JP2002058162A - Surge voltage suppression filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a small-sized surge voltage suppression filter that is connected only to the output line of a PWM inverter and does not apply surge voltage to the alternating-current motor at the end of a cable. SOLUTION: A surge voltage suppression filter includes resistors parallel- connected with the individual coils of a choke coil and is provided between the lines on the side of each coil connected with the alternating-current motor with a series circuit of a capacitor and a resistor through star connection. The choke coil and the capacitors are placed in a case, and the resistors are installed at the lower part of the case with a space in between. Ring cores, formed by winding thin strips of an amorphous hyperfine crystal alloy, are used for cores of the coils of the choke coil to constitute a surge voltage suppression filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable connecting a PWM inverter and an AC motor; M as shown in FIG. 3 in order to suppress a surge voltage generated at an input terminal of the AC motor driven by the PWM inverter. The present invention relates to a surge voltage suppression filter inserted between the filters.

[0002]

2. Description of the Related Art An AC motor is driven by being connected to a PWM inverter by a cable.
A distributed constant network is formed by the inductance and the capacitance between the lines or the ground, and the longer the cable, the greater the influence of the distributed constant network. On the other hand, the PWM inverter controls the output voltage by being turned on and off by a high-frequency carrier signal, so that a surge voltage at the time of switching induces a resonance phenomenon in the above-mentioned distributed constant network, and a surge more than twice depending on the cable length. Voltage was applied to the AC motor, causing burnout and voltage breakdown of the motor windings.

In order to suppress the above surge voltage, as disclosed in Japanese Patent Application Laid-Open No. H11-262247, a PWM
A method of inserting a choke coil having a resistor connected in parallel to an output line of an inverter, and a method disclosed in Japanese Patent Application Laid-Open No. H11-262245.
As disclosed in Japanese Patent Application Laid-Open No. H11-260, measures have been taken by a method of inserting a damping circuit composed of a resistor and a capacitor between input lines of an AC motor. However, since the cable length varies depending on the place of use and the stray capacitance with the ground changes, it is difficult to obtain the expected surge suppression effect.
As shown in the above, measures were also studied using both of the above two methods, but the work of installing a choke coil with a resistor connected in parallel to the output line of the PWM inverter and the resistance between the input line of the AC motor at the rear end of the cable The work of installing a damping circuit consisting of a vessel and a capacitor was performed in two places, which was a complicated work. Further, depending on the mounting method, heat generated by the damping resistor is transferred to the coil connected in parallel and the capacitor connected in series, thereby promoting the deterioration of the coil and the capacitor.

Further, since a direct current is superimposed on the choke coil, a magnetic core which is hardly magnetically saturated is required. Although the silicon steel sheet has a high saturation magnetic flux density, its magnetic permeability is not so large, so a large magnetic core having a large magnetic path cross-sectional area has been used. In addition, since ferrite does not have a large saturation magnetic flux density and easily saturates magnetically, a core having a large magnetic path cross-sectional area is used. When the saturation magnetic flux density of the core is low and the magnetic saturation occurs, a gap is provided in the outer periphery of the closed magnetic path core, and as a semi-closed magnetic path core in which one part is an open magnetic path, magnetic saturation is also avoided. Since the magnetic permeability is reduced, a large magnetic core having a large magnetic path cross-sectional area must be used.

[0005]

A choke coil having a resistor connected in parallel to an output line of a PWM inverter is inserted, and a damping circuit including a resistor and a capacitor is inserted between input lines of an AC motor at a rear end of the cable. It is an object of the present invention to eliminate the complexity of performing the operation at two locations and to make the configuration such that the heat generated by the resistor does not deteriorate the nearby coils and capacitors. Another object of the present invention is to provide a small surge voltage suppression filter which does not use a large core for the magnetic core of the choke coil and is hardly magnetically saturated.

[0006]

A first invention is a surge voltage suppression filter inserted between a PWM inverter and an AC motor, and is connected in parallel to each choke coil of a three-phase output line of the PWM inverter. Equipped with a resistor
A surge voltage characterized by comprising a series circuit of a star-connected capacitor and a resistor between lines connected to a cable connected to the AC motor of each choke coil, wherein the resistor is mounted outside the case. It is a suppression filter.

As shown in the circuit diagram of FIG. 2, each coil of the choke coils of the three-phase output line of the PWM inverter is provided with a resistor connected in parallel, and each coil is connected between the lines on the connection side to the AC motor. By configuring a surge voltage suppression filter including a series circuit of a star-connected capacitor and a resistor, the surge voltage suppression filter may be installed at the subsequent stage of the PWM inverter as shown in FIG. 3, and the resistor may be connected to the output line of the PWM inverter. The work of inserting a choke coil connected in parallel and the work of inserting a damping circuit consisting of a resistor and a capacitor between the input lines of the AC motor at the rear end of the cable are not performed in two places. I'm sorry. Further, since the surge voltage suppressing circuit is arranged in series with the line and between the lines, the surge voltage can be suppressed even if the line length changes. FIG. 4 shows the drive voltage waveforms of the AC motor before and after the countermeasure without inserting the surge voltage suppression filter when the AC motor is driven with the connection shown in FIG.

