JP2007020293A - Inverter controller and refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent such trouble that power consumption increases or a protective circuit works and a DC brushless motor stops, by preventing the occurrence of a synchronous mode. <P>SOLUTION: This inverter controller can prevent the occurrence of the synchronous mode by storing the time of detecting the position of the rotor of the DC brushless motor and the number of revolutions on the occurrence of the synchronous mode with which n times (n is an integer) of a carrier cycle accords in the storage means of a refrigerator control circuit 116 in advance as an output inhibition band, and inhibiting the use of the number of revolutions on the occurrence of the synchronous mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inverter control device that drives a motor by a PWM-controlled switching element, and is particularly suitable for a home-use refrigerator-freezer.

  Conventionally, in this type of inverter control device, a drop in current can be reduced by increasing the carrier frequency in a relatively low rotation region and shortening the energization OFF time in one cycle, and vibration and noise due to current ripple can be reduced. In other rotational speed regions, the carrier frequency is set small to reduce the leakage current (see, for example, Patent Document 1).

  The conventional inverter circuit will be described below with reference to the drawings.

  FIG. 4 is a block diagram of a conventional inverter control device described in Patent Document 1, and FIG. 5 is a diagram illustrating an example of a conventional carrier frequency control pattern.

  In FIG. 4, the conventional inverter control device includes a main circuit unit 2 and a control circuit unit 3 connected to a DC power supply unit 1.

  The DC power supply unit 1 is configured by an electrolytic capacitor, a diode bridge circuit, and the like (not shown), converts AC power into DC power, and supplies DC power to the main circuit unit 2.

  The main circuit unit 2 includes six switching elements Ua, Ub, Va, Vb, Wa, Wb and six freewheeling diodes D1, D2,... D6, and each freewheeling diode is connected in parallel with the switching elements. Has been. The switching elements Ua and Ub are connected in series to connect the arm part Uab, the switching elements Va and Vb are connected in series to connect the arm part Vab, the switching elements Wa and Wb are connected in series, and the arm part Wab is connected to the arm part Uab. By forming and connecting these three arm portions Uab, Vab, and Wab in parallel, a three-phase bridge is formed. The common nodes U0, V0, and W0 of the switching elements of the three-phase arm portions Uab, Vab, and Wab are connected to the corresponding motor terminals U, V, and W, respectively.

  The control circuit unit 3 includes an induced voltage detection unit 4, a rotor position calculation unit 5, a commutation control circuit unit 6, a speed control circuit unit 7, a PWM carrier frequency generation circuit unit 8, a duty control unit 9, and a PWM carrier frequency switching. It is composed of a command circuit unit 10 and an energization waveform switching command unit 11 and is a 120 ° energization PWM control inverter. The time for detecting the rotor position is 60 ° in electrical angle.

  Hereinafter, the operation principle of the control circuit unit 3 will be described.

  First, the induced voltage of each phase generated by the rotational drive of the motor is detected by the induced voltage detection unit 4 connected to the output terminals U, V, W of the main circuit unit 2. Based on the induced voltage waveform detected by the induced voltage detector 4, the rotor position calculator 5 calculates the rotor position from the zero cross point of the induced voltage. Next, based on the rotor position information calculated by the rotor position calculation unit 5, the commutation control circuit unit 6 generates ON / OFF signals for the switching elements Ua, Ub, Va, Vb, Wa, Wb of the main circuit unit 2. The switching element provided in the main circuit unit 2 is driven.

  On the other hand, the speed control circuit unit 7 connected in parallel with the rotor position calculation unit 5 receives the signal from the induced voltage detection unit 4 and calculates the rotation speed of the motor so that the rotation speed of the motor becomes equal to the command value. In addition, the voltage value is controlled by PWM (pulse width modulation) control.

  Further, upon receiving the rotational speed information of the speed control circuit unit 7, the PWM carrier frequency switching command circuit unit 10 determines the current fluctuation due to the current increase at the ON time and the current decrease at the OFF time in the duty control of the PWM carrier, that is, the current Select an appropriate carrier frequency to reduce the ripple amplitude and suppress vibration and noise. The carrier frequency selection can be easily extracted by experimentally obtaining the optimum carrier frequency characteristic with respect to the rotational speed in advance and storing it in a database in the PWM carrier frequency switching circuit.

