JP2017135798A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a period in which noise is generated during control using a low carrier frequency correspondingly to a magnitude of a load of each of air conditioners, as further as possible when starting a motor to be driven by an inverter on which PWM control is performed while switching a carrier frequency from the low frequency to a high frequency.SOLUTION: An on-duty time calculation part within a carrier frequency switching instruction section 30 calculates an on-duty time and outputs it to a comparison part within the carrier frequency switching instruction section 30. When an error notice signal is inputted, an on-duty time threshold generation section 35 stores a stored on-duty time threshold while increasing it for the unit of 2μS and outputs it to the comparison part. When the on-duty time becomes equal to or greater than the on-duty time threshold, the comparison part switches a frequency switching signal to a high carrier frequency. When the error notice signal is inputted, the on-duty time threshold generation section 35 outputs a re-activation signal to an inverter control section 3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an air conditioner, and more particularly to a configuration for starting a compressor motor by an inverter.

Conventionally, the technique shown in Patent Document 1 is disclosed as a drive control device for a motor used in a refrigerator, an air conditioner, or the like. In Patent Document 1, a motor of a compressor used in a refrigerator is driven by an inverter, and the inverter is controlled using a switching signal generated by PWM control.
Further, in Patent Document 1, when starting the motor of this compressor, the frequency of the carrier signal used for generating the switching signal (PWM signal) is low when the rotational speed of the motor is lower than a predetermined threshold, Further, it is increased when the rotation speed becomes equal to or higher than the threshold value. As a result, the rotational position signal of the motor generated from the induced voltage generated in the motor winding by increasing the on-time of the switching signal by lowering the frequency of the carrier signal when the rotational speed of the motor is lower than a predetermined threshold. By detecting the rotational position by widening the pulse width, the step-out is prevented and the motor is reliably started.

FIG. 5 shows an air conditioner 90 using the technique disclosed in Patent Document 1. The air conditioner 90 includes an outdoor unit 80 and an indoor unit 50 that are communicatively connected to each other.
The outdoor unit 80 is connected to an input end 1 to which an AC power supply (not shown) is connected, a rectifier 4 connected to the input end 2, a converter 5 connected to the output side of the rectifier 4, and an output end of the converter 5. An inverter 6, a compressor motor 7 connected to the output terminal of the inverter 6, an outdoor unit controller 9 for controlling the entire outdoor unit 80 according to an instruction from the indoor unit 50, and a drive signal for driving the inverter 6 are output. The drive circuit 8 is provided. The motor 7 includes U-phase, V-phase, and W-phase windings (not shown).

  Further, the outdoor unit controller 9 detects a rotational position of the motor 7 based on the induced voltage generated in each winding of the motor 7 and outputs a rotational position signal, and an instruction from the outdoor unit controller 9. A switching signal for driving the motor 7 in accordance with the rotation speed command value generated is generated by PWM control and output to the drive circuit 8 to control the motor 7 by the 120-degree energization method, and the rotation speed of the motor 7 is set. A carrier frequency switching instructing unit 70 for outputting a frequency switching signal for switching between two types of carrier frequencies for generating a switching signal based on one of the two types of carrier frequencies according to the input frequency switching signal. A carrier signal generation unit 10 that generates a carrier signal and outputs the carrier signal to the inverter control unit 3 is provided.

The inverter control unit 3 receives the rotational speed command value from the outdoor unit control unit 9 and generates a switching signal that causes the motor 7 to rotate at the rotational speed specified by the rotational speed command value. The inverter control unit 3 performs control so that the energized phase of each winding of the motor 7 is switched every 60 degrees of electrical angle based on the input rotational position signal. Further, the inverter control unit 3 receives the carrier signal from the carrier signal generation unit 10, and determines and outputs the duty of the switching signal so as to generate a torque corresponding to the load of the motor 7 using this carrier signal. To do. In other words, the inverter control unit 3 increases the on-duty time of the switching signal (the time during which a switching element (not shown) in the inverter 6 is turned on) when the load of the motor 7 is large and does not reach the designated rotational speed. When the load of 7 is small and exceeds the designated rotational speed, the on-duty time is shortened. In this way, the inverter control unit 3 determines the duty of the switching signal so that the instructed rotational speed can be maintained.
The carrier signal generation unit 10 receives a frequency switching signal output from the carrier frequency switching instruction unit 70, and outputs a carrier signal having a frequency of 4 kHz when the frequency switching signal is high level and 2 kHz when the frequency switching signal is low level.

