DE102018219870A1 - transformer - Google Patents

Abstract

The invention relates to a transformer (10). The transformer comprises a magnetic core (14) which forms a first magnetic circuit (34) and a second magnetic circuit (38), a primary winding (42) which is arranged on both magnetic circuits (34, 38) and a first secondary winding (46), which is arranged on the first magnetic circuit (34), and a second secondary winding (50), which is arranged on the second magnetic circuit (38), wherein a magnetic permeability (μ) of the first magnetic circuit (34) and a magnetic permeability (µ) of the second magnetic circuit (38) are different from each other.

Description

The present invention relates to a transformer.

Transformers are used to transform an input voltage into at least an output voltage. The ratio of the input voltage to the output voltage is ideally proportional to the number of turns of the primary winding and the at least one secondary winding.

State of the art

From the DE 40 01 840 C2 is known a transformer with a transformer core, which consists of a middle leg and two parallel side legs, which are connected to the middle leg via yokes. The transformer has a primary winding which is arranged around the middle leg and three secondary windings which are each arranged around the side legs and the middle leg.

The background of the invention is that, in the case of the transformers currently available with steplessly adjustable output voltages, this is, however, dependent on the input voltage and the winding ratio. As an alternative, there is the possibility that the voltages on the secondary winding must be regulated. Additional components such as transformers and control circuits (inverters, converters, step-up, step-down converters, etc.) are therefore necessary. This significantly increases the cost of such an assembly.

The object of the present invention is therefore to provide a transformer with which the output voltage can be adjusted continuously, so that such additional components can be saved.

Disclosure of the invention

The object is achieved by a transformer with the features of claim 1. The dependent claims, which refer back in each case, represent advantageous developments of the invention.

The transformer according to the invention comprises a magnetic core which forms a first magnetic circuit and a second magnetic circuit, a primary winding which is arranged on both magnetic circuits, a first secondary winding which is arranged on the first magnetic circuit, and a second secondary winding, which is arranged on the second magnetic circuit, wherein a magnetic permeability of the first magnetic circuit and a magnetic permeability of the second magnetic circuit are different from one another.

A magnetic circuit is understood to mean a part of the magnetic core through which the same magnetic flux flows. In the invention, two magnetic circles are formed, in which the magnetic flux of the two magnetic circles unite in the area of the primary winding to form an overall flux. Magnetic permeability in the sense of the invention is understood to mean the magnetic conductivity of a material.

The invention has the advantage that a different voltage can be generated for each magnetic circuit due to the frequency dependency of the output voltage by using different permeabilities by changing the input frequency. The output voltage can thus be infinitely varied by varying the frequency, so that only one transformer is required to generate several different output voltages. As a result, such a transformer can save costs for the provision of further transformers, etc. In addition, the space required to provide multiple output voltages is reduced.

The first magnetic circuit is preferably formed by manganese-zinc ferrite and the second magnetic circuit by nickel-zinc ferrite. These ferrites have the advantage that a high magnetic permeability is possible with them in the unsaturated case. Since the ferrites are hardly electrically conductive and therefore almost no eddy current losses occur, they are also suitable for high frequencies up to a few megahertz. This allows a high frequency range to be covered.

The advantages of the combination of materials is that manganese-zinc ferrite and nickel-zinc ferrite can be operated in the same frequency range, but nevertheless have different permeability. A transformer according to the invention can thereby be implemented.

In an advantageous embodiment of the invention, the number of turns of the secondary windings is the same. This means that both secondary coils are the same. This can simplify the manufacturing process.

In a preferred embodiment, the primary winding has the same number of windings as at least one of the secondary windings. This simplifies the manufacture of such a transformer and is therefore more economical to manufacture.

The input voltage of the primary winding is advantageously 12V, 24V, 48V or 400V. Such voltages are particularly common in the field of electromobility, so that a transformer is created which is very well suited for use in an electromobility.

The invention additionally comprises a motor vehicle with the transformer according to the invention. With such a motor vehicle, the advantages mentioned for the transformer can be achieved.

• 1 Schematischer Aufbau eines Ausführungsbeispiels des erfindungsgemäßen Transformators,
• 2 Diagramm der Sekundärspannungen in Abhängigkeit der Frequenz, gemäß eines Ausführungsbeispiels des Transformators, anhand von realen Materialien.
• 3 Tabelle mit Werten der Sekundärspannungen und der magnetischen Impedanzen bei drei verschiedenen Frequenzen, und
• 4 Diagramm der magnetischen Impedanzen in Abhängigkeit der Eingangsfrequenz.

