JP2012130091A - Fan controller, fan control method and refrigeration cycle system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fan controller capable of utilizing natural winds more efficiently than before.SOLUTION: The fan controller includes: an AC motor 8M for driving a fan; a power source part 2 for rotating the AC motor 8M by supplying power to the AC motor 8M; and a control part 9 for controlling power supply by the power source part 2. When a set determination interval elapses after making the power source part 2 start or restart the power supply, the control part 9 makes the power source part 2 tentatively stop the power supply. Then, during the tentative stop of the power supply by the power source part 2, the control part 9 receives sensing signals Vus and Vvs that change corresponding to the strength of the natural wind, and determines whether or not to make the power source part 2 restart the power supply on the basis of the sensing signals Vus and Vvs.

Description

  The present invention relates to a fan control device and a fan control method for controlling a motor for driving a fan, and further relates to a refrigeration cycle system such as an air conditioner equipped with the fan control device.

  A brushless motor is often used to drive an outdoor fan of an air conditioner. When the outdoor fan is not driven to rotate by the brushless motor, the outdoor fan can freely rotate by an external force such as natural wind.

  Japanese Patent Application Laid-Open No. 2000-125854 (Patent Document 1) discloses a brushless motor driving device capable of controlling braking, stopping, and positioning even when rotating due to an external factor such as natural wind. Specifically, the drive device includes a single Hall element that detects the magnetic pole position of the rotor of the brushless motor, an inverter circuit, and a control unit that controls on and off of the switching element of the inverter circuit. The control means is configured to cause the PWM current to flow through the stator winding in at least one energization pattern of a plurality of energization patterns that are switched and energized during operation in synchronization with the output signal of the Hall element before starting the brushless motor. Is controlled to turn on and off to perform braking, stopping and positioning.

  In the outdoor unit for an air conditioner described in Japanese Patent Application Laid-Open No. 2003-148788 (Patent Document 2), the rotational speed of a motor that is freely rotated by natural wind is the rotation of a hall element or the like before the fan motor is started. It is detected by a position detection circuit. When the detected motor rotation speed is sufficient for the operation of the outdoor unit, the operation of the compressor or the like is started without starting the fan motor as it is. This is because the use of natural wind as it is is more efficient in heat exchange and can reduce wasted power than the fan motor itself rotates and counters natural wind.

JP 2000-125854 A JP 2003-148788 A

  Since the method described in the above Japanese Patent Application Laid-Open No. 2003-148788 (Patent Document 2) detects the number of rotations when the outdoor fan is rotating freely before the fan motor is started, the fan motor It cannot be used during the rotation drive. Therefore, when natural wind blows after the fan motor is activated, power is wasted.

  An object of the present invention is to provide a fan control device and method that can use natural wind more efficiently than before, and a refrigeration cycle system including the fan control device.

  A fan control device according to an aspect includes an AC motor that drives a fan, a power supply unit that rotates the AC motor by supplying power to the AC motor, and a control unit that controls power supply by the power supply unit. . The control unit temporarily stops the power supply unit from supplying power when a set determination interval elapses after the power supply unit starts or restarts power supply. The control unit receives a sensing signal that changes according to the strength of the natural wind during the temporary stop of the power supply by the power supply unit, and determines whether or not the power supply unit restarts the power supply based on the sensing signal Determine whether.

  Preferably, the control unit determines whether or not the magnitude of the armature current of the AC motor is within a predetermined reference range during power supply by the power supply unit. If not, the control unit is within the reference range. The determination interval is set shorter than in some cases.

  In a preferred embodiment, the power supply unit includes an inverter that converts a DC voltage into an AC voltage and supplies the AC motor to the AC motor by a switching operation of a plurality of bridge-connected switching elements. The control unit controls the supply of AC voltage from the inverter to the AC motor by controlling the switching operation of the plurality of switching elements. Then, during the temporary stop of the power supply by the power supply unit, the control unit turns off one of all the switching elements on the upper arm side and all the switching elements on the lower arm side constituting the inverter and sets the other to a predetermined duty. A braking operation is performed in which the ratio is repeatedly turned on and off. The control unit receives the detected value of the armature current or the armature voltage of the AC motor generated by the natural wind during the braking operation and the rotation of the fan together with the AC motor as the sensing signal.

