JP2003061394A - 4 element/6 element switching three-phase inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a 4 element/6 element switching three-phase inverter in which efficiency can be improved in low rotational region. SOLUTION: In an inverter for supplying AC three-phase power to a motor driving a compressor by switching a three-phase bridge connection switching element connected between the plus and minus voltage terminals of a DC power supply supplying power of a plus voltage with reference to a zero voltage and of a minus voltage of the same magnitude as the plus voltage, a switch for connecting the zero voltage terminal with the neutral of any one arm of the three-phase bridge is provided. The switch is turned on at the time of low speed rotation to stop switching operation of one arm and the inverter is operated by switching the remaining four elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving the efficiency of an inverter that drives a three-phase motor having a wide range of rotational speed, which is represented by a compressor motor of an air conditioner.

[0002]

2. Description of the Related Art Conventionally, a three-phase motor for driving a compressor of an air conditioner is rotated at a predetermined rotation speed by electric power generated by an inverter having a switching element connected in a three-phase bridge. FIG. 19 is a block diagram showing a configuration of a motor drive inverter according to a conventional technique. In this figure, the power of the AC power supply 1 is converted into DC by the rectifier 2 and becomes DC power smoothed by the capacitor C1. This DC power is converted into AC power by an inverter module 3 connected in a three-phase bridge by three arms of switching elements U and UB, V and VB, and W and WB, and drives a motor 4. Motor 4
The load is a compressor (not shown), and the inverter module 3 is PWM-controlled so that the voltage and the frequency have a substantially proportional relationship in accordance with the required load.

[0003]

FIG. 20 is a diagram showing the relationship between the motor rotation speed and the loss according to the above method. As shown in this figure, losses other than the inverter module 3,
That is, the DC conversion loss and the motor loss are almost proportional to the rotation speed of the motor, but the loss of the inverter module is almost constant regardless of the rotation speed. Therefore, there has been a problem that the motor rotation speed is low and the overall efficiency becomes low in a low output operation region.

The present invention has been made under such a background. In the normal rotation range, the present invention operates as a three-phase inverter with six elements, and in the low rotation range, it operates as an inverter with four elements. An object is to provide a 4-element / 6-element switching 3-phase inverter capable of improving efficiency.

[0005]

According to a first aspect of the present invention, there is provided a plus voltage terminal starting from a zero voltage, and the plus voltage terminal of a direct current power supply for supplying a minus voltage having the same voltage value as the plus voltage. In an inverter that supplies three-phase AC power to a motor by switching a three-phase bridge connection switching element connected between the negative voltage terminal and the negative voltage terminal, in an arm of any one of the zero voltage terminal and the three-phase bridge A switch for connecting a point and a switch is provided, and when the switch is turned on, the switching operation of the one arm is stopped to operate by switching the remaining four elements. Provide a three-phase inverter.

According to the present invention, a switch for connecting the zero voltage terminal and the midpoint of one of the three-phase bridge connection switching elements is provided, and the switch is turned on to deactivate the one arm. Thus, a three-phase inverter with four elements can be obtained.

According to a second aspect of the present invention, in the four-element / six-element switching three-phase inverter according to the first aspect, the motor is a motor for driving a compressor of an air conditioner.

According to the present invention, the compressor motor of the air conditioner having a wide range of rotation speed can be set to 4 depending on the rotation speed.
The motor can be driven by switching to an element inverter or a six element inverter.

According to a third aspect of the present invention, in the four-element / six-element switching three-phase inverter according to the first or second aspect, the switch has a low output voltage of the inverter and a low rotation speed of the motor. It is characterized by turning on.

According to the present invention, the inverter loss can be reduced by operating as a 6-element inverter during normal rotation and by operating as a 4-element inverter when the motor rotation speed is low.

The invention as defined in claim 4 is from claim 1 to claim 3.
In a mode in which the switch of the four-element / six-element switching three-phase inverter is turned on to operate by switching four elements, the positive voltage and the negative voltage are applied to the winding of the motor by the switching operation. At the timing when the PWM control pulse width is made smaller, the PW is applied at the timing when the plus voltage and the zero voltage or the zero voltage and the minus voltage are applied to the winding of the motor by the switching operation.
It is characterized in that the M control pulse width is increased.

