JP2980439B2 - Noise reduction method and power conversion device for electromagnetic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing noise generated by vibration or electromagnetic force of an iron core of an electromagnetic device such as a transformer or a reactor, and a transformer, a reactor or the like for reducing noise. To a power converter using the same.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional power converter in which an AC output of an inverter for converting DC power to AC power is supplied to a load via an inverter transformer. In FIG. 1, a first inverter 2 and a second inverter 3, which reversely convert DC power of a storage battery 1 into AC power,
A first inverter transformer 4 connected to the output side of the first inverter 2; a second inverter transformer 5 similarly connected to the output side of the second inverter 3; After connecting the secondary side of the inverter transformer 4 and the second inverter transformer 5 in series, an AC reactor 6 and an AC capacitor 7, which constitute an AC filter for shaping an AC output,
And a PWM control circuit 8 for generating a pseudo PWM sine wave.

[0003] This type of power converter uses a DC power from a PWM control circuit 8 as shown in FIG.
The first inverter 2 and the second inverter 3 reversely convert a direct current to an alternating current by the M pseudo sine wave signal. The first inverter transformer 4 is used to insulate the DC circuit and the AC circuit and to synthesize a waveform and output a desired AC voltage.
And the second inverter transformer 5 are connected to the inverter.

FIG. 6 is a time chart showing waveforms at various points in FIG. In the figure, INV1 output (FIG. 5)
In the above, the output of the first inverter 2) and the output of INV2 are output as the same PWM pseudo sine wave, and are synthesized by the first inverter transformer 4 and the second inverter transformer 5, and the AC reactor 6 and the AC A sine-wave AC from which higher harmonics have been removed can be obtained by the AC filter circuit constituted by the capacitor 7. This sine wave AC is the AC of FIG.
Equivalent to output.

[0005]

Referring to FIG. 5, a first inverter transformer 4 and a second inverter transformer 5 are shown.
Vibrates at the switching frequency component of the PWM pseudo sine wave of each inverter circuit. Generally, the frequency that can be heard by human ears is about 20HZ to 16KHZ, so it is desirable that the switching frequency be higher. However, the first inverter 2 and the second inverter 5 in FIG.
It is difficult to perform switching at a higher speed as the output capacity of the power converter increases to several hundred KVA or more. The reasons are as follows: (1) There is no device that switches high current at high speed. (2) When a large current is switched at high speed, a surge voltage is easily generated due to the reactance of the wiring. (3) The higher the switching speed, the greater the loss generated in the inverter circuit, and the more the cooling technology cannot keep up. (4) High-speed switching generates a lot of high-frequency noise.

For the above reasons, at present, the switching frequency of a PWM inverter having an output capacity of several hundred KVA or more is several KHZ. That is, the inverter transformer vibrates at this several KHZ, and is heard as noise by human ears.

FIG. 5 shows a power converter having two inverters and two inverter transformers.
Even in a power converter including one inverter and one inverter transformer, noise is still generated.

[0008] Further, not only in the power converter, but also in an apparatus using electromagnetic equipment such as a transformer or a reactor,
Noise is generated due to vibration or electromagnetic force of the iron core of the electromagnetic device.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and has been made in consideration of the above-described problems. It is an object of the present invention to provide a power converter that can reduce noise generated from the device without increasing the switching frequency more than necessary.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention has been made to reduce the noise generated by the vibration or electromagnetic force of an iron core of an electromagnetic device such as a transformer or a reactor. Two sets of devices are provided, the phases of the input AC voltages thereof are opposite to each other, and the two sets of electromagnetic devices are arranged side by side on the same mount.

Further, in a power converter for supplying an AC output of an inverter for converting DC power to AC power to a load via an inverter transformer, two sets of the inverter and the inverter transformer are provided. A control circuit for controlling the AC output voltage of one of the inverters so that the AC output voltage of the other inverter has an opposite phase, and synthesizing the AC output on the secondary side of the inverter transformer. And the two sets of inverter transformers are arranged side by side on the same frame.

[0012]

According to the present invention, the first inverter circuit is provided with a PW
A second inverter transformer generates an M pseudo sine wave, outputs an AC voltage by a first inverter transformer, and generates a reverse phase of the PWM pseudo sine wave by a second inverter circuit. Means that when the first inverter transformer has a positive polarity, it has a negative polarity, and when the first inverter transformer has a negative polarity, it has a positive polarity. That is, if the first and second inverter transformers have the same rating and the same capacity, the first inverter transformer and the second inverter transformer have the same vibration frequency, and the phases of the frequencies are opposite to each other. Have the same peak value and cancel each other's vibrations.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention. The same circuit elements as those in FIG.

According to the present invention, as shown in FIG. 1, a PWM pseudo sine wave is supplied to a first inverter circuit 2, and a PWM pseudo sine wave having a phase opposite to that of the PWM pseudo sine wave is supplied to the first inverter circuit. A PWM control circuit 208 which is applied to a second inverter circuit 3 having the same rating and the same capacity as that of the inverter circuit 2 is added.
The output terminal is connected to the C output terminal, and the v terminal is connected to the v terminal on the secondary side of the first inverter transformer 4. or,
The first inverter transformer 4 and the second inverter transformer 5 have the same rating and the same capacity. FIG. 2 is a time chart for explaining the operation of FIG.