  In the above embodiment, preferably, the control unit calculates the rotational speed of the AC motor based on the zero-cross cycle of the armature current or the armature voltage of the AC motor generated during the braking operation, and the calculated rotational speed. When the power becomes less than or equal to a predetermined reference rotational speed, the power supply is restarted.

  Alternatively, the control unit causes the power supply unit to resume power supply when the magnitude of the armature current or the armature voltage of the AC motor generated during the braking operation becomes equal to or less than a predetermined reference value.

  In another embodiment of the preferred embodiment, the fan control device further includes a position sensor that detects the position of the rotor of the AC motor. In this case, the control unit receives the fluctuation of the position sensor generated by the natural wind during the temporary stop of the power supply by the power supply unit and the fan rotates together with the AC motor as a sensing signal, and outputs the position sensor. Based on the fluctuation, the rotational speed of the AC motor is calculated, and when the calculated rotational speed is equal to or lower than a predetermined reference rotational speed, the power supply is restarted.

  In still another preferred embodiment, the fan is provided to facilitate heat exchange of the heat exchanger, and the fan and the heat exchanger are housed in a common housing. The fan control device further includes an anemometer housed in the housing. In this case, the control unit receives the output of the anemometer as a sensing signal while the power supply by the power supply unit is temporarily stopped, and supplies power to the power supply unit when the anemometer output falls below a predetermined reference value. Let it resume.

  In another aspect, the present invention is a method for controlling a fan driven by an AC motor. This fan control method includes a step of temporarily stopping power supply to the AC motor when a set determination interval has elapsed after starting or resuming power supply to the AC motor, and a step of supplying power to the AC motor. Receiving a sensing signal that changes according to the strength of the natural wind during a temporary stop, and determining whether or not to resume power supply to the AC motor based on the sensing signal.

  In another aspect, the present invention is a refrigeration cycle system, an indoor heat exchanger that performs heat exchange between the refrigerant and indoor air, an outdoor heat exchanger that performs heat exchange between the refrigerant and outdoor air, A compressor that compresses the refrigerant that has passed through one of the heat exchanger and the outdoor heat exchanger and supplies the compressed refrigerant to the other, an expansion valve provided in the refrigerant path between the indoor heat exchanger and the outdoor heat exchanger, A fan for promoting heat exchange of the outdoor heat exchanger and the fan control device for driving and controlling the fan are provided.

  According to the present invention, the intensity of the natural wind is monitored by periodically stopping the fan motor and detecting the rotation of the fan due to the natural wind. If natural wind having a sufficient strength for heat exchange and blowing is blown, the natural wind is directly used for heat exchange and blowing without restarting the fan motor. Thus, power consumption can be reduced by using natural wind more efficiently than in the past.

It is a figure which shows the whole structure of the air conditioner 50 to which the fan control apparatus by Embodiment 1 of this invention is applied. It is sectional drawing which shows a structure in an example of the principal part of the outdoor unit 61 used for the air conditioner 50 shown in FIG. It is a block diagram which shows the structure of the fan control apparatus 1 by Embodiment 1 of this invention. FIG. 4 is a diagram illustrating an example of a waveform of a U-phase current Iu detected by a resistance element R1 in FIG. It is a flowchart which shows the control procedure of AC motor 8M by the PWM control part 6 of FIG. 7 is a flowchart showing a control procedure of AC motor 8M by PWM control unit 6 in the fan control device according to Embodiment 2 of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

<Embodiment 1>
[Overall configuration of air conditioner]
FIG. 1 is a diagram showing an overall configuration of an air conditioner 50 to which a fan control device according to Embodiment 1 of the present invention is applied. The air conditioner 50 is shown as an example of a refrigeration cycle system.