According to the present invention, in the mode in which the inverter operates as a four-element inverter, the timing at which the plus voltage and the minus voltage are applied to the winding of the motor and the plus voltage and the zero voltage or the zero voltage and the minus voltage are applied. The current flowing through the winding of the motor can be made to have the same current value depending on the timing, and the torque ripple can be reduced.

The invention according to claim 5 is the same as claims 1 to 4.
In the four-element / six-element switching three-phase inverter described in any one of 1, the switching element is an IGBT.

According to the present invention, the use of the IGBT as the switching element makes it possible to use the inverter at high voltage and high output.

The invention described in claim 6 is from claim 1 to claim 4.
In the four-element / six-element switching three-phase inverter described in any one of 1, the switching element is a MOSFET.

According to the present invention, the loss of the inverter during low current operation can be reduced by using the MOSFET as the switching element.

The invention described in claim 7 is from claim 1 to claim 6.
In the four-element / 6-element switching three-phase inverter according to any one of items 1 to 5, the zero voltage is set to a midpoint between two capacitors of the same capacity connected in series between the plus voltage and the minus voltage. .

According to the present invention, the zero voltage point can be created with a simple structure, and the 4-element / 6-element switching 3
It can be the power source for a phase inverter.

The invention according to claim 8 is the same as claims 1 to 7.
In the 4-element / 6-element switching 3-phase inverter according to any one of items 1 to 4, the switching of the switching element is
It is characterized in that it is performed based on an output signal from the position detection circuit which can be used in both the mode operating by switching of the four elements and the mode operating by switching of the six elements.

According to the present invention, one position detection circuit can be shared (switched) when using 4 elements and 6 elements.

According to a ninth aspect of the present invention, in the four-element / six-element switching three-phase inverter according to the eighth aspect, the position detection circuit applies to each phase voltage of the three-phase AC power output from the inverter. Pseudo-neutral point circuit that generates a pseudo-neutral point based on a corresponding signal, and a comparison circuit that outputs the output signal based on a comparison result between a signal corresponding to each phase voltage and the pseudo-neutral point It is characterized by having and.

According to the present invention, it is possible to form a position detection circuit for 4 and 6 elements in common with a simple structure.

According to a tenth aspect of the present invention, in the four-element / six-element switching three-phase inverter according to any one of the first to ninth aspects, the DC power source is obtained by a bridge rectification circuit that rectifies an AC voltage. Any one of two voltage doubler capacitors connected in series, both ends of which are connected to the DC output side terminal of the bridge rectifier circuit, a connection point of the two voltage doubler capacitors and an AC input side terminal of the bridge rectifier circuit It is characterized by having a specific switch for short-circuiting or opening one of them.

The invention as set forth in claim 11 is the four-element / 6-element switching three-phase inverter according to claim 10,
The frequency of the three-phase AC power when the specific switch and the switch are switched is set to be different from each other. The switching frequency of each of the specific switch and the switch is set so that the overall efficiency is improved.

According to a twelfth aspect of the present invention, in the four-element / six-element switching three-phase inverter according to the tenth or eleventh aspect, the AC voltage is a voltage boosted by a booster circuit including a PAM circuit. Characterize.

The invention of claim 13 is the same as that of claim 12.
In the element / six element switching three-phase inverter, the booster circuit includes an AC reactor that is inserted in series in either line of the AC input before being boosted, a load side of the AC reactor, and the AC input. It has a semiconductor switch as the PAM circuit which short-circuits with another line for a predetermined period of each cycle of the AC input, and operates only in a voltage region where boosting is required.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a 4-element / 6-element switching 3-phase inverter according to an embodiment of the present invention. In this figure, reference numeral 1
Is an AC power supply, which is converted into DC power by the rectifier 2. Capacitors C3 and C4 connected in series for smoothing are connected to the DC side.
The connection point of 4 is a zero voltage point. The inverter module 3 has a configuration in which the arms of the switching elements U, UB, the switching elements V, VB and the switching elements W, WB are connected in a three-phase bridge, and the middle point of each arm is at three terminals of the motor 4. It is connected. Further, a switch SW is connected between the connection point of the switching elements V and VB and the zero voltage point. Although the IGBT is used as the switching element in this embodiment, a MOSFET may be used.

When the switch SW is turned off, the inverter module 3 operates as a normal three-phase inverter to supply the motor 4 with three-phase power. When the switch SW is turned on, one terminal of the motor is connected to the zero voltage point. At this time, the switching elements V and VB stop operating and the inverter operation is performed by the four elements, and the three phases are applied to the motor 4. Supply power.

