JP2005218208A - Method for activating brushless motor and refrigerator with brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a brushless motor for surely activating a compressor. <P>SOLUTION: A rotational movement of a rotor 117 to an initial location X is provided with a first step (ta-tb) for increasing a DC exciting current to a first current value so as to rotate and move the rotor 117 to a pre-exciting location Y separated from the initial location X, and a second step (tb-tc) for increasing the DC exciting current to a second current value higher than the first current value so as to rotate and move the rotor 117 to the initial location X. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for controlling a brushless motor, and more particularly to a starting method thereof.

  Conventionally, reciprocating compressors have been employed in refrigeration cycles such as refrigerators and air conditioners, and DC brushless motors have become the mainstream as the driving source for these compressors.

  This DC brushless motor is composed of a stator consisting of a multi-phase winding coil and a rotor consisting of a plurality of permanent magnet poles, and detects the position based on the current and voltage flowing between the windings and rotates without a sensor. Some are performing control.

  Since the rotor stop position cannot be recognized when the brushless motor is started, a forced rotation is performed by rotating the rotor to a predetermined speed by supplying a current to a plurality of winding coils based on a preset energization pattern. In general, in order to prevent a sudden rotational movement of the rotor, the forced commutation is performed after the rotor is rotationally moved to an initial position by direct current excitation.

  Specifically, by gradually increasing the current value of DC excitation, the rotor rotates to the initial position, and when increased to a preset current value, the rotor rotates to the initial position. As a result, the current commutation is shifted to forced commutation.

For this reason, since there is no sudden change in the current value, the rotor is also prevented from abruptly rotating and can be started without being stepped out (for example, Patent Document 1).
JP-A 61-1290

  However, in the case of a brushless motor having four or more poles, the arrangement of the magnetic poles is 180 ° symmetrical, so that the rotor cannot be rotated to the initial position or the rotor is moved immediately before the transition from DC excitation to forced commutation. There was a case where the motor suddenly turned and stepped out.

For example, as shown in FIG. 14, in the case of a 4-pole rotor, there are _two initial positions X ₁ and X ₂ depending on the arrangement of the magnetic poles. Specifically, when an N-pole magnetic field is generated on the opposite side of the W phase by direct current excitation, one end S1 or the other end S2 rotates and moves to either X ₁ X ₂ depending on the stop position of the S pole of the rotor 200. .

However, when the stop position of the one end S1 or the other end S2 of the rotor 200 is at an intermediate point Z of the X ₁ and X ₂ as shown in FIG. 15, increasing the current to a predetermined current value by the DC excitation of a magnetic field Depending on the balance, it may not be able to rotate.

In this case, increasing the current of the DC excitation to a predetermined current value, the rotor 200 for shifting to the forced commutation and deemed to have stopped with X ₁ or X _2, for example, in case of counterclockwise rotation is immediately after the transition forced commutation from the magnetic pole is moved as indicated by a broken line, actually rotor 200 is stopped at an intermediate point Z once attracted toward the X _2. Then, since the magnetic poles change so that the rotor 200 rotates counterclockwise, the rotor 200 cannot rotate with respect to the command speed, and there is a risk of stepping out.

  Further, even if the step-out is not performed, the brushless motor of the compressor generates vibration due to a rapid change in the speed of the rotor 200, and a frame (not shown) that holds the rotor 200 collides with the hermetic casing of the compressor to generate noise. There was a thing.

Further, as shown in FIG. 16, when the stop position of the rotor 200 is in the vicinity of the intermediate point Z, the rotor 200 does not rotate due to the balance of the magnetic field immediately after the DC excitation is started, but the current is a predetermined value, For example, when the pressure is increased to 1.7 A or more, the difference in magnetic force between X ₁ and X ₂ is large, so that the magnetic force is dragged closer to X ₁ or X ₂ . In this case, for example, when to have been dragged by X _1, the current value of the DC excitation magnetic force is large at X ₁ because it is higher, so that the rotor 200 is rapidly rotated and moved.

