JPH0484405A - Choke for improving power factor - Google Patents

Abstract

PURPOSE:To increase the degree of improving power factor at both high loading and low loading by installing a magnetic bias means in a core and also by installing a flux controller in part of the core so as to be close to a magnetic saturation point and to pass almost of the magnetic field generated by the core in a direction reverse to the DC magnetic field. CONSTITUTION:A choke 21 is equipped with a winding 26 for conduction and a magnetic bias means consisting of permanent magnets 28 mounted to each outer side 27a of feet at both sides of a E-type core 22, wherein a L-type yoke 24 is mounted to the outer side 28a of the permanent magnet 28 with one end part 24a of the L-type yoke 24 in contact with end portion 23a of I-type core 23. Between the I-type core 23, the middle foot 25 of E-type core 22, and each tip of feet 27 at both sides, gaps 29 and 30 are prepared. In the I-type core 23, in order to contract part of a flux passage a pair of flux controllers 31 and 32 whose sectional area is partly reduced are installed on the right side and the left side, respectively, and the flux controllers 31 and 32 are made close to a magnetic saturation point by a DC magnetic field of the permanent magnet 28.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a power factor correction choke used in an AC input section of an electrical device such as an inverter.

[Prior Art and Problems] Conventionally, for example, an AC input section of an inverter is connected to a rectifier circuit that rectifies power from an AC power source and a capacitor that supplies the rectified power to the inverter as a DC input. , a 5-iron core choke is used to improve the power factor, and this choke uses the straight line portion a-b of the core B/H characteristic diagram shown in Figure 13 to obtain a large inductance. Was. Therefore, the inductance does not change regardless of the magnitude of the load (current flow amount).In this case, if the degree of power factor improvement at high loads is increased, the degree of power factor improvement at low loads decreases.

The present invention aims to eliminate the above-mentioned drawbacks of the conventional technology and to increase the degree of power factor improvement both at high loads and at low loads.

[Means for Solving the Problems] In order to achieve the above object, the inventor of the present invention has conducted extensive research and found that by decreasing the inductance at low currents and increasing the inductance at high currents, the inductance can be improved even at high loads. It was found that the power factor was improved even under low loads. This is the basis of this invention.

In order to reduce the inductance when the current is small and increase the inductance when the current is large, the invention of claim 1 provides a capacitor that supplies electrical equipment with DC input obtained by rectifying power from an AC power source with a rectifier circuit. , in the choke connected between the AC power supply, a magnetic bias means for applying a DC magnetic field to the core is provided, and at least a part of the core is brought close to the magnetic saturation point by the DC magnetic field, and is energized. A magnetic flux adjustment section is provided that allows most of the magnetic field generated by the winding to pass through in a direction opposite to the DC magnetic field.

In claim 2, for example, a pair of the magnetic flux adjusting sections are provided, and the magnetic field generated by the winding is directed to one magnetic flux adjusting section in the same direction as the DC magnetic field, and to the other magnetic flux adjusting section, the magnetic field is directed to the DC magnetic field. Set them so that they are applied in the opposite direction to the magnetic field.

As claimed in claim 3, the specific structure of the choke is as follows:
The core is an EI type, a current-carrying winding is wound around the middle leg of the E shape, a gap is provided between the tips of the middle leg and both legs, and the I-shaped core, and each outer surface of the above-mentioned both legs is A permanent magnet that generates the DC magnetic field is attached to the yoke, and a yoke whose one end contacts the end of the I core is attached to the outer surface of each permanent magnet, and a part of the magnetic flux path is connected to the I core. It is possible to have a structure in which the magnetic flux adjusting section is formed by constricting the magnetic flux adjusting section.

Further, as in claim 4, the core is also of EI type,
A current-carrying winding is wound around the E-shaped middle leg, a gap is created between the tip of the middle leg and the I core, the I-shaped core is divided into two parts, and the above-mentioned DC magnetic field is generated in the divided part. It is possible to have a structure in which a permanent magnet is inserted.

