JPH03149807A - Transformer for converter - Google Patents

Abstract

PURPOSE:To provide not so large profile size and weight, to reduce loss without heavy weight, not to increase the installation are a and to reduce its cost by coaxially winding an AC side winding and a DC side winding on legs of main legs of a core with side legs having two or more main legs with a gap, and connecting the AC side windings in series. CONSTITUTION:A core is formed of two or more main legs 17 with a gap, side legs 18 without gap and a yoke 19 for adhering the legs 17, 18. An AC side winding 22 and a DC side winding 21 are coaxially wound on the legs 17, and the winding 22 of the leg 17 is connected in series. For example, two main legs 17 having a gap 20 formed of a magnetic insulator are provided, the legs are adhered by a yoke 19 of upper and lower parts, a core is formed as a single-phase 4-leg core. The windings 21, 22 are coaxially wound on the leg 17, a ground shield 16 is provided between the windings 21 and 22, the winding 22 is connected for two legs in series, and terminals U-X are then externally extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a converter transformer used in a large-capacity semiconductor power conversion device.

(Prior technology) Power supplies for magnetic levitation trains receive commercial frequency three-phase AC power from the power company's grid, convert it to DC using a converter, and then convert the DC output to any desired power using an inverter. A power conversion device that obtains variable voltage, variable frequency power is used. An example of this is shown in FIG.

FIG. 3 shows only the U-phase portion of the three-phase circuit.

In FIG. 3, the converter section connects an AC power source 2 to the primary side of a converter transformer 1 called an input transformer.
A converter 3 having a full bridge configuration consisting of a GTO (gate turn-off thyristor) and a diode is connected to the secondary side, and a DC voltage EDC is generated at a terminal of a smoothing capacitor 4.

In the inverter section 1, the terminals of a smoothing capacitor 4 are connected to the primary side of a converter transformer 5 called an output transformer via a converter 6 with a full bridge configuration consisting of a GTO and a diode, and an output transformer is connected to the secondary side. A converter 7 having a half-bridge configuration consisting of a GTO and a diode is connected in series and connected to a load 8.

This method consists of a series multiple voltage converter and an inverter, and is called a PWM (pulse width modulation) method, and the voltage and frequency can be varied arbitrarily by controlling the converters 3 and 6.7 using PWM. The power is supplied to the load 8, and good characteristics can be obtained in terms of quick dissolution of operation, power factor on the power source side, and high frequency.

This power converter also has the function of regenerating energy from the linear motor, which is the load 8, eight times on the power source side.

Converter transformer al on the powder converter side as shown in No. 3N
l is from the multiple unit transformers 9 of NJII from T11 to T, and the converter transformer 5 on the inverter side is T.
Each of M sets of unit transformers 10 from 81 to T□ is composed of one converter 3. -6 has a limited capacity, and each unit transformer 9.
A large number of unit transformers 99.10 are connected in series in order to adjust the pulse width and phase every 10 to obtain an arbitrary composite voltage.

The unit transformers 9 and 10 have one iron core and two windings, but the winding on the side connected to the power supply 2 or load 8 is called the AC side winding, and is connected to the converter 3 or 6. The winding on the connected side is called the DC side winding.

A conventional unit transformer 9 or 10 has DC side windings 1 on two main legs 11 of a single-phase two-leg iron core, respectively, as shown in FIG.
4 and an AC side winding 15 are wound coaxially, and the DC side and AC side windings of both main legs 11 are connected in parallel.

Also, both the DC side and AC side windings 14. It is common to install a ground shield 16 between Is, and its role is to prevent contact between both windings and to connect the AC side winding 15 to the DC side winding 14.
Converter 3, 6.7 that reduces the transition voltage to
This is to protect.

In normal transformer cores, the gap at the core punched joint is made as small as possible to reduce magnetic resistance and excitation current, but for this unit transformer core, on the contrary, magnetic resistance must be increased to a certain extent. There is. Therefore, as shown at 411, gaps 13 are formed at four joints between the main leg 11 and the yoke 12 to which magnetic insulators are attached.

There are two reasons why this gap 13 is required.

Since the converters 3 and 6.7 are PWM controlled, a DC component current is generated due to slight deviations in on-timing, control deviations, and differences in impedance characteristics of the unit transformers 9.10. Direct current flows through winding 14.1
5, DC bias magnetization occurs in the iron core, the iron core becomes saturated, and the exciting current increases.

In addition to deteriorating the characteristics of the power converter, the loss of each unit transformer 9, 10 increases, and noise and vibration increase.

