JP2002101685A - Inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter capable of suppressing vibration, noise and heat and preventing the drop of revolution when a permanent magnet electric motor is driven by alternating current in a PWM system. SOLUTION: The inverter controls a permanent magnet electric motor using a permanent magnet on a rotor by performing conversion again after converting alternating current power into direct current, direct current voltage is variable on a part for converting alternating current into direct current, the PWM system is employed on the part for inverting direct current into alternating current to make the alternating current output voltage variable by a modulation rate, in a range in which the frequency is low, the PWM modulation rate is changed in the state that direct current voltage is fixed, in a range in which the frequency is high, direct current voltage is changed in the state that the PWM modulation rate is fixed, and the revolution of the permanent magnet electric motor 4 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for driving a permanent magnet motor using a permanent magnet for a rotor.

[0002]

2. Description of the Related Art A conventional PWM control type inverter device for controlling a permanent magnet motor having a permanent magnet incorporated in a rotor will be described with reference to FIGS. 8 and 9. FIG.

[0003] In FIG. 8, reference numeral 101 denotes an AC power supply;
Is a rectifier circuit, 103 is a transistor module, 104
Denotes a permanent magnet motor mounted on a compressor (not shown) and uses a permanent magnet for a rotor, 105 denotes a magnet position detection circuit of the motor 104, 106 denotes a transistor module control circuit, and 107 denotes a microcomputer. In this apparatus, the rectifier circuit 102 is a voltage doubler rectifier circuit, assuming that the AC power supply voltage is 100 V.

Here, the DC output voltage of the rectifier circuit 102 is
The DC output voltage of the rectifier circuit 102 is about 2√2 times the AC power supply voltage, although the voltage slightly varies due to power supply voltage fluctuations or load fluctuations, but is almost uniquely determined by the voltage of the AC power supply 101.

In order to continuously drive the permanent magnet motor 104 by direct current (DC), one of three windings having a three-phase structure is not energized, and the position of the winding is determined by the induced voltage of the magnet. It was used as a detection coil, and the other two windings were energized to generate torque, and the position was detected and driven by sequentially switching the combination of energized and non-energized phases.

On the other hand, in recent years, a method of alternating current (AC) driving such a permanent magnet motor has been developed. The inverter device will be described with reference to FIG. 9, reference numeral 111 denotes an AC power supply, 112 denotes a rectifier circuit, 113 denotes a transistor module, 114 denotes a permanent magnet motor mounted on a compressor (not shown), and uses a permanent magnet for a rotor.
Is a current detection circuit of the electric motor 114, 116 is a transistor module control circuit, and 117 is a microcomputer. In this case, the rectifier circuit 112 is a double voltage rectifier circuit, assuming that the AC power supply voltage is 100 V.

The DC output voltage of the rectifier circuit 112 is
The DC output voltage of the rectifier circuit 112 is about 2√2 times the AC power supply voltage, although the voltage slightly changes due to the power supply voltage fluctuation or the load fluctuation, but it is almost uniquely determined by the voltage of the AC power supply 111.

In this case, in order to drive the permanent magnet motor 114 with an alternating current at a variable frequency and a variable voltage, the phase of each phase is detected from the current of the motor 114 input from the current detection circuit 118, and the microcomputer 117 controls the magnet position. And a PWM waveform approximated to a sine wave is output from the transistor module 113 to the permanent magnet motor 114 through the transistor module control circuit 116.

[0009]

In such a PWM type inverter device, as the DC voltage is higher and the PWM modulation rate is lower, the ratio of the carrier frequency component to the basic waveform component is larger and the distortion is larger. It is known. When the PWM modulation rate exceeds 1, PWM
It is also known that a portion where the waveform is continuous due to the inability to perform the M modulation occurs, and the distortion also increases. Such distortion causes a harmonic current to flow through the permanent magnet motor, causing a problem that vibration, noise, and heat generation increase.

On the other hand, in order to maintain the sine wave approximation, PW
The modulation rate of M needs to be 1 or less, the applied voltage to the permanent magnet motor becomes smaller than in the case of the conventional two-phase energized direct current (DC) drive shown in FIG. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional technical problem. When an AC motor is used to drive a permanent magnet motor by a PWM method, vibration, noise and heat generation are suppressed and the number of rotations is reduced. An object of the present invention is to provide an inverter device that can also prevent a decrease.

[0012]

SUMMARY OF THE INVENTION An inverter device of the present invention converts an AC power into a direct current, then converts it back into an alternating current, and controls a permanent magnet motor using a permanent magnet for a rotor. The DC voltage is made variable at the part where AC is converted to DC, and the PWM method is adopted at the part where DC is converted back to AC, and the AC output voltage is made variable according to the modulation factor. PWM in fixed state
The modulation rate is changed, and in a high frequency range, the DC voltage is changed while the PWM modulation rate is fixed to control the rotation speed of the permanent magnet motor.