In FIG. 1, the voltage between the output lines of the first inverter circuit 2 is the INV1 output of FIG. 2. In other words, the waveform applied to the primary side U and V terminals of the first inverter transformer. Becomes The PWM control circuit 208 controls ON / OFF of the switching device of the second inverter circuit 3 so that the output line voltage of the second inverter circuit 3 becomes the waveform of the INV2 output of FIG. I have. Now, in FIG. 2, at time t0, the first inverter circuit 2
A voltage is applied from the U terminal on the primary side of the first inverter transformer 4 to the V terminal. And the second invar
The inverter circuit 3 is connected to the primary side V of the second inverter transformer 5.
A voltage is applied from the terminal to the U terminal. As a result, the secondary side of the first inverter transformer 4 is connected from the terminal v to the terminal u.
A positive voltage is output toward the terminal, a positive voltage is output from the u terminal to the v terminal on the secondary side of the second inverter transformer 5, and a combined voltage is generated as an AC output. .

Next, at time t1, the first inverter circuit 2 is in a state where no voltage is applied to the primary side of the first inverter transformer 4, and the second inverter circuit 3
Is a state in which no voltage is applied to the primary side of the second inverter transformer 5. Thus, the state where the voltage is applied and the state where the voltage is not applied continue. This is because the directions of exciting the transformers are opposite, and the vibration directions of the transformers are opposite between the first inverter transformer 4 and the second inverter transformer. They will cancel each other out.

In other words, the noise audible to humans is due to the vibration of the air due to the vibration of the inverter transformer. If the frequencies are the same and the phases are opposite, the noise audible to human ears is theoretically eliminated. Time t2, t3
Is the operation when the AC output produces a negative output, which is the opposite of the above description, and the detailed description is omitted here.

By repeating these series of operations, the power converter outputs a sine wave AC waveform, and can reduce noise generated from the device without increasing the switching frequency more than necessary. In the above-described embodiment, the AC reactor 6 and the AC capacitor 7
The effect of the present invention is the same even if the AC filter composed of Further, the inverter circuit described above is a PWM circuit.
The effect of the present invention is not limited to the inverter, and the effect of the present invention is the same for a general square wave inverter.

Further, in the present invention, the same effect can be obtained in the three-phase inverter by similarly connecting the inverter waveform and the inverter transformer so as to cancel the vibration generated in at least two sets of inverters.

FIG. 3 is a block diagram showing another embodiment of the present invention. According to the present invention, as shown in FIG. 3, a rectifying transformer 12 for converting an AC power supply 11 to a desired voltage,
A converter circuit 13 for converting the alternating current of the output of the rectifying transformer 12 to direct current, a direct current capacitor 14 for smoothing the ripple of the direct current, an inverter circuit 2 for converting direct current power to alternating current, and a phase conversion of the output of the inverter circuit 2 , An inverter transformer 15, a converter circuit 13, and a COV / INV control circuit for controlling the inverter circuit 2.

FIG. 4 is a time chart for explaining the operation of FIG. 3, in which the output of the inverter circuit 2 operates in the opposite phase to the input of the rectifying transformer 12 and outputs the waveform of the INV output. Accordingly, the inverter transformer 15 can cancel the noise caused by the vibration of the rectifying transformer 12.

In the above description, two sets of inverter transformers and the like have the same rating and the same capacity. However, if the noise reduction effect is sacrificed to some extent, they are not necessarily the same rating and the same. It does not have to be of capacity.

[0023]

As described above, according to the present invention,
Noise generated by vibration or electromagnetic force of an iron core of an electromagnetic device such as a transformer or a reactor can be reduced, and in a power conversion device, the switching frequency of an inverter circuit should be increased more than necessary. In addition, it is possible to provide a power conversion device that can reduce noise generated from the device and generate less harmonic noise.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a power converter showing one embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of FIG. 1;
G.

FIG. 3 is a configuration diagram of a power converter showing another embodiment of the present invention.

FIG. 4 is a time chart for explaining the operation of FIG. 3;
G.

FIG. 5 is a configuration diagram of a conventional power converter.

FIG. 6 is a time chart for explaining the operation of FIG. 5;
G.

[Explanation of symbols]

1 ... storage battery 2 ... first
Inverter circuit 3 ... second inverter circuit 4 ... first
Inverter transformer 5 ... second inverter transformer 6 ... AC reactor 7 ... AC capacitor 8 ... PW
M control circuit 11 ... AC power supply 12 ... Rectifier transformer 13 ... Converter circuit 14 ... DC capacitor 15 ... Inverter transformer 208 ... PW
M control circuit 209… COV / INV control circuit

Claims (3)

(57) [Claims] In order to reduce noise generated due to vibration or electromagnetic force of an iron core of an electromagnetic device such as a transformer or a reactor, two sets of the electromagnetic device are provided, and the phases of input AC voltages thereof are set to be opposite to each other. And the two sets of electromagnetic devices are arranged side by side on the same gantry. 2. An electric power converter in which an AC output of an inverter for converting DC power into AC power is supplied to a load via an inverter transformer, wherein two sets of the inverter and the inverter transformer are provided. A control circuit for controlling the AC output voltage of one of the inverters so that the AC output voltage of the other inverter has an opposite phase, and synthesizing the AC output on the secondary side of the inverter transformer. Wherein the two sets of inverter transformers are arranged side by side on the same frame. 3. A converter for converting AC power to DC power, a rectifying transformer connected to an input of the converter, and an inverter connected to an output of the converter.
In a power converter having an inverter and an inverter transformer connected to the output of the inverter, a control circuit for controlling the AC output voltage of the inverter to the opposite phase with respect to the AC input voltage of the converter is provided. A power converter, wherein a rectifying transformer and an inverter transformer are arranged side by side on the same base.