  Referring to FIG. 1, an air conditioner 50 includes a compressor 53, a four-way valve 54, an outdoor heat exchanger 55, an expansion valve 56, an indoor heat exchanger 57, an outdoor fan device 58, and an indoor fan. Device 59. The compressor 53, the four-way valve 54, the outdoor heat exchanger 55, the expansion valve 56, and the indoor heat exchanger 57 constitute a refrigeration cycle (also referred to as a heat pump cycle). By switching the four-way valve 54, the refrigerant circulates along the path indicated by the solid line arrow CL in FIG. 1 during the cooling operation, and the refrigerant circulates along the path indicated by the broken line arrow HT during the heating operation. The outdoor fan device 58 and the indoor fan device 59 are provided to promote heat exchange in the outdoor heat exchanger 55 and the indoor heat exchanger 57, respectively.

  Air conditioner 50 further includes inverter circuits 52, 2, 60 and a control unit 51 that controls these inverter circuits, expansion valve 56, and the like. An AC voltage from the AC power supply 4 is converted into a DC voltage by the converter circuit 3 and supplied to each of the inverter circuits 52, 2, 60. Inverter circuits 52, 2, 60 convert the DC voltage received from converter circuit 3 into an AC voltage and supply it to compressor 53, outdoor fan device 58, and indoor fan device 59, respectively.

  FIG. 2 is a cross-sectional view showing a configuration of an example of a main part of the outdoor unit 61 used in the air conditioner 50 shown in FIG.

  With reference to FIG. 2, an outdoor heat exchanger 55, a compressor 53, and an outdoor fan device 58 are attached to the outdoor unit 61. When viewed from the front of the outdoor unit 61 (downward in FIG. 2), the outdoor heat exchanger 55 is arranged so as to be bent substantially at right angles to the left side and the back of the outdoor unit 61. The compressor 53 is disposed on the right side in the outdoor unit 61. The outdoor fan device 58 includes a fan 8F and an AC motor 8M that rotationally drives the fan 8F. The outdoor fan device 58 is arranged on the front surface side of the outdoor heat exchanger 55, and sucks outside air from the back surface direction (A direction) and the left side surface direction (B direction) in FIG. 2 and discharges it in the front direction (C direction) when rotating. To do. Thereby, the heat exchange of the outdoor heat exchanger 55 is promoted.

[Configuration of fan control unit]
FIG. 3 is a block diagram showing the configuration of the fan control device 1 according to the first embodiment of the present invention. Referring to FIG. 3, fan control device 1 includes a converter circuit 3, an inverter circuit 2, an AC motor 8 </ b> M, and an outdoor fan control unit 9, and rotationally drives fan 8 </ b> F in FIG. 2. In the case of FIG. 3, AC motor 8M is a three-phase synchronous motor. For example, a permanent magnet synchronous motor (also referred to as a brushless motor) is preferably used.

  The inverter circuit 2 detects power armature currents of the power bipolar transistors Q1 to Q6 connected in a three-phase bridge, the diodes D1 to D6 connected in antiparallel to the transistors Q1 to Q6, respectively, and the AC motor 8M. Resistance elements R1, R2, and R3. Transistors Q1, Q4 and resistance element R1 are connected in series between positive electrode side node Np and negative electrode side node Nn in this order to form a U-phase arm. A DC voltage is applied from the converter circuit 3 between the positive node Np and the negative node Nn. Similarly, transistors Q2, Q5 and resistance element R2 are connected in series between positive electrode side node Np and negative electrode side node Nn in this order to form a V-phase arm. Transistors Q3, Q6 and resistance element R3 are connected in series between positive node Np and negative node Nn in this order to form a W-phase arm. Connection node Nu of transistors Q1 and Q4, connection node Nv of transistors Q2 and Q5, and connection node Nw of transistors Q3 and Q6 are connected to U-phase, V-phase and W-phase armature windings of AC motor 8M, respectively. The