According to the present invention, in an inverter device for controlling a permanent magnet motor using a permanent magnet for a rotor after converting AC power to DC and then converting it back to AC, a portion for converting AC to DC is used. The DC voltage is made variable and the DC output is reconverted into a PWM by adopting the PWM method to make the AC output voltage variable according to the modulation rate. In the low frequency range, the DC modulation rate is fixed and the DC voltage is fixed. In the range where the frequency is high, the DC voltage is changed while the PWM modulation rate is fixed to control the rotation speed of the permanent magnet motor.
There is no need to reduce the pulse width by M more than necessary, and a sine wave approximate waveform with less distortion can be obtained. In addition, when the AC output voltage is high, it is possible to prevent the waveform from being continuous due to the failure of the PWM modulation, and it is possible to apply AC power with little distortion to the permanent magnet motor as a whole.

According to a second aspect of the present invention, in the frequency range in which the PWM modulation rate is fixed in the above, the modulation rate is set to 1.

According to the invention of claim 2, in addition to the above, P
In the frequency range where the WM modulation rate is fixed, the modulation rate is set to 1
Therefore, it is possible to reduce the harmonic components as much as possible, apply a waveform with less distortion to the permanent magnet motor, and reduce vibration, noise, and heat generation.

According to a third aspect of the present invention, in the above-described invention, the permanent magnet motor is for driving a compressor of an air conditioner.

According to the third aspect of the present invention, in addition to the above-mentioned inventions, the permanent magnet motor is used for driving the compressor of the air conditioner. It has the following effects.

According to a fourth aspect of the present invention, in the inverter apparatus of the first or second aspect, the permanent magnet motor is for driving a compressor of a refrigeration and / or refrigeration unit.

According to the fourth aspect of the present invention, in the first or second aspect of the present invention, the permanent magnet motor is used for driving the compressor of the refrigerating and / or refrigerating apparatus. In a refrigerating and / or refrigerating apparatus requiring a high starting torque, the present invention with a small distortion of the applied AC waveform exerts a remarkable effect.

According to a fifth aspect of the present invention, in the above-described invention, the stator of the permanent magnet motor has a stator winding having a concentrated winding structure.

According to the fifth aspect of the present invention, in each of the above-mentioned inventions, the stator of the permanent magnet motor has a stator winding having a concentrated winding structure. In a permanent magnet motor having a stator having a concentrated winding structure which is easy to perform, the present invention with a small distortion of the applied AC waveform exerts a remarkable effect.

[0022]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of an inverter device to which the present invention is applied. In this figure, 1 is an AC power supply, 9 is a DC voltage variable rectifier circuit, 3 is a transistor module, 4 is a compressor mounted on a compressor (not shown), and a permanent magnet motor using a permanent magnet for a rotor, 6 is a transistor module control circuit, 7 is a microcomputer, 11 is a DC voltage detection circuit, 10 is a DC voltage control circuit, and 8 is a current detection circuit of the electric motor 4.

The compressor on which the permanent magnet motor 4 is mounted constitutes a refrigerating cycle of an air conditioner, a refrigerating and / or refrigerating apparatus. In the present invention, the DC voltage variable rectifier circuit 9 is used in place of the rectifier circuits 102 and 112 shown in FIGS. Here, the voltage of the AC power supply 1 is assumed to be 100 V as in the conventional example shown in FIGS.

On the other hand, the variable DC voltage rectifier circuit 9 is a circuit usually called an "active filter", and has two purposes: reduction of harmonic distortion of AC power supply current and variable output DC voltage. Here, the minimum value of the output voltage of the DC voltage variable rectifier circuit 9 is about √2 times the AC power supply voltage plus about 10 V because it satisfies minimizing power supply current harmonic distortion.

Although the maximum value of the DC voltage variable rectifier circuit 9 has a relationship with the withstand voltage of the parts used, the maximum value can be output without any problem at least 2√2 times the AC power supply voltage. That is, the output voltage of the DC voltage variable rectifier 9 is the same as that of the conventional system shown in FIGS.
About 0.5 of the output voltage of the rectifier circuits 102 and 112 at
It can be freely set between about double and about 1.3 times.

The microcomputer 7 sets a required DC output voltage by the DC voltage control circuit 10 and the DC voltage detection circuit 11. The microcomputer 7 drives the permanent magnet motor 4 by generating a necessary PWM approximate sine wave output from the transistor module control circuit 6 and the current detection circuit 8 and applying the output to the permanent magnet motor 4.