FIG. 2 shows a use area of a normal inverter operation in which six elements are used as switching elements and a switch S.
It is a figure explaining a use field when W is turned on and an inverter operation by four elements is performed. It is desirable that the voltage applied to the motor and the frequency have a substantially proportional relationship, and therefore the rotation speed of the motor and the output voltage of the inverter are as shown in FIG.
It will be a straight line rising to the right as shown in. Here, in a high rotation region where the motor rotation speed is in the range of 60 rps to 120 rps and in the region where the inverter output voltage is high, the inverter performs inverter operation using six elements, and the motor rotation speed is in the low rotation range of 0 rps to 60 rps. In the rotation region where the inverter output voltage is low, the inverter performs an inverter operation using four elements.

Next, the drive timing of each switching element when the switch SW is turned on and the four-element inverter operation is performed will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing the timing when each switching element is turned on. The section from time t1 to t3 in this figure is a period in which the switching element U is PWM-turned on. Further, the section from time t2 to t4 is a period in which the switching element WB is PWM-turned on. Note that time t
From 1 to t7, the electrical angle is 2π, and from time t1 to t3
Of the electrical angle of 2π /
Equivalent to 3. Only the switching element U is turned on in the section (T1) from the time t1 to t2, the voltage of the capacitor C3 is PWM-applied to the winding of the motor 4, and the switching element U is connected in the section (T2) from the time t2 to t3. Both WB are turned on, and the voltage of the sum of the capacitors C3 and C4 is PWM-applied to the winding of the motor 4.

FIG. 4 is a diagram for explaining the PWM pulse width of the switching element. T1 in this figure is time t1 in FIG.
Corresponding to the section (T1) from t2 to t2, the voltage of the capacitor C3 is applied to the winding of the motor 4, and the switching element U is turned on for the electrical angle 2π / 6 by repeating the pulse width a. Subsequently, T2 in this figure corresponds to a section (T2) from time t2 to t3 in FIG. 3, both switching elements U and WB are turned on, and the sum of the capacitors C3 and C4 is added to the winding of the motor 4. The voltage is PWMed and applied. In the section T2, the same current as that of T1 is applied to the winding of the motor 4, so that the repetitive pulse width is (a × k) and the electrical angle is 2π /
During 6 the switching elements U and WB are both turned on.
Here, k usually takes a value around 0.75.

Next, the loss of the switching element will be described with reference to FIGS. 5 and 6. FIG. 5A shows time t.
In the operation mode from 1 to t2 (T1), the capacitor C3
The voltage of 1 passes through the switching element U and the current Ic1 flows through the motor winding. FIG. 5 (b) shows a period between time t2 and t3 (T
In the operation mode of 2), the voltage of the sum of the voltages of the capacitors C3 and C4 passes through the switching elements U and WB, and the current Ic2 flows through the motor winding. The loss of the switching element in the operation mode of T1 in which the current is supplied to the motor winding through one switching element is Vce × Ic = a [W]
Then, the loss of the switching element in the operation mode of T2 in which the current is supplied to the motor winding through the two switching elements is 2 × Vce × Ic = 2a [W].

FIG. 6 is a table summarizing the loss of the switching element for each of the operation when the switching element is four elements and the operation when the switching element is six elements. In the four-element operation, the operation mode of T1 is four times in one cycle as shown in FIG. 3, and a loss of 4a [W] occurs. Also, T2
As can be seen from FIG. 3, there are two operation modes, and a loss of 4a [W] occurs. Therefore, the total loss is 8a [W]. In 6-element operation, there is no T1 operation mode, and no loss occurs. Further, the operation mode of T2 is 6 times in one cycle, and a loss of 12a [W] occurs. Therefore, the total loss is 12a [W]. After all, the loss during operation of four elements is ⅔ of that during operation of six elements, and the loss of the inverter module can be reduced by switching to the operation of four elements during low speed rotation.

Next, a 4-element / 6-element switching 3-phase inverter according to a second embodiment of the present invention will be described with reference to FIGS. 7 and 8. In addition, in this 2nd Embodiment, the same code | symbol is attached about the same component as the said 1st Embodiment, and the detailed description is abbreviate | omitted. Note that FIG.
The switch SW1 of corresponds to the switch SW of FIG.

