JP2005337583A - Refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerator with a compressor having low speed operation during a failure of a cooling fan even when using an inverter circuit for vector control of a compressor. <P>SOLUTION: The refrigerator comprises a refrigerating cycle having the reciprocating compressor 15 to be rotated with a three-phase brushless DC motor 28 and the C-fan 25 arranged for cooling the compressor 15. When a failure of the C-fan 25 is detected, the brushless DC motor 28 is controlled not to execute field weakening control in the vector control. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a refrigerator that drives a motor of a compressor by an inverter circuit.

In refrigerators that use flammable refrigerant, determine whether the compressor is operating or stopped to avoid the risk of ignition due to refrigerant leakage even if the compressor cooling fan fails. There has been proposed a refrigerator in which a cooling fan is driven and a failure detection device determines whether the cooling fan has failed and, when it has failed, the compressor is rotated at a low speed so that the overload relay does not operate ( For example, see Patent Document 1).
JP 2003-121032 A

  In recent inverter-controlled refrigerators, a d-axis current that is a current component corresponding to the magnetic flux of the rotor of a brushless DC motor that rotates a reciprocating compressor and a q-axis that is a current component corresponding to the torque of the brushless DC motor. Vector control is performed to control the rotational speed of the compressor by converting into current. Even in the operation of the compressor in such vector control, it is necessary to ensure safety so as not to ignite the flammable refrigerant as described above. However, the compressor is controlled to rotate at a low speed when the cooling fan fails. There is a problem that it is difficult to implement.

  Therefore, in view of the above problems, the present invention provides a refrigerator capable of operating the compressor at a low speed when a cooling fan fails even if the refrigerator performs vector control of the compressor using an inverter circuit.

  The present invention includes a reciprocating compressor rotated by a three-phase brushless DC motor, a condenser, and a refrigeration cycle having at least an evaporator, and a cooling fan for cooling the compressor is arranged to control the brushless DC motor. In the refrigerator in which the driving device is arranged, and the main control device that controls the driving device is arranged, the driving device includes an inverter circuit that supplies a three-phase driving current to a stator winding of the brushless DC motor; A PWM circuit for supplying a PWM signal to the inverter circuit, a drive current detecting means for detecting the three-phase drive current, and a magnetic flux of the rotor of the brushless DC motor based on the detected three-phase drive current. Converts d-axis current, which is a corresponding current component, and q-axis current, which is a current component corresponding to the torque of the brushless DC motor. Dq conversion means, control means for outputting a reference q-axis current and a reference d-axis current based on the converted d-axis current and q-axis current, and a speed command signal input from the main controller, and the reference q A voltage conversion means for converting an axis current and a reference d-axis current into a reference q-axis voltage and a reference d-axis voltage; and the PWM circuit by converting the converted reference q-axis voltage and reference d-axis voltage into a three-phase voltage. Three-phase conversion means for outputting to the motor, and the drive device increases the reference q-axis voltage together with the rotational speed in the low-speed rotation range of the brushless DC motor, and makes the reference d-axis voltage substantially constant. The maximum torque control method is executed, the reference q-axis voltage is kept constant at the maximum reference q-axis voltage in the high-speed rotation range of the brushless DC motor, and the reference d-axis voltage is decreased with the rotation speed. Execute field control method The main control unit, upon detecting a failure of the cooling fan, a refrigerator and controlling so as not to perform the field weakening control method to the driving device.

  In the refrigerator according to the present invention, when the main control device detects a failure of the cooling fan, the drive device is controlled not to execute the field weakening control method. That is, when the cooling fan fails, the compressor is stopped or the compressor is controlled by the maximum torque control method. By controlling the compressor by the maximum torque control method in this way, the brushless DC motor rotates or stops in the low-speed rotation region, so that heat generation of the compressor can be suppressed and the cooling fan does not rotate. Even if it exists, the temperature rise can be suppressed.

  Hereinafter, the refrigerator 1 of one Embodiment of this invention is demonstrated.

(1) Structure of the refrigerator 1 First, the structure of the refrigerator 1 is demonstrated based on FIG.

  FIG. 1 is a cross-sectional view of a refrigerator 1 showing the present embodiment.

  The cabinet of the refrigerator 1 is formed of a heat insulating box 9 and an inner box 8, and is partitioned into a refrigeration temperature zone 30 and a freezing temperature zone 31 by the heat insulating partition wall 2, and the cold air in both temperature zones 30, 31 is completely independent. Each cold air is not mixed.

