JP2001292579A - Inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control harmonics in the power supply and EMI noise in an inverter. SOLUTION: In a PWM inverter, a first capacitor serial circuit 7, in which one ends of a first DC reactor 2a inserted into the positive side of a linear bus in the output side of a rectifier circuit, a second DC reactor 2b inserted in the load of the DC bus and having an inductance identical to that of the first DC reactor 2a and a first capacitor serial circuit 7 are connected to the connecting point of the first EC reactor 2a and the rectifier circuit 1. The other ends thereof are connected to the connecting point side of the second DC reactor 2b and the connecting circuit, a second capacitor serial circuit 8, a connecting point at which two capacitors of the first capacitor serial circuit are connected and a connecting point, at which two capacitors of the second capacitor serial circuit are grounded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for suppressing power supply harmonics and EMI noise in an inverter device.

[0002]

2. Description of the Related Art A conventional DC reactor built-in inverter for suppressing power supply harmonics is configured as shown in FIG. In the figure, 21 is a diode rectifier circuit, 22 is a DC reactor, 23 is a smoothing capacitor, 2
4 is an inverter unit, 25 is an inrush current suppression resistor, and 26 is an inrush current suppression resistor short circuit contactor. Reference numeral 30 denotes an inverter device incorporating the above-described components, and RT to T, U
ＷW and the like are external terminals provided in the inverter device.

[0003]

However, in the prior art, since the DC reactor is connected to only one side of the rectified output, it is effective in suppressing power supply harmonics.
There was almost no effect on EMI noise. The present invention has been made in view of such a problem, and P
An object is to reduce both EMI noise and power supply harmonics generated by a WM inverter device.

[0004]

According to a first aspect of the present invention, there is provided a PWM inverter having a first rectifying circuit having a first side inserted on a positive side of a linear bus on the output side.
DC reactor, and inserted into the load of the DC bus,
A second DC reactor having the same inductance as the first DC reactor and two circuits in which two capacitors having the same capacitance are connected in series are referred to as a first capacitor series circuit and a second capacitor series circuit, respectively. A first capacitor series circuit having one end connected to a connection point between the first DC reactor and the rectifier circuit and the other end connected to a connection point between the second DC reactor and the connection circuit; A second capacitor series circuit in which one end of the second capacitor series circuit is connected to the connection point between the first DC reactor and the positive electrode of the smoothing capacitor, and the other end is connected to the connection point side between the second DC reactor and the negative electrode of the smoothing capacitor. A circuit, a connection point connecting two capacitors in the first capacitor series circuit, and a connection point connecting two capacitors in the second capacitor series circuit. It is obtained by grounding the connection point. According to a second aspect of the present invention, the connection point in the first capacitor series circuit and the connection point in the second capacitor series circuit are both connected to a reference potential of the circuit.
According to a third aspect of the present invention, the first DC reactor and the second DC reactor are DC reactors with built-in permanent magnets in which permanent magnets are provided in such a direction as to cancel a magnetic flux generated by a DC current flowing through the reactors. It is.

[0005]

FIG. 1 is a circuit block diagram showing a configuration of a power section of an inverter device according to the present invention. In the figure, 1 is a diode rectifier circuit for converting an AC voltage to a DC voltage, 2a and 2b are DC reactors having the same inductance value and divided, 3 is a smoothing capacitor, and 4 is an inverter unit. Inverter unit 4 is IGB
It is driven by PWM based on a gate drive signal composed of T and output from a control circuit (not shown). 5 is an inrush current suppression resistor, 6 is an inrush current suppression resistor short-circuiting contactor, C
1 to C4 are capacitors. Reference numerals 7 and 8 denote first and second capacitor series circuits in which two capacitors having the same capacity are connected in series. Reference numeral 10 denotes an inverter device incorporating the above-described components, and RT to U, U to W, and the like are external terminals provided in the inverter device. R to T are three-phase AC currents,
U to W are connected to loads such as electric motors. G is a ground which is a circuit reference potential, and is normally connected to the housing of the inverter device 10. The circuit reference potential G can be used without necessarily being grounded (grounded), but grounding is more effective.

