JP4601561B2 - Cooling system - Google Patents

Description

  The present invention relates to a cooling device having a refrigeration cycle using a compressor driven by an electric motor.

  In general, in a laser processing machine, the load on the laser side varies greatly depending on the material of the workpiece, the plate thickness, the processing speed, the processed surface roughness, and the like. Therefore, the cooling device that supplies (circulates) the coolant to the laser processing machine is required to have a cooling performance that can sufficiently follow such load fluctuations, and in particular, such as a mirror that greatly affects the processing accuracy. In order to ensure the thermal stability of the optical parts and avoid the deterioration of the processing quality, a high degree of precision cooling accuracy with little temperature fluctuation is required.

Conventionally, a cooling device disclosed in Japanese Patent Application Laid-Open No. 2001-74318 is known as a cooling device for such applications. The cooling device includes a refrigeration unit, a cooling water supply unit, and a control system, and the refrigeration unit includes a compressor, a condenser, an electronic expansion valve, a heat exchanger, and an accumulator, thereby constituting a refrigeration cycle in which refrigerant circulates. Then, the temperature of the cooling water is controlled by varying the rotation frequency of the compressor within a certain range by the inverter. In this case, the compressor is usually driven by an electric motor, and the rotational frequency (rotational speed) of the electric motor is variably controlled by an inverter (see JP 2000-146318 A).
JP 2001-74318 A JP 2000-146318 A

  However, the conventional cooling device described above has the following problems to be solved.

  First, when the compressor is driven by a DC motor that is advantageous in terms of efficiency (energy saving), there is a problem that the rotation stops due to out-of-step even in the event of an instantaneous power failure due to the principle of the DC motor. In this case, since the trace does not remain, it is not easy to specify the cause of the step-out. In the end, it takes time to investigate the cause of step-out, and it is impossible to take quick and accurate measures.

  Second, if the DC motor stops due to step-out, retry (restart) may be performed. However, if the cause of step-out is an internal factor such as a DC motor failure, restart will cause secondary trouble. Retrying in a state where the cause is unknown is not desirable from the viewpoint of ensuring safety and reliability.

  The object of the present invention is to provide a cooling device that solves the problems in the background art.

  In order to solve the above-described problems, the present invention provides a power failure detection means M1 for detecting a power failure and an electric motor 3 when the cooling device 1 having the refrigeration cycle C using the compressor 2 driven by the electric motor 3 is configured. Step-out detection means M2 for detecting step-out of the DC motor 3d when the DC motor 3d is used, power failure detection data D1 detected by at least the power failure detection means M1, and step-out detection data detected by the step-out detection means M2. Data storage means M3 for storing D2 and restarting means M5 for executing a retry of the DC motor 3d on condition of detection of power failure by the power failure detection means M1 and detection of step-out by the step-out detection means M2. And

  In this case, according to a preferred aspect of the invention, the power failure detection means M1 monitors the detection result of the AC voltage detection means M11 for detecting the presence or absence of the supplied AC power supply voltage Va and the AC voltage detection means M11, and the AC power supply The power supply voltage monitoring means M12 that outputs the power failure detection data D1 when the voltage Va is not detected can be provided, and the step-out detection means M2 can be configured to include the terminal voltages Vu, Wu, Wv, Ww of the DC motor 3d. Winding voltage detecting means M21 for detecting Vv, Vw, and induced voltage Vug ... for a predetermined period Ts in which induced voltage Vug ... can be detected from windings Wu, Wv, Ww of DC motor 3d, and induced voltage Vug ... Can be configured to include induced voltage monitoring means M22 for outputting step-out detection data D2 when the predetermined voltage condition is not satisfied. Further, the data storage means M3 stores time data D1t related to the occurrence time of the power outage together with the power outage detection data D1 when the power outage is detected by the power outage detection means M1, and at the time of step out detection by the step out detection means M2. A function of storing time data D2t related to the occurrence time of step-out together with step-out detection data D2 can be provided. On the other hand, the cooling device 1 can be provided with data display means M4 for displaying the power failure detection data D1, step-out detection data D2, and time data D1t, D2t stored in the data storage means M3.

  According to the cooling device 1 according to the present invention having such a configuration, the following remarkable effects can be obtained.