  In FIG. 5, the horizontal axis represents the number of rotations and the vertical axis represents the carrier frequency.

  As shown in FIG. 5, the carrier frequency is set large in the relatively low rotational speed region, and the carrier frequency is set small in the other rotational speed regions.

Therefore, since the carrier frequency is increased in a relatively low rotational speed region, the energization OFF time in one cycle is shortened, current drop can be reduced, and vibration and noise due to current ripple can be reduced.
JP 2001-186787 A

  However, in the above-described conventional configuration shown in Patent Document 1, when the carrier frequency is switched in the control pattern of FIG. 5, a shift in commutation timing occurs continuously (this phenomenon is called a synchronous mode), and as a result, An excessive motor current continues to flow, resulting in an increase in power consumption. Further, the protection circuit is activated and the DC brushless motor may be stopped.

  This time, the cause of this synchronous mode has been clarified.

  FIG. 6 is a time chart of conventional position detection, and FIG. 7 is a principle diagram of a conventional synchronous mode.

  In FIG. 6, VU, VV, and VW are terminal voltages of the stator of the DC brushless motor, and CVU, CVV, and CVW are virtual neutral point voltages that are ½ of the terminal voltages VU, VV, and VW as reference voltages. The terminal voltages VU, VV, VW and the reference voltage are compared by a comparator. In FIG. 6, the PWM control is omitted.

  In the conventional inverter control device, the commutation timing for switching the phase of the stator through which current flows is determined as follows.

  First, the induced voltage and the reference voltage in a non-energized section of VU, VV, and VW are compared, a point where they intersect (hereinafter referred to as a zero cross point) is detected, and the position of the rotor of the DC brushless motor is detected from this point. . And it commutates at a timing delayed by 30 ° in electrical angle from this zero cross point. In other words, the rotor position is detected during a non-energization time T corresponding to an electrical angle of 60 °, and the delay time until commutation corresponds to just T / 2.

  Next, the principle that the synchronization mode occurs will be described with reference to FIG.

  FIG. 7 is an enlarged view of the electrical angle of 240 ° in the position detection section in FIG. 6, with the vertical axis representing voltage and the horizontal axis representing time. It is assumed that the motor has 6 poles. The terminal voltage is PWM controlled, the operating speed is 55.6 r / s, the carrier frequency is 3 kHz, and the duty is 48%. Accordingly, the non-energization time T corresponding to an electrical angle of 60 ° for detecting the position of the rotor is 1000 μs and the carrier period C is 333.3 μs, and the time T and three times the carrier period C coincide. Since the duty is 48%, the ON time is 160 μs, and the OFF time is 173.3 μs.

  In the position detection section at the initial electrical angle of 60 ° in the VU phase in FIG. 7, the correct zero cross point to be detected is the point A, but at the point A, the switching element is OFF and the terminal voltage is 0V. Therefore, the zero cross point cannot be detected. As a result, the zero-cross point is detected at the next moment (point B) when the switching element is turned on. In this case, the commutation timing is delayed by time R. And the same thing is repeated also in the next non-energization section, and the delay of commutation timing occurs stably and continuously. The above is the mechanism for generating the synchronous mode, which has been clarified this time.

  Here, the synchronization mode occurs when the position detection time, that is, the time T corresponding to the electrical angle of 60 °, and the carrier cycle n times (n is an integer) roughly match, so the smaller the Duty, the higher the probability that it will occur. Become.

  When the synchronous mode occurs and the commutation timing is delayed, the torque generated by the motor is reduced and the brake torque is activated. Therefore, an extra current flows in order to supplement the torque necessary for driving the motor. This excess current increases as the time R for which the commutation timing is delayed increases.

  When the motor is continuously operated in this state, a state in which the commutation timing is delayed by the time R continues to occur continuously, and abnormal motor current continues to flow.

  As a result, excessive power is consumed. In an actual inverter device, when an abnormal current flows, a protection circuit generally operates and the motor may stop.

  The present invention solves the above-described conventional problems, and provides an energy saving and highly reliable inverter control device.

  In order to solve the above-described conventional problems, the inverter control device of the present invention causes the refrigerator control circuit to store in advance an output prohibition band that prohibits output at a predetermined rotation speed, and prohibits operation at the synchronous mode generation speed. Thus, the occurrence of the synchronous mode can be prevented.