FIG. 7 shows 4 elements / 6 according to the second embodiment.
It is a block diagram which shows the structure of an element switching three-phase inverter. In this figure, reference numeral 1 is a 50/60 Hz AC input power supply, which is connected via a partial switching PAM circuit 12 to the AC input side of a bridge rectification circuit composed of diodes D1 to D4.

The partial switching PAM circuit 12 includes an AC reactor L1 which is inserted in series with one of the lines of the AC input power source 1, a load side of the AC reactor L1 and another line of the AC input power source 1. Diode D5
A bridge rectifier circuit composed of D8 to D8 is connected, and the DC side of the bridge rectifier circuit is short-circuited or opened by the gate control of the IGBT Q1. The diodes D5 to D8 and the IGBT Q1 are the PAM circuit 1
It constitutes 2a.

On the DC output side of the bridge rectifier circuit,
Two voltage doubler capacitors C1 and C2 connected in series are connected, and a switch SW2 for shorting or opening the midpoint of the two voltage doubler capacitors C1 and C2 and one end on the AC side of the bridge rectifier circuit is provided. There is. Further, the smoothing capacitor C3 is connected to the DC side to reduce the ripple of the DC voltage applied to the inverter module 3. The inverter module 3 is an inverter that outputs a variable frequency by a predetermined control, and the output drives the motor 4.

The converter circuit 15 has a partial switching PAM circuit 12, a bridge rectifier circuit composed of diodes D1 to D4, a switch SW2, and two voltage doubler capacitors C1 and C2.

In the second embodiment, the CPU 20
Position detection circuit 2 for detecting the magnetic pole position of the rotor of the motor 4
1 is provided.

The position detecting circuit 21 has four elements for realizing the above operation of switching the four elements / 6 elements of the first embodiment.
Each element / 6 element operation (4 element / 6 element inverter)
This is a position detection circuit that can be commonly used in.

The CPU 20 controls the inverter module 3 based on the position detection signals U, V, W detected by the position detection circuit 21 as in the first embodiment. That is, the CPU 20 controls the inverter module 3 by 6-element control and 4-element / 6-element switching control (switch SW1 on / off and waveform switching).
And 4 element control is performed. Further, the CPU 20 controls ON / OFF switching of the switch SW2 as described later.

The configuration of the position detection circuit 21 will be described with reference to FIG. The position detection circuit 21 includes voltage dividing circuits 22u, 22v, 22w for inputting the three-phase voltages Vu, Vv, Vw output from the inverter module 3, respectively.
It includes low-pass filter circuits 23u, 23v, 23w, a pseudo neutral point circuit 24, and comparison circuits 25u, 25v, 25w.

The voltage dividing circuits 22u, 22v, 22w have a voltage kVu, which is obtained by multiplying the voltages Vu, Vv, Vw by k, respectively.
Outputs kVv and kVw. Low-pass filter circuit 23
u, 23v, and 23w remove the high frequency components of the voltages kVu, kVv, and kVw, and output the voltages E'u, E'v, and E'w. The pseudo neutral point circuit 24 uses the pseudo neutral point (E'u
+ E'v + E'w) / 3 = V'n is generated.

The comparator circuits 25u, 25v, 25w respectively have voltages E'u, E'v, E'w and a pseudo neutral point V'n.
And if the voltages E'u, E'v, E'w are larger than the pseudo neutral point V'n, the high position detection signal U,
V, W are output, and if the voltages E'u, E'v, E'w are smaller than the pseudo neutral point V'n, the low position detection signal U,
Outputs V and W.

Next, the operation of the position detection circuit 21 will be described.

FIG. 8 shows the configuration of a position detection circuit that can be used in common with a 4-element / 6-element inverter. less than,
The operation of the position detection circuit during each control will be described.

(1) Operation of position detection circuit of 6-element inverter When the position detection circuit 21 of FIG. 8 is applied to the 6-element inverter of FIG. 7 (or FIG. 1), E ′ detected from each phase of UVW u, E'v, E'w signals, pseudo neutral point V'n ((E'u + E'v + E'w) / 3) signals, and
The position detection signals U, V and W obtained therefrom are shown in FIG.