Furthermore, as in claim 5, instead of inserting a permanent magnet into the I core, the middle leg of the E-shaped core is vertically divided into two parts, and a permanent magnet that generates the DC magnetic field is inserted into the divided part. It is also possible to do this.

[Function] According to the invention of claims 1 to 4, at least a part of the core is brought close to the magnetic saturation point by the direct current magnetic field by the magnetic bias means, and most of the magnetic field generated by the energizing winding is There is a magnetic flux adjustment section that allows the magnetic flux to pass in the opposite direction to the DC magnetic field, so when the current flowing through the current-carrying winding is small,
The magnetic flux density of the above magnetic flux adjusting section is still close to the magnetic saturation point, so the inductance becomes small.
When the above-mentioned current is large, the magnetic flux density of the above-mentioned magnetic flux adjustment section becomes a straight line part with a large slope of the B/H characteristic diagram, so
Inductance increases.

The charging current to the capacitor is only in the upper part of the sine wave current waveform, excluding the lower part near the zero point, so if a choke is not inserted between the capacitor and the AC power supply, the current waveform will be as follows: This results in a narrow chevron shape that differs greatly from a sinusoidal waveform, resulting in a lower power factor. On the other hand, in this invention, the inductance of the choke is small when the current is small and large when the current is large.
As a result of the narrow current waveform being suppressed to a small value at the bottom portion (small current portion) and largely suppressed at the top portion (large current portion), the current waveform approaches a sine wave as a whole, thereby improving the power factor.

Here, as in claim 2, a pair of the magnetic flux adjusting sections is provided, and the magnetic field generated by the winding is directed to one magnetic flux adjusting section in the same direction as the DC magnetic field and to the other magnetic flux adjusting section. If the magnetic bias is set to be applied in the opposite direction to the above DC magnetic field, even if the direction of the magnetic bias is kept constant, the magnetic flux of either one will be applied alternately according to the reversal of the polarity of the AC flowing through the winding. The adjustment section acts as a magnetic flux adjustment section that allows most of the magnetic field generated by the winding to pass through in a direction opposite to the DC magnetic field.

Further, as in claim 3, if the core is an EI type and a permanent magnet is attached to the outer surface of the front leg of the E type core, a large magnetic bias can be easily applied by the two permanent magnets. Moreover, the magnetic field due to the winding current is mainly E
Since it passes through the I-type core and is difficult to pass through the permanent magnet, the force that demagnetizes the permanent magnet is small.

Furthermore, as in claim 4, if the core is an EI type and the permanent magnet is inserted into a divided portion in which the I type core is divided into two at the center, a magnetic bias can be applied with a single small permanent magnet. It becomes possible. Furthermore, since the magnetic field generated by the winding current does not cross the permanent magnet in its magnetization direction, the force for demagnetizing the permanent magnet is small.

On the other hand, as in claim 5, if the core is of EI type, the E
If the middle leg of the mold core is vertically divided into two and a permanent magnet is inserted into the split part, the permanent magnet is sandwiched between the split surfaces with a large area of the middle leg, so the permanent magnet is held firmly and the Since the permanent magnet becomes larger in proportion to the larger dividing surface, it is possible to use a permanent magnet made of a material that has a lower magnetic flux density but is cheaper than the permanent magnet of the fourth aspect. Further, for the same reason as in the case of claim 4, there is less demagnetization of the permanent magnet.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1a, 10 is an inverter, which is a type of electrical equipment, and is a so-called capacitor input type inverter that receives DC input via a rectifier circuit 12 that rectifies power from an AC power source 11 and a smoothing capacitor 13. be.

This inverter 10 converts the DC input from the capacitor 13 into an AC output and supplies it to the load 14 .

A chain yoke 21 of the present invention is inserted between the AC power source 11 and the rectifier circuit 12. This choke 21 is connected to the rectifier circuit 12 and the capacitor 1, as shown in FIG. 1b.
It may be connected between 3 and 3.