  The inverter control device of the present invention provides a high-efficiency and high-reliability inverter control device and refrigerator that do not generate a synchronous mode by prohibiting operation at the synchronous mode generation speed.

  The content of claim 1 is based on a power circuit composed of a plurality of motor drive switching elements, a position detection circuit that detects the position of a rotor of a DC brushless motor that drives a compressor, and the position detection circuit. A rotation speed calculation circuit for calculating the rotation speed of the DC brushless motor from position information of the rotor, a rotation speed control circuit for controlling the actual rotation speed of the DC brassless motor to a command rotation speed output from the refrigerator control circuit, and the rotation An inverter control circuit including a drive circuit that operates the switching element of the power circuit at an arbitrary carrier frequency by an output from the number control circuit, and a refrigerator control circuit that outputs a rotation speed command to the rotation speed control circuit, In the refrigerator control circuit, a synchronous mode in which the time for detecting the position of the rotor coincides with n times the carrier cycle (n is an integer). It is equipped with a storage means that can store in advance an output prohibition band that prohibits output of the rotational speed, and is synchronized by storing in advance in the refrigerator control circuit the rotational speed that occurs in the synchronous mode as the prohibited rotational speed. Mode generation can be prevented.

  According to a second aspect of the present invention, in the first aspect of the invention, an output prohibition instruction is output from the inverter control circuit to the storage means of the refrigerator control circuit, and an output prohibition band of the refrigerator control circuit is set by the output prohibition instruction. Because the output prohibition band can be rewritten in the refrigerator control circuit, the output prohibition band can be set with a single refrigerator control circuit for a plurality of types of inverter control circuits, improving development and production efficiency. To do.

  The content of claim 3 is that in the invention of claim 1, the range of the prohibited rotation speed of the output prohibited band is ± 2 r / s with respect to the synchronous mode rotation speed R. Even when the motor rotation speed fluctuates slightly, the generation of the synchronous mode can be surely prevented.

  The content of claim 4 is the invention according to claim 1, wherein the number of poles of the DC brushless motor is 6 or more, and the greater the number of poles, the easier it is to generate the synchronous mode. A highly reliable inverter control device can be provided.

  The content of Claim 5 is what uses the inverter control apparatus as described in any one of Claim 1 to 4 for a refrigerator, and can reduce noise, improve performance, and prevent the occurrence of synchronous mode. Because. An energy-saving and highly reliable refrigerator can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of an inverter control apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a principle diagram for preventing synchronous mode.

  In FIG. 1, an inverter control device 102 is connected to a commercial power source 101 and drives an AC / DC converter 103 that converts commercial AC voltage into DC voltage, a power circuit 104 that drives a DC brushless motor 109, and a power circuit 104. Drive circuit 105, a position detection circuit 106 that detects the rotor position of the DC brushless motor 109 from the output of the power circuit 104, and a rotation speed calculation that calculates the rotation speed of the DC brushless motor 109 from the rotor position information of the position detection circuit 106 The circuit 107 and a rotation speed control circuit 108 that controls the rotation speed of the DC brushless motor 109 calculated by the rotation speed calculation circuit 107 to the command rotation speed output from the refrigerator control circuit 116 are configured.

  The command rotational speed is output as an operation command signal 117 from the refrigerator control circuit 116.

  The DC brushless motor 109 is a 6-pole salient pole concentrated winding IPM (Interior Permanent Magnet) motor.

  The power circuit 104 includes six switching elements 110, 111, 112, 113, 114, and 115 called IGBTs (insulated gate bipolar transistors) connected in a three-phase bridge.

  The position detection circuit 106 is composed of a comparator or the like, and compares the terminal voltage of the DC brushless motor 109 with a reference voltage by the comparator and outputs the result.

  The rotation number calculation circuit 107 detects the rotation speed of the DC brushless motor 109 by counting the output signal of the position detection circuit 106 for a certain period or measuring the pulse interval.

  The rotation speed control circuit 108 compares the rotation speed of the DC brushless motor 109 calculated by the rotation speed calculation circuit 107 with the command rotation speed output from the refrigerator control circuit 116, calculates the duty value, and sends it to the drive circuit 105. Output the calculation result.

