A series-parallel type coreless transformer based on the principle of maximum magnetic flux linkage

Abstract

The present invention discloses a series - parallel type coreless transformer based on the principle of maximizing magnetic flux linkage, which includes a primary circuit and a secondary circuit; the primary circuit includes a primary capacitor, a primary coil, and a sinusoidal voltage source that provides energy for the transformer, and the sinusoidal voltage source, the primary capacitor, and the primary coil are connected in series; the secondary circuit includes a secondary capacitor, a secondary coil, and a load resistor, and the secondary capacitor, the secondary coil, and the load resistor are connected in parallel; there is no core connection between the primary coil and the secondary coil. The present invention realizes the same voltage transformation function as the traditional core transformer and can achieve efficient energy transmission. Compared with the existing coreless transformers, it solves the problem that the transformer cannot efficiently transfer energy due to weak magnetic field coupling in the case of no core, and the transmission power reaches the kW level, realizing the coreless of the transformer, greatly reducing the volume, cost, and loss of the transformer, and is expected to replace the traditional core transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of transformers, and in particular to a series - parallel type coreless transformer based on the principle of maximum magnetic flux linkage. Background Art

[0002] Traditional transformers mainly include a primary coil, a secondary coil, and an iron core (magnetic core), and the primary coil and the secondary coil are coupled through the iron core.

[0003] However, the presence of the iron core limits the structure and shape of the transformer, is not conducive to integrated design, and hinders the further reduction of the transformer cost and the improvement of efficiency. Therefore, coreless transformers have always been the goal that domestic and foreign researchers hope to overcome, and their advantages are very obvious:

[0004] 1. Reduce the weight, volume, and cost of the transformer;

[0005] 2. There is no iron loss, improving the efficiency of the transformer;

[0006] 3. There is no problem of iron core saturation;

[0007] 4. It is easier for integrated design.

[0008] Over the years, scholars from all over the world have proposed various types of coreless transformers such as Tesla coreless transformers, superconducting coreless transformers, PCB coreless transformers, and semiconductor coreless transformers. However, these coreless transformers all have obvious deficiencies. Tesla coreless transformers are mainly used for transient high - voltage discharge tests, cannot continuously output a constant power, and have no load - carrying capacity; superconducting coreless transformers require an extremely low - temperature environment and have extremely high operating costs, and are usually only used in scenarios such as pulse power supplies; PCB coreless transformers have the advantage of high integration, but have extremely high operating frequencies, usually reaching several MHz to dozens of MHz, while the transmitted power is relatively low, usually within 100W, and the maximum efficiency does not exceed 90%; semiconductor coreless transformers have the advantage of extremely high integration, but like PCB coreless transformers, they have the disadvantages of extremely high operating frequencies, low transmitted power, and low efficiency. Summary of the Invention

[0009] The purpose of the present invention is to overcome the deficiencies of the prior art, and propose a series - parallel type coreless transformer based on the principle of maximum magnetic flux linkage. By applying the principle of maximum magnetic flux linkage to design the series - parallel type coreless transformer, it realizes the same voltage transformation function as traditional iron - core transformers and can achieve efficient energy transmission. Compared with existing coreless transformers, it solves the problem that the transformer cannot efficiently transfer energy due to weak magnetic field coupling in the case of no iron core, and the transmitted power reaches the kW level, realizing the coreless of the transformer, greatly reducing the volume, cost, and loss of the transformer, and is expected to replace traditional iron - core transformers.

[0010] To achieve the above object, the technical solution provided by the present invention is: a series-parallel type coreless transformer based on the principle of maximum magnetic flux, including a primary circuit and a secondary circuit; the primary circuit includes a primary capacitor, a primary coil, and a sinusoidal voltage source that provides energy for the transformer, and the sinusoidal voltage source, the primary capacitor, and the primary coil are connected in series; the secondary circuit includes a secondary capacitor, a secondary coil, and a load resistor, and the secondary capacitor, the secondary coil, and the load resistor are connected in parallel; there is no core connection between the primary coil and the secondary coil; among them, the primary capacitor and the secondary capacitor need to meet the following maximum magnetic flux conditions:

[0011]

[0012] In the formula, C P is the capacitance value of the primary capacitor, C S is the capacitance value of the secondary capacitor, L P is the inductance value of the primary coil, L S is the inductance value of the secondary coil, k is the coupling coefficient between the primary coil and the secondary coil, and ω is the angular frequency of the sinusoidal voltage source.

[0013] Further, the change rule of the tangent of the phase difference of the magnetic flux satisfies the equation:

[0014]

[0015] In the formula, θ ψ is the phase difference of the magnetic fluxes generated by the primary coil and the secondary coil, and R L is the resistance value of the load resistor.

[0016] Further, the voltage ratio K V between the sinusoidal voltage source and the load resistor satisfies the relational expression:

[0017]

[0018] In the formula, V P is the voltage across the sinusoidal voltage source, and V S is the voltage across the load resistor.