The choke 21 has an E-type core 2 as shown in FIG.
2. I-shaped core 23, left and right pair of L-shaped yokes 24, above E
The current-carrying winding [26] wound around the middle leg 25 of the type core 22, and the outer surfaces 27a of the front legs 27 and 27 of the E-type core 22.
The above-mentioned yoke 24 is provided with a magnetic bias means consisting of a permanent magnet 28, 28 attached to the yoke 24, and the above-mentioned yoke 24 is in a state where its one end 24a is in contact with the end 23a of the I-shaped core 23.
It is attached to the outer surface 28a of the permanent magnet 28.

I core 23, middle leg 25 and front leg 2 of E-type core 22
There is a gap of 29.30 between each tip of 7.
is provided.

In the I-type core 23, in order to narrow down a part of the magnetic flux path,
A pair of left and right magnetic flux adjusting sections 31 and 32 whose cross-sectional area is partially reduced are provided, and the magnetic flux adjusting sections 31 and 32 approach the magnetic saturation point due to the DC magnetic field of the permanent magnet 28. The choke 21 as a whole has a symmetrical structure with a center line 33 in between.

Here, "approaching the magnetic saturation point" means B/H in Figure 3.
It means to deviate from the straight line section a-b (strictly speaking, there is a slight bend) of the curve.

In the configuration shown in FIG. 2 above, the DC magnetic field generated by the permanent magnet 28 is applied to the gap 29.
0, the three legs 25, 27 .
27, the body 48 of the E-type core 22, the I core 23
and a magnetic flux adjusting section 31 that passes through the Lfi yoke 24 as shown by arrow A and has a relatively small area within this magnetic path.
, 32 approaches the magnetic saturation point, that is, B/ in FIG.
A point C is reached in a region outside the straight line section a-b of the H characteristic diagram. Here, since two permanent magnets 28 are provided, a large magnetic bias can be easily applied.

In this state, when alternating current is applied between both terminals 35 and 36 of the winding 26, if a positive voltage is applied to one terminal 35 and a negative voltage is applied to the other terminal 36, the N pole of the first winding 26 will be turned upward. A magnetic field B1 is generated so as to occur. This magnetic field B1 passes through the gap 29, 30 and through the E-type core 22 and I core 23, but since the permanent magnet 28 acts as a gap for the magnetic field B1, it passes through the yoke 24 and the permanent magnet 28. Therefore, the permanent magnet 28 is less demagnetized by the magnetic field Bl.

The magnetic field B1 due to the winding 26 is applied to the left magnetic flux adjusting section 31.
is applied in the opposite direction to the DC magnetic field A, and is applied to the right magnetic flux adjustment section 32 in the same direction as the DC magnetic field A. As a result, of the magnetic field B1, the magnetic flux passing through the magnetic flux adjusting section 32 on the right side is restricted, and the magnetic flux passing through the magnetic flux adjusting section 31 on the left side increases, so that most of the magnetic field B1 generated by the winding 26 is on the left side. It fits within a closed magnetic path passing through the magnetic flux adjustment section 31 of. Since the gap 30 exists in the closed magnetic path through which the magnetic field B1 passes, the closed magnetic path has a characteristic that it is difficult to be saturated even with a large current value of the winding 26.

Here, when the current flowing through the winding 26 is a small current, the magnetization strength of the left magnetic flux adjustment section 31 that constitutes the closed magnetic path of the magnetic field Bl is between the point C and the point b in FIG. Therefore, the magnetic permeability (corresponding to the gradient of the B/H curve) of the magnetic flux adjustment section 31 is low, and on the other hand, in the case of a large current, the magnetization strength of the magnetic flux adjustment section 31 is between points b and a. Therefore, the magnetic permeability of the magnetic flux adjustment section 31 becomes high. Therefore, the inductance of the choke 21 is small in a small current region and large in a large current region.