  The control part 51 demonstrated in FIG. 1 contains the outdoor fan control part 9 which controls the outdoor fan apparatus 58, and the indoor unit control part 10 which performs the operation control of the whole air conditioner. The indoor unit control unit 10 outputs a fan motor start command and a stop command to the PWM control unit 6 of the outdoor fan control unit 9 in accordance with a user start operation and stop operation. The indoor unit control unit 10 further outputs a fan motor rotation speed command value to the PWM control unit 6 of the outdoor fan control unit 9 according to the outside air temperature, the temperature of the outdoor heat exchanger, or the like.

  The outdoor fan control unit 9 includes a current detection circuit 5, a PWM control unit 6, and a PWM signal generation circuit 7. The current detection circuit 5 detects the U-phase current that flows when the transistor Q4 is on as the voltage Vus generated in the resistance element R1, and generates the V-phase current that flows when the transistor Q5 is on in the resistance element R2. The voltage Vvs is detected. The current detection circuit 5 amplifies these voltages Vus and Vvs by an amplifier (not shown), and converts the amplified signal into a digital signal by an A / D (Analog to Digital) converter (not shown).

  The PWM control unit 6 is configured by a microcontroller unit (MCU: Micro Control Unit), and implements the following functions when the MCU executes arithmetic processing according to a program.

First, PWM control unit 6 calculates U-phase current Iu and V-phase current Iv based on digital signals representing voltages Vus and Vvs received from current detection circuit 5. W-phase current Iw is
Iw = − (Iu + Iv) (1)
Is calculated by

  Further, the PWM control unit 6 determines each of the transistors Q1 to Q6 based on the calculated armature current of each phase and the fan motor start command, stop command, and rotation speed command value received from the indoor unit control unit 10. The PWM signal pulse width command value (duty ratio command value) corresponding to is generated and sent to the PWM signal generation circuit 7.

  The PWM signal generating circuit 7 generates a pulse signal corresponding to the command value of the pulse width received from the PWM control unit 6 and outputs it to the gates of the transistors Q1 to Q6. For example, in the case of the triangular wave comparison method, the PWM control unit 6 generates a voltage command signal corresponding to the command value of the pulse width of the PWM signal and outputs the voltage command signal to the PWM signal generation circuit 7. The PWM signal generation circuit 7 compares the voltage command signal received from the PWM controller 6 with a triangular wave signal (carrier signal) to generate a pulse signal having a duty ratio corresponding to the voltage command signal. As a result, a drive voltage corresponding to the voltage command signal is output from the inverter circuit 2 to the AC motor 8M.

[Detection of motor speed during free run]
When the supply of power to AC motor 8M is stopped, if natural wind blows on fan 8F in FIG. 2, AC motor 8M runs free together with fan 8F. At this time, if pulse signals having the same duty ratio (for example, an appropriate magnitude of about 10%) are output to the gates of the transistors Q4 to Q6 on the lower arm side at the same timing, a braking force is applied to the AC motor 8M. (Hereinafter referred to as “braking operation”). The transistors Q1 to Q3 on the upper arm side remain off. If the duty ratio is moderate, the AC motor 8M stops completely in the case of no wind and weak natural wind. In other cases, the AC motor is rotated at a rotational speed corresponding to the strength of the natural wind. 8M continues to rotate.

  When the rotor of AC motor 8M is rotated by an external force (natural wind), an induced electromotive force is generated in the armature winding of each phase of AC motor 8M. When each of the transistors Q4 to Q6 on the lower arm side is in the ON state during the braking operation, the induced electromotive force causes the U-phase current Iu, V-phase current Iv, and W-phase current Iw (armature) to the resistance elements R1, R2, and R3, respectively. Current) flows. Since these armature currents (corresponding to the sensing signals of the present invention) are alternating current with a period corresponding to the rotational speed of the rotor, the rotational speed of the AC motor 8M is calculated by detecting the period of the armature current. be able to.