Since each input signal E'u, E'v, E'w is defined by the potential difference from the midpoint P of the capacitors C1, C2, E'u, E'in the 6-element inverter circuit.
v, E′w are the induced voltages Eu of the UVW phases of the motor 4,
Using Ev and Ew, E'u = kEu, E'v = kE
v, E'w = kEw. Induced voltage Eu, E of each phase
Since v and Ew are out of phase by 120 degrees, ((E'u + E'v + E'w) / 3) at the pseudo neutral point is 0.
Becomes Then, each E'u, E'v, E'w is compared with the pseudo neutral point V'n, and each UVW phase is E'u-V'n = kEu, E'v-V'n = kEv,
When E'w-V'n = kEw> 0: Hi output E'u-V'n = kEu, E'v-V'n = kEv,
When E′w−V′n = kEw <0: UV output of the position detection signal can be obtained by setting Lo output.

(2) Similar to the operation of the position detecting circuit of the four-element inverter, the four-element inverter shown in FIG.
When the position detection circuit 21 is applied, E'u, E'v, E'w signals detected from each phase of UVW, pseudo neutral point V'n ((E'u + E'v + E'w) / 3 ) Signal and position detection signals U, V, W obtained therefrom are shown in FIG.
Shown in.

Each of the input signals E'u, E'v, E'w is defined by the potential difference from the midpoint P of the capacitors C1 and C2. In the 4-element inverter circuit, the midpoint P of the capacitor is connected to the V phase. ing. Therefore, E'u = kEu-kEv E'v = kEv-kEc (= 0) E'w = kEw-kEv V'n = (E'u + E'v + E'w) / 3 = -kEv. Therefore, each E'u, E'v, E'w signal is compared with the pseudo neutral point V'n, and each UVW phase has E'u-V'n = kEu, E'v-V'n = kEv,
When E'w-V'n = kEw> 0: Hi output E'u-V'n = kEu, E'v-V'n = kEv,
When E′w−V′n = kEw <0: By setting the Lo output, UVW of the position detection signal similar to that of the 6-element can be obtained.

Next, the operation of the 4-element / 6-element switching 3-phase inverter according to the second embodiment of the present invention will be described with reference to FIGS. 7 and 11.

In FIG. 7, the voltage of the AC power supply 1 is applied to the AC input side of the bridge rectification circuit by the diodes D1 to D4 via the AC reactor L1 of the partial switching PAM circuit 12 connected in series to the line. Bridge rectifier circuit and IGBTQ by D5-D8
By shorting the AC input side for a predetermined time in the half cycle of the AC input by 1, it is possible to apply a voltage higher than the AC input voltage to the AC input side of the bridge rectification circuit by the diodes D1 to D4.

This is because a current flows due to the AC input voltage being applied to both ends of the AC reactor L1 due to the short circuit of the IGBT Q1 and energy is accumulated.
When the GBTQ1 is opened, a voltage is generated by the counter electromotive force due to the stored energy, and if the polarity of the AC input voltage is not inverted at this point, this AC input voltage and the voltage of the AC reactor L1 are added. This is because the applied voltage is applied to the AC input side of the bridge rectification circuit formed by the diodes D1 to D4.

The partial switching PAM circuit 1
2 operates only in an operating region where the PAM control unit 13 of the CPU 20 needs to boost the AC input voltage.

Next, the switch SW2 is short-circuited (double pressure).
Alternatively, switching of the rectified voltage by opening (1 × pressure) will be described. The on / off control of the switch SW2 is controlled by CP
Performed by U20. The control of the SW2 is described in detail in Japanese Patent Laid-Open No. 2001-95262 by the present inventors.

When the switch SW2 is short-circuited (turned on),
The voltage doubler capacitor C1 is charged by half-wave rectification by the diode D1, the voltage doubler capacitor C2 is charged by half-wave rectification by the diode D3 in the next half cycle, and the voltage on the DC side is the voltage of the voltage doubler capacitor C1 and the voltage doubler capacitor. It becomes the sum of the voltages of C2, and double voltage rectification is performed. Since the voltage on this DC side contains ripples,
It is smoothed by the smoothing capacitor C3 and supplied to the inverter module 3.

When the switch SW2 is opened (off),
Both ends of the voltage doubler capacitors C1 and C2 connected in series are charged by the full-wave rectified voltage, and the 1-time voltage rectification is performed.

As shown in FIG. 11, in the high rotation operation region at the time of starting (refer to "starting operation region" in FIG. 11) requiring high voltage, the switch SW2 is short-circuited to perform double pressure rectification ( (See "Double pressure" in FIG. 11), and if necessary, boosting is performed by the partial switching PAM circuit 12 (FIG. 1).
(See "PAM Boost" in 1).