  In this case, in the case of a brushless motor of a compressor, vibration is generated due to a rapid change in the speed of the rotor 200, and a frame (not shown) that holds the rotor 200 may collide with a hermetic case of the compressor and generate noise.

  The present invention has been made paying attention to this point, and an object thereof is to reliably start a brushless motor.

  In order to solve the above problems, a brushless motor starting method of the present invention includes a brushless motor having a stator having a three-phase winding and a rotor having four or more poles, and an inverter circuit for energizing the winding. In a method for starting a brushless motor, the speed of the rotor is controlled based on the current or voltage flowing in the winding after rotating the rotor to the initial position by direct current excitation through the inverter circuit and then rotating the rotor by forced commutation. The rotational movement of the rotor to the initial position includes a first step of increasing the DC excitation current to a first current value so that the rotor is rotationally moved to a preliminary excitation position separated from the initial position; And a second step of increasing the DC excitation current to a second current value higher than the first current value so as to rotate and move to a position. To.

  According to the said invention, a brushless motor can be started reliably.

  An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 9, which is a longitudinal sectional view of the refrigerator according to the present invention, the refrigerator body 1 has a refrigerator compartment 3, a vegetable compartment 4, a switching compartment 5, and a freezer compartment 6 in the heat insulating box 2 in order from the top. The front opening of the main body 1 is provided with doors 7 to 10 that close the storage chambers 3 to 6 in an openable and closable order from the top. Although not shown in particular, an ice making chamber is provided with the switching chamber 5.

  On the back surface of the refrigerating chamber 3 and the back surface of the freezer compartment 6, a refrigerating chamber cooler 12 (hereinafter referred to as “R EVA”) and a freezing chamber cooler 14 (hereinafter referred to as “F EVA”) constituting the refrigerating cycle.

The refrigerator compartment fan 11 (hereinafter referred to as “R fan”) and the freezer compartment fan 13 (hereinafter referred to as “F fan”) are respectively provided on the upper portions thereof. When each of the fans 11 and 13 is operated, the cold air generated by the R EVA 12 and the F EVA 14 is supplied to each chamber, and cooling is performed according to the set temperature of each chamber.

  A machine room 15 is provided at the bottom of the back surface of the main body 1, and a compressor 16 and a drive device 32 for controlling a motor of the compressor 16 described later are provided therein. FIG. 10 is a longitudinal sectional view showing the compressor 16, and the structure of the compressor 16 will be described below.

  A frame 102 is elastically supported through a spring 102a at a substantially middle portion in the vertical direction in the sealed case 101 of the compressor 16, and a compressor structure 103 is provided on the upper side of the frame 102 and a frame is provided on the lower side. A motor 17 is provided. Further, a pivotal support hole 102b is provided at the center of the frame 102, and a rotary shaft 105 that is a main shaft is rotatably fitted therein.

  A flange portion 105a that is slidably mounted on the upper surface of the frame 102 is integrally formed at the upper end portion of the rotation shaft 105, and a crank that is eccentric with respect to the central axis of the rotation shaft 105 is formed on the upper portion of the flange portion 105a. The pin 105b is continuously provided. For this reason, when the rotary shaft 105 is driven to rotate, the flange portion 105 a rotates while being in sliding contact with the upper surface of the frame 102, and the crank pin 105 b rotates eccentrically with respect to the rotation of the rotary shaft 105.

  Reference numeral 106 denotes a cylinder constituting the compressor structure 103, and a cylinder chamber 108 is formed so that the piston 107 can reciprocate in a reciprocating manner. The piston 107 is connected to one end of the crank 109 via a ball joint mechanism 110, and the other end 111 of the crank 109 is rotatably fitted to the crank pin 105b.

For this reason, with the eccentric rotation of the crank pin 105 b, the crank 109 can swing with the ball joint mechanism 110 as a fulcrum, and the piston 107 reciprocates in the cylinder chamber 108.

  In addition, a valve mechanism 115 is provided at the left end of the cylinder 106 so that refrigerant gas is sucked through a suction chamber and a discharge chamber (not shown), and high-pressure gas compressed in the cylinder chamber 108 is discharged into the refrigeration cycle. It has become.