  On the other hand, the carrier frequency switching instruction unit 70 includes a rotation speed detection unit 71 and a switching determination unit 72 therein. The carrier frequency switching instruction unit 70 receives a rotation position signal, and this rotation position signal is input to the rotation number detection unit 71. The rotation speed detection unit 71 measures the time for which the motor 7 rotates once, and calculates the rotation speed (unit: rps) for 1 second by dividing 1 second by this measured time.

  The calculated number of rotations per second is input to the switching determination unit 72. The switching determination unit 72 compares the input rotation number with a predetermined rotation speed threshold (10 rps), and inputs the input rotation. When the number is equal to or greater than the rotation speed threshold, the frequency switching signal is set to a high level, and when the number is less than the rotation speed threshold, the frequency switching signal is set to a low level and output. For this reason, the inverter control unit 3 executes PWM control using a carrier signal having a carrier frequency of 4 kHz when the rotational speed of the motor 7 is less than 10 rps, and when it is 2 kHz or 10 rps or more.

  As described above, the inverter control unit 3 widens the on-duty time of the switching signal by using a low carrier frequency when starting the motor 7 having a low rotation speed, so that the induced voltage waveform of the winding of the motor 7 at the start-up time. Is controlled so that the rotational position can be reliably detected by the rotational position detector 11. On the other hand, the inverter control unit 3 prevents the detection delay of the commutation timing for switching the energized phase by increasing the carrier frequency during normal operation of the motor 7 having a high rotational speed.

  Next, the operation of the air conditioner 90 configured as described above will be described. Most general air conditioners are compatible with both cooling and heating. For this reason, the operation temperature range of the air conditioner 90, for example, a range of −10 ° C. to + 46 ° C., the air conditioner 90 is set to operate at the lowest or highest temperature in the environment where it is installed. Specific problems may occur.

Specifically, there is a problem that a difference in the starting time of the motor 7 of the compressor occurs depending on the operation timing of the air conditioner 90. When the motor 7 is started in winter, the load becomes heavy because the viscosity of the lubricating oil in the compressor is high. On the other hand, when starting in the summer, the load becomes lighter because the viscosity of the lubricating oil is lower than in the winter. For this reason, the increase speed of the rotation speed at the start-up of the motor 7 is slower in the winter than in the summer. Further, when the operation is started immediately after the operation is stopped, the load becomes heavy even when the pressure in the refrigerant circuit is still high. For this reason, when the operation is started immediately as compared with a case where a sufficient time is taken from the stop of the operation to the resumption of the operation, the increase speed of the rotation speed may be slow.
Therefore, as will be described later, the timing of switching the carrier frequency from 2 kHz to 4 kHz is delayed, so that the period of the carrier frequency is 2 kHz is lengthened, and the noise generation period is lengthened correspondingly. This operation will be described with reference to FIG. This noise will be described in detail later.

  FIG. 6 is an explanatory view for explaining conventional rotation control of the motor 7. The horizontal axis in FIG. 6 indicates time, and FIG. 6 (1) on the vertical axis indicates on-duty time (unit: μS (microseconds)) of the switching signal, and the solid line indicates the speed of increase in the rotational speed of the motor 7. The broken line indicates the case where the engine speed is fast (the load is light), and the broken line indicates the case where the rotational speed increase speed is slow (the load is heavy). FIG. 6B shows the rotation speed (unit: rps) of the motor 7. The solid line shows a case where the rotation speed of the motor 7 is high (load is light), and the broken line shows a low rotation speed increase speed. Each case (heavy load) is shown. Note that t0 to t3 are times.

  In FIG. 6, when the rotational speed command value is input from the outdoor unit control unit 9, the inverter control unit 3 sets the on-duty time of the switching signal to 19 μS from t0 when the motor 7 is completely stopped, and the open loop method. As a result, the rotational speed of the motor is gradually increased. For example, when the rotational position of the motor 7 can be detected by the rotational position signal at t1, the control is switched from the open loop control to the closed loop control using the rotational position. However, after that, the rotational speed is increased while increasing the on-duty time.

  On the other hand, when the rotation frequency signal is input to the carrier frequency switching instruction unit 70, the rotation number detection unit 71 detects the current rotation number and outputs this rotation number to the switching determination unit 72. For example, when the air conditioner 90 is lightly loaded and the speed of rotation of the motor 7 is high, the rotational speed becomes 10 rps or more after t2. The switching determination unit 72 changes the frequency switching signal from the low level to the high level at t2 when the rotational speed becomes equal to or higher than the rotational speed threshold (10 rps). The carrier signal generation unit 10 outputs a carrier signal whose carrier frequency is changed from 2 kHz to 4 kHz to the inverter control unit 3 by the frequency switching signal. As a result, the on-duty time of the switching signal output from the inverter control unit 3 is reduced from 26 μS to 13 μS.