Next, when the AC voltage is reversed and a negative voltage is applied to one terminal 35 and a positive voltage is applied to the other terminal 36 as shown in FIG. 4, an N pole is generated downward in the winding 26. Magnetic field B
2 occurs. In this case, contrary to the case in Figure 2,
Since the magnetic flux passing through the left magnetic flux adjusting section 31 is restricted and the magnetic flux passing through the right magnetic flux adjusting section 32 increases, the magnetic field B2 becomes
Most of it falls within a closed magnetic path passing through the magnetic flux adjustment section 32 on the right side, and due to changes in the magnetic permeability of the magnetic flux adjustment section 32, the inductance of the choke 21 becomes small when the current is small and becomes large when the current is large.

In other words, when alternating current is applied to both terminals 35, 36, each time the polarity is reversed, the main passage of the lines of magnetic force created by the alternating current is switched between both magnetic flux adjustment parts 31, 32. Therefore, as long as the ring 21 is made symmetrically, even if the direction of the magnetic bias by the permanent magnet 28 is kept constant, it will function in the same way when the winding current is reversed between positive and negative. The inductance characteristics of this choke 21 are shown in FIG.

Next, the reason why changing the inductance as shown in FIG. 5 improves the power factor of the power supplied to the inverter IO in FIG. 1a or 1b will be explained.

First, when the load is low, there is a lot of charge stored in the capacitor 13, so the supply current supplied from the AC power supply 11 to the capacitor 13 via the rectifier circuit 12 is only at the top of the sine wave current waveform. In the absence of the choke 21 of the invention, as shown in FIG. 6, compared to the supply voltage 41 which is a sine wave from the AC power source 11, the supply current has a steep waveform 42 with a narrow width.

On the other hand, when the choke 21 of the present invention is used, when the current waveform 42 is small, that is, the tail portion of the waveform 42
2a, the inductance is small, so the current is only slightly suppressed, but at the time of large current, that is, at the top 42b of the waveform, the inductance is large, so
Current is strongly suppressed. Therefore, as shown in FIG. 7, the bottom portion 42a is slightly lowered and the top portion 42b is significantly lowered, so that a waveform 43 close to a sine wave of the output voltage 41 is obtained. As a result, the power factor improves.

On the other hand, if a choke with constant inductance is used regardless of the magnitude of the current as in the past, the entire current waveform is uniformly suppressed, as shown in Figure 8.
It is not possible to expect an improvement in the power factor as in the case of using the choke 21 of the present invention.

Next, when the load is high, the electric charge stored in the capacitor 13 is small, so the current supplied to the capacitor 13 is
Since this is the part excluding the top of the sine wave current waveform and the middle part below it, that is, the bottom part near the zero point, the supplied current without the senrin 21 of this invention is shown in FIG. As shown, this results in a slightly wider and smoother waveform 42, but this waveform 42 is still quite significantly different from a sine wave.

On the other hand, when the choke 21 of the present invention is used, the bottom portion 42a of the current waveform 42 is pushed down slightly, and the top portion 42b is pushed down significantly, resulting in a waveform 47 that is close to a sine wave, and as a result, the power factor is reduced. improves. Even at this high load, if a conventional choke with a constant inductance is used, a waveform close to a sine wave cannot be obtained, as in the case of the low load, so the power factor will not improve sufficiently.

In fact, a traditional choke with constant inductance and a fifth
When the power factor of the power supplied to the inverter 10 was compared using the choke 21 of the present invention having the characteristics shown in the figure, the results shown in FIG. 10 were obtained. As can be seen from FIG. 10, an improvement in power factor was observed for 3 points at low load (100V, 8A) and 4 points at high load (100V, 1I3A).

By the way, in the embodiment shown in FIG. 2 above, the permanent magnet 2
8 is required, and L-shaped yokes 24 are also required on both sides, making the choke 21 larger.