Next, the operation will be described. The three-phase AC power supply voltage is rectified by the diode rectifier circuit 1. The rectified voltage is supplied to a balanced LC filter including DC reactors 2a and 2b and capacitors C1 to C4 provided on the positive and negative sides of the DC bus, and a smoothing capacitor 3 for smoothing the ripple of the rectified DC voltage. Power supply harmonics are first suppressed by the direct currents 2a and 2b. DC voltage is supplied to the inverter unit. The inverter unit 4 switches the IGBT to supply a variable voltage / variable frequency AC voltage to the load. Since the AC voltage waveform generated by the inverter unit 4 is a voltage based on PWM, EMI noise composed of high-frequency noise equal to or higher than the carrier frequency is emitted to the load side and the power supply side. The EMI noise emitted to the power supply side passes through the combined impedance on the positive side of the DC bus composed of the DC reactor 2 and the capacitors C1 and C3 between the positive side of the DC bus and the ground terminal G, or the negative side of the DC bus and the ground terminal. G
It is led to the ground terminal G through the combined impedance on the negative side of the DC bus composed of the DC reactor 2 and the capacitors C2 and C4 between them.

[0007] The DC reactors 2a, 2a and 2a are combined so that their combined impedances are equal to each other.
b and the capacitors C1 and C2
And C3 and C4 have the same capacity. Therefore, the combined impedance between the ground G and the positive and negative DC buses can be balanced, and EMI noise can be effectively reduced. It is desirable to use small DC reactors 2a and 2b so that they can be built into inverter device 10.
For this reason, if a permanent magnet is used in a magnetic circuit and a permanent magnet built-in type DC reactor that applies a bias magnetomotive force in a direction to cancel a magnetic flux generated by a direct current is applied, the inverter device can be reduced in size and weight.

[0008]

According to the present invention, a DC reactor is divided and arranged, and a capacitor is connected between both ends of the DC reactor and ground, thereby suppressing power supply harmonics and connecting an external EMI filter. Without doing so, EMI noise can be suppressed in a small space and at low cost.

[Brief description of the drawings]

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

FIG. 2 is a circuit block diagram showing a configuration of a conventional inverter device incorporating a DC reactor.

[Explanation of symbols]

 1, 21 Diode rectifier circuit 2a, 2b, 22 DC reactor 3, 23 Smoothing capacitor 4, 24 Inverter section 5, 25 Inrush current suppression resistor 6, 26 Inrush current suppression contactor 7 First capacitor series circuit 8 Second capacitor series circuit 10, 30 Inverter device C1, C2, C3, C4 Capacitor G Ground

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02M 7/06 H02M 7/06 HF term (Reference) 5H006 AA01 AA07 CA07 CB01 CC08 FA02 GA01 HA83 HA84 5H007 AA01 AA08 CA01 CB05 CC01 FA03 FA12 GA03 HA02 5H740 BA11 BA18 BB05 BB08 MM12 NN02 NN06 PP02 PP10

Claims (3)

[Claims] In a PWM inverter device, a first DC reactor inserted on the positive side of a straight bus on the output side of a rectifier circuit, and an inductance same as that of the first DC reactor inserted into a load of the DC bus. And two circuits in which two capacitors of equal capacity are connected in series as a first capacitor series circuit and a second capacitor series circuit, respectively, and one end of the first capacitor series circuit is connected to a first DC A first capacitor series circuit connected to a connection point between the reactor and the rectifier circuit and the other end connected to a connection point between the second DC reactor and the connection circuit; A second terminal connected to the connection point between the DC reactor and the positive electrode of the smoothing capacitor and the other end connected to the connection point between the second DC reactor and the negative electrode of the smoothing capacitor An inverter device comprising: a capacitor series circuit; and a connection point connecting two capacitors in the first capacitor series circuit and a connection point connecting two capacitors in the second capacitor series circuit. 2. The inverter device according to claim 1, wherein the connection point in the first capacitor series circuit and the connection point in the second capacitor series circuit are both connected to a reference potential of the circuit. 3. The DC reactor according to claim 1, wherein the first DC reactor and the second DC reactor are DC reactors with built-in permanent magnets provided with permanent magnets in a direction to cancel a magnetic flux generated by a DC current flowing through the reactors. Inverter device.