FIG. 4 is a diagram illustrating an example of a waveform of the U-phase current Iu detected by the resistance element R1 of FIG. As described with reference to FIG. 3, the current flowing through the resistance element R <b> 1 is taken into the MCU configuring the PWM control unit 6. As shown in FIG. 4, the MCU measures a time T1 [second] (corresponding to a half cycle) from the first zero cross to the next zero cross of the U-phase current Iu by a timer built in the MCU. If the AC motor has the number of pole pairs p (number of poles = 2p), the rotation speed N [rpm] is
N = 60 / (2 × p × T1) (2)
Is calculated by

  When performing a braking operation that applies a braking force to the AC motor 8M, the same duty ratio (for example, 10%) is applied to the gates of the transistors Q1 to Q3 on the upper arm side at the same timing instead of the transistors Q4 to Q6 on the lower arm side. A pulse signal having a moderate magnitude) may be output. At this time, the transistors Q4 to Q6 on the lower arm side remain off. However, in order to detect the armature current when the upper arm is turned on, contrary to the case of FIG. 3, the upper arm side transistors Q1 to Q3 are respectively connected between the collector and the positive node Np. It is necessary to provide resistance elements R1, R2, and R3.

  Instead of the above-described method using the armature current, the number of rotations of the motor during free run by natural wind may be detected by using a Hall element that detects the magnetic pole position of the rotor. In this case, the above braking operation is not necessary.

[Fan motor control procedure]
FIG. 5 is a flowchart showing a control procedure of AC motor 8M by PWM controller 6 of FIG. In the initial state of FIG. 5, AC motor 8M is in a stopped state. The direction of the natural wind is assumed to be a direction that prevents the rotation of the AC motor 8M (backward wind from C to A in FIG. 2).

  Referring to FIGS. 3 and 5, in step S <b> 1, PWM control unit 6 determines whether an activation command has been received from the outside (indoor unit control unit 10). If the PWM control unit 6 determines that an activation command has been received (YES in step S1), the process proceeds to step S2, and if not, step S1 is repeated.

  In step S2, the PWM control unit 6 outputs a PWM pulse at the same value and with an appropriate duty ratio (for example, 10%) to the transistors Q4 to Q6 on the lower arm side of the three-phase bridge circuit. To order. The PWM signal generation circuit 7 outputs a signal having a pulse width corresponding to a command from the PWM control unit 6 to the transistors Q4 to Q6 on the lower arm side (braking operation).

  In the next step S3, the PWM control unit 6 receives the detected value of the U-phase current from the current detection circuit 5, and based on the time (half cycle) from the first zero cross to the next zero cross of the U-phase current due to natural wind The rotational speed of AC motor 8M is calculated.

  In the next step S4, the PWM controller 6 determines whether or not the rotational speed calculated in step S3 is higher than a predetermined rotational speed (for example, 200 rpm). The 200 rpm exemplified here demonstrates beforehand through experiments that if there is such natural wind, heat radiation (heat exchange) is promoted by free running using natural wind rather than self-rotating against it. Value. When the rotation speed is higher than a predetermined value (200 rpm) (YES in step S4), the PWM control unit 6 advances the process to step S13 and uses natural wind without starting the AC motor 8M. The PWM control unit 6 advances the process to step S5 when the rotation speed is equal to or less than a predetermined value (200 rpm) (NO in step S4).

  In step S5, the PWM control unit 6 has passed a predetermined time (for example, 3 seconds) from the start of outputting a PWM signal to the lower-arm transistors Q4 to Q6 (start of braking operation) in step S2. Judge whether. This time of 3 seconds is a waiting time required for the rotation speed of the AC motor 8M to be stabilized during the braking operation. If the predetermined time (3 seconds) has not elapsed (NO in step S5), the PWM control unit 6 returns the process to step S3, and if the predetermined time (3 seconds) has elapsed (YES in step S5), the process proceeds to step S3. Proceed to S6.