As shown in FIG. 2 (FIG. 2 shows the rotational speed of the permanent magnet motor 4 on the horizontal axis and the output voltage Vdc of the DC voltage variable rectifier circuit 9 on the vertical axis) as shown in FIG. The output voltage Vdc is set to a minimum value or a constant voltage close to this in a low range of the rotation speed (frequency) from min to N1, and in a high range of the rotation speed (frequency) from N1 to max, Output voltage V in proportion to
increase dc.

Here, as shown in FIG. 7, the pulse applied to the permanent magnet motor 4 regardless of the pulse width regardless of whether the rotation speed of the permanent magnet motor 4 is high or low as in the prior art. When the voltage is kept high and constant at Va, a pulse having a narrow width and a high height is obtained at a low rotation speed (frequency), even if the rotation speed (frequency) is high. Although the ratio of the carrier frequency voltage component to the component increases and the distortion increases, in the present invention, the voltage Vc can be set high when the rotation speed is high as shown in FIG. In the range, the voltage is Vb
, The fundamental wave voltage component is sufficiently ensured at both a high rotation speed (frequency) and a low rotation speed (frequency), and distortion can be reduced.

On the other hand, as shown in FIG.
Represents the rotation speed of the permanent magnet motor 4 on the horizontal axis, the PWM duty (modulation rate) of the transistor module 3 on the vertical axis), and the rotation speed (frequency) of the permanent magnet motor 4 is m
In the low range from in to N1, the PWM duty is increased in proportion to the rotation speed, and in the high range of the rotation speed (frequency) from N1 to max, the PWM duty is fixed to a constant value a.

Thus, as a result, the permanent magnet motor 4
The relationship between the rotation speed of the transistor module 3 and the output voltage Vac of the transistor module is shown in FIG. 4 (FIG. 4 shows the rotation speed of the permanent magnet motor 4 on the horizontal axis and the output voltage Va of the transistor module 3 on the horizontal axis).
c is shown on the vertical axis), and is proportional to the rotation speed min to max.

Next, such control will be described with reference to the flowchart shown in FIG. The microcomputer 7 determines in step 31
A frequency command from an input device (not shown) is read, and in step 32, the DC voltage control circuit 10 is controlled so as to obtain a rectifier circuit output voltage based on the relationship in FIG. Next, in step 33, the DC voltage, which is the output voltage of the DC voltage variable rectifier circuit 9, is read from the DC voltage detection circuit 11.

Here, at step 34, it is determined whether or not the DC voltage has the target value as shown in FIG. 2, and if not, the process returns to step 32 to return to the DC voltage control circuit. The control value is changed to 10, and control is performed so that the target DC voltage is obtained.

When the DC voltage has reached the target value as shown in FIG. 2, in step 35, PW is calculated based on the relationship shown in FIG.
Determine M modulation rate and control transistor module control circuit 6
Control.

Thus, the relationship between the rotation speed of the permanent magnet motor 4 and the output voltage of the transistor module 3 is controlled so as to satisfy the relationship shown in FIG. These controls are performed so as to comprehensively achieve the relationship shown in FIG.

When the relationship (3) between the rotation speed of the permanent magnet motor 4 (output frequency of the transistor module 3) and the PWM duty (modulation rate) according to the present invention is compared with that of the conventional system, the present invention is applicable to most of the rotation speeds. In the case, a larger PWM modulation rate can be secured. Further, even at the worst rotational speed, a PWM modulation rate equivalent to that of the conventional system can be secured.

Thus, most of the rotational speeds (frequency)
In the above, the distortion of the voltage applied to the permanent magnet motor 4 can be made smaller than in the conventional method, and as a result, the
Vibration, noise and heat generation can be reduced.

Next, an embodiment of a control method according to claim 2 of the present invention will be described. The circuit configuration of the second embodiment, the relationship between the number of rotations of the permanent magnet motor (transistor module output frequency) and each parameter, and the operation flowchart of the microcomputer are the same as those of the first embodiment. Is shown.

The control method according to the second aspect of the present invention is characterized in that the PWM duty (modulation rate) a between the rotation speeds N1 and max in FIGS.
By setting the PWM duty (modulation rate) a to 1 between N1 and max, the voltage distortion included in the output voltage of the transistor module 3 during this period is minimized.
Thereby, vibration, noise, heat generation, and the like of the permanent magnet motor 4 can be significantly reduced as compared with the conventional system.

The functions of the microcomputer described above may be realized not only by the microcomputer but also by, for example, the microcomputer and the DSP or the DSP alone.

