JPH04255488A - Inverter device - Google Patents

Abstract

PURPOSE:To improve the power efficiency by providing a power factor improving circuit consisting of a series circuit of a reactor and a capacitor in an AC line, and putting the inductance of the reactor at a specified value or more at the time of the current at 180% of nominal input and the ratio of inductance at the time of 180% current/at the time of 50% current at a specified value or more. CONSTITUTION:A power factor improving circuit consisting of a series circuit of a reactor 3 and a capacitor 4 in the AC line of an inverter device 7. At this time, the inductance of the reactor 3 is made 1.8mH or more at the time of the current at 180% of nominal input and the ratio of the inductance at the time of 180% current/at the time of 50% current is made 0.85 or more. Hereby, the high frequency current is suppressed, and the power input factor improves, and the peak current is suppressed, and power factor at 85% or more can be gotten.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an inverter device.
In particular, the present invention relates to an inverter device suitable as a power source for a variable speed motor that is a drive source for a vacuum cleaner.

0002

[Prior Art] A conventional inverter device for a vacuum cleaner is
As described in JP-A No. 2-237492, etc.,
The variable speed motor was controlled as instructed.

0003

SUMMARY OF THE INVENTION The above-mentioned prior art does not take into account the power factor of the power source, and a capacitor input type power source has a problem of poor power factor.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter power source suitable for improving the power factor of the power source and producing a vacuum cleaner with strong suction power.

[0005]

[Means for solving the problem] The above purpose is to rectify alternating current and convert it to direct current through a smoothing capacitor, and to provide an inverter circuit that converts this direct current voltage to alternating current, and to connect the alternating current line to a parallel circuit of a reactor and a capacitor. A power factor correction circuit consisting of a power factor correction circuit is provided, and the inductance of the reactor is set to 1.8 mH or more at a current of 180% of the nominal input, and
The ratio of inductance at % current/50% current is 0.8
This is achieved by increasing the number to 5 or more.

[0006]

[Operation] Due to the filtering action of the power factor correction circuit, which consists of a parallel circuit of a reactor and a capacitor installed in the power supply line,
Harmonic currents are suppressed to improve the power factor of the power source, and since the reactor constant is set to an optimal value, the peak current is suppressed and a power factor of 85% or more can be obtained. As a result, it is possible to provide a vacuum cleaner that can supply maximum power to the inverter device while keeping the current within the allowable current value of the electric wire of the cord reel, and can provide a strong suction force.

[0007]

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 7. In this embodiment, the target is a vacuum cleaner, and it is assumed that a variable speed motor is used as the drive source. Possible variable speed motors include inverter-driven induction motors, reluctance motors, and brushless motors whose speed changes by controlling the input. First, an example will be described in which a brushless motor, which has a long life and good control response, is used as a fan motor.

FIG. 1 shows the overall configuration of a control circuit of an inverter device. In FIG. 1, 7 indicates an inverter device. 1 is an AC power supply, and this power supply 1 is passed through a cord reel 2, a power factor correction circuit that is a parallel circuit of a reactor 3 and a capacitor 4, rectified by a rectifier circuit 5, smoothed by a capacitor 6, and then sent to an inverter circuit 8. It supplies DC voltage Ed. The inverter circuit 8 is a 120 degree conduction type inverter composed of transistors TR1 to TR6 and free wheel diodes D1 to D6 connected in parallel to the respective transistors TR1 to TR6. Transistors TR1 to TR3
constitutes the positive arm. Transistor TR4~TR
6 constitutes a negative arm, and each conduction period is pulse width modulated (PWM) with the output signal 13S of the triangular wave generation circuit 13 at 120 electrical degrees. R1 is a relatively low resistance connected between the emitters of transistors TR4 to TR6 constituting the negative arm and the negative side of capacitor 6.