  The motor 17 includes a rotor 117 fitted to a rotating shaft 105 that protrudes downward from the frame 102, and a stator 118 that is fixed to the frame 102 with a narrow gap between the peripheral surface of the rotor 117. ing.

  Further, as shown in FIG. 14 which is an explanatory diagram of the motor 17, the motor 17 is a DC brushless motor. In this embodiment, the motor 17 is a three-phase six-slot four-pole motor, and on the inner peripheral side of the three-phase six-slot stator 118. A 4-pole rotor 117 is configured to rotate.

  Next, the operation of the compressor 16 will be described. When the motor 17 is energized and the rotary shaft 105 is driven to rotate, the crank pin 105b rotates eccentrically integrally. In response to this eccentric rotation, the piston 107 reciprocates in the cylinder chamber 108 via the crank 109 and the ball joint mechanism 110.

  Further, the refrigerant gas evaporated by each of the evaporators 12 and 14 is introduced into the sealed case 101, and this refrigerant gas is moved to the cylinder via the valve mechanism 115 when the piston 107 moves toward the bottom dead center (suction process). It is sucked into the chamber 108.

  On the other hand, when the piston 107 moves toward the top dead center (compression process), the refrigerant gas is compressed and guided to the refrigeration cycle from the discharge pipe via the valve mechanism 115. Thus, the compression process and the suction process are repeated by the rotation of the motor 17, whereby the refrigerant in the refrigeration cycle is circulated to cool the room.

  Next, the drive device 32 that controls the rotation of the motor 17 will be described. As shown in FIG. 11 showing a control block diagram, an inverter circuit 42, a rectifier circuit 44, an AC power supply 46, a PWM forming unit 48, an AD converting unit 50, a dq converting unit 52, and a speed detecting unit 54 , 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. .

  When the motor 17 is rotated, the inverter circuit 42 causes a three-phase drive current to flow through the three-phase (u-phase, v-phase, w-phase) stator windings 40u, 40v, 40w of the motor 17. The inverter circuit 42 is a full-bridge inverter circuit composed of six switching transistors Tr1 to Tr6 which are power switching semiconductors. A driving current is connected in series to the switching transistors Tr1 and Tr4, Tr2 and Tr5, and Tr3 and Tr6, respectively. Detection resistors R1, R2, and R3 are connected to detect.

  The rectifier circuit 44 rectifies an AC voltage from an AC power source 46 that is a commercial power source (AC 100 V) and supplies the rectified voltage to the inverter circuit 42.

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

  The AD converter 50 detects the voltage values at the shunt resistors R1, R2, and R3, 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 converter 52 corresponds to the drive currents Iu, Iv, and Iw output from the AD converter 50 to the d-axis (direct-axis) current Id that is a current component corresponding to the magnetic flux and the torque of the motor 17. The current component is converted into a current Iq of the q-axis (quadrature-axis). 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. 12 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 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 motor 17 based on the detected q-axis current Iq and d-axis current Id. Based on the q-axis current and the d-axis current, the rotation angle θ which is the position of the rotor 117 of the motor 17 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 between the reference rotational speed ωref and the current rotational speed ω, outputs the reference q-axis current Iref 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 and the d-axis current PI control unit 62 perform PI control and current / voltage conversion, respectively, and output a reference q-axis voltage Vq and a reference d-axis voltage Vd.

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

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

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

  According to such a driving device 32, the rotational speed is detected based on the detected d-axis current Id and q-axis current Iq, and the speed control is performed based on the rotational speed ω and the speed command signal S from the main control unit. (Feedback control) is performed, and the PWM signal from the PWM forming unit 48 is output to the inverter circuit 42 so that the motor 17 rotates at the rotational speed ωref matched with the speed command signal S. Based on this signal, the inverter circuit 42 outputs a three-phase drive current to the three-phase stator winding 40 of the motor 17 to control the rotation of the rotor 117.

  In the initial pattern output unit 66, a rotation pattern for starting the compressor 16 is set, and at the time of startup, operation is started according to the set pattern. Initial rotation position currents Idinit, Iqinit, starting d-axis current Idinit, and starting q-axis current Iqinit are set in advance.