  Further, for example, when the air conditioner 90 is heavy and the rotational speed of the motor 7 is slow, the rotational speed becomes 10 rps or more after t3. The switching determination unit 72 changes the frequency switching signal from the low level to the high level at t3 when the rotational speed becomes equal to or higher than the rotational speed threshold (10 rps). The carrier signal generation unit 10 outputs a carrier signal whose carrier frequency is changed from 2 kHz to 4 kHz to the inverter control unit 3 by the frequency switching signal. As a result, the on-duty time of the switching signal output from the inverter control unit 3 is reduced from 70 μS to 35 μS.

  In this way, the inverter control unit 3 has the rotation speed of the motor 7 equal to or greater than the rotation speed threshold, and the on-duty time of the switching signal output at this time becomes longer. As a result, the rotation position detection unit 11 reliably rotates. When the rotational speed (10 rps) at which the position can be detected is reached, the frequency of the carrier signal is switched from a low frequency to a high frequency to control the motor 7.

  As a result, when the load is light, the carrier frequency is switched at t2 when the on-duty time is 26 μS, but when the load is heavy, the on-duty time is already 26 μS or more at t2, It is necessary to wait until t3 when the on-duty time becomes 70 μS, and an on-duty time of 44 μS, which is a difference between 26 μS and 70 μS from t2 to t3, is an excessive margin. For this reason, when starting the motor 7 of the air conditioner 90 when the load is heavy, compared to when starting the motor 7 when the load is light, noise generated when the carrier frequency is 2 kHz between t2 and t3. Since the period is long, the unpleasant period becomes long.

Next, the noise generation mechanism will be described.
Noise is generated inside the motor 7 due to changes in the current flowing through the windings of the motor 7, and the magnitude of this noise tends to increase when the carrier frequency of the switching signal is low compared to when the carrier frequency of the switching signal is high. There is.
FIG. 7 is an explanatory diagram for explaining a difference in noise due to a difference in carrier frequency. The horizontal axis in FIG. 7 is time. On the vertical axis, FIG. 7 (1) shows a switching signal when the carrier frequency is 4 kHz and the duty is 50%, and FIG. 7 (2) shows a switching signal when the carrier frequency is 2 kHz and the duty is 50%. . In FIG. 7, a broken line indicates a ripple current flowing in the winding of the motor 7.

When the inductance value of the motor winding and the voltage applied to the winding are the same, the period of the ripple current flowing through the winding becomes longer when the carrier frequency is lower than when the carrier frequency is higher. Therefore, in the current of the motor 7 that periodically changes as shown in FIG. 6B, the peak Ip2 of the ripple current value with the carrier frequency of 2 kHz is larger than the peak Ip4 of the current value with the carrier frequency of 4 kHz. .
If the change in the current flowing through the winding of the motor 7 is large, the vibration of the winding due to the change in current also increases, and noise is generated by the vibration of the winding.
Therefore, the vibration (noise) of the winding of the motor 7 due to the change in the ripple current is larger when the carrier frequency is 2 kHz than when it is 4 kHz. That is, in FIG. 6, when the rotational speed increase speed is fast, this noise is loud from t0 to t2 when the carrier frequency is low, and when the rotational speed is slow, the carrier frequency is low from start time t0 to t3. Noisy.

  Then, the rotational speed threshold for switching the carrier frequency is determined by the rotational position detection unit 11 at a carrier frequency of 4 kHz in consideration of a value when the load is lighter than when the load is heavy even at the same rotational speed. The rotational position is determined in advance to the minimum value that can be detected. Specifically, when the rotational speed increase speed of the motor 7 is high, the carrier frequency capable of detecting the rotational position is predetermined at 10 rps, which is a rotational numerical value at which the on-duty time is 13 μS and the carrier frequency is 4 kHz. When the rotational speed is 10 rps when the rotational speed increase speed is low, the on-duty time at the switched carrier frequency is 35 μS, which is more than necessary than the minimum on-duty time 13 μS that can detect the rotational position. Large, that is, an excessive margin.