  (1) Since the data storage means M3 for storing at least the power failure detection data D1 detected by the power failure detection means M1 and the step-out detection data D2 detected by the step-out detection means M2 is provided, the cause of the step-out can be easily identified. Thus, it is possible to quickly investigate the cause of the abnormal stop of the DC motor 3d, and to take quick and appropriate measures. In particular, when the compressor 2 stops due to step-out, even if it can be restarted, the temperature of the controlled coolant is disturbed. Whether the disturbance is due to step-out or another cause, It is possible to easily determine whether the step-out is caused by a power failure or another cause.

  (2) Since the restarting means M5 for executing the retry of the DC motor 3d on condition that the power failure detection means M1 detects the power failure and the step-out detection means M2 is detected, it is possible to prevent a retry other than the instantaneous power failure. Therefore, secondary troubles can be avoided and safety and reliability can be improved.

  (3) According to a preferred embodiment, the power failure detection means M1 monitors the AC voltage detection means M11 for detecting the presence or absence of the AC power supply voltage Va and the detection result of the AC voltage detection means M11 and does not detect the AC power supply voltage Va. If the AC power supply voltage monitoring means M12 that sometimes outputs the power failure detection data D1 is provided, the target power failure detection data D1 can be obtained easily and reliably.

  (4) According to a preferred embodiment, the step-out detection means M2 is divided into winding voltage detection means M21 for detecting the terminal voltages Vu, Vv, Vw of the windings Wu, Wv, Ww of the DC motor 3d, and the winding of the DC motor 3d. The induced voltage Vug... In a predetermined period Ts in which the induced voltage Vug... Can be detected from the lines Wu, Wv, Ww, and the step-out detection data D2 is output when the induced voltage Vug. If the voltage monitoring means M22 is provided, the target step-out detection data D2 can be obtained easily and reliably.

  (5) According to a preferred embodiment, the data storage means M3 stores the time data D1t when the power failure is detected by the power failure detection means M1 together with the power failure detection data D1, and detects the step out by the step out detection means M2. If the function to store the time data D2t at the time of the failure together with the step-out detection data D2 is provided, it is possible to know the occurrence time in addition to the occurrence of power outage and step-out, so that quicker and more accurate cause investigation and Measures can be taken.

  (6) If the data display means M4 for displaying the power failure detection data D1, the step-out detection data D2 and the time data D1t and D2t stored in the data storage means M3 is provided according to a preferred mode, the cooling device 1 is operating. Even so, the history of power outages or step-outs can be confirmed on the spot, so that necessary measures can be taken more quickly.

  Next, the best embodiment according to the present invention will be given and described in detail with reference to the drawings.

  First, the configuration of the cooling device 1 according to the present embodiment will be specifically described with reference to FIGS.

  In FIG. 2, 1 shows the whole structure of the cooling device which concerns on this embodiment. The cooling device 1 includes a coolant tank 11 that stores the coolant L. The coolant tank 11 can be connected to an object to be cooled H such as a laser processing machine via a coolant supply line 12s and a coolant return line 12r. Further, in the middle of the coolant supply line 12s, the liquid feed pump 13 for supplying the coolant L stored in the coolant tank 11 to the object H to be cooled and the coolant L supplied by the liquid feed pump 13 are provided. A cooler (heat exchanger) 14 to be cooled is connected. Further, the coolant supply line 12 s is provided with a fluid pressure gauge 15 for detecting the pressure of the coolant L and a liquid temperature sensor 16 for detecting the temperature of the coolant L, and the coolant tank 11 is provided with a liquid supply line 17. , A drain line 18, a liquid level gauge 19, and a ball tap 20 are provided.

  On the other hand, the cooler 14 is connected to a refrigeration cycle C that cools the coolant L flowing through the coolant supply line 12s by heat exchange. The refrigeration cycle C includes a compressor 2, a condenser 21, a refrigerant strainer 22, an electronic expansion valve 23, and the like as main functional units. The refrigerant inflow side of the cooler 14 is connected to the refrigerant outflow side of the electronic expansion valve 23. In addition to the connection, the refrigerant inflow side of the compressor 2 is connected to the refrigerant outflow side of the cooler 14. Thereby, the refrigerant circuit 24 in which the refrigerant circulates in the direction of the arrow Fc is configured. In addition, 27 is a bypass circuit connected between the refrigerant | coolant outflow side of the compressor 2, and the refrigerant | coolant outflow side of the electronic expansion valve 23, and this bypass circuit 27 is comprised by the serial circuit of the capillary tube 25 and the electromagnetic valve 26. FIG. The basic function of such a refrigeration cycle C is the same as that of a known refrigeration cycle.