On the other hand, in the embodiment shown in FIG.
A gap 29 is provided between the tip of the middle leg 25 and the I-shaped core 23, and the IN core 23 is divided into two at the center opposite to the tip of the middle leg 25.
A permanent magnet 28 that generates a DC magnetic field is inserted. In this example, the body 48 of the EJ cocoa 2 is connected to the E-type core 22.
The magnetic flux adjusting portions 31 and 32 are made thinner than the other portions of the I core 23 and the I core 23.

According to the configuration shown in FIG. 11, the L-shaped yoke 24 shown in FIG.
can be omitted, and since it becomes possible to apply a magnetic bias using one small permanent magnet 28, the choke 21 can be made smaller. Here, since the permanent magnet 28 is small, it is preferable to use a rare earth material such as samarium or cobalt, which provides strong magnetic force, as the material for the permanent magnet 28.

Furthermore, since the permanent magnet 28 is located at the center of the I-type core 23, the alternating magnetic fields Bl and B2 due to the current in the winding 26 move the permanent magnet 28 in its magnetization direction (left and right direction in FIG. 11).
Since the magnetic fields B1 and B2 do not intersect with each other, the permanent magnet 28 is less demagnetized by the magnetic fields B1 and B2.

FIG. 12 shows still another embodiment, in which the middle leg 25 of the E-shaped core 22 is vertically divided into two parts, and a permanent magnet 28 is inserted into the divided part. In addition, I-type core 23
is formed to be thinner than the E-shaped core 22, and serves as the magnetic flux adjusting portions 31 and 32.

According to the embodiment shown in FIG. 12, the choke 21 is also made smaller, and the dividing surface 49 of the middle leg 25 has a large area.
Since the permanent magnet 28 is sandwiched between the two, the permanent magnet 28 is firmly held. Moreover, since the permanent magnet 28 is larger than that shown in FIG. 11, it is possible to use a material that has a lower magnetic flux density than the rare earth but is cheaper, such as a ferrite magnet. In addition, an alternating magnetic field B1 due to the current of the winding 26,
Since B2 does not cross the permanent magnet 28 in its magnetization direction, the permanent magnet 28 is less demagnetized by the magnetic fields B1 and B2.

In addition, in each of the above embodiments, only a part of the core is thinned,
The reason for using the magnetic flux adjusting portion is to reduce the magnetic resistance of the entire magnetic circuit by making the other portions of the core thicker. Therefore, if the magnetic flux density produced by the winding 26 is not very high, the entire core may be made thinner so that the DC magnetic field of the permanent magnet 28 causes the entire core to approach the magnetic saturation point.

Further, as the magnetic bias means, an electromagnet having a winding excited by direct current can also be used.

Furthermore, the present invention can be used not only for inverters but also for other electric devices having a capacitor input ffi having a rectifier circuit for power factor correction.

[Effects of the Invention] As described above, according to the inventions of claims 1 to 4, the inductance of 1,000 volts is small when the current is small and becomes large when the current is large, so that the current width is narrower than the voltage waveform of the sine wave. The waveform is suppressed to a small size at the tail portion (low current portion),
As a result of being largely suppressed at the top (high current section), the overall waveform approaches a sine wave, improving the power factor.

According to the invention of claim 2, even if the direction of the magnetic bias is kept constant, one of the magnetic flux adjusting sections alternately adjusts the polarity of the alternating current flowing through the winding in accordance with the reversal of the polarity of the alternating current flowing through the winding. Since it acts as a magnetic flux adjustment section that allows most of the magnetic field to pass in the opposite direction to the DC magnetic field, the structure of the choke is simplified.

According to the third aspect of the invention, a large magnetic bias can be easily applied using the two permanent magnets.

According to the fourth aspect of the invention, it is possible to apply a magnetic bias using one small permanent magnet, so that the choke is miniaturized.