  The inside of the refrigerated temperature zone 30 is partitioned into the refrigerated storage room 4 and the vegetable compartment 5 by the refrigeration partition plate 3, and the inside of the freezing temperature zone 31 is composed of the first freezer compartment 6 and the second freezer compartment 7, Has open / close doors 4a, 5a, 6a and 7a, respectively. The refrigerated storage room 4 is provided with a temperature sensor (hereinafter referred to as R sensor) 34 for detecting the internal temperature and a deodorizing device 35.

  A refrigeration room evaporator 10 and a refrigeration room cooling fan (hereinafter referred to as “R fan”) 11 are arranged on the back of the vegetable room 5, and the R fan 11 is arbitrarily operated by the internal temperature fluctuation or door opening / closing. The rear surface of the refrigerated storage chamber 4 serves as a cold air circulation path 18 for supplying cold air into the refrigerated temperature zone 30. A defrost heater 26 is disposed below the freezer evaporator 12.

  A freezer compartment evaporator 12 and a freezer compartment cooling fan (hereinafter referred to as “F fan”) 13 are arranged on the back walls of the first and second freezer compartments 6 and 7 and circulates cold air to circulate the first and second freezer compartments 6. 7 are cooled.

  A machine room 14 is provided in the lower portion of the back wall of the refrigerator 1. FIG. 2 is a cross-sectional view of the machine room 14, and the inside of the machine room 14 is divided into two by a machine room cooling fan (hereinafter referred to as “C fan”) 25. The compressor 15 is arranged in one of the compartments, and the main space 33 for controlling the refrigerator 1 and the board storage portion 72 in which the wiring board to which the compressor driving device 32 is wired are stored in the other space. ing. A condenser 21 is disposed in front of the machine room 14, and air that has entered from the front of the cabinet of the refrigerator 1 is sucked into the machine room 14 by the C fan 25, and from an exhaust port 74 that opens to the back of the machine room 14. Discharged. In this case, the condenser 21, the substrate storage unit 72, and the compressor 15 are cooled by the air flowing by the C fan 25.

(2) Structure of refrigeration cycle The structure of the refrigeration cycle will be described with reference to FIG.

  The refrigerant that is the compressed fluid of the refrigeration cycle is isobutane (R600a) that is a natural combustible refrigerant.

  In the refrigeration cycle, the compressor 15 and the condenser 21 are arranged, and after the combustible refrigerant discharged from the compressor 15 passes through the condenser 21, the refrigerant flow path is alternately switched by the refrigerant switching mechanism of the switching valve 22. The refrigeration mode and the refrigeration mode can be realized alternately.

  The refrigerating capillary tube 23 and the refrigerating room evaporator 10 are sequentially connected to one outlet of the switching valve 22, and the freezing capillary tube 24 and the freezing room evaporator 12 are sequentially connected to the other outlet of the switching valve 22. An accumulator 16 is connected to the evaporator 12.

(3) Operation state of refrigerator 1 An operation state is demonstrated to the refrigerator 1 of the said structure.

  In the refrigeration mode when the refrigerant flow path is switched by the switching valve 22 and the refrigeration temperature zone 31 is cooled, after the flammable refrigerant is decompressed by the refrigeration capillary tube 24 and enters the freezer compartment evaporator 12 to cool the refrigeration temperature zone 31, Return to the compressor 15 again. And cold air circulates in the store | warehouse | chamber by the driving | operation of F fan 13, and the 1st and 2nd freezer compartments 6 and 7 are cooled.

  In the refrigerating mode at the time of cooling in the refrigerating temperature zone 30, the combustible refrigerant is decompressed by the refrigerating capillary tube 23, enters the refrigerating chamber evaporator 10, cools the refrigerating temperature zone 30, passes through the freezer compartment evaporator 12, and is compressed again Return to 15. The refrigerator compartment 4 and the vegetable compartment 5 are cooled by the operation of the R fan 11.

(2) Structure of the electric system of the refrigerator 1 The structure of the electric system of the refrigerator 1 is demonstrated based on the block diagram of FIG.