  The refrigerant circuit 24 in the refrigeration cycle C includes a low pressure switch 31, an intake temperature sensor 32, a condensation temperature sensor 33, an ambient temperature sensor 34, a high pressure switch 35, a cooler inlet temperature sensor 36, and a condenser fan 37, respectively. Attached. In this case, the pressure switches 31 and 35 mainly function as protection switches, and the condenser fan 37 is used for cooling the condenser 21 and is driven by a fan motor 38. Further, a DC motor 3 d (electric motor 3) is used for driving the compressor 2, and the DC motor 3 d is connected to the inverter unit 39. The sensors 32, the fan motor 38, the inverter unit 39, and the electronic expansion valve 23 and the electromagnetic valve 25 are connected to the controller 40, respectively. The controller 40 constitutes a main part of the control system K and has a function of controlling the entire cooling device 1 including the refrigeration cycle C.

  FIG. 3 shows a main configuration of the cooling device 1 according to the present embodiment. In FIG. 3, 3d is the DC motor (sensorless brushless DC motor) described above, and has three windings Wu, Wv, Ww (field coil W) connected in a star connection. Therefore, the DC motor 3d operates by a 120 ° energization method. The inverter unit 39 includes an inverter circuit 41 and a DC power supply circuit 42. The AC input section of the DC power supply circuit 42 is connected to a three-phase AC power supply (commercial power supply) 43, and the output section of the inverter circuit 41 is a DC motor. Connect to 3d (windings Wu, Wv, Ww). Further, the DC output part of the DC power supply circuit 42 is connected to the input part of the inverter circuit 41. On the other hand, the controller 40 includes a controller main body 44 using a microcomputer (microcomputer), an operation unit 45 using an operation panel connected to the controller main body 44, and a display unit 46 using a liquid crystal display panel. . Therefore, the controller main body 44 has a computer function including a CPU 47, a memory 48, and the like, and executes various processing functions and control functions (sequence control) according to a control program stored in advance, and the communication function and the like according to the necessity. It has various functions.

  FIG. 1 is a functional block diagram showing the main configuration of FIG. 3, a power failure detection means M1 for detecting a power failure, a step-out detection means M2 for detecting a step-out of the DC motor 3d, and a power failure detection means. Data storage means M3 for storing power failure detection data D1 detected by M1 and step-out detection data D2 detected by step-out detection means M2 is provided.

  In this case, the power failure detection means M1 includes AC voltage detection means M11 and AC power supply voltage monitoring means M12. The AC voltage detection means M11 includes an AC voltage detection function unit 51 that detects an AC voltage Vai for one phase in the AC power supply voltage Va supplied from the three-phase AC power supply 43, and an AC voltage obtained from the AC voltage detection function unit 51. A zero cross point detection function unit 52 that detects a zero cross point of Vai and outputs a zero cross detection signal Dz corresponding to the zero cross point. The AC power supply voltage monitoring means M12 monitors the detection result of the zero cross point detection function unit 52, that is, the presence or absence of the zero cross detection signal Dz, and outputs the power failure detection data D1 when there is no zero cross detection signal Dz. 53. Therefore, a three-phase AC power supply 43 is connected to the controller main body 44 (see FIG. 3).

  The step-out detection means M2 includes winding voltage detection means M21 and induced voltage monitoring means M22. The winding voltage detection means M21 has a winding voltage detection function unit 54 that detects the terminal voltages Vu, Vv, Vw of the windings Wu, Wv, Ww of the DC motor 3d, and the induced voltage monitoring means M22 With respect to the terminal voltages Vu, Vv, Vw detected from the voltage detection function unit 54, the induced voltage Vug ... in a predetermined period Ts in which the induced voltage Vug ... can be detected from the windings Wu, Wv, Ww of the DC motor 3d is monitored. And the monitoring function unit 55 that outputs the step-out detection data D2 when the induced voltage Vug... Does not satisfy a predetermined voltage condition. Therefore, the DC motor 3d side is connected to the controller main body 44 so that the terminal voltages Vu, Vv, Vw can be detected (see FIG. 3).