  The drive circuit 105 calculates the commutation timing from the output of the position detection circuit 106, performs duty control according to the calculation result of the rotation speed control circuit 108, and switches the switching elements 110, 111, 112 of the power circuit 104. , 113, 114, 115 are turned ON / OFF.

  The refrigerator control circuit 116 outputs an operation command signal 117 to the rotation speed control circuit 108 in the inverter control device 102 according to the temperature in the refrigerator cabinet. In addition, it has storage means for storing the output prohibition band of the operation command signal 117, and when the rotational speed at which the synchronous mode is generated is known in advance, the synchronous mode generated rotational speed should be written in the storage means. Thus, since the rotation speed is not output, the generation of the synchronous mode can be prevented.

  In the present embodiment, as in the prior art, the inverter is a 120 ° energization PWM control inverter, and the time for detecting the position of the rotor is 60 ° in electrical angle.

  The time T corresponding to 60 ° in electrical angle varies depending on the number of poles of the DC brushless motor 109 and the operating rotational speed.

  In the present embodiment, a 6-pole DC brushless motor is used, T = 1000 μs at 55.6 r / s, and T = 965 μs at 57.6 r / s, and the larger the number of poles and the higher the number of revolutions. T becomes smaller.

  Since the synchronous mode occurs at an operating speed where the time T for detecting the rotor position and n times the first carrier period (n is an integer) roughly match, the operating speed generated by the carrier frequency is calculated in advance. Can be sought.

  When the carrier frequency is 3 kHz, 166.7 r / s (n = 1), 83.3 r / s (n = 2), 55.6 r / s (n = 3), 41.7 (n = 4), 33.3 r / s (n = 5), 27.8 r / s (n = 6), and so on.

  Therefore, the operation rotational speed at which the synchronous mode corresponding to the carrier frequency to be used is generated is stored in advance in the storage means of the refrigerator control circuit 116 so that the synchronous mode generated rotational speed is not output.

  In the present embodiment, since a carrier frequency of 3 kHz is used, 166.7 r / s (n = 1), 83.3 r / s (n = 2), 55.6 r / s are set as the output prohibition speed. (N = 3) and 41.7 (n = 4) are stored in the storage means of the refrigerator control circuit 116.

  Here, in the operation speed at which the synchronous mode occurs, the time T becomes longer as the operation speed decreases, but the carrier period is constant, and the time T is equal to n times the carrier period (n is an integer). Since n increases and the ratio of the OFF time of the switching element decreases, the probability of occurrence of the synchronous mode decreases. Even if it occurs, the commutation delay is small, and the influence becomes small. It was experimentally confirmed that when n is 5 or more, the synchronous mode hardly occurs. Therefore, in the present embodiment, the specification is such that only the synchronous mode generation rotational speed in which n is 4 or less is stored in the storage means of the refrigerator control circuit 116.

  About the inverter circuit comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The AC voltage supplied from the commercial power supply 101 is converted into a direct current by the AC / DC conversion unit 103, and the six switching elements 110 to 115 constituting the power circuit 104 are operated by the output signal of the drive circuit 105. The voltage converted into the voltage drives the DC brushless motor 109.

  Then, the position detection circuit 106 compares the terminal voltage of the DC brushless motor 109 with a reference voltage by a comparator and outputs the result. The rotation number calculation circuit 107 counts the output signal of the position detection circuit 106 for a certain period, The rotational speed of the DC brushless motor 109 is detected by measuring the pulse interval.

  The rotation speed control circuit 108 compares the rotation speed of the DC brushless motor 109 calculated by the rotation speed calculation circuit 107 with the command rotation speed output from the refrigerator control circuit 116, calculates the duty value, and sends it to the drive circuit 105. Output the calculation result. Specifically, when the rotational speed of the DC brushless motor 109 is lower than the command rotational speed output from the refrigerator control circuit 116, the duty is increased to increase the rotational speed, and conversely, when the rotational speed is high, the duty is decreased. To reduce the rotational speed.

  The drive circuit 105 calculates the commutation timing from the output of the position detection circuit 106, and the command rotation speed from the refrigerator control circuit 116 and the operation rotation of the DC brushless motor 109 according to the calculation result in the rotation speed control circuit 108. The duty control is performed so that the numbers match, and the switching elements 110, 111, 112, 113, 114, and 115 of the power circuit 104 are turned ON / OFF.