  In step S6, the PWM control unit 6 performs pulse control on the transistors Q1 to Q6 of the three-phase bridge circuit so that an appropriate DC current flows through the three-phase winding for positioning.

  In the next step S7, the PWM control unit 6 keeps the current constant while gradually increasing the AC frequency supplied to the three-phase winding from the DC in a state where the AC motor 8M maintains the synchronous operation. Then, the transistors Q1 to Q6 are pulse-controlled.

  In the next step S8, the PWM controller 6 starts a normal control operation that eliminates reactive power by phase control or the like. Further, the PWM control unit 6 initializes (clears) the count number of the counter counter for monitoring the back wind to zero. Further, the PWM control unit 6 starts counting (time measurement) by a timer.

  In the next step S9, the PWM controller 6 determines whether the count by the timer has passed 1 second. If 1 second has elapsed (YES in step S9), the process proceeds to step S10. If 1 second has not elapsed, step S9 is repeated. In step S10, the PWM control unit 6 initializes the count by the timer to 0, and proceeds to step S11. In step S11, the PWM control unit 6 increments the count number of the monitoring counter by +1, and proceeds to step S12. According to the processing procedure of steps S9 to S11, the count number of the monitoring counter is incremented by 1 every second.

  In step S12, the PWM control unit 6 determines whether or not the count value of the monitoring counter exceeds a predetermined value (for example, 600). If the count value exceeds the predetermined value (eg, YES in step S13), the process proceeds to step S13. If the value is equal to or less than the value (600) (NO in step S13), the process returns to step S9.

  In step S13, the PWM control unit 6 stops the power supply from the inverter circuit 2 to the AC motor 8M by turning off all the transistors Q1 to Q6 of the three-phase bridge circuit. In subsequent step S14, the PWM control unit 6 waits for 10 seconds and then returns to step S1. Thereafter, each step described above is repeated.

  According to the procedure of steps S9 to S14 described above, when the count number of the monitoring counter reaches a predetermined value (for example, 600), that is, after the inverter circuit 2 starts or restarts power supply to the AC motor 8M, When the determination interval elapses, power supply to AC motor 8M is temporarily stopped to determine the strength of natural wind. While the power supply is stopped, it is determined whether or not the rotational speed of AC motor 8M caused by natural wind exceeds a predetermined value (for example, 200 rpm) (step S4). Then, while the rotational speed of AC motor 8M exceeds a predetermined value in step S4 (YES in step S4), the motors in step S6 and subsequent steps are not restarted. As a result, when natural wind having a sufficient strength for heat exchange and blowing is blown, the natural wind can be used as it is for heat exchange and blowing, and power consumption can be reduced as compared with the conventional case.

<Embodiment 2>
FIG. 6 is a flowchart showing a control procedure of AC motor 8M by PWM control unit 6 in the fan control device according to Embodiment 2 of the present invention. In the initial state of FIG. 6, AC motor 8M is in a stopped state. The natural wind direction is assumed to be a direction that prevents rotation of the AC motor 8M (a reverse wind direction from C to A in FIG. 2).

  The control procedure in FIG. 6 is different from the control procedure shown in FIG. 5 in that steps S101 to S103 are included instead of step S11 in FIG. The other steps in FIG. 6 are the same as those in FIG. 5, and therefore, the same reference numerals as those in FIG.

  Referring to FIGS. 3 and 6, the process up to step S10 is the same as in FIG. In step S10, the PWM controller 6 initializes the count by the timer to 0, and proceeds to step S101.