  As shown in FIG. 8, a three-phase brushless DC motor (hereinafter referred to as a “comp motor”) 28 that drives the compressor 15, a drive device (hereinafter referred to as a “comp drive device”) 32 that drives the compressor motor 28, and this compressor It is comprised from the main control part 33 of the refrigerator 1 which controls the drive device 32. FIG. The main control unit 33 is arranged inside the machine room 14 as described above, and is connected to door switches 4b to 7b provided on the doors 4a to 7a of the rooms 4, 5, 6 and 7, respectively. Furthermore, the main controller 33 is connected to a deodorizing device 35, a defrosting heater 26, an R sensor 34, an R fan 11, an F fan 13, and a C fan 25, and the temperature of the room in which the refrigerator 1 is placed, That is, an outside air temperature sensor 70 that measures the outside air temperature is connected.

  The compressor 15 is a reciprocating compression mechanism, and a compression mechanism portion is mounted on the upper side in the vertical sealed case, and a compressor motor 28 is provided on the lower side.

  As shown in FIG. 4, the compressor motor 28 is a brushless DC motor and is a three-phase six-slot four-pole motor. That is, the four-pole rotor 117 rotates on the inner peripheral side of the three-phase six-slot stator 118. The rotor 117 is an IPM (Inner Permanent Magnet) rotor in which a magnet 119 is provided. When a voltage is applied to each phase of the comp motor 28 by the comp driving device 32, the same control is performed symmetrically 180 ° inside the motor.

(3) Structure of Comp Drive Device 32 The structure of the comp drive device 32 will be described with reference to FIG.

  The compressor driving device 32 includes an inverter circuit 42, a rectifying circuit 44, an AC power supply 46, a PWM forming unit 48, an AD converting unit 50, a dq converting unit 52, a speed detecting unit 54, and a speed command output unit 56. A speed PI control unit 58, a q-axis current PI control unit 60, a d-axis current PI control unit 62, a three-phase conversion unit 64, and an initial pattern output unit 66.

  The compressor motor 28 that rotates the compressor 15 is a three-phase brushless DC motor as described above. The inverter circuit 42 causes a three-phase drive current to flow through the three-phase (u-phase, v-phase, and w-phase) stator windings 40u, 40v, and 40W of the comp motor 28.

  The inverter circuit 42 is a full bridge inverter circuit composed of transistors Tr1 to Tr6 which are six power switching semiconductors. Although not shown in the figure, a diode is connected in reverse to the switching transistors Tr1 to Tr6 in parallel. A detection resistor R1 for detecting a drive current is connected in series to the switching transistors T1 and Tr4, a detection resistor R2 is connected in series to the switching transistors Tr2 and Tr5, and a detection resistor R28 is connected in series to the switching transistors Tr28 and Tr6. Is connected.

  The rectifier circuit 44 is supplied with an AC voltage from an AC power supply 46 that is a commercial power supply (AC 100 V), and rectifies and supplies it to the inverter circuit 42.

  The PWM forming unit 48 supplies a PWM signal to the gate terminals of the six switching transistors Tr1 to Tr6. The PWM forming unit 48 performs pulse width modulation based on three-phase voltages Vu, Vv, and Vw, which will be described later, and turns on / off the switching transistors Tr1 to Tr6 at a predetermined timing.

  The AD converter 50 detects the voltage values at the shunt resistors R1, R2, and R28, converts the voltage values of each phase from analog values to digital values, and outputs three-phase drive currents Iu, Iv, and Iw.

  The dq conversion unit 52 corresponds to the drive currents Iu, Iv, and Iw output from the AD conversion unit 50 to the d-axis (direct-axis) current Id that is a current component corresponding to the magnetic flux and the torque of the comp motor 28. It is converted to a q-axis (quadrature-axis) current Iq.

In this conversion method, three-phase Iu, Iv, and Iw are converted into two-phase Iα and Iβ as shown in the equation (1). FIG. 6 is a vector diagram showing the relationship between the three-phase current and the two-phase current.

Next, the two-phase currents Iα and Iβ converted in this way are converted into a q-axis current Iq and a d-axis current Id using the formula (2). The relationship between the two-phase drive current, the converted (detected) q-axis current Iq, and the d-axis current Id is as shown in the vector diagram of FIG.

  The speed detector 54 detects the rotation angle θ and the rotation speed ω of the comp motor 28 based on the detected q-axis current Iq and d-axis current Id. Based on the q-axis current and the d-axis current, a rotation angle θ which is the position of the rotor of the comp motor 28 is obtained, and the rotational speed ω is obtained by differentiating this θ.

  The main control unit 33 of the refrigerator 1 outputs a speed command signal S based on the q-axis current Iq sent from the dq conversion unit 52.