  Next, the principle of preventing the synchronous mode will be described with reference to FIG.

  FIG. 2 shows a DC brushless motor 109 when the rotation speed is 60.0 r / s and the duty is increased to 50% when the carrier frequency is 3 kHz, 55.6 r / s (n = 3), and the duty is 48%. It is the figure showing terminal voltage of this, and has shown a mode that it escapes from synchronous mode. The position detection time is shortened from 1000 μs to 926 μs by increasing the rotation speed, and the rising slope of the induced voltage is also changed. As a result, it can be seen that the position can be detected at the correct position detection timing, and the zero-cross point can be recognized almost accurately. Even if VV is delayed by the time B-A, the next zero-cross point is recognized correctly when the current is ON, and the recognition of the zero-cross point is not continuously delayed. Can be prevented.

  Thus, even if there is a state where the zero-cross point cannot be recognized correctly by not using the synchronous mode rotation speed, the commutation timing is continuously and stably without falling into a situation where it cannot be recognized continuously. Can be prevented from falling into a synchronous mode.

  In the present embodiment, a range of ± 2 r / s with respect to the synchronous mode generation rotational speed is provided and stored in the storage means of the refrigerator control circuit 116 as an output inhibition band.

  In the refrigerator, the motor speed may fluctuate slightly due to load fluctuations, and by providing a width in the output prohibition band, it is possible to prevent the motor speed from fluctuating to coincide with the synchronous mode generation speed. The generation of the synchronous mode can be surely prevented.

  Here, in the present embodiment, the normal carrier frequency is set to 3 kHz, and the operation speed at which the synchronous mode is generated at this carrier frequency is 55.6 r / s (n = 3), 41.7 r / s (n = 4), 33.3 r / s (n = 5), 27.8 r / s (n = 6),. Therefore, the above rotational speed is stored as a prohibited rotational speed in the memory of the microcomputer constituting the refrigerator control circuit 116.

  Further, instead of storing the synchronous mode generation rotational speed in the refrigerator control circuit 116 in advance, the synchronous mode generation rotational speed corresponding to the carrier frequency used in the inverter control device 102 is calculated, and the refrigerator is transmitted by communication as an output prohibition command. There is also means for outputting to the control circuit 116 and setting a write output prohibition band in the memory of the refrigerator control circuit 116. With this means, there is no need to give an instruction from the refrigerator control circuit 116, so that the inverter control device 102 can independently set the output inhibition band.

  In particular, in recent years, the refrigerator control circuit 116 has been developed in-house, and the inverter control device 102 is generally purchased from a plurality of manufacturers. By using this invention, the inverter control device 102 can be used for a plurality of manufacturers. Since the output prohibition band can be set by one refrigerator control circuit 116, it is not necessary to develop the refrigerator control circuit 116 according to the type of the inverter control device 102. Therefore, the development delivery time of the refrigerator control circuit 116 is shortened and the development efficiency is improved. Has a great effect.

  In these operation rotation speeds in which the synchronous mode occurs, the carrier cycle becomes smaller as the carrier frequency becomes larger, and both the OFF time and the ON time of the switching element become shorter, and the number of PWM waveforms included in the time T also increases. The probability of occurrence is low. Or even if it happens, the delay of commutation is small and the influence will not come out.

  Further, when the number of poles of the DC brushless motor is increased, more commutations are required to rotate the rotor once. Therefore, the time T corresponding to an electrical angle of 60 ° is reduced. When the time T is reduced, the number of carrier pulses input during the time T is reduced, so that the synchronous mode is likely to occur as in the case where the operating rotational speed is increased.

  The synchronous mode is noticeably generated when the number of poles of the DC brushless motor 109 is 6 or more. In this case, the synchronous mode is generated by outputting an operation speed command that does not generate the synchronous mode to the drive circuit 105. The effect of preventing this can be obtained more remarkably.

  As described above, according to the present embodiment, since the generation of the synchronous mode can be prevented, the power consumption does not increase and the DC brushless motor does not stop because the protection circuit is activated. A highly reliable inverter control device can be provided.