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. It shows:

• 1 Schematic structure of an embodiment of the transformer according to the invention,
• 2nd Diagram of the secondary voltages as a function of frequency, according to an exemplary embodiment of the transformer, using real materials.
• 3rd Table with values of the secondary voltages and the magnetic impedances at three different frequencies, and
• 4th Diagram of the magnetic impedances as a function of the input frequency.

In 1 is a schematic structure of an embodiment of a transformer according to the invention 10th shown. The transformer 10th has a magnetic core 14 on which is a middle leg 18th , a first leg 22 and a second leg 26 trains. These thighs 18th , 22 , 26 are about yokes 30th connected with each other.

The first leg 22 forms with the middle leg 18th a first magnetic circuit 34 out. The second leg forms accordingly 26 with the middle leg 18th a second magnetic circuit 38 out. The first magnetic circuit 34 has a first permeability µ ₁ on while the second magnetic circuit 38 a second permeability µ ₂ having. The first permeability µ ₁ is different from the second permeability µ ₂ .

The transformer 10th also has a primary winding 42 with a number of turns of N ₁ on which around the middle leg 18th is wrapped. In addition, the transformer 10th a first secondary winding 46 with a number of turns of N _2.1 on which around the first leg 22 is wrapped. A second secondary winding 50 that have a number of turns of N _2.2 has, is around the second leg 26 wrapped.

On the primary winding 42 becomes an input voltage U ₁ with a frequency f ₁ created. This results in the middle leg 18th an overall flow Φ _total . In the first leg 22 this results in a first magnetic flux Φ ₁ . On the first secondary winding 46 becomes a first secondary voltage U _2.1 generated. Accordingly, there is in the second leg 26 a second magnetic flux Φ ₂ , resulting in the second secondary winding 50 a second secondary voltage U _2.2 results.

The total flow Φ _total is calculated using the formula ${\mathrm{\Phi }}_{Ges}\left(f\right)=\frac{U_1}{j\cdot {\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="DE102018219870A1\_0007.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1\cdot {\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="DE102018219870A1\_0007.png"\; state="\{\{state\}\}">N</figure-callout>}}_1}.$

bestimmt wird. Der Wert |Z₁| gibt dabei den Betrag der ersten magnetischen Impedanz der ersten Sekundärwicklung 46 an, während |Z₂| den Betrag der zweiten magnetischen Impedanz der zweiten Sekundärwicklung 50 beschreibt. Entsprechend wird der zweiten magnetischer Fluss Φ₂ nach der Formel ${\mathrm{\Phi }}_2\left(f\right)={\mathrm{\Phi }}_{ges}\frac{\left|Z_1\right|}{\left|Z_1\right|+\left|Z_2\right|}$

berechnet.Here ω ₁ = 2πf _{1 is} the angular frequency and j is the imaginary unit. The first magnetic flux Φ ₁ is calculated according to the current divider rule so that the first magnetic flux Φ ₁ according to the formula ${\mathrm{\Phi }}_1\left(f\right)={\mathrm{\Phi }}_{Ges}\frac{\left|Z_{\mathrm{2nd}}\right|}{\left|{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="DE102018219870A1\_0007.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1\right|+\left|Z_{\mathrm{2nd}}\right|}$

is determined. The value | Z ₁ | gives the amount of the first magnetic impedance of the first secondary winding 46 on while | Z ₂ | the amount of the second magnetic impedance of the second secondary winding 50 describes. Accordingly, the second magnetic flux Φ ₂ according to the formula ${\mathrm{\Phi }}_{\mathrm{2nd}}\left(f\right)={\mathrm{\Phi }}_{Ges}\frac{\left|{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="DE102018219870A1\_0007.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1\right|}{\left|{\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="DE102018219870A1\_0007.png"\; state="\{\{state\}\}">Z</figure-callout>}}_1\right|+\left|Z_{\mathrm{2nd}}\right|}$

calculated.