  Next, start control (initial pattern) when starting operation from the stopped state of the compressor 16 will be described with reference to FIGS.

  In order to control the rotation of the compressor 16 by the normal speed control from the stopped state, the initial position moving step, the forced commutation step, and the speed control step are sequentially switched. Since the initial position moving step will be described later, the forced commutation step will be described.

In the forced commutation step, as shown in FIG. 1 which is a startup time chart of the brushless motor of the present invention, at a timing tc after the end of the initial position movement step, a preset speed, here 150 Hz / s ² is set. Rotate to accelerate. Specifically, a fixed starting d-axis current is output, and the position cannot be detected, so that the rotor 117 is assumed to be rotating normally and is rotated at an accelerated speed. Therefore, speed control, that is, control in the q-axis direction is not performed, and the starting q current Iqinit is zero. Then, the rotor 117 performs forced commutation until a timing td at which it is assumed that the switching speed to the speed control, here 10 Hz / s, is reached on a preset pattern.

  In the speed control step, the rotational speed (the rotational position of the rotor 117) is detected from the timing td based on the d-axis current Id and the q-axis current Iq detected as described above. Speed control (feedback control) is performed based on the speed command signal S, and the PWM signal from the PWM forming unit 48 is output to the inverter circuit 42 so that the motor 17 rotates at the rotational speed ωref that matches the speed command signal S. . Based on this signal, the inverter circuit 42 outputs a three-phase drive current to the three-phase stator winding 40 of the motor 17 to control the rotation of the rotor 117.

Next, the initial position moving step will be described. When the drive command of the compressor 16 is output from the main control unit 33 to the initial pattern output unit 66 at the timing ta, the rotor 117 is set to a pre-excitation position Y, which will be described later, here Y ₁ or Y ₂ as shown in FIG. The initial pattern output unit 66 gradually increases the rotation initial position currents Idinit and Iqinit up to the first current value, for example, 1A over a predetermined time, for example, 3 seconds, so that the rotational pattern moves. Go (first step). Since the rotor 117 needs to be stopped at the initial position X, the rotation initial position current Iqinit is set to zero.

At the timing tb when the DC excitation current reaches the first current value, the current value is once reduced to zero, and the rotor 117 is rotated to the initial position X, here X ₁ or X ₂ shown in FIG. The initial pattern output unit 66 gradually increases the rotation initial position currents Idinit and Iqinit to the speed PI output unit up to a second current value higher than the first current value, for example, 2A, for a predetermined time, for example, 3 seconds. (Second step). Then, at the timing of tc when the DC excitation current reaches the initial current value, the process proceeds to the above-described forced commutation step, and the rotor 117 rotates as shown in FIG.

  Here, the reason why the first step is provided will be described. The applicant changed the stop position of the rotor 117 from the initial position X as appropriate, and measured the current value when the rotor was rotationally moved from each stop position to the initial position X. At each stop position, the current value at which abnormal noise was generated due to the frame 102 colliding with the sealed case 101 due to a rapid change in the speed of the rotor 117 during direct current excitation to the initial position X was measured.

  FIG. 7 shows the results of this experiment. The solid line represents the relationship between the stop position and the rotatable current value, and the broken line represents the relationship between the stop position and the current value at which abnormal noise occurs. From this result, as the stop position of the rotor 117 is closer to the initial position X, the rotor 117 is rotated and moved at a lower current, and the current value at which abnormal noise is generated is high. Therefore, step-out and abnormal noise are generated when DC excitation is performed. There is nothing.

  However, as shown in FIG. 3, when the rotor 117 stops at an intermediate point Z, that is, near 90 °, the distance from both poles is almost equal, so the balance of the magnetic force is maintained. The current value when doing so increases. Further, since the rotational distance to the initial position X is long, the rotor 117 is accelerated by direct current excitation, and a rapid speed change is likely to occur. Therefore, the current value that generates abnormal noise is reduced.