  On the other hand, the memory 48 described above constitutes a main part of the data storage unit M3, and the data storage unit M3 includes a data generation function unit 56 and a clock function unit 57 in addition to the memory 48. In this case, the data generation function unit 56 is provided with the power failure detection data D1 from the monitoring function unit 53 and the step-out detection data D2 from the monitoring function unit 55. In addition, when the power failure detection data D1 and the step-out detection data D2 are provided, the time data D1t related to the time of occurrence of power failure and the time data D2t related to the time of occurrence of step-out are obtained from the clock function unit 57 by the data generation function unit 56. To be granted. Thereby, the memory 48 has a function of storing the power failure detection data D1 and the time data D1t together and storing the step-out detection data D2 and the time data D2t together.

  On the other hand, the display unit 46 described above constitutes a main part of the data display means M4. The data display means M4 can display the power failure detection data D1, step-out detection data D2, and time data D1t, D2t stored in the memory 48 on the display unit 46. Further, the controller main body 44 has a function of executing a retry (restart) of the DC motor 3d on condition that a power failure is detected by the power failure detection means M1 and a step-out detection is detected by the step-out detection means M2. The restarting means M5 is configured.

  Next, operation | movement (function) of the cooling device 1 which concerns on this embodiment is demonstrated with reference to FIGS.

  First, by operating the liquid feed pump 13, the coolant L stored in the coolant tank 11 is supplied to the object to be cooled H via the coolant supply line 12s, and the object to be cooled H is exchanged by heat exchange. The cooled coolant L is returned to the coolant tank 11 via the coolant return line 12r. At this time, the coolant L flowing through the coolant supply line 12 s is cooled by the cooler 14. That is, the coolant L flowing into the cooler 14 is cooled by heat exchange with the cooled refrigerant in the refrigeration cycle C. In FIG. 2, arrows Fw... Indicate the direction in which the coolant L flows.

  On the other hand, in the refrigeration cycle C, the refrigerant circulates in the refrigerant circuit 24 in the direction of the arrow Fc by the operation of the compressor 2, and the refrigerant is cooled by the refrigeration cycle C. Further, the temperature (liquid temperature) of the coolant L supplied to the object to be cooled H is detected by the liquid temperature sensor 16 and applied to the controller 40. Thereby, the controller 40 gives a control command to the inverter circuit 41, and controls the rotational speed (rotational frequency) of the DC motor 3d, thereby performing the foot-back control so that the liquid temperature becomes the set temperature. In this case, the DC voltage Eo is applied from the DC power supply circuit 42 to the input part of the inverter circuit 41, and the inverter circuit 41 switches the DC voltage Eo by an internal switching element. As a result, the two windings Wu... In series in the DC motor 3d are sequentially applied with the drive voltage Ed having a voltage magnitude of Eo and different phases, and a rotating magnetic field is generated in the star-connected field coil W. Occurs and the motor rotor rotates. Since the winding current sequentially flows through the two windings Wu ... in series, the voltage at the center Pc of the field coil W is Eo / 2.

  By the way, since the compressor 2 is driven by the DC motor 3d, in principle, the rotation may stop due to step-out even in the event of an instantaneous power failure. When the DC motor 3d stops due to an instantaneous power failure, it is not easy to determine whether the cause of the stop of the DC motor 3d is actually due to an instantaneous power failure or due to another abnormality such as a failure. The cooling device 1 according to the present embodiment is configured so that this determination can be performed easily and reliably. Hereinafter, the operation of the main part will be specifically described.

  During operation of the cooling device 1, the AC voltage detection function unit 51 shown in FIG. 1 is supplied with the AC power supply voltage Va from the three-phase AC power supply 43, and the AC voltage detection function unit 51 receives the AC voltage detection function unit 51 shown in FIG. An AC voltage Vai for one phase is detected. Further, the zero cross point detection function unit 52 detects the zero cross point (a point at which the voltage becomes 0 volts) of the AC voltage Vai and outputs a zero cross detection signal Dz corresponding to the zero cross point shown in FIG. Further, the monitoring function unit 53 monitors the detection result of the zero cross point detection function unit 52, that is, the presence or absence of the zero cross detection signal Dz. At this time, if the power supply frequency is 60 Hz, one cycle is 16.6 ms. Therefore, the zero cross detection signal Dz is generated every 8.3 ms, and if the power supply frequency is 50 Hz, one cycle is 20 ms. A zero cross detection signal Dz is generated every 10 ms. Therefore, when the zero-cross detection signal Dz is never generated within 12 ms (when there is nothing), it can be determined that a power failure has occurred. If the monitoring function unit 53 detects a power failure, the monitoring function unit 53 gives the power generation detection data D1 to the data generation function unit 56. The target power failure detection data D1 can be obtained easily and reliably by the power failure detection means M1 functioning in this way.