According to the fifth aspect of the present invention, not only is the tie yoke made smaller, but also the permanent magnet is sandwiched between the large-area dividing surfaces of the middle legs of the E-shaped core, so that the permanent magnet is firmly held. Moreover,
The permanent magnet will be larger as the dividing surface is larger, so
There is also the advantage that an inexpensive magnet material can be used although the magnetic flux density is low.

Furthermore, according to the third to fifth aspects of the invention, there is little demagnetization of the permanent magnet due to the magnetic field of the winding current.

[Brief explanation of drawings]

1a and 1b are circuit diagrams showing the circuits of electrical equipment using the choke according to the present invention, FIG. A characteristic diagram showing the B/H characteristics of the choke of the same embodiment, FIG. 4 is a front view for explaining the operation of the same embodiment, and FIG. 5 is a characteristic diagram showing the relationship between current and inductance of the same embodiment. Figure 6 is a waveform diagram showing the voltage and current waveforms at low load when no choke is used, Figure 7 is a waveform diagram showing the current waveform when the choke of the same example is used, and Figure 8 is the conventional waveform. Figure 9 is a waveform diagram showing the current waveform when using a choke, Figure 9 is a waveform diagram showing the current waveform at high load, Figure 10 is a characteristic diagram showing the relationship between load and power factor, and Figure 11 is another diagram. FIG. 12 is a front view of a choke showing another embodiment, and FIG. 13 is a characteristic diagram showing B/H characteristics of a conventional choke. 10... Inverter (electrical equipment), 11... AC power supply, 12... Rectifier circuit, 13... Capacitor, 14
Load, 21 Choke, 22 E-type core, 23 I-type core, 23a-end, 24-3-ri, 24a one end, 25... Middle leg, 26... Winding wire, 27... Side leg, 27a... Outer surface, 28...
Permanent magnet (magnetic bias means), 28a...outer surface,
31.32...Magnetic flux adjustment section. Fig. 18 AC power supply rectifier circuit capacitor choke Fig. 1b Fig. 3132, magnetic flux adjustment section Fig. 11 Fig. 4th b Fig. 13

Claims (5)

[Claims] (1) A chiyoke connected between a capacitor that supplies DC input obtained by rectifying power from an AC power source to an electrical device and the AC power source, including a core and a current-carrying wire wound around the core. and a magnetic bias means for applying a direct current magnetic field to the core, wherein at least a portion of the core is near the magnetic saturation point with the direct current magnetic field, and a majority of the magnetic field generated by the winding is provided. A power factor improving cheese yoke is provided with a magnetic flux adjusting section that allows the magnetic flux to pass in the opposite direction to the DC magnetic field. (2) In claim 1, a pair of magnetic flux adjustment sections are provided,
A power factor correction chain is set so that the magnetic field generated by the winding is applied to one magnetic flux adjustment section in the same direction as the DC magnetic field, and to the other magnetic flux adjustment section in the opposite direction to the DC magnetic field. . (3) In claim 2, the core is of EI type, and its E
A current-carrying winding is wound around the middle leg of the mold, a gap is provided between the tips of the middle leg and both legs, and the I-shaped core, and the DC magnetic field is applied to each outer surface of the both legs. Permanent magnets that generate
A yoke for power factor improvement, wherein a yoke that contacts an end of the I-shaped core is attached, and the magnetic flux adjustment section is formed by narrowing a part of the magnetic flux path in the I-shaped core. (4) In claim 2, the core is of EI type, and its E
A current-carrying winding is wound around the middle leg of the mold, a gap is provided between the tip of the middle leg and the I-shaped core, and the I-shaped core is divided into two parts at the center. A choke for power factor improvement in which a permanent magnet that generates the above-mentioned DC magnetic field is inserted. (5) In claim 2, the core is of EI type, and its E
A current-carrying winding is wound around the middle leg of the mold, a gap is provided between the tip of the middle leg and the I core, the middle leg is vertically divided into two parts, and the direct current is applied to the divided part. A power factor correction choke that has a permanent magnet inserted that generates a magnetic field.