  Accordingly, in the vicinity of the intermediate point Z, the current value that generates abnormal noise is lower than the current value that can be rotated. Therefore, when attempting to prevent step-out and abnormal noise, the current value is 1.7 A or less. Although it is necessary to perform direct current excitation with a current value, the rotor 117 cannot be rotated. Further, if a current value of 1.7 A or more is used, the rotor 117 can be rotated and moved, but there is a risk that abnormal noise may occur or step out as described above.

That is, if the stop position of the rotor 117 is about ± 5 ° around 90 ° from FIG. 7, the above-mentioned problem occurs. It can be regarded as a range in which step-out may occur (hereinafter, this range is referred to as an initial position non-rotatable region Z _{1 to} Z ₂ ).

Therefore, in the present invention, in order to prevent the occurrence of step-out and abnormal noise and to reliably rotate and move the rotor 117 to the initial position X by direct current excitation, the rotor 117 is moved to the preliminary excitation position Y as a preliminary step. then pivot movement, the rotor 117 is prevented that stopped at the initial position the rotation prohibited area Z ₁ ~Z _2.

Specifically, as shown in FIG. 8, by performing direct current excitation at a position where the preliminary excitation position Y is separated from the initial position X, in this case, at a position of 45 °, the rotor 117 does not rotate in the initial position rotation region Z _1. even had stopped to Z _2, for rotational movement to the pre-excitation position Y by the first step, it can be reliably rotated and moved to the initial position X from the pre-excitation position Y at the second step.

Further, in the first step DC excitation, the rotor 117 is stopped at the intermediate point O of the preliminary excitation position Y or in the vicinity O _{1 to} O ₂ , and the second current value is increased to the same value as in the second step. In this case, there is a possibility that abnormal noise may occur or step out even in the first step, but the rotor 117 does not rotate suddenly because it is increased only to the first current value lower than the second current value. The above problems can be solved.

Further, since the region can only be increased up to the first current value in the first step, the regions O _{1 to} O ₂ that cannot be rotated are expanded, but even if the region stops in this region, the initial position non-rotatable region Z _1. because it is to Z ₂ outside it can be reliably rotated and moved to the initial position X in the second step.

As the setting range of the preliminary excitation position Y, the rotor 117 is stopped in the initial position non-rotatable regions Z _{1 to} Z ₂ until the current due to DC excitation reaches the first current value lower than the second current value. Therefore, in the range of 0 ° to 20 ° that is too close to the initial position X, the rotor 117 is rotated in the first step when the rotor 117 is stopped in the initial position non-rotatable region Z _{1 to} Z ₂ . On the other hand, in the range of 80 ° to 100 ° that is too close to the intermediate point Z of the initial position X, the rotor 117 is stopped in the initial position non-rotatable region Z _{1 to} Z ₂ in the first step. Therefore, the range is set to 20 ° to 80 °. In consideration of variations, it is preferable to set within a range of 30 ° to 70 °.

  According to the above-described configuration, in the first step, the direct current excitation is performed to the first current value lower than the second current value so that the rotor rotates to the preliminary excitation position, and then the rotor is moved to the initial position in the second step. Since the direct current excitation is performed so as to rotate, the rotor can be reliably rotated and moved to the initial position in the second step, and can be started up without being stepped out.

  Moreover, since it can prevent a rapid speed change of the rotor by applying it to the start of the compressor used in the refrigerator, the rotor can be reliably rotated to the initial position without generating abnormal noise.

Next, another embodiment will be described with reference to FIG. In the first Suttepu As described above, the first current is lower than the second value, for example, since only up to 1A does not increase, the rotor 117 to an intermediate point Z and nearby Z-Z ₂ of the initial position X is stopped It may be difficult to rotate. Therefore, in the first step, in order to reliably rotate and move the rotor 117, in this embodiment, when the DC excitation current rises to the first current value, the current value is continuously energized for a predetermined time. .

  Specifically, as shown in FIG. 2, the current value is gradually increased so that the rotor 117 rotates and moves to the preliminary excitation position Y at the timing of te. And if it rises to a 1st electric current value at the timing of tf, it will energize continuously with a 1st electric current value for a predetermined time, here 2 seconds.