In a low-speed operation region in a steady state where a low voltage is required (refer to the "steady-state operation region" in FIG. 11), the switch SW2 is opened to perform 1-time voltage rectification ("1-time operation in FIG. 11"). Pressure (bridge) ”), partial switching P if necessary
Boosting is performed by the AM circuit 12 ("PA in FIG. 11"
M boost ”).

Although there is a portion where the relationship between the two is not proportional in the characteristic of the motor rotation speed vs. the smoothing capacitor voltage shown in FIG. 11, the rotation region which is normally used is a region around 60 rps and 120 rps, which is large. There is no disadvantage.

FIGS. 12 and 13 show a method of switching the switches SW1 and SW2 in the configuration of FIG. The relationship between the switches SW1 and SW2 is shown in FIGS.
There are 3 possible ways. Which one is selected depends on how to use it at that time, whichever is more efficient.

In both the examples of FIGS. 12 and 13, the switch SW1 is turned on and the switch SW2 is turned off in the region where the frequency is the smallest, and the switch SW1 is turned off and the switch SW2 is turned on in the region where the frequency is the highest. It is common in that it is done.

In FIG. 12, the switching frequency when switching the switch SW1 from ON to OFF is lower than the switching frequency when switching the switch SW2 from OFF to ON, whereas in FIG. 13, the switch SW1 is switched from ON to OFF. The switching frequency when the switch SW2 is turned on is higher than the switching frequency when the switch SW2 is turned on.

In the present invention, instead of the converter circuit 15 of FIG. 7, any of the converter circuits 15a to 15e of FIGS. 14 to 18 can be appropriately adopted.

As shown in FIG. 14, the converter circuit 15
Unlike the converter circuit 15 of FIG. 7, a does not include the PAM circuit 12a and the switch SW2. The converter circuit 15a is similar to the converter circuit 15 of FIG.
It has voltage doubler converters D1, D3, C1 and C2.

As shown in FIG. 15, the converter circuit 15
Unlike the converter circuit 15 of FIG. 7, b does not have the PAM circuit 12a. The converter circuit 15b is shown in FIG.
Similarly to the converter circuit 15 of FIG.
It has voltage doubler converters D1 to D4, C1 and C2.

As shown in FIG. 16, the converter circuit 15
Unlike the converter circuit 15 of FIG. 7, c is a switch S
It does not have W2. The converter circuit 15c, like the converter circuit 15 of FIG.
It has voltage doubler converters D1, D3, C1 and C2.

As shown in FIG. 17, the converter circuit 15
Unlike the converter circuit 15 of FIG. 7, d does not have the PAM circuit 12a and the switch SW2, and has the bridge (1 × pressure) converters D1 to D4, C1 and C2.

As shown in FIG. 18, the converter circuit 15
Unlike the converter circuit 15 of FIG. 7, e is a switch S.
It does not have W2, and also has bridge (one-time pressure) converters D1 to D4, C1 and C2.

The operation of one embodiment of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and the design change and the like within the scope not departing from the gist of the present invention. Even so, it is included in the present invention. For example, it is also possible to use a bidirectional semiconductor switch as the switch SW2 and control the semiconductor switch to obtain an intermediate voltage between the double voltage rectification and the double voltage rectification steplessly.
Further, in the embodiment, although it is described that the rotation speed of the motor is used in the vicinity of 60 rps and 120 rps, the rotation speed is appropriately selected according to the capacity of the motor used and the like. It is not limited to the numerical value of. For example, the switching element is not limited to the IGBT and may be a MOSFET.

[0071]

As described above, according to the present invention, the following effects can be obtained. According to the invention of claim 1, a switch is provided for connecting the zero voltage terminal and the midpoint of one of the arms of the three-phase bridge connection switching element, and the switch is turned on to deactivate the one arm. Thus, a three-phase inverter with four elements can be obtained.

According to the invention of claim 2, the compressor motor of the air conditioner having a wide rotation speed range can be switched to a four-element inverter or a six-element inverter according to the rotation speed to drive the motor.

According to the invention of claim 3, at the time of normal rotation, 6
The inverter loss can be reduced by operating as a four-element inverter and operating as a four-element inverter when the motor rotation speed is low.

According to the invention of claim 4, in the mode of operating as a four-element inverter, the timing at which the plus voltage and the minus voltage are applied to the winding of the motor, the plus voltage and the zero voltage, or the zero voltage and the minus voltage. The current flowing through the winding of the motor can have the same current value at the timing when the voltage is applied, and the torque ripple can be reduced.