  The speed command output unit 56 outputs a reference rotation speed ωref based on the speed command signal S from the main control unit 33 and the rotation speed ω from the speed detection unit 54. The reference rotational speed ωref is input to the speed PI control unit 58 together with the current rotational speed ω.

  The speed PI control unit 58 performs PI control based on the difference amount Δω between the reference rotation speed ωref and the current rotation speed ω, outputs the reference q-axis current Iqref and the reference d-axis current Idref, and the current q-axis current. Iq and the current d-axis current Id are output to the q-axis current PI control unit 60 and the d-axis current PI control unit 62, respectively.

  The q-axis current PI control unit 60 performs PI control, performs current / voltage conversion, and outputs a reference q-axis voltage Vq.

  The d-axis current PI control unit 62 performs PI control and current / voltage conversion, and outputs a reference d-axis voltage Vd.

The three-phase converter 64 first converts the reference d-axis voltage Vd and the reference q-axis voltage Vq into a two-phase voltage based on the equation (3).

The converted two-phase voltages Vα, Vβ are converted into three-phase voltages Vu, Vv, Vw based on the equation (4).

  The converted three-phase voltages Vu, Vv, and Vw are output to the PWM forming unit 48 described above.

  According to the compressor driving device 32 described above, the rotational speed is detected based on the detected d-axis current Id and q-axis current Iq, and feedback control is performed based on the rotational speed ω and the speed command signal S from the main control unit. The PWM forming unit 48 outputs a PWM signal to the inverter circuit 42 so that the compressor motor 28 rotates at the rotational speed ωref that matches the speed command signal S. Based on this, the inverter circuit 42 outputs a three-phase drive current to the three-phase stator winding 40 of the compressor motor 28. The control method during normal operation other than during startup will be described in detail later.

  The initial pattern output unit 66 is set with a starting motor constant when the compressor 15 is started. At the time of starting, the starting characteristics are determined by the set starting motor constant. The startup motor constants set are the initial rotation position θinit, the startup acceleration speed ωinit, the startup d-axis current Idinit, and the startup q-axis current Iqinit. The startup acceleration speed ωinit is output to the speed command output unit 56, and the initial rotation speed The position θinit is output to the dq converter 52, and the starting d-axis current Idinit and the starting q-axis current Iqinit are output to the speed PI control unit 58.

(4) Control Method During Normal Operation Next, a control method during normal operation of the refrigerator 1 will be described.

  The control method during normal operation is divided into a maximum torque control method in which the rotational speed of the comp motor 28 is performed in the low speed rotation region and a field weakening control method in the high speed rotation region.

  When the compressor motor 28 is activated and the rotational speed increases, the maximum torque control method is performed up to a predetermined rotational speed, and the field weakening control method is performed when the predetermined rotational speed is exceeded. The timing of switching between the maximum torque control method and the field weakening control method will be described with reference to the graph of FIG.

  The vertical axis in FIG. 8 indicates the value of the output voltage from the inverter circuit 42, and the horizontal axis indicates time.

When the rotational speed increases, the output voltage increases and reaches the field-weakening control start voltage. This field-weakening control start voltage means the maximum value of the line voltage theoretically obtained from the output voltage V0 (= 280 V) in FIG. 5 and is expressed as in equation (5).

  When the field-weakening control start voltage is exceeded, the maximum torque control method is switched to the field-weakening control method, and this field-weakening control method is performed until the DC voltage V0 is reached.

  On the other hand, when the rotational speed decreases and the output voltage becomes lower than the field weakening control release voltage, the maximum torque control method is restored. The field weakening control release voltage is set to a value lower than the field weakening control start voltage by a predetermined voltage. Since the line voltage can be calculated from Vq and Vd input to the three-phase converter 64, the line voltage calculated based on this becomes the maximum value theoretically derived from the DC voltage V0. Shift to field weakening control method.

  In FIG. 9, the horizontal axis indicates the frequency (that is, the rotation speed), the vertical axis indicates the d-axis current and the q-axis current value (A), and how the q-axis current and the d-axis current change depending on the frequency. It shows what to do.

  As shown in FIG. 7, in the maximum torque control method, the d-axis current is constant around 0 A, and the q-axis current increases with frequency. On the other hand, in the field weakening control method, the d-axis current decreases with frequency, and the q-axis current is maintained at the value of the maximum reference q-axis current.