Reference numeral 9 denotes a brushless motor that is a variable speed motor for driving the fan 17, and has a rotor R made of two-pole permanent magnets and armature windings U, V, and W of a stator S. . The load current ID flowing through these windings U, V, and W can be detected as a voltage drop across the resistor R1. The control circuit of the brushless motor 9 controls the magnetic pole position of the rotor R using the Hall element 1.
A magnetic pole position detection circuit 14 that detects at 0, etc., a current detection circuit 11 that detects and amplifies the load current ID described above, and a base driver 16 that drives the transistors TR1 to TR6.
, and a microcomputer 12 that drives the base driver 16 based on the detection signal 14S obtained from the detection circuit 14. 15 is an operation switch.

The magnetic pole position detection circuit 14 receives a signal from the Hall element 10 and generates a magnetic pole position signal 14S of the rotor R. This magnetic pole position signal 14S is used not only for current switching (commutation) of the armature windings U, V, and W, but also as a signal for detecting rotational speed. The microcomputer 12 receives this magnetic pole position signal 14.
The speed is determined by counting the number of S within a certain sampling.

The detection circuit 11 for detecting the load current ID of the brushless motor 9 converts the voltage drop across the resistor R1 into a DC component via a peak hold circuit (not shown), amplifies the voltage drop, and detects the load current ID of the brushless motor 9. This is what you get.

The microcomputer 12 includes a central processing unit (CPU) 12-1, a read-only memory (ROM) 12-2, and a random access memory (RAM) 12-3, which are connected to an address bus (not shown). and are interconnected by a control bus or the like. And ROM12-2
The program includes programs necessary to drive the brushless motor 9, such as speed calculation processing and speed control processing (ASR).
), current control processing (ACR), etc. are stored. On the other hand, the RAM 12-3 is used to read and write various external data necessary for executing various programs stored in the ROM 12-2.

The transistors TR1 to TR6 are each driven by an output signal 16S of the base driver 16 in response to a firing signal 12S generated and processed by the microcomputer 12.

In this type of brushless motor 9, the current flowing through the armature winding corresponds to the output torque of the motor, so that the output torque can be varied by changing the applied current. That is, by adjusting the applied current, the output of the motor can be changed continuously and arbitrarily. In addition, by changing the drive frequency of the inverter, the brushless motor 9
The rotation speed can be changed freely.

The inverter device 7 of the present invention uses such a brushless motor 9 as a drive source for a vacuum cleaner.

Next, FIG. 2 shows the voltage and current of the AC power supply. In Figure 2 (a), VS is the power supply voltage,
IS is the power supply current when the power factor correction circuit is used, and IS' is the power supply current when the power factor correction circuit is not used. It is known that in the capacitor input type inverter device 7, a current with a high peak value, such as IS', is generated, and the power factor of the power source decreases. A power factor correction circuit is used to improve this problem. The input PS of the inverter device 7 is determined by the following equation using the power source power factor p.f.

[0017]

[Equation 1] PS=VS×IS×p・f

...(Math. 1) In the formula (Math. 1), input PS = 10
00W, VS = 100V, and the power factor of a capacitor input type power supply is usually p・f = 70%, so IS
=14.3A. The maximum cord reel for household vacuum cleaners is 1.25 mm2 in consideration of windability, and the allowable current value is 14A. In other words, if a power factor correction circuit is not installed, the allowable current is 14A.
over. In order not to exceed the allowable current of 14A, it is necessary to lower the input, and lowering the input inevitably reduces the suction power of the vacuum cleaner. In order to obtain a vacuum cleaner with strong suction power considering the allowable current of the cord reel, a power factor correction circuit is required, and the power factor of the power supply p.f.
= 85% or more. In a power factor correction circuit consisting of a parallel circuit of a reactor and a capacitor, the capacitor terminal voltage VC and capacitor current IC are shown in Figure 2 (b).
, (c), a resonant current flows through the capacitor. The circuit equation of the parallel circuit is shown by the following equation.