Therefore, a method of determining the carrier frequency switching timing based on the on-duty time of the switching signal instead of determining the rotation frequency based on the number of rotations is conceivable. That is, for example, when the carrier frequency switching instruction unit 70 constantly monitors the on-duty time and the on-duty time is a carrier frequency of 4 kHz, a time width that allows the rotational position detection unit 11 to detect the rotational position, for example, 13 μS is reached. In this method, the carrier frequency is switched from 2 kHz to 4 kHz.
However, the on-duty time of the switching signal output from the inverter control unit 3 and the time width of the induced voltage whose rotational position can be detected by the rotational position detecting unit 11 are not simply proportional, and the time width of the detectable induced voltage can be detected. Since it depends on the rotational speed as well as the on-duty time, the above-described method for monitoring the on-duty time cannot be adopted when the purpose is to avoid an excessive margin.

Next, the relationship between the time width of the induced voltage, the on-duty time, and the rotational speed will be described with reference to FIG.
FIG. 4A is a block diagram showing an internal circuit of the rotational position detector 11, and FIG. 2B is an explanatory diagram for explaining its operation.
Inside the rotational position detector 11, resistors 11a to 11d for detecting the voltage of a virtual neutral point of the induced voltage generated in each of the U-phase, V-phase, and W-phase windings of the motor 7, and a noise removing capacitor 11h, a comparator 11f, a reference voltage generation source 11e, and an integration circuit 11g.
One ends of the resistors 11a to 11c are connected to the U phase, V phase, and W phase of the winding of the motor 7, respectively, and the other ends of the resistors 11a to 11c are connected in common with one end of the resistor 11d, and the other end of the resistor 11d is Connected to ground. A capacitor 11h is connected in parallel with the resistor 11d.

On the other hand, one end of the resistor 11d is connected to the + input end of the comparator 11f, the reference voltage source 11e is connected to the − input end of the comparator 11f, and the output end of the comparator 11f is connected to the input end of the integrating circuit 11g. The rotation position signal is output from the output terminal of the integrating circuit 11g. An induced voltage appears at a virtual neutral point where the resistors are connected in common.

  FIG. 4 (2) is an explanatory diagram for explaining the operation of the rotational position detector 11. The horizontal axis indicates time, and in the vertical axis, FIGS. 4 (2) and (A) indicate switching signals, and FIG. ) (B) shows the voltage at the virtual neutral point when the rotational speed of the motor 7 is low, FIGS. 4 (2) and (C) show the output signal of the comparator 11f when the rotational speed is low, and FIG. D) shows the voltage at the virtual neutral point when the rotational speed of the motor 7 is high, and FIGS. 4 (2) and 4 (E) show the output signal of the comparator 11f when the rotational speed is high.

  As shown in FIGS. 4 (2) (B) and 4 (2) (D), the induced voltage appearing at the virtual neutral point has a pulse waveform, but the rise of the waveform is gentle due to the influence of the capacitor 11h. It is inclined to. For this reason, the pulse width of the output signal of the comparator 11f depends not only on the on-duty time of the switching signal but also on the magnitude of the induced voltage, that is, the rotation speed. As shown in FIGS. 4 (2) and (A), even when the on-duty time of the switching signal is the same, as shown in FIGS. 4 (2) (B) and 4 (2) (D), the reference voltage is used. The pulse width of the output signal of the comparator 11f differs depending on the magnitude of the induced voltage compared with the reference voltage output from the generation source 11e, and the output signal of the comparator 11f is higher at a higher rotational speed than at a lower rotational speed. The pulse width becomes wider. That is, even when the on-duty time of the switching signal is short, the induced voltage becomes high when the rotational speed is high, and the output signal of the comparator 11f is a sufficient pulse that can pass through the integrating circuit 11g and output the rotational position signal. It becomes width.

  On the other hand, even if the rotational speed is low and the induced voltage is low, when the on-duty time is long, the comparator 11f can output an output signal having a wide waveform that can pass through the integrating circuit 11g. A rotational position signal can be output.

  Thus, the pulse width of the output signal of the comparator 11f is not only related to the on-duty time of the switching signal, but also has a relationship corresponding to the number of rotations. For this reason, in order for the rotational position detection unit 11 to reliably detect the rotational position signal based on the induced voltage, it is necessary to satisfy both the on-duty time and the rotational speed conditions.

  As described above, the inverter control unit 3 outputs a switching signal with a longer on-duty time when the rotational speed increase speed is slow even when the rotational speed is the same, compared to when the rotational speed increase speed is fast. In other words, the inverter control unit 3 continues even if the carrier frequency is switched from 2 kHz to 4 kHz even if the rotational speed is low as long as the on-duty time is such that the rotational position detection unit 11 can detect the position. Position detection. For this reason, since this switching can be performed earlier than the conventional method of switching the carrier frequency only by the rotation speed threshold value, the noise generation time can be shortened as a result.

  However, for this purpose, the carrier frequency must be switched at a timing at which the rotational position signal due to the induced voltage can be reliably detected by the rotational position detector 11 in consideration of both the rotational speed and the on-duty time. Since the on-duty time for switching the carrier frequency differs depending on the operation timing of the air conditioner 90 and the load condition of the motor 7, the optimum on-duty time for switching the carrier frequency avoiding an excessive margin is determined. As a result, since the carrier frequency is switched using the on-duty time including an excessive margin as a threshold, there is a problem that the generation period of noise generated during control using a low carrier frequency becomes long.

Japanese Patent Laid-Open No. 11-318097 (page 7-8, FIG. 1)

  The present invention solves the above-mentioned problems and copes with the load size of each air conditioner when starting a motor driven by an inverter that is PWM controlled by switching the carrier frequency from a low frequency to a high frequency. Thus, the generation period of noise generated during control using a low carrier frequency is made as short as possible.

In order to solve the above-described problems, the present invention according to claim 1 of the present invention includes an input terminal to which an AC power supply is connected, a DC power supply unit connected to the input terminal, and the DC power supply unit. An inverter connected to the output terminal, a motor connected to the output terminal of the inverter, a rotational position detection unit that detects the rotational position of the motor and outputs a rotational position signal, and an instructed rotational speed command value A control means for generating and outputting a switching signal for driving the inverter by PWM control, controlling the motor by a 120-degree energization method, and outputting an error notification signal when the rotational position signal is not input;
An on-duty time threshold value generating means for generating an on-duty time threshold value that is an on-duty time of the switching signal for determining that the motor can be started based on the rotational position signal;
When the on-duty time of the switching signal becomes equal to or greater than the on-duty time threshold value generated by the on-duty time threshold value generating means, the carrier frequency of the carrier signal for generating the switching signal is switched from a low frequency to a high frequency. Carrier frequency switching instruction means for outputting a frequency switching signal;
Carrier signal generation means for generating the carrier signal having a carrier frequency corresponding to the input frequency switching signal and outputting the carrier signal to the control means;
When the control means starts the motor,
The carrier frequency switching instruction means outputs the frequency switching signal for selecting the low frequency carrier signal,
The control means increases the number of rotations of the motor while gradually increasing the on-duty time using a closed loop method using the rotation position signal,
The on-duty time threshold generation unit increases the on-duty time threshold by a predetermined time when the error notification signal is input after the carrier frequency switching instruction unit outputs the frequency switching signal for selecting the high frequency. The on-duty time threshold value thus stored and increased is output to the carrier frequency switching instruction means, and the control means is caused to restart the motor.

  By using the above means, according to the air conditioner of the present invention, at the time of starting the motor driven by the inverter controlled by PWM by switching the carrier frequency from the low frequency to the high frequency, the individual air conditioner The generation period of noise generated at the time of control using a low carrier frequency corresponding to the magnitude of the load can be made as short as possible.

It is a block diagram which shows the Example of the air conditioner by this invention. It is a block diagram which shows the inside of the carrier frequency switching instruction | indication part by this invention. It is explanatory drawing explaining rotation control of the motor by this invention. It is explanatory drawing explaining operation | movement of a rotation position detection part. It is a block diagram which shows the conventional air conditioner. It is explanatory drawing explaining rotation control of the conventional motor. It is explanatory drawing explaining the difference in the noise by the difference in a carrier frequency.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail as examples based on the attached drawings. In addition, illustration and description of a heat exchanger, a refrigerant circuit, a fan motor, and the like that are not related to the present application are omitted. The same name and number are assigned to blocks having the same function in the blocks described in the background art.

FIG. 1 is a block diagram showing an air conditioner 20 using a technique according to the present invention. The air conditioner 20 includes an outdoor unit 40 and an indoor unit 50 that are communicatively connected to each other.
The outdoor unit 40 is connected to an input end 1 to which an AC power supply (not shown) is connected, a rectifier 4 connected to the input end 2, a converter 5 connected to the output side of the rectifier 4, and an output end of the converter 5. An inverter 6, a compressor motor 7 connected to the output terminal of the inverter 6, an outdoor unit controller 9 that controls the entire outdoor unit 40 according to an instruction from the indoor unit 50, and a drive signal that drives the inverter 6 are output. The drive circuit 8 is provided. The rectifier 4 and the converter 5 constitute a DC power supply unit 12. The motor 7 includes U-phase, V-phase, and W-phase windings (not shown).

  Further, the outdoor unit controller 9 detects a rotational position of the motor 7 based on the induced voltage generated in each winding of the motor 7 and outputs a rotational position signal, and an instruction from the outdoor unit controller 9. A PWM signal that is a switching signal for driving the motor 7 is generated in accordance with the rotation speed command value and is output to the drive circuit 8 to control the motor 7 by a 120-degree energization method and rotate when the carrier frequency is switched from 2 kHz to 4 kHz. An inverter control unit 3 that outputs an error notification signal when a state in which the position signal cannot be detected occurs, and an on-duty of a switching signal stored in advance to determine that the motor 7 can be started based on the rotational position signal An on-duty time threshold generation unit 35 (on-duty time threshold generation) that generates and outputs an on-duty time threshold that is a time. Means), an error notification signal, an on-duty time threshold value, and a switching signal are input, and a carrier frequency switching instruction unit 30 (carrier frequency switching instruction means) that outputs a frequency switching signal for switching between two types of carrier frequencies is input. A carrier signal generation unit 10 is provided that generates a carrier signal having one of two types of carrier frequencies according to the frequency switching signal and outputs the carrier signal to the inverter control unit 3.

  The inverter control unit 3 receives the rotational speed command value from the outdoor unit control unit 9 and generates a switching signal so as to rotate the motor 7 at the rotational speed specified by the rotational speed command value. The inverter control unit 3 performs control so that the energized phase of each winding of the motor 7 is switched every 60 degrees of electrical angle based on the input rotational position signal. Further, the inverter control unit 3 receives the carrier signal from the carrier signal generation unit 10, and uses this carrier signal to set the duty ratio of the switching signal so that the rotation number of the motor 7 can be maintained. Determine and output.

The carrier signal generation unit 10 receives a frequency switching signal output from the carrier frequency switching instruction unit 30 and outputs a carrier signal having a frequency of 4 kHz when the frequency switching signal is high level and 2 kHz when the frequency switching signal is low level.
Note that the duty of the switching signal means the ratio of the high level period (on period) and the low level period (off period) of the switching signal, and the on duty period of the switching signal means the high level period of the switching signal. Means the time. Then, a switching element (not shown) in the inverter 6 is turned on during this high level period.

On the other hand, the on-duty time threshold generation unit 35 stores an on-duty time threshold of 24 μS as an initial value in advance, and outputs the stored on-duty time threshold to the carrier frequency switching instruction unit 30. If the inverter control unit 3 cannot detect the rotational position signal when the carrier frequency is switched from 2 kHz to 4 kHz by the carrier frequency switching instruction unit 30, an error notification signal is input to the on-duty time threshold generation unit 35.
When this error notification signal is input, the on-duty time threshold value generation unit 35 adds a predetermined time value (2 μS) to the stored on-duty time threshold value, stores the addition result, and the carrier frequency switching instruction unit 30. Output to. As described above, the on-duty time threshold value generation unit 35 increases the on-duty time threshold value by 2 μS every time the error notification signal is input. However, the on-duty time threshold value generation unit 35 stores an on-duty time threshold value of 24 μS as an initial value at the time of initial reset for initializing the air conditioner 20.
Further, the on-duty time threshold generation unit 35 waits for a predetermined waiting time after the error notification signal is input, for 3 minutes in which the pressure of a refrigerant circuit (not shown) is balanced in this embodiment, and after this waiting time has elapsed, A restart instruction signal is output to the inverter control unit 3. The inverter control unit 3 to which the restart instruction signal is input executes restart of the motor 7.

FIG. 2 is a block diagram showing the inside of the carrier frequency switching instruction unit 30.
The carrier frequency switching instruction unit 30 includes an on-duty time calculation unit 31 (on-duty time calculation unit) and a comparison unit 32 (comparison unit). The carrier frequency switching instruction unit 30 receives an error notification signal and an on-duty time threshold value, and these signals are input to the comparison unit 32.

  The on-duty time calculation unit 31 receives one of the switching signals for switching on / off the switching elements in the inverter 6. The on-duty time calculation unit 31 detects the time from the rising edge to the falling edge of the input switching signal and outputs the detected time to the comparison unit 32 as the on-duty time.