It is extremely difficult to completely prevent this DC bias magnetism phenomenon!
Therefore, even if a DC current of up to about 1% of the rated current flows, by providing the gap 13 mentioned above, the magnetic resistance of the iron core is increased, the amount of biased magnetism is decreased, and the iron core is prevented from becoming saturated. This is the first reason.

The second reason is by forming the gap 13.

It is possible to reduce the variation in excitation impedance between the unit transformers 9 and 10 to within a few percent.

In other words, variations in excitation impedance caused by variations in magnetic properties due to the material from which the iron core is punched and irregularities in gap dimensions at joints can be reduced by manufacturing the gap 13 so that it is accurately spaced between each device. , because it can be improved.

The reason for reducing the variation in excitation impedance is that when converting power from the AC side winding 15 side to the DC side winding 14 side, the reason for reducing the variation in excitation impedance is that when power is converted from the AC side winding 15 side to the DC side winding 14 side, This is to ensure that the voltages applied to each unit transformer 9 and 10 are approximately the same, and to maintain good operation as a power converter.

(Problem to be solved by the invention) In the conventional power conversion device, the unit transformer 9 required
．． Since the capacity of IO was small and the number of units connected in series was small, the core was made independent for every unit transformer 9°10,
Its winding 14. Wrap ts around two legs of a single-phase two-leg iron core,
Even by doubling the number of windings.

There were no problems in manufacturing or use.

However, the power converter for magnetic levitation railways has a large capacity, the capacity of the unit transformers 9 and 10 is also large, and the number of units connected in series becomes large, resulting in a large scale.

The larger the device, the larger its external dimensions.

Not only does the price increase due to the increased weight, but
A large installation space is required, and losses also increase.

The present invention has been made to solve the above problems,
The object of the present invention is to provide a converter transformer that is not too large in external size or weight, can reduce generated loss, does not require a large installation space, and is less expensive.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an alternating current for one unit transformer in one of the main legs of an iron core with side legs having two or more main legs with gaps. A side winding and a DC side winding are wound, and all of the AC side windings are connected in series to be connected to a power source or a load.

(Function) With this configuration, the iron core is not independent for each unit transformer, but multiple unit transformers can be configured with one iron core, and the winding can be used for one unit transformer.
Since it can be wrapped around the legs, there is no need to double the number of windings as in the past.

Furthermore, since a gap is formed in the main leg, saturation of the iron core due to DC biased magnetization can be prevented, and variations in excitation impedance can be reduced.

(Example) An embodiment of the present invention will be described below with reference to FIG.

In Figure 1, there are two main legs 17 made of magnetic insulators with a gap of 2°, and side legs 18 with no gap on either side of the main legs 17, which are joined by upper and lower yokes 19. However, the core is configured as a single-phase four-legged core. A DC side winding 21 and an AC side winding 22 are coaxially wound around each main leg 17, and a ground shield 16 is attached between both the DC side and AC side windings 21 and 22.

Then, the AC side winding 22 connects two legs in series and brings out the terminals U-X to the outside, and the DC side winding 21 connects the terminals U1-X*uxXz to the outside for each main leg. It's being pulled out.

Fig. 2 is a diagram showing the magnetic equivalent circuit of the winding configuration shown in Fig. 1. el#e2 displayed on the power supply is the excitation current that flows magnetic flux through this iron core and the winding through which the excitation current flows. This is the magnetomotive force obtained by multiplying the number of windings of Connect each winding so that the main landing gear faces downward.

R□, R,,R, expressed as resistance is the magnetic resistance of each magnetic path, R□ is the magnetic circuit of the main landing gear 17 including the gap 20, and R2 is the magnetic resistance of the main landing gear 17 at the upper or lower yoke 19.
R3 is a magnetic circuit corresponding to the series circuit between the yoke 19 and the side legs 18 between the main leg 17 and the side legs 18.

φ□, φ2. indicated by arrows. φ,, φ, indicate the magnetic flux flowing in each magnetic path.

From this equivalent circuit, the magnetic fluxes φ□ and φ2 can be obtained using the equations ω and ■.

however.

R,=2(R1・R,+R,・R,+R,・R□)(
R, +R3)/R3''...■ In the core configuration shown in FIG. 1, the resistor R□ has a gap 20, so its value is much larger than the resistors R, , R3 which do not have a gap.

If the resistances R, , R3 are small and have negligible values compared to the resistance R1, the magnetic fluxes φ□ and φ2 are expressed by the following equation.