[0040]

As described in detail above, according to the present invention, in an inverter device for controlling a permanent magnet motor using a permanent magnet for a rotor after converting AC power to DC and then converting it back to AC. The DC voltage is made variable in the portion that converts DC to DC, and the PWM output system is adopted in the portion that converts DC back to AC, and the AC output voltage is made variable according to the modulation rate.
In the low frequency range, PW
When the M modulation rate is changed and the frequency is high, the DC voltage is changed and the rotation speed of the permanent magnet motor is controlled while the PWM modulation rate is fixed. It is not necessary to reduce the pulse width more than necessary, and a sine wave approximation waveform with less distortion can be obtained. In addition, when the AC output voltage is high, it is possible to prevent the waveform from being continuous due to the failure of the PWM modulation, and it is possible to apply AC power with little distortion to the permanent magnet motor as a whole.

According to the second aspect of the present invention, in addition to the above, P
In the frequency range where the WM modulation rate is fixed, the modulation rate is set to 1
Therefore, it is possible to reduce the harmonic components as much as possible, apply a waveform with less distortion to the permanent magnet motor, and reduce vibration, noise, and heat generation.

According to the third aspect of the present invention, in addition to the above-mentioned inventions, the permanent magnet motor is used for driving the compressor of the air conditioner. It has the following effects.

According to the fourth aspect of the present invention, in the first or second aspect of the present invention, the permanent magnet motor is used for driving the compressor of the refrigerating and / or refrigerating apparatus, so that the motor is started with a pressure difference between the compressors. In a refrigerating and / or refrigerating apparatus requiring a high starting torque, the present invention with a small distortion of the applied AC waveform exerts a remarkable effect.

According to the fifth aspect of the present invention, in each of the above-mentioned inventions, the stator of the permanent magnet motor has a stator winding having a concentrated winding structure, so that noise is generated due to concentration of magnetic flux in a portion where the winding is applied. In a permanent magnet motor having a stator having a concentrated winding structure which is easy to perform, the present invention with a small distortion of the applied AC waveform exerts a remarkable effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an inverter device according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the rotation speed of a permanent magnet motor and the output voltage of a DC voltage variable rectifier circuit according to the present invention.

FIG. 3 is a diagram showing the relationship between the permanent magnet motor rotation speed and the PWM duty (modulation rate) of the transistor module according to the present invention.

FIG. 4 is a diagram showing the relationship between the rotation speed of a permanent magnet motor and the output voltage of a transistor module according to the present invention.

FIG. 5 is a flowchart of a control operation according to the present invention.

FIG. 6 is a schematic diagram of PWM control according to the present invention.

FIG. 7 is a schematic diagram of conventional PWM control.

FIG. 8 is a configuration diagram of a conventional inverter device.

FIG. 9 is a configuration diagram of another conventional inverter device.

[Explanation of symbols]

 Reference Signs List 1 AC power supply 3 Transistor module 4 Permanent magnet motor 6 Transistor module control circuit 7 Microcomputer 8 Current detection circuit 9 DC voltage variable rectification circuit 10 DC voltage control circuit 11 DC voltage detection circuit

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tetsuo Nomoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Yuichi Izawa 2-5-1 Keihanhondori, Moriguchi-shi, Osaka No.5 Sanyo Electric Co., Ltd. F-term (reference) 5H006 AA02 CA01 CA07 CB01 CC02 CC08 DC05 5H007 AA02 BB06 CA01 CB02 CB05 CC12 CC23 DB07 DC02 DC05 EA02 5H560 AA02 BB04 BB12 DA15 DC12 DC13 EB01 GG11 RR04 SS03 XA03

Claims (5)

[Claims] 1. An inverter device for converting an AC power into a DC, then converting the AC power back into an AC, and controlling a permanent magnet motor using a permanent magnet for a rotor. Variable
The DC output is reconverted to AC by using a PWM method to make the AC output voltage variable according to the modulation factor, and in a low frequency range, the DC voltage is fixed with the DC voltage fixed.
In the range where the frequency is high, the PW
An inverter device wherein the DC voltage is changed while the M modulation factor is fixed to control the rotation speed of the permanent magnet motor. 2. The modulation rate is set to 1 in a frequency range in which the PWM modulation rate is fixed.
Inverter device. 3. The inverter device according to claim 1, wherein the permanent magnet motor is for driving a compressor of an air conditioner. 4. The inverter device according to claim 1, wherein the permanent magnet motor is for driving a compressor of a refrigeration and / or refrigeration device. 5. The inverter apparatus according to claim 1, wherein the stator of the permanent magnet motor has a stator winding having a concentrated winding structure.