  The comparison unit 32 is input with an on-duty time and an on-duty time threshold, and always compares the on-duty time and the on-duty time threshold. To level. The comparator 32 sets the frequency switching signal to a low level when the on-duty time is less than the on-duty time threshold. Note that an error notification signal is input to the comparison unit 32, and when the error notification signal changes from a high level to a low level, the frequency switching signal is changed from a high level to a low level to switch the carrier frequency from 4 kHz to 2 kHz.

FIG. 3 is an explanatory diagram for explaining the rotation control at the start of starting the motor 7 according to the present invention.
The horizontal axis of FIG. 3 indicates time, the vertical axis of FIG. 3 (1) indicates the on-duty time (unit: μS) of the switching signal, FIG. 3 (2) indicates the error notification signal, and FIG. 3 is a frequency switching signal, FIG. 3 (4) is a target period of the method for controlling the rotation of the motor 7, FIG. 3 (5) is an on-duty time threshold value stored in the on-duty time threshold value generator 35, Reference numeral 3 (6) denotes a restart instruction signal. Note that t10 to t16 are times.

  In FIG. 3, when the rotational speed command value is input from the outdoor unit control unit 9, the inverter control unit 3 turns on the duty of the switching signal from t10 when the motor 7 is completely stopped as shown in FIG. When the time is fixed at 19 μS and the rotational speed of the motor is gradually increased by the open loop control as shown in FIG. 3 (4). For example, when the rotational position of the motor 7 can be detected by the rotational position signal at t11, Switch from open-loop control to closed-loop control using rotational position. However, after switching to this control, the inverter control unit 3 simultaneously increases the rotational speed while increasing the on-duty time of the switching signal.

  As shown in FIG. 3 (3), the carrier frequency switching instruction unit 30 outputs the frequency switching signal at a low level (the carrier frequency is 2 kHz) at the time t10 when the start of the motor 7 is started. And the inverter control part 3 will raise rotation speed, increasing the on-duty time of a switching signal, if it switches to control by the closed loop system which used the rotation position at t11.

  Then, as shown in FIG. 3 (1), the carrier frequency switching instruction unit 30 reaches the initial value of the on-duty time threshold value of 24 μS at the on-duty time t12, so that the frequency switching signal is changed from the low level to the high level, Then, a frequency switching signal for switching the carrier frequency from 2 kHz to 4 kHz is output, and the carrier signal generator 10 outputs a 4 kHz carrier signal from t12. For this reason, the inverter control unit 3 outputs a 4 kHz switching signal.

  On the other hand, the rotational position detection unit 11 tries to detect the rotational position of the motor 7 driven by the 4 kHz switching signal. However, as described in the background art, when the load of the motor 7 of the air conditioner 20 is light, even if the on-duty time is 24 μS, the voltage of the induced voltage at the virtual neutral point is low or the pulse width of the induced voltage is small. If it is narrow, the output signal of the comparator 11f of the rotational position detector 11 cannot pass through the integrating circuit 11g, and as a result, the rotational position detector 11 cannot output the rotational position signal.

For this reason, the inverter control unit 3 stops the rotation of the motor 7 at t12 and outputs an error notification signal that is a high-level pulse signal. The carrier frequency switching instruction unit 30 to which the error notification signal is input outputs the frequency switching signal from the high level (4 kHz) to the low level (2 kHz) at t13 when the error notification signal changes from the high level to the low level.
On the other hand, the on-duty time threshold value generation unit 35 adds a predetermined time value (2 μS) to the on-duty time threshold value (24 μS) stored therein, and stores this calculation result (26 μS) as a new on-duty time threshold value. And output to the carrier frequency switching instruction unit 30. Further, the on-duty time threshold value generation unit 35 has passed 3 minutes after the error notification signal is input as shown in FIG. 3 (6), that is, after the inverter control unit 3 stops the rotation of the motor 7. At t14, a restart instruction signal that is a high-level pulse signal is output.

  On the other hand, the inverter control unit 3 to which the restart instruction signal is input sets the on-duty time of the switching signal to 19 μS from t14 when the motor 7 is completely stopped in order to restart the motor 7, and FIG. As shown in Fig. 3, when the rotational speed of the motor is gradually increased by the control of the open loop system and the rotational position of the motor 7 can be detected by the rotational position signal at t15, for example, the rotational position is used from the control by the open loop system. Switch to closed loop control. However, after switching to this control, the inverter control unit 3 simultaneously increases the rotational speed while increasing the on-duty time of the switching signal.

  As shown in FIG. 3 (3), the carrier frequency switching instruction unit 30 outputs the frequency switching signal at a low level (the carrier frequency is 2 kHz) at the time t14 when the start of the motor 7 is started. And the inverter control part 3 will raise rotation speed, increasing the on-duty time of a switching signal, if it switches to control by the closed loop system which used the rotation position at t15.