[0018]

[Math. 2] IS=Y×VS

...(Number 2)

[0019]

[Formula 3] Y=j(ωC-1/ωL)

...(Equation 3) Here, Y is admittance, and in order to make the harmonic current of the power supply current zero, it is sufficient to set Y=0. Focusing on the third-order component, C=110μF, f=15
At 0Hz, L=10.23 mH. A 10mH reactor is too heavy to be used for a vacuum cleaner. In addition, the suction characteristics of a vacuum cleaner are measured by applying a sine wave voltage, so if you apply a sine wave voltage to an inverter device and measure the power factor, you will get a different result from the value measured with a commercial power source. Ta.

FIG. 3 shows a circuit for measuring the inductance of a reactor using the inverter power supply 18 using the impedance method. In FIG. 3, the reactor 3 consists of an E core 3A, an I core 3B, and a coil 19, with a gap g provided between the EI cores.

FIG. 4 shows inductance characteristics with respect to effective current for typical reactors A, B, and C among various prototype reactors. This reactor is input 1
The target is 000W. Reactor A has the largest inductance. FIG. 5 shows the results of actually measuring the power factor of the power source using an inverter power source. From Figure 5, the power supply power factor of reactor A, which has the largest inductance, is smaller than that of reactors B and C, and reactors B and C have achieved the target power supply power factor of 85%.
The result was that (the capacitor used was C=
110 μF, but in the range of C=85 to 150 μF, there was a slight difference in power factor, but not much difference). FIG. 6 shows the waveforms of the power supply voltage and power supply current at this time. From FIG. 6, the difference between reactor A and reactors B and C is in the peak of the current. In other words, it was discovered that the power factor could not be improved simply by setting a large inductance, but that an optimum value existed.

Various prototype reactors were manufactured and conditions for achieving the target power factor of 85% were studied. The results of this study are shown in FIG. 7, where the horizontal axis represents inductance and the vertical axis represents the reduction rate of inductance. The inductance on the horizontal axis shows the inductance at 180% current of the rated current (10A if the input is 1000W), and the reduction rate of inductance on the vertical axis shows the inductance at 180% current/
This is the ratio of inductance at 50% current. From Figure 7,
In order to obtain the target power factor of 85% or more, the inductance at 180% current should be 1.8 mH or more and the inductance reduction rate should be 85% or more. As a result, maximum power can be supplied to the inverter device using a 1.25 mm2 cord reel that takes into account windability, and a vacuum cleaner with strong suction power can be obtained.

[0023]

According to the present invention, by setting the constant of the reactor of the power factor correction circuit to an optimum value, the maximum input can be supplied to the inverter device, and a vacuum cleaner with strong suction force can be provided.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a control circuit of an inverter device according to the present invention.

FIG. 2 is a diagram showing power supply voltage, power supply current, capacitor voltage, and capacitor current.

FIG. 3 is a schematic diagram showing a reactor and an inverter power supply.

FIG. 4 is a characteristic diagram of effective current and inductance of a reactor.

FIG. 5 is a characteristic diagram of reactor inductance and power factor.

FIG. 6 is a diagram showing power supply voltage and power supply current when reactors A, B, and C are used.

FIG. 7 is a diagram showing inductance and inductance reduction rate for achieving a target power source power factor.

[Explanation of symbols]

2... Cord reel, 3... Reactor, 4... Capacitor,
7...Inverter device.

Claims (2)

[Claims] Claim 1: An inverter device comprising an inverter circuit that rectifies alternating current and converts it into direct current, and converts the direct current voltage into alternating current, in which a power factor correction circuit consisting of a parallel circuit of a reactor and a capacitor is provided in the alternating current line. , the inductance of the reactor is 1. at 180% current of the nominal input.
8 mH or more, and the inductance ratio at 180% current/50% current is 0.85 or more. 2. An inverter device comprising an inverter circuit that rectifies alternating current and converts it into direct current, and converts the direct current voltage into alternating current, wherein the inverter circuit receives input from the alternating current power supply via a cord reel, and the cord A power factor correction circuit consisting of a parallel circuit of a reactor and a capacitor is provided on the output line of the reel, and the inductance of the reactor is set to 1.8 mH or more at a current of 180% of the nominal input, and
Inductance ratio at 80% current/50% current is 0
．． 85 or more.