φ, key ・・・・・・ (to) R
1 From these equations, the magnetic flux φ1. φ2 is determined by the relationship only with the main landing gear 17, and in the conventional example, the gap 20 of the main landing gear ■7
This prevents the negative effects of DC bias magnetism mentioned above.
Variations in excitation impedance can be reduced by managing and manufacturing the gaps 20 so that they are the same for each main leg 17.

And (f), from formula a, the influence of magnetic coupling between the windings of the other main landing gear 17 can be ignored, and this is equivalent to the case where separate iron cores are used as in the conventional case.

In other words, even if multiple winding groups are wound around the same core,
Since the magnetic coupling is the same as that of the separate core system, there is no problem even if PWM control is performed for each winding group.

As a means to further reduce the value of the resistance R,,R, (8) The side legs 18 and yoke 19 have high magnetic permeability.

Use highly oriented materials with better properties.

(b) The cross-sectional area of the side legs 18 and yoke 19 may be half of the cross-sectional area of the main leg 17 in a normal transformer core, but it should be made somewhat larger so that the magnetic flux density of the side legs 18 and yoke 19 is lower. do.

(c) The joint portion between the side leg 18 and the yoke 19 may be a frame-shaped lap joint, and if necessary, it may be a so-called step-lap structure in which the punched plates are shifted in a stepped manner.

(d) The joint between the main leg 17 and the yoke 19 has a so-called V-notch structure that eliminates separation of the yoke 19 at the joint, so that magnetic flux flows smoothly.

These four means are employed in combination so as to be optimal depending on the specifications of the converter transformer.

Next, the effects of the embodiment will be explained.If the device corresponding to that shown in FIG. 1 were to be constructed in a conventional manner, two devices as shown in FIG. 4 would be required.

First, regarding the iron core, whereas the conventional type requires two iron cores, the present invention only requires one iron core, and although the side legs are redundant, the number of main legs on which the windings are wound is reduced from four to two. can be halved.

The number of windings can be halved from four groups to two groups, and the number of ground shields 16 is also reduced from four to two.

Even if the number of winding groups is halved, the capacity per group is doubled, so the capacity is the same, but the capacity is twice as much as the conventional one, which manufactures two pieces with half the capacity. However, manufacturing one piece requires fewer materials, reduces losses, allows for smaller size and lighter weight, and has advantages in terms of workmanship.

In Fig. 1, the main legs 17 are two legs, so the two unit transformers have the same iron core, but in the 3111th converter transformer 1, the main legs 17 are N legs, and there are N units. It is also possible to use the same core for the transformer 9, or if the number of N is large, it may be divided into two or three parts and two or three main landing gears 17 are provided.

Similarly, in the 31i-th converter transformer 5, the main leg 17 is an M leg, and the M-unit 2-unit transformer 10 is divided into two or three compartments if there are many M units on the same core.

, the passenger car and the number of wire rows N or M of the converter transformer.
Therefore, it is only necessary to select and design an optimal configuration that is transportable.

〔Effect of the invention〕

As described above, according to the present invention, an iron core is constituted by two or more main legs with gaps, a side leg without a gap, and a yoke connecting them, and an AC side winding is attached to each of the ↓ legs. and the DC side winding are coaxially wound.

Since the AC side windings of each main landing gear are connected in series,
The capacity per group is twice that of the conventional example, but the number of iron cores and winding groups can be halved compared to the conventional example, so the external dimensions and weight of the product can be made smaller and lighter.
No-load loss and load loss can also be reduced, thereby requiring less installation space and providing a low-cost converter transformer.

[Brief explanation of the drawing]

Fig. 1 is a structural explanatory diagram showing an embodiment of a converter transformer according to the present invention; Fig. 2 - a magnetic equivalent circuit diagram for explaining the operation of the embodiment; FIG. 4 is a schematic diagram showing an example of a unit transformer constituting a conventional converter transformer. 1.5--1 converter transformer 2-AC power supply 3.6. Hu...Converter 4-...Smoothing capacitor 8...Load (linear motor) 9.10...Unit transformer 1 port-grounding shield 1
7... Main landing gear 18... Side landing gear
19... Yoke 20 - Gap 21
...DC side winding 22-...AC side winding agent Patent attorney Nori Chika Ken Yudo Deshimaru Ken T-] He÷e, small↓e2-1223 ψ? 乃-P3R2 Fig. 2 151 V Z7 Ul Fig. 4

Claims (1)

[Claims] An iron core is composed of two or more main legs with gaps, a side leg without a gap, and a yoke that joins these legs, and an AC side winding and a DC side winding are coaxially connected to each leg of the main legs. A converter transformer characterized in that the AC side windings of each main landing gear are connected in series.