  On the other hand, the terminal voltage Vu, Vv, Vw of the windings Wu, Wv, Ww of the DC motor 3d is detected by the winding voltage detection function unit 54 shown in FIG. The monitoring function unit 55 monitors the terminal voltages Vu, Vv, Vw detected from the winding voltage detection function unit 54. That is, the induced voltage Vug... In the predetermined period Ts in which the induced voltage Vug... Can be detected from the windings Wu, Wv, Ww of the DC motor 3d is monitored, and the step-out is performed when the induced voltage Vug. Detection data D2 is output. In this case, since the voltage at the center Pc of the field coil W is always Eo / 2, as shown in FIG. 5, for example, if the induced voltage Vug of the winding Wu becomes Eo / 2, the winding Wu The terminal voltage becomes zero. In the DC motor 3d using the sensorless brushless DC motor, this timing is determined as the inversion position of the induced voltage Vug with respect to the rotational position of the motor rotor, and the energization timing for the winding is controlled. Therefore, if it is normal, the inversion position of the induced voltage Vug can be detected in the predetermined period Ts shown in FIG. 5. However, if the inversion position is not detected due to some abnormality, it can be determined that the step-out (abnormality) has occurred.

  Further referring to this point, as shown in FIG. 5, even when the drive voltage Ed is in the off period, the winding current (induced voltage Vug) does not immediately become 0, but decreases at a constant slope. In order to detect the inversion position, the terminal voltage of the winding Wu needs to be zero. However, when a step-out (abnormality) occurs, the terminal voltage of the winding Wu does not become zero. For example, in an overload operation state in which a large current flows, even when the reversal position is reached, the winding current (induced voltage Vug) becomes excessive and the reversal position cannot be detected. In addition, when the output of the inverter circuit 41 is stopped due to an instantaneous power failure or the like, a deviation in the energization timing with respect to the winding Wu occurs with respect to the rotational position of the motor rotor, and the motor rotor is locked and the reverse position cannot be detected. . Therefore, the monitoring function unit 55 determines that step out (abnormal) is detected when the reverse position is not detected, and provides step-out detection data D2 to the data generation function unit 56 when step out (abnormal) is detected. The target step-out detection data D2 can be obtained easily and reliably by the step-out detection means M2 functioning in this way.

  On the other hand, if the power generation detection data D1 is given to the data generation function unit 56, the data generation function unit 56 takes the time at that time from the clock function unit 57 as time data D1t, and the power generation detection data D1 and the time of occurrence of the power outage The time data D1t is written into the memory 48 together. Similarly, if the step-out detection data D2 is given to the data generation function unit 56, the data generation function unit 56 takes the time at that time as time data D2t from the clock function unit 57, and steps out from the step-out detection data D2. The time data D2t that is the time of occurrence of the key (abnormality) is written in the memory 48 together. Thus, when a power failure and step-out (abnormality) are detected, all the power failure detection data D1, time data D1t, step-out detection data D2, and time data D2t are stored (stored) in the memory 48 as histories regardless of the cause. Is done. With such data storage means M3, it is possible to know the occurrence time in addition to the occurrence of power failure and step-out, and to investigate the cause and take countermeasures more quickly and accurately.

  When a step-out (abnormality) or power failure is detected, the restart means M5 temporarily stops the control command to the inverter circuit 41, stops the operation of the DC motor 3d, and executes a retry (restart). To do. In this case, the number of retries is up to 3. If it starts within 3 times, it will be judged to be out of step due to an instantaneous power failure, and operation will continue. On the other hand, when the system does not start up even after three retries, the controller main body 44 outputs an alarm (warning) and stops the operation of the cooling device 1 because other abnormal causes such as failure are considered. The abnormal process is performed. Since such restart means M5 can prevent operation (retry) other than instantaneous power failure, secondary troubles can be avoided, and safety and reliability can be improved. If necessary, retry can be executed only by detecting step-out.