According to the invention of claim 5, by using the IGBT as the switching element, it is possible to use the inverter at high voltage and high output.

According to the sixth aspect of the invention, by using the MOSFET as the switching element, it is possible to reduce the loss of the inverter during low current operation.

According to the seventh aspect of the invention, the zero voltage point can be created with a simple structure, and it can be used as a power source for a 4-element / 6-element switching 3-phase inverter.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a 4-element / 6-element switching 3-phase inverter according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a usage area of a normal inverter operation in which 6 elements are used as switching elements and a usage area in which an inverter operation of 4 elements is performed by turning on a switch SW.

FIG. 3 is a diagram showing a timing when each switching element is turned on.

FIG. 4 is a diagram illustrating a PWM pulse width of a switching element.

5 is a diagram showing a flow path of a current for each operation mode.
(A) is an operation mode from time t1 to t2 (T1), and FIG. 5 (b) is an operation mode from time t2 to t3 (T2).

FIG. 6 is an operation when four switching elements are provided,
The table which summarized the loss of the switching element about each operation at the time of 6 elements.

FIG. 7 is a block diagram showing a configuration of a 4-element / 6-element switching 3-phase inverter according to a second embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a position detection circuit used in a 4-element / 6-element switching 3-phase inverter according to a second embodiment of the present invention.

FIG. 9 is a waveform diagram showing a position detection signal by the 6-element inverter of the position detection circuit used in the 4-element / 6-element switching 3-phase inverter according to the second embodiment of the present invention.

FIG. 10: 4 elements / 6 according to a second embodiment of the present invention
The wave form diagram which shows the position detection signal by the 4-element inverter of the position detection circuit used for an element switching 3-phase inverter.

FIG. 11: 4 elements / 6 according to the second embodiment of the present invention
Switch SW used for element switching 3-phase inverter
FIG. 6 is a diagram for explaining the switching timing of 2;

FIG. 12: 4 elements / 6 according to a second embodiment of the present invention
Switch SW used for element switching 3-phase inverter
2 is a diagram showing an example of a relationship between switching frequencies of 1 and a switch SW2. FIG.

FIG. 13: 4 elements / 6 according to a second embodiment of the present invention
Switch SW used for element switching 3-phase inverter
The figure which shows the other example of the relationship of each 1 and the switching frequency of switch SW2.

FIG. 14 is a circuit diagram showing the configuration of another example of a converter circuit used in a 4-element / 6-element switching 3-phase inverter according to the present invention.

FIG. 15 is a circuit diagram showing the configuration of still another example of the converter circuit used in the 4-element / 6-element switching 3-phase inverter according to the present invention.

FIG. 16 is a circuit diagram showing the configuration of still another example of the converter circuit used in the 4-element / 6-element switching 3-phase inverter according to the present invention.

FIG. 17 is a circuit diagram showing the configuration of still another example of the converter circuit used in the 4-element / 6-element switching 3-phase inverter according to the present invention.

FIG. 18 is a circuit diagram showing the configuration of still another example of the converter circuit used in the 4-element / 6-element switching 3-phase inverter according to the present invention.

FIG. 19 is a block diagram showing a configuration of a motor drive inverter according to a conventional technique.

FIG. 20 is a diagram showing a relationship between a motor rotation speed and a loss of a motor drive inverter according to a conventional technique.

[Explanation of symbols]

1 ... AC power supply 2 ... Rectifier 3 ... Inverter module 4 ... Motor 12 ... Partial switching PAM circuit 12a ... PAM circuit 13 ... PAM control unit 15 ... Converter circuit 15a ... Converter circuit 15b ... Converter circuit 15c ... Converter circuit 15d ... Converter circuit 15e ... Converter circuit 20 ... CPU 21 ... Position detection circuit 22u ... Voltage dividing circuit 22v ... voltage dividing circuit 22w ... voltage dividing circuit 23u ... Filter circuit 23v ... Filter circuit 23w ... Filter circuit 24 ... Pseudo neutral point circuit 25u ... Comparison circuit 25v ... Comparison circuit 25w ... Comparison circuit C1 ... Capacitor C2 ... Capacitor C3, C4 ... Capacitor D1 ... Diode D2 ... Diode D3 ... Diode D4 ... Diode D5 ... Diode D6 ... Diode D7 ... Diode D8 ... Diode L1 ... AC reactor Q1 IGBT SW ... switch SW1 ... switch SW2 ... switch U, UB ... Switching element V, VB ... Switching element W, WB ... Switching element