  In step S101, the PWM control unit 6 calculates a mean square value (corresponding to an effective value) for a predetermined period (for example, 10 ms) for the armature current (U-phase current) of the AC motor 8M. The PWM control unit 6 determines whether the calculated effective value is greater than a predetermined reference value (for example, 0.5 A). When the PWM control unit 6 determines that the effective value is greater than the predetermined reference value (0.5 A) (YES in step S101), the process proceeds to step S102, and the count number of the monitoring counter is incremented by +2. . If the reference value (0.5 A) or less (NO in step S101), the PWM control unit 6 proceeds to step S103, and counts up the count number of the monitoring counter by +1. After the count number of the monitoring counter is incremented in step S102 or S103, the process proceeds to step S12. The procedure after step S12 is the same as that in FIG.

  Since the load of AC motor 8M becomes large when the reverse wind is blowing on the fan, the motor current increases as compared with the case where there is no natural wind. Therefore, by detecting the motor current (armature current) during rotational driving of the fan motor, it can be used as a rough guide for the strength of the natural wind. In steps S101 to S103 described above, the PWM control unit 6 increases the count-up amount of the monitoring cycle counter when the back wind is blowing on the fan, that is, when the motor current is larger than a predetermined reference value. As a result, since the period until AC motor 8M is stopped in step S13 is shorter than usual, useless power consumption can be reduced.

  In step S101 described above, cases are classified according to one threshold value. However, it is also possible to change the increment of the count value of the monitoring counter in a stepwise manner depending on the case of multi-stage threshold values.

  In the second embodiment, it is assumed that the direction of the natural wind is a direction that prevents the rotation of the AC motor 8M (a reverse wind from C to A in FIG. 2), but AC also assists the rotation of the AC motor 8M ( The same control can be performed even in the case of normal wind (from A to C in FIG. 2). When the wind is blowing on the fan, the load on the AC motor 8M is reduced, so that the motor current is reduced as compared with the case where there is no natural wind. Therefore, in step S101 in FIG. 6, it is determined whether or not the motor current is within an appropriate range between the upper limit and the lower limit. If the motor current is outside the appropriate range, the process proceeds to step S102. By proceeding to step S103, the method of the second embodiment can be applied to both the normal wind and the reverse wind.

<Modification>
The PWM control unit 6 may calculate the number of rotations of the AC motor 8M that rotates together with the fan 8F by natural wind based on the zero cross cycle of the armature voltage of the AC motor 8M generated during the braking operation. In this case, the fan control device is further provided with a voltmeter for detecting a voltage generated in the armature winding of each phase of AC motor 8M.

  More simply, without detecting the zero-crossing period, the PWM control unit 6 causes the inverter circuit to transfer to the AC motor 8M when the detected value of the armature current or the armature voltage of the AC motor 8M falls below a predetermined reference value. The power supply may be resumed.

  As another modified example, as described above, a position sensor (for example, a Hall element) that detects the magnetic pole position of the rotor may be provided. The PWM controller 6 detects the rotational speed of the AC motor 8M during free-running by natural wind based on the output of the position sensor. In this case, the braking operation described in the first embodiment is not necessary.

  As yet another modification, an anemometer for detecting the strength of natural wind may be provided. This anemometer is preferably installed in the casing of the outdoor unit 61 in which the outdoor heat exchanger 55, the compressor 53, and the outdoor fan device 58 are provided in FIG. In this case, in order to detect the magnitude of the natural wind with the anemometer, it is necessary to temporarily stop the power supply from the inverter circuit to the AC motor 8M in order to stop the rotation of the fan 8F. The PWM control unit 6 receives the output of the anemometer during the temporary stop of the power supply, and restarts the power supply when the anemometer output becomes a predetermined reference value or less.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Fan control apparatus 2,52,60 Inverter circuit, 3 Converter circuit, 4 AC power supply, 5 Current detection circuit, 6 PWM control part, 7 PWM signal generation circuit, 8F fan, 8M AC motor, 9 Outdoor fan control part, DESCRIPTION OF SYMBOLS 10 Indoor unit control part, 50 Air conditioner, 51 Control part, 53 Compressor, 54 Four-way valve, 55 Outdoor heat exchanger, 56 Expansion valve, 57 Indoor heat exchanger, 58 Outdoor fan apparatus, 59 Indoor fan apparatus, D1 ~ D6 diode, Q1-Q6 power bipolar transistor, R1-R3 resistive element.