  As described above, the thresholds (field control start voltage and field control release voltage) of the maximum torque control method and the field weakening control method are performed using the output voltage as described above, and the rotation speed is not a threshold value. As a result, since the output voltage is proportional to the rotational speed, the maximum torque control method is performed in the low speed region, and the field weakening control method is performed in the high speed region.

  Next, the maximum torque control method and the field weakening control method will be described in order.

(5) Maximum Torque Control Method The maximum torque control method performed in the low speed range will be described with reference to FIGS.

  First, the rotor 117 of the comp motor 28 is an IPM rotor as described above, and the relationship among the magnet torque, reluctance torque, and combined torque of the magnet 119 is as shown in FIG.

  As shown in FIG. 10, the combined torque is the sum of the magnet torque and the reluctance torque, and the period of the magnet torque corresponds to the phase of the induced voltage. The induced voltage is a voltage between the stator windings.

  FIG. 11 shows the relationship between the drive current flowing from the inverter circuit 42 to the stator windings 40u, 40v, 40w and the induced voltage.

  The phase difference between the drive current and the induced voltage is determined by the relationship between the position of each stator winding 40 and the rotation position of the rotor 117, that is, determined in advance by a mechanical positional relationship. . In FIG. 11, the drive current is advanced by an advance angle γ with respect to the induced voltage. In the maximum torque control method, γ = 10 °.

In this maximum torque control method, the speed PI control unit 58 calculates the reference q-axis current based on the equation (6).

  However, n is performed every carrier wave period (second) of the PWM period when PWM control is performed, and the reference q-axis current has a discrete value. Kp is a frequency control proportional gain (A / Hz), and Ki is a frequency control integral gain (A · sec / Hz). Δω is a difference amount between ω detected by the speed detector 54 and the reference rotational speed output from the speed command output unit 56.

Next, the reference d-axis current is calculated based on the equation (7).

  Where φ is the motor magnetic flux (wb), Ld is the d-axis motor inductance (H), and Lq is the q-axis motor inductance (H). This control cycle is different from the PWM cycle of the equation (6), and is performed in the control cycle of the drive device 32. The control cycle is set longer than the control cycle of the q-axis current.

  As described above, the reference q-axis current and the reference d-axis current are calculated based on the equations (6) and (7), converted into a three-phase voltage by the three-phase converter 64, and PWM control is performed. FIG. 7 shows changes in the reference q-axis current and the reference d-axis current calculated in this way.

(6) Contents of field weakening control method Next, a field weakening control method performed in a high speed range will be described.

  When the reference q-axis current increases in the maximum torque control method and reaches the maximum reference q-axis current as described above, it becomes a constant value and does not increase any more, so the maximum torque control method is switched to the field weakening control method.

  In the field weakening control method, when the number of rotations is increased and the value of the output voltage approaches the theoretical value of the line voltage, the rotation cannot be performed at a higher number of rotations. Therefore, in the maximum torque control method, the phase difference γ between the drive current and the induced voltage is made constant, but the phase of the drive current with respect to the induced voltage is further advanced to advance to the maximum advance angle γ = 85 °. In the maximum torque control method, the lead angle γ = 10 ° as described above.

  The reference d-axis current is calculated from the equation (7). From the current value calculated by the equation (7), the reference d-axis current is set to become a lower voltage with the rotation speed. That is, the reference d-axis current obtained by the equation (7) is corrected, the correction amount is increased with the frequency, and the reference d-axis current is calculated to decrease with the frequency as shown in FIG. Thus, when the reference d-axis current decreases, the phase γ of the drive current advances with respect to the induced voltage, and the rotation speed can be increased.

  The maximum number of revolutions in the field weakening control method is set when the drive current advance angle γ reaches 85 °. This is because if the advance angle γ becomes 90 °, the torque becomes zero.

(7) Control method at the time of failure of the C fan 25 The C fan 25 is also controlled by an inverter in the same manner as the compressor motor 28, and can control the rotation speed by a speed command signal from the main control unit 33. . Then, the main controller 33 always detects the current value from the motor that rotates the C fan 25, and when the drive current becomes 0, it is determined that the C fan 25 is in failure.

  When the main control unit 33 detects a failure of the C fan 25, the compressor 15 is not cooled, and it is necessary to prevent the compressor 15 from being heated. Therefore, in order to prevent the rotation speed of the comp motor 28 from increasing, the comp drive device 32 performs control so that the above-described field weakening control method cannot be performed. Specifically, in order to prevent the compressor motor 28 from rotating at a rotation speed that leads to the field weakening control method, the output voltage is always detected, and when the output voltage tries to reach the field weakening control start voltage, the speed command A speed command signal S is output to the output unit 56 so as to reduce the rotational speed.