(Embodiment 2)
FIG. 3 is a block diagram of the refrigerator in the second embodiment of the present invention.

  Hereinafter, the present embodiment will be described with reference to FIG. In addition, about the same structure as Embodiment 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  The hermetic electric compressor 218 includes a hermetic container 219, an electric element 220 including a stator and a rotor in the hermetic container 219, and a compression element 221.

  In FIG. 3, the inverter circuit is the inverter control device 102 used in the first embodiment, is connected to the commercial power supply 101, and drives the hermetic electric compressor 218. The inverter control device 102 and the hermetic electric compressor 218 are installed in the refrigerator 222, and the refrigerator control circuit 116 is installed in the refrigerator 222. Then, an operation command is output from the refrigerator control circuit 116 to the inverter control device 102 to start and operate the hermetic electric compressor 218.

  Since the occurrence of the synchronous mode can be prevented by operating the refrigerator 222 with the inverter control device 102 of the first embodiment in the configuration as described above, an energy-saving and highly reliable refrigerator that does not generate the synchronous mode is provided. can do.

  Further, even when the motor rotation speed slightly fluctuates due to a load change of the refrigerator by having a range of ± 2 r / s with respect to the rotation speed of the synchronous mode and storing it in the storage means of the refrigerator control circuit 116 as an output prohibition band. The generation of the synchronous mode can be surely prevented.

  Further, by outputting an output prohibition command from the inverter control device 102 to the storage means of the refrigerator control circuit 116 and setting an output prohibition band of the refrigerator control circuit 116, one refrigerator control is performed for a plurality of inverter control devices 102. Since the circuit 116 can cope with this, it is possible to shorten the development delivery time and improve the development efficiency.

  Further, when the DC brushless motor 109 having 6 or more poles in which the synchronous mode is remarkably generated is used, the effect of preventing the synchronous mode is more remarkably obtained.

  As described above, since the inverter control device and the refrigerator according to the present invention can prevent the occurrence of the synchronous mode, the power consumption increases or the protection circuit works to stop the DC brushless motor. In addition, it is also useful as an inverter driving device for hermetic electric compressors for vending machines and air conditioners.

Block diagram of the inverter control apparatus in Embodiment 1 of the present invention Principle of prevention of synchronous mode in the same embodiment Block diagram of refrigerator in Embodiment 2 of the present invention Block diagram of a conventional inverter control device Conventional carrier frequency control pattern diagram Conventional position detection time chart Principle diagram of conventional synchronous mode

Explanation of symbols

DESCRIPTION OF SYMBOLS 102 Inverter control apparatus 104 Power circuit 105 Drive circuit 106 Position detection circuit 107 Rotational speed arithmetic circuit 108 Rotational speed control circuit 109 DC brushless motor 110, 111, 112, 113, 114, 115 Switching element 116 Refrigerator control circuit 222 Refrigerator

Claims (5)

  A power circuit composed of a plurality of motor driving switching elements, a position detection circuit for detecting the position of the rotor of the DC brushless motor that drives the compressor, and the DC brushless motor based on the position information of the rotor by the position detection circuit. A rotation speed calculation circuit for calculating the rotation speed, a rotation speed control circuit for controlling the actual rotation speed of the DC brassless motor to a command rotation speed output from the refrigerator control circuit, and an output from the rotation speed control circuit An inverter control circuit including a drive circuit that operates a switching element of the circuit at an arbitrary carrier frequency, and a refrigerator control circuit that outputs a rotation speed command to the rotation speed control circuit, the refrigerator control circuit including a position of a rotor The output of the synchronous mode rotation speed in which n times the carrier period and n times the carrier period (n is an integer) are prohibited Inverter control device provided with a storage means capable of prestored force bandgap.   The inverter control device according to claim 1, wherein an output prohibition command is output from the inverter control circuit to a storage means of the refrigerator control circuit, and an output prohibition band of the refrigerator control circuit is set by the output prohibition command.   The inverter control device according to claim 1, wherein the rotational speed range of the output prohibition band is ± 2 r / s with respect to the synchronous mode rotational speed R.   The inverter control device according to claim 1, wherein the number of poles of the DC brushless motor is six or more.   A refrigerator using the inverter control device according to any one of claims 1 to 4.

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