Claims (9)

An AC motor that drives the fan;
A power supply unit that rotates the AC motor by supplying power to the AC motor;
A control unit for controlling power supply by the power supply unit,
The control unit temporarily stops power supply to the power supply unit when a set determination interval has elapsed after starting or resuming power supply to the power supply unit,
Whether the control unit receives a sensing signal that changes according to the strength of natural wind during a temporary stop of power supply by the power supply unit, and causes the power supply unit to resume power supply based on the sensing signal. A fan control device that determines whether or not.   The control unit determines whether or not the magnitude of the armature current of the AC motor is within a predetermined reference range during power supply by the power supply unit, and if not within the reference range, the reference range The fan control device according to claim 1, wherein the determination interval is set to be shorter than that in the case of being inside. The power supply unit includes an inverter that converts a DC voltage into an AC voltage by a switching operation of a plurality of switching elements connected in a bridge and supplies the AC voltage to the AC motor,
The control unit controls the supply of AC voltage from the inverter to the AC motor by controlling the switching operation of the plurality of switching elements,
The control unit turns off one of all switching elements on the upper arm side and all switching elements on the lower arm side constituting the inverter while the power supply is temporarily stopped by the power supply unit, and sets the other to a predetermined state. Perform a braking operation that repeatedly turns on and off at a duty ratio,
The control unit receives the detected value of the armature current or the armature voltage of the AC motor generated by the natural wind during the braking operation and rotation of the fan together with the AC motor as the sensing signal. The fan control device according to claim 1 or 2.   The control unit calculates the rotation speed of the AC motor based on a zero-cross cycle of the armature current or the armature voltage of the AC motor generated during the braking operation, and the calculated rotation speed is a predetermined reference rotation speed. The fan control device according to claim 3, wherein power supply is resumed to the power supply unit when the following occurs.   The said control part makes the said power supply part restart a power supply, when the magnitude | size of the armature current or armature voltage of the said AC motor produced during the said braking operation becomes below a predetermined reference value. The fan control device described in 1. The fan control device further includes a position sensor that detects a position of a rotor of the AC motor,
The control unit receives, as the sensing signal, output fluctuation of the position sensor generated by the natural wind during the temporary stop of power supply by the power source unit and the fan rotating together with the AC motor, The rotation speed of the AC motor is calculated based on the output fluctuation of the position sensor, and when the calculated rotation speed is equal to or lower than a predetermined reference rotation speed, the power supply is restarted. The fan control device described in 1. The fan is provided to facilitate heat exchange of the heat exchanger;
The fan and the heat exchanger are housed in a common housing,
The fan control device further includes an anemometer housed in the housing,
The control unit receives the output of the anemometer as the sensing signal during a temporary stop of power supply by the power supply unit, and when the output of the anemometer becomes a predetermined reference value or less, The fan control device according to claim 1, wherein the power supply is resumed. A method for controlling a fan driven by an AC motor,
Temporarily stopping power supply to the AC motor when a set determination interval has elapsed since starting or resuming power supply to the AC motor;
Whether or not to resume the power supply to the AC motor based on the sensing signal upon receiving a sensing signal that changes according to the strength of natural wind during the temporary stop of the power supply to the AC motor Determining a fan control method. An indoor heat exchanger for exchanging heat between the refrigerant and indoor air;
An outdoor heat exchanger for performing heat exchange between the refrigerant and outdoor air;
A compressor that compresses the refrigerant that has passed through one of the indoor heat exchanger and the outdoor heat exchanger and supplies the compressed refrigerant to the other;
An expansion valve provided in the refrigerant path between the indoor heat exchanger and the outdoor heat exchanger;
A fan for promoting heat exchange of the outdoor heat exchanger;
A refrigeration cycle system comprising: the fan control device according to claim 1, wherein the fan is driven and controlled.

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