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02P 6/18 H02P 6/02 371S F term (reference) 5H006 BB05 CA01 CA02 CB01 CB04 CB08 CB09 CC01 CC02 DA04 DB07 5H007 AA02 BB06 CA01 CA02 CB02 CB05 CC03 CC12 DA06 DB02 DB13 DC05 EA02 5H560 AA02 BB04 DA14 DB14 DB20 DC13 EB01 GG04 RR01 SS07 TT15 UA05 UA06 XA08 XA12 5H576 AA10 BB02 BB04 CC05 DD02 DD04 DD05 EE11 EE19 FF07 FF08 GG07 HA03 HA04 HB02 JJ03 KK05 LL16 LL24 LL41

Claims (13)

[Claims] 1. A three-phase connected between the positive voltage terminal and the negative voltage terminal of a DC power supply that supplies a positive voltage with a zero voltage as a starting point and a negative voltage having the same voltage value as the positive voltage. In an inverter that supplies three-phase AC power to a motor by switching a bridge-connected switching element, a switch that connects the zero-voltage terminal and a midpoint of one of the arms of the three-phase bridge is provided, and the switch is provided. When the switch is turned on, the switching operation of the one arm is stopped and the remaining four elements are switched to operate, whereby a four-element / six-element switching three-phase inverter. 2. The motor is a motor for driving a compressor of an air conditioner.
The 4-element / 6-element switching 3-phase inverter described. 3. The four-element / six-element switching three-phase inverter according to claim 1 or 2, wherein the switch is turned on when the output voltage of the inverter is low and the rotation speed of the motor is low. 4. The PWM control pulse width is reduced at a timing when the positive voltage and the negative voltage are applied to the winding of the motor by the switching operation in a mode in which the switch is turned on and the operation is performed by switching four elements. The PWM control pulse width is increased at a timing when the positive voltage and the zero voltage or the zero voltage and the negative voltage are applied to the winding of the motor by the switching operation.
4. A 4-phase / 6-element switching 3-phase inverter according to any one of 1. 5. The switching element according to claim 1, wherein the switching element is an IGBT.
3 phase inverter with 6 elements switching. 6. The switching element is a MOSFET
5. The four-element / 6-element switching three-phase inverter according to any one of claims 1 to 4. 7. The zero voltage is defined as a midpoint between two capacitors of the same capacity connected in series between the positive voltage and the negative voltage. 3 phase inverter with 6 elements switching. 8. The switching of the switching element is a mode which operates by switching of the four elements, and 6
8. The four-element device according to claim 1, wherein the operation is performed based on an output signal from a position detection circuit that can be used for both modes of operating by switching elements.
6 element switching 3 phase inverter. 9. The position detecting circuit includes a pseudo neutral point circuit that generates a pseudo neutral point based on signals corresponding to respective phase voltages of the three-phase AC power output from the inverter, and each of the phases. 9. The four-element / six-element switching three-phase system according to claim 8, further comprising a comparison circuit that outputs the output signal based on a comparison result of signals corresponding to voltages and the pseudo neutral point. Inverter. 10. The DC power supply is obtained by a bridge rectifier circuit for rectifying an AC voltage, is connected in series, and has two voltage doubler capacitors, both ends of which are connected to a DC output side terminal of the bridge rectifier circuit, 10. A specific switch for short-circuiting or opening one of a connection point of two voltage doubler capacitors and an AC input side terminal of the bridge rectifier circuit, according to any one of claims 1 to 9. 3 phase inverter with 6 elements switching. 11. The four-element / six-element switching 3 according to claim 10, wherein the frequencies of the three-phase AC power when the specific switch and the switch are respectively switched are set to be different from each other. Phase inverter. 12. The four-element / six-element switching three-phase inverter according to claim 10, wherein the AC voltage is a voltage boosted by a booster circuit including a PAM circuit. 13. The booster circuit comprises: an AC reactor inserted in series with one of the lines of the AC input before being boosted; a load side of the AC reactor and another line of the AC input. 13. The four-element device according to claim 12, further comprising: a semiconductor switch serving as the PAM circuit that short-circuits between them for a predetermined period in each cycle of the AC input, and operates only in a voltage region where boosting is required. / 6 element switching 3-phase inverter.