  By the way, even when it is activated by retry, the history is saved (stored) in the memory 48, so that the history can be confirmed during maintenance or as necessary. In this case, by operating the operation unit 45, the power failure detection data D1, the step-out detection data D2, and the time data D1t and D2t stored in the memory 48 can be read and displayed on the display unit 46. In this case, if both a power failure and a step-out (abnormality) are detected at substantially the same timing (time), it can be determined that the step-out is caused by an instantaneous power failure that can be started by retry. On the other hand, when a step-out (abnormality) is detected even though a power failure is not detected, the step-out may have occurred due to another abnormal cause such as a failure. The cause can be investigated. Even when the operation of the cooling device 1 is stopped due to the abnormality processing, it can be easily determined whether it is due to a power failure or due to another abnormality. Therefore, by providing such a data display means M4, even when the cooling device 1 is in operation, the history related to power failure or step-out can be confirmed on the spot, and necessary measures can be taken more quickly. .

  Thus, according to the cooling device 1 according to the present embodiment, the data storage means M3 for storing at least the power failure detection data D1 detected by the power failure detection means M1 and the step-out detection data D2 detected by the step-out detection means M2. Therefore, it is possible to easily identify the cause of the step-out, and to quickly investigate the cause of the abnormal stop of the DC motor 3d, and to take quick and appropriate measures. In particular, when the compressor 2 is stopped due to step-out, the temperature (liquid temperature) of the controlled coolant L is disturbed even if it can be restarted. Is this disturbance due to step-out occurring? It is possible to easily determine whether it is due to another cause, or whether the cause of the step-out is due to a power failure or another cause.

  As described above, the best embodiment has been described in detail. However, the present invention is not limited to such an embodiment, and the detailed configuration, shape, quantity, and the like are within the scope not departing from the gist of the present invention. It can be changed, added, or deleted arbitrarily. For example, whether or not to use the time data D1t and D2t is arbitrary. Basically, it is only necessary to detect (store) whether or not a power failure and a step-out (abnormality) have occurred simultaneously. The time data D1t and D2t may include not only the time of occurrence but also the duration (continuation period). In addition, although the type shown in FIG. 2 was illustrated as the cooling device 1, this invention is applicable to various types of cooling devices other than illustration.

The functional block diagram which shows the principal part structure in the cooling device which concerns on the best embodiment of this invention, Overall configuration diagram of the cooling device, Main part configuration diagram of the cooling device, Signal waveform diagram explaining the detection principle of the power failure detection means provided for the cooling device, Signal waveform diagram explaining the detection principle of the step-out detection means provided in the cooling device,

Explanation of symbols

  1: cooling device, 2: compressor, 3: electric motor, 3d: DC motor, C: refrigeration cycle, M1: power failure detection means, M11: AC voltage detection means, M12: AC power supply voltage monitoring means, M2: step-out detection Means, M21: winding voltage detection means, M22: induced voltage monitoring means, M3: data storage means, M4: data display means, M5: restarting means, D1: power failure detection data, D1t: time data, D2: step out Detection data, D2t: time data, Wu ...: DC motor winding, Va: AC power supply voltage, Vu ...: winding terminal voltage, Vug ...: induced voltage, Ts: predetermined period

Claims (5)

  In a cooling apparatus having a refrigeration cycle using a compressor driven by an electric motor, a power failure detection means for detecting a power failure and a step-out detection means for detecting a step-out of the DC motor when a DC motor is used for the electric motor. Data storage means for storing at least power failure detection data detected by the power failure detection means and step-out detection data detected by the step-out detection means, detection of power failure by the power failure detection means, and step-out detection by the step-out detection means. And a restarting means for performing a retry of the DC motor on condition that a key is detected.   The power failure detection means monitors the detection result of the AC voltage detection means for detecting the presence or absence of the supplied AC power supply voltage, and outputs the power failure detection data when the AC power supply voltage is not detected. 2. The cooling device according to claim 1, further comprising AC power supply voltage monitoring means for performing the operation.   The step-out detecting means monitors winding voltage detection means for detecting a terminal voltage of the winding of the DC motor, and the induced voltage in a predetermined period in which the induced voltage can be detected from the winding of the DC motor, The cooling apparatus according to claim 1, further comprising induced voltage monitoring means for outputting the step-out detection data when the induced voltage does not satisfy a predetermined voltage condition.   The data storage means stores time data related to the occurrence time of a power outage together with the power outage detection data when a power outage is detected by the power outage detection means, and a step out occurs when the step out detection is detected by the step out detection means. The cooling apparatus according to claim 1, further comprising a function of storing time data relating to time together with the step-out detection data.   5. The cooling apparatus according to claim 4, further comprising data display means for displaying the power failure detection data, the step-out detection data, and the time data stored in the data storage means.

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