  As a result, even when the C fan 25 fails, the compressor 15 is heated, and ignition of the combustible refrigerant can be completely prevented. In addition, the C fan 25 also cools the board storage portion 72 in which the main control unit 33 and the drive device 32 are arranged, and the heat dissipation characteristics of the main control unit 33 and the drive device 32 deteriorate due to the failure of the C fan 25. Even in such a situation, since the compressor 15 does not rotate at a high rotational speed, it is possible to prevent the heat of the main control unit 33 and the compressor driving device 32 from increasing.

(Example of change)
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

  In the said embodiment, although it demonstrated with the combustible refrigerant | coolant, a nonflammable refrigerant | coolant may be sufficient.

  The refrigerator of the present invention is suitable for a household refrigerator.

It is a longitudinal cross-sectional view of the refrigerator which shows this embodiment. It is a cross-sectional view of a machine room. FIG. 3 is a structural diagram of a refrigeration cycle. It is explanatory drawing of a compressor motor. It is a block diagram of a refrigerator. It is a vector diagram which performs αβ change from three phases. It is a graph which shows the boundary of the field-weakening control method and the maximum torque control method. It is a graph which shows the relationship between the reference d-axis current, the reference q-axis current and the frequency. It is a vector diagram which performs αβ change from three phases. It is a graph which shows the relationship between a magnet torque, a reluctance torque, and a synthetic | combination torque. It is a graph which shows the relationship between the drive current and the induced voltage in the maximum torque control method. It is a graph which shows the relationship between the drive current and induced voltage in a field-weakening control method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigerator 14 Machine room 15 Compressor 25 C fan 28 Comp motor 32 Comp drive device 33 Main control part 42 Inverter circuit 48 PWM formation part 52 dq conversion part 64 Three-phase conversion part 66 Initial pattern output part

Claims (4)

A reciprocating compressor rotating with a three-phase brushless DC motor, a condenser, and a refrigeration cycle having at least an evaporator;
A cooling fan for cooling the compressor is arranged,
A driving device for controlling the brushless DC motor is disposed;
In the refrigerator provided with a main control device for controlling the drive device,
The driving device includes:
An inverter circuit for supplying a three-phase drive current to the stator winding of the brushless DC motor;
A PWM circuit for supplying a PWM signal to the inverter circuit;
Drive current detection means for detecting the three-phase drive current;
Based on the detected three-phase drive current, a d-axis current that is a current component corresponding to the magnetic flux of the rotor of the brushless DC motor, and a q-axis current that is a current component corresponding to the torque of the brushless DC motor, Dq conversion means for converting to
Control means for outputting a reference q-axis current and a reference d-axis current based on the converted d-axis current, the q-axis current, and a speed command signal input from the main controller;
Voltage converting means for converting the reference q-axis current and the reference d-axis current into a reference q-axis voltage and a reference d-axis voltage;
Three-phase conversion means for converting the converted reference q-axis voltage and reference d-axis voltage into a three-phase voltage and outputting the same to the PWM circuit;
Have
The driving device executes a maximum torque control method for increasing the reference q-axis voltage together with the rotation speed in the low-speed rotation range of the brushless DC motor and maintaining the reference d-axis voltage substantially constant, and the brushless DC motor Executing a field-weakening control method for maintaining the reference q-axis voltage constant at the maximum reference q-axis voltage in the high-speed rotation range of the motor and reducing the reference d-axis voltage together with the rotational speed;
The main control device performs control so that the drive device does not execute the field-weakening control method when a failure of the cooling fan is detected. The refrigerator according to claim 1, wherein the main controller is also cooled by the cooling fan. The main control device controls the drive device not to execute the field-weakening control method only when the outside air temperature detected by the outside air temperature sensor is equal to or higher than a certain temperature and when the failure of the cooling fan is detected. The refrigerator according to claim 1. The timing for switching from the maximum torque control method in the low-speed rotation region to the field weakening control method in the high-speed rotation region is such that the rotation speed increases and the line voltage of each phase reaches the maximum output voltage. The refrigerator according to claim 1, wherein the refrigerator is switched when the voltage reaches a maximum reference q-axis voltage.

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