bestimmt. Der Wert I, welcher die Länge des magnetischen Kreises angibt, beschreibt die Länge, die der entsprechende magnetische Fluss Φ₁ bzw. Φ₂ im Magnetkern zurücklegt. Der Wert A, beschreibt dahingegen eine Querschnitt des Magnetkern, für welche der magnetische Fluss Φ₁ bzw. Φ₂ ein Normalenvektor ist. Das Verhältnis der Länge des magnetischen Kreises I zum Querschnitt des Magnetkerns gibt eine Konstante an, währenddessen eine Permeabilität µ mit der Frequenz f veränderlich ist. Die Impedanz Z und die Permeabilität µ unterscheiden sich somit lediglich durch eine Konstante und sind umgekehrt proportional.The first and second magnetic impedance Z ₁ , Z ₂ are according to the formula $Z\approx \frac{l}{\mu A}$

certainly. The value I, which indicates the length of the magnetic circuit, describes the length that the corresponding magnetic flux Φ ₁ respectively. Φ ₂ in the magnetic core. The value A, on the other hand, describes a cross section of the magnetic core for which the magnetic flux Φ ₁ respectively. Φ ₂ is a normal vector. The ratio of the length of the magnetic circuit I to the cross section of the magnetic core indicates a constant, during which a permeability μ can be varied with the frequency f. The impedance Z and the permeability µ therefore differ only by a constant and are inversely proportional.

2nd shows a diagram of the secondary voltages U _2.1 , U _2.2 depending on the frequency f ₁ , according to an embodiment of the transformer 10th , based on real materials. This diagram is for a transformer 10th have been created using the first magnetic circuit 34 through a manganese-zinc ferrite and the second magnetic circuit 38 is formed by nickel-zinc ferrite. This diagram is for a first one Number of turns N ₁ the primary winding 42 of N ₁ = 100, a number of turns of the first secondary winding 46 of N _2.1 = 5, a number of turns of the second secondary winding of N ₂ , ₂ = 10 and an input voltage U ₁ created by 400V.

The diagram shows that the voltage profile of the first secondary voltage U _2.1 and the second secondary voltage U _2.2 depending on the frequency f ₁ is different. This is done by changing the frequency f ₁ a different secondary voltage U ₂ , ₁ , U _2.2 adjustable. This can be done with a transformer 10th , through the targeted selection of permeabilities µ ₁ , µ ₂ a large voltage range can be set. This allows multiple transformers 10th be replaced. Alternatively, one of the two secondary voltages can also be regulated in order to eliminate their interdependency.

In 3rd is shown a table, which is based on the in 2nd shown diagram, at three different frequencies f ₁ the current values of the secondary voltages U _2.1 and U ₂ , ₂ , the first magnetic impedance Z ₁ for the first secondary winding 46 the material of the first magnetic circuit 34 and the second magnetic impedance Z ₂ for the second secondary winding 50 of the material of the second magnetic circuit 38 , are shown.

4th shows a diagram of the first magnetic impedance Z ₁ and the second magnetic impedance Z ₂ depending on the frequency f ₁ . This diagram clearly shows that the impedances Z ₁ , Z ₂ with the frequency f ₁ change differently so that different secondary voltages U _2.1 and U _2.2 can be generated.

QUOTES INCLUDE IN THE DESCRIPTION

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Patent literature cited

• DE 4001840 C2 [0003]

Claims (6)

Transformer (10) comprising: - a magnetic core (14) which forms a first magnetic circuit (34) and a second magnetic circuit (38), - a primary winding (42) which is connected to both magnetic circuits (34, 38) - a first secondary winding (46), which is arranged on the first magnetic circuit (34), and - a second secondary winding (50), which is arranged on the second magnetic circuit (38), characterized in that a magnetic Permeability (µ ₁ ) of the first magnetic circuit (34) and a magnetic permeability (µ ₂ ) of the second magnetic circuit (38) are different from each other. Transformer (10) according to one of the preceding claims, characterized in that the first magnetic circuit (34) is formed from manganese-zinc ferrite and the second magnetic circuit (38) is formed from nickel-zinc ferrite. Transformer (10) according to one of the preceding claims, characterized in that a number of turns (N _2.1 , N _2.2 ) of the secondary windings (46, 50) is the same. Transformer (10) according to one of the preceding claims, characterized in that the primary winding (42) has the same number of windings (N ₁ ) as at least one of the secondary windings (46, 50). Transformer (10) according to one of the preceding claims, characterized in that the input voltage (U ₁ ) of the primary winding (42) is 12V, 24V, 48V or 400V. Motor vehicle comprising a transformer (10) according to one of the preceding claims.

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