Then, after the current value is returned to zero at the timing of tg when a predetermined time has elapsed, the process proceeds to the second step, and the forced commutation is performed at the timing of th, and the speed control is performed at the timing of ti. Yes.

  According to the configuration described above, in the first step, after the current value is increased to the first current value, the rotor is stopped at a place where it is difficult to rotate in the initial position non-rotable region by energizing continuously for a predetermined time. Can be reliably rotated.

  In this case, as indicated by the dotted line in FIG. 2, the current may be lower than the first current at the timing tj. As a result, it is possible to prevent the rotor 117 from rotating at the timing tg immediately before shifting to the second step.

  In the above-described embodiment of the present invention, the brushless motor used in the refrigerator has been described. However, the present invention is not limited to this and can be applied to various brushless motor activation methods. Moreover, although it demonstrated using vector control, it cannot be overemphasized, and the same effect can be show | played also by normal inverter control. Furthermore, the magnetic pole, current value, and DC excitation position of the rotor may be changed as appropriate without departing from the scope of the invention.

  The present invention can reliably start the compressor, and can be applied to various brushless motor starting methods.

It is a time chart which shows the starting method of the brushless motor of this invention. It is a time chart which shows the other starting method of this invention. It is explanatory drawing which shows the state which the rotor stopped at the intermediate point of the initial position. It is explanatory drawing which shows the state which rotated the rotor to the pre-excitation position. It is explanatory drawing which shows the state which rotated the rotor to the initial position. It is explanatory drawing which shows the state which forcedly commutated the rotor. It is a graph which shows the relationship between the stop position of a rotor, and an electric current value. It is explanatory drawing which shows the range of a pre-excitation position. It is a longitudinal cross-sectional view which shows the refrigerator of this invention. It is a longitudinal cross-sectional view which shows the compressor of this invention. It is a control block diagram of the present invention. It is a vector diagram which performs αβ change from three phases. It is a vector diagram which changes dq from αβ. It is explanatory drawing which shows a brushless motor. It is explanatory drawing which shows the state which the rotor has stopped in the initial position. It is explanatory drawing which shows the state which the rotor has stopped in the initial position vicinity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Refrigerator main body 16 ... Compressor 17 ... Motor 32 ... Drive apparatus 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 101 ... Sealing case 102 ... Frame 117 ... Rotor 118 ... Rotor X ... Initial position Y ... Pre-excitation position Z ... Intermediate point of initial position O ... Intermediate point of pre-excitation position

Claims (4)

A brushless motor having a stator having a three-phase winding and a rotor having four or more poles, and an inverter circuit for energizing the winding, and rotating the rotor to an initial position by direct current excitation via the inverter circuit In the starting method of the brushless motor that controls the speed based on the current or voltage flowing in the winding after rotating by forced commutation after moving,
The rotational movement of the rotor to the initial position includes a first step of increasing the DC excitation current to a first current value so that the rotor rotates to a pre-excitation position spaced from the initial position, and the rotor is moved to the initial position. And a second step of increasing the DC excitation current to a second current value higher than the first current value so as to rotate and move to the brushless motor. The method of starting a brushless motor according to claim 1, wherein the pre-excitation position is in a range of 20 ° to 80 ° with reference to the initial position. 2. The DC excitation current in the first step is raised to the first current value, and then a current equal to or lower than the first current is allowed to flow for a predetermined time, and then the process proceeds to the second step. 3. A method for starting the brushless motor according to 2. A reciprocating compressor, a brushless motor having a stator having a three-phase winding and a rotor having four or more poles as a driving source of the compressor, and an inverter circuit for energizing the winding, and through the inverter circuit In a brushless motor that controls the speed based on the current or voltage flowing in the winding after rotating the rotor to the initial position by direct current excitation and rotating it by forced commutation,
A first step of increasing the DC excitation current to a first current value so that the rotor rotates to a pre-excitation position spaced from the initial position; and a DC excitation current so that the rotor rotates to the initial position. And a second step of increasing the current to a second current value higher than the first current value. A refrigerator equipped with a brushless motor.

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