  Then, since the carrier frequency switching instruction unit 30 has reached the on-duty time threshold of 26 μS as shown in FIG. 3A, the on-duty time is t16, so the frequency switching signal is changed from low level to high level. That is, a frequency switching signal for switching the carrier frequency from 2 kHz to 4 kHz is output, and the carrier signal generator 10 outputs a 4 kHz carrier signal from t16. For this reason, the inverter control unit 3 outputs a 4 kHz switching signal.

  As described above, when the motor 7 is restarted, the on-duty time threshold value generating unit 35 increases the on-duty time threshold value from 24 μS at the time of initial startup to 26 μS prior to restarting. For this reason, the carrier frequency is switched to 4 kHz at t16, and the on-duty time becomes 13 μS. This is because the on-duty time is increased from 12 μS at the first activation. For this reason, at the time of this restart, the output signal of the comparator 11f of the rotational position detector 11 can pass through the integrating circuit 11g, and as a result, the rotational position signal can be output. Therefore, the inverter control unit 3 can continuously control the motor 7. The inverter control unit 3 outputs an error notification signal again when the position detection signal cannot be detected in the same manner even after restarting. The on-duty time threshold generation unit 35 repeats the operation after t12 until the inverter control unit 3 can start the motor 7 normally.

  As described above, when the motor 7 driven by the inverter 6 that is PWM-controlled by switching the carrier frequency from a low frequency to a high frequency is started, the on-duty time threshold generation unit 35 is configured to The optimum on-duty time threshold value can be generated corresponding to the load size of the air conditioner, and as a result, the period in which the carrier frequency operates at 2 kHz can be minimized. The noise generation period at a carrier frequency of 2 kHz can be shortened compared to a method in which the carrier frequency is simply switched only by the rotation speed.

  In the present embodiment, the carrier frequency switching instruction unit 30 and the on-duty time threshold generation unit 35 are described as hardware, but the present invention is not limited to this, and may be realized by software.

DESCRIPTION OF SYMBOLS 1 Input terminal 2 Input terminal 3 Inverter control part 4 Rectifier 5 Converter 6 Inverter 7 Motor 8 Drive circuit 9 Outdoor unit control part 10 Carrier signal generation part 11 Rotation position detection part 11a, 11b, 11c, 11d Resistance 11e Reference voltage source 11f Comparator 11g integration circuit 12 DC power supply unit 20 air conditioner 30 carrier frequency switching instruction unit (carrier frequency switching instruction means)
31 On-duty time calculation unit (on-duty time calculation means)
32 Comparison part (comparison means)
35 On-duty time threshold generation unit (on-duty time threshold generation means)
40 outdoor unit 50 indoor unit

Claims (1)

An input terminal to which an AC power supply is connected, a DC power supply unit connected to the input terminal, an inverter connected to an output terminal of the DC power supply unit, a motor connected to the output terminal of the inverter, and the motor A rotational position detector that detects the rotational position of the motor and outputs a rotational position signal; and generates and outputs a switching signal for driving the inverter according to the instructed rotational speed command value by PWM control, and the motor is energized 120 degrees. Control means for controlling by a method and outputting an error notification signal when the rotational position signal is not inputted;
An on-duty time threshold value generating means for generating an on-duty time threshold value that is an on-duty time of the switching signal for determining that the motor can be started based on the rotational position signal;
When the on-duty time of the switching signal becomes equal to or greater than the on-duty time threshold value generated by the on-duty time threshold value generating means, the carrier frequency of the carrier signal for generating the switching signal is switched from a low frequency to a high frequency. Carrier frequency switching instruction means for outputting a frequency switching signal;
Carrier signal generation means for generating the carrier signal having a carrier frequency corresponding to the input frequency switching signal and outputting the carrier signal to the control means;
When the control means starts the motor,
The carrier frequency switching instruction means outputs the frequency switching signal for selecting the low frequency carrier signal,
The control means increases the number of rotations of the motor while gradually increasing the on-duty time using a closed loop method using the rotation position signal,
The on-duty time threshold generation unit increases the on-duty time threshold by a predetermined time when the error notification signal is input after the carrier frequency switching instruction unit outputs the frequency switching signal for selecting the high frequency. The air conditioner characterized in that the on-duty time threshold value thus stored and increased is output to the carrier frequency switching instruction means and the control means is caused to restart the motor.

Images