According to a second aspect of the present invention, there is provided a surge voltage suppression filter, wherein the resistor is attached to a lower portion outside a case with a space therebetween.

Since the resistor is mounted outside the case, it does not heat the choke coil and the damping capacitor inside the case and does not promote deterioration. In addition, since the resistor is attached to the lower part outside the case and is not exposed to the surface, it does not burn when contacting during maintenance and inspection, and because it is attached to the lower part outside the case with a space, heat transfer to the case Nothing to do. In addition, since it is attached to the lower part of the case, the heated air flows through the space in the lower part outside the case without contact and burns during maintenance and inspection, so that heat radiation is improved.

According to a third aspect of the present invention, in the surge voltage suppression filter, each of the choke coils is wound around a ring core formed by winding a magnetic ribbon of an amorphous ultrafine crystal alloy. This is a surge voltage suppression filter.

As shown in the BH characteristic diagram of FIG. 5, when a core formed by winding a magnetic ribbon of an amorphous ultrafine crystalline alloy is used, a conventional silicon steel sheet or manganese zinc (Mn, Zn) is used. Compared with a core made of a system ferrite, the core has a high saturation magnetic flux density and a high magnetic permeability, so that a small-sized core having a small magnetic path cross-sectional area can be formed. The core formed by winding a magnetic ribbon of an amorphous ultrafine crystal alloy has a higher permeability and a higher frequency characteristic of Q characteristics than a silicon steel plate of the same thickness. Suitable for core material, can maintain the surge voltage suppression effect in the high frequency band.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In a case, three choke coils and three capacitors shown in the circuit diagram of FIG. 2 are arranged, and six resistors are mounted in a lower part outside the case with a space between the case and the space. Further, a ring core in which a magnetic ribbon of an amorphous ultrafine crystal alloy is wound on the magnetic core of the choke coil is used.

[0013]

EXAMPLE 1 A ring core formed by winding a magnetic ribbon of an amorphous ultrafine crystalline alloy having a thickness of 0.02 mm and a width of 17 mm was used to obtain a ring core having a thickness of 20 mm, an outer diameter of Φ;
The choke coil was housed in a 3 mm resin case, and three choke coils were formed by winding a Φ; 3 mm polyester-coated copper wire for 10 turns. Next, three film capacitors each having a capacitance of 30 nF and the three choke coils are arranged in a case shown in FIG. 1 having an external connection terminal and a mounting base, and the epoxy resin is poured and dried and cured. Was.

Next, as shown in the side view of FIG. 1, from the back of the case, six resistors of 20 Ω, 200 W are screwed and fixed in pairs to the frame of the mounting base. Fig. 2
Based on the circuit diagram of FIG. 1, wiring was connected to a choke coil and a capacitor to form a surge voltage suppression filter shown in the plan view and the side view of FIG.

[0015]

The operation of inserting a choke coil in which a resistor is connected in parallel to the output line of a PWM inverter and the operation of inserting a damping circuit consisting of a resistor and a capacitor between the input lines of an AC motor at the rear end of the cable. Eliminates the complexity of applying to locations, and does not degrade coils and capacitors due to heat generated by resistors. Further, a small surge voltage suppression filter which is hard to be magnetically saturated by using a ring core obtained by winding an amorphous ultrafine alloy thin plate around a magnetic core of a choke coil can be formed.

[0016]

[Brief description of the drawings]

FIG. 1 shows a plan view and a side view of a surge voltage suppression filter according to a first embodiment.

FIG. 2 shows a circuit diagram of a surge voltage suppression filter of the present invention.

FIG. 3 shows a usage example of a surge voltage suppression filter.

FIG. 4 shows output waveforms of an inverter depending on the presence or absence of a surge voltage suppression filter.

FIG. 5 shows a magnetic saturation characteristic diagram of a ferrite core and an amorphous ultrafine crystal alloy core.

FIG. 6 shows an example of a conventional measure for suppressing surge voltage.

Claims (3)

[Claims] 1. A surge voltage suppression filter inserted between a PWM inverter and an AC motor, comprising: a resistor connected in parallel to each choke coil of a three-phase output line of the PWM inverter; A surge voltage suppression filter comprising a series circuit of a star-connected capacitor and a resistor between lines on a connection side to a cable connected to an AC motor, wherein the resistor is mounted outside a case. 2. The surge voltage suppression filter according to claim 1, wherein said resistor is attached to a lower part outside a case with a space therebetween. 3. The surge voltage suppression filter according to claim 1, wherein each of the choke coils is wound around a ring core formed by winding a magnetic ribbon of an amorphous ultrafine crystal alloy. A surge voltage suppression filter, characterized in that: