units 1(1) and 1(2) and a second state in which current is supplied to each of cooling units 1(1), 1(2) individually.

[0044] Then, in each of cooling units 1(1), 1(2), control circuit 32 detects a faulty AC motor 6 based on a determination condition using the difference in temperature detected by discharge temperature sensors 4(1)-(4), respectively, and currents I1-I4 detected by current detection circuit 11, and controls relays 12(1)-12(6) to stop only the faulty AC motor 6. Therefore, in cooling system 31 having multiple cooling units 1, a faulty AC motor 6 can be reliably detected as in the first embodiment.

[0046] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0047] In the drawings, 1 is a cooling unit, 4 (1-4) is a blowing temperature sensor, 5 is a heat exchanger, 6 (1,2) is an AC motor, 7 (1,2) is a fan, 10 is an AC power supply, 11 is a current detection circuit, 12 (1-6) are relays, 13 is a control circuit, 14 is a cooling device, 22 is a cooling unit, 23 is a cooling device, 31 is a cooling system, and 32 is a control circuit.

Claims

1. A heat exchanger for cooling the air; Two fans each blowing air to a different portion of the heat exchanger; Two AC motors for driving the two fans, respectively; two blowout temperature sensors provided corresponding to the two fans and configured to detect a blowout temperature of air having passed through the heat exchanger; a current path switching unit that switches between a first state in which an AC power source energizes both of the two AC motors and a second state in which an AC power source energizes each of the two AC motors individually; a current detection unit that is provided upstream of the current path switching unit and detects a current flowing through the AC motor; a control unit that detects a faulty AC motor based on a judgment condition related to the current detected by the current detection unit, which is set according to the difference between the temperatures detected by the two blow-out temperature sensors, and that controls the current path switching unit to stop only the faulty AC motor.

2. the control unit detects, as the determination condition, a value of a current supplied to each AC motor in the second state after the temperature difference in the first state becomes equal to or greater than a threshold value; 2. The cooling device according to claim 1, wherein the detected current values ​​are compared, and an AC motor is judged to be faulty when a difference between the current values ​​is equal to or greater than a second state predetermined value.

3. The control unit determines an average value of the current detected in the first state, The determination condition includes determining whether or not a difference between a current value detected after the temperature difference becomes less than a threshold value and the average current value is equal to or greater than a first state predetermined value, If the difference in the current values ​​is equal to or greater than the first state predetermined value, a value of a current supplied to each of the AC motors in the second state is detected, 3. The cooling device according to claim 2, wherein the detected current values ​​are compared, and an AC motor is judged to be faulty when a difference between the current values ​​is equal to or greater than a second state predetermined value.

4. A heat exchanger for cooling the air; Two fans each blowing air to a different portion of the heat exchanger; Two AC motors for driving the two fans, respectively; two blowout temperature sensors provided corresponding to the two fans and configured to detect a blowout temperature of air having passed through the heat exchanger; two cooling devices each including a current path switching unit that switches between a first state in which an AC power source is energized to both of the two AC motors and a second state in which an AC power source is energized individually to each of the two AC motors; a host current path switching unit that switches between a first state in which the AC power source applies current to both of the two cooling devices and a second state in which the AC power source applies current to each of the two cooling devices individually; a current detection unit that is provided upstream of the upper current path switching unit and detects a current flowing through the AC motor; In each cooling device, a faulty AC motor is detected based on a judgment condition related to a current detected by the current detection unit, the judgment condition being set according to a difference between the temperatures detected by the two blowout temperature sensors, respectively; a control unit that controls the current path switching unit and the upper current path switching unit to stop only the failed AC motor.

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