[0019] The working principle of the above-mentioned series-parallel type coreless transformer based on the principle of maximum magnetic flux of the present invention is: the sinusoidal voltage source in the primary circuit provides energy for the load. When the parameters meet the principle of maximum magnetic flux, the phase difference between the current of the primary coil and the current of the secondary coil is the smallest. At this time, a relatively small coil current can generate a sufficiently large magnetic flux, so efficient energy transmission can still be achieved without a core. Therefore, the coreless transformer designed by the present invention can achieve almost the same functions as a traditional core transformer.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. Compared with traditional iron-core transformers, the transformer of the present invention has a simple structure and does not require an iron core.

[0022] 2. Compared with traditional iron-core transformers, the transformer of the present invention has significantly reduced weight, volume and cost, no iron loss, and significantly improved efficiency.

[0023] 3. Compared with existing ironless transformers, the transformer of the present invention has a low operating frequency and a large output power.

[0024] 4. Compared with existing ironless transformers, the transformer of the present invention can operate normally within the full load range, has a constant voltage ratio, and the voltage ratio is proportional to the square root of the ratio of the inductances of the primary and secondary coils, which is consistent with the law of traditional transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the circuit schematic diagram of the series-parallel type ironless transformer.

[0026] Figure 2 is the curve diagram of the relationship between the magnetic flux linkage phase difference and the load resistance.

[0027] Figure 3 is the curve diagram of the relationship between the voltage ratio and the load resistance.

[0028] Figure 4 is the curve diagram of the relationship between the voltage ratio and the output power.

[0029] Figure 5 is the curve diagram of the relationship between the efficiency and the output power.

[0030] Figure 6 is the waveform diagram of the primary coil current and the secondary coil current. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be further described in detail below with reference to the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0032] As Figure 1 shown, the series-parallel type ironless transformer based on the principle of magnetic flux linkage maximization provided in this embodiment includes a primary circuit and a secondary circuit; the primary circuit includes a primary capacitor, a primary coil, and a sinusoidal voltage source, and the primary capacitor, the primary coil, and the sinusoidal voltage source are connected in series, and the voltage across the sinusoidal voltage source is V P , the angular frequency is ω; the secondary circuit includes a secondary capacitor, a secondary coil, and a load resistor; the secondary capacitor, the secondary coil, and the load resistor are connected in parallel; there is no iron core connection between the primary coil and the secondary coil.

[0033] Figure 1 The flux linkage relationship of the series - parallel type coreless transformer based on the principle of maximum flux linkage can be expressed as follows:

[0034]

[0035] Wherein, ψ PP , ψ SS are the flux linkages generated by the primary coil and the secondary coil respectively; ψ PS is the part of ψ SS linked with the primary coil; ψ SP is the part of ψ PP linked with the secondary coil; ψ P , ψ S are the total flux linkages of the primary coil and the secondary coil respectively; L P is the inductance value of the primary coil, L S is the inductance value of the secondary coil, I P is the primary current of the coreless transformer, and is also the current of the primary coil; I LS is the current of the secondary coil.

[0036] According to Figure 1 , by the phasor method and Kirchhoff's law, we can get:

[0037]

[0038] Wherein, V P is the voltage across the sinusoidal voltage source, C P is the capacitance value of the primary capacitor, C S is the capacitance value of the secondary capacitor, R L is the resistance value of the load resistor, V S B is the voltage across the load resistor; I S is the secondary current of the coreless transformer, and is also the current flowing through the load resistor; I CS is the current flowing through the secondary capacitor. Then the relationship between the primary coil current and the secondary coil current can be expressed as:

[0039] I LS = γI P (3)

[0040]

[0041] Wherein, the secondary impedance Z S can be expressed as:

[0042]

[0043] The tangent of the phase difference θ ψ of the flux linkage can be expressed as:

[0044]

[0045] According to the principle of maximizing the magnetic flux linkage, Re(γ) > 0 should be satisfied, that is, Im(Z S ) < 0, to maximize the magnetic flux linkage. Then it can be obtained that the secondary capacitor should satisfy:

[0046]

[0047] Regarding the coreless transformer as a two-port network, the T-parameter matrix of this two-port network can be expressed as:

[0048]

[0049] According to the properties of the T-parameter matrix, the voltage ratio K V can be expressed as:

[0050]

[0051] It is easy to know that by setting a 12 = 0 in Equation (11), a constant voltage ratio independent of the load can be obtained. Substituting a 12 = 0 into Equation (9), we can get:

[0052]

[0053] In the formula, k is the coupling coefficient, and it has a relationship with the mutual inductance M, the primary coil, and the secondary coil Substituting Equation (12) into Equation (11), the voltage ratio of the series-parallel type coreless transformer based on the principle of maximizing the magnetic flux linkage can be obtained:

[0054]

[0055] It can be seen from the above formula that the voltage ratio is proportional to the square root of the ratio of the primary and secondary coils, which is consistent with the law of traditional transformers.

[0056] From Equation (13), the output power P o expression can be obtained:

[0057]

[0058] To illustrate the accuracy and feasibility of the present invention, in this embodiment, a series-parallel type coreless transformer based on the principle of maximizing the magnetic flux linkage is designed for simulation. The theoretical voltage ratio is 2:1, and the parameters of the designed coreless transformer are as follows: the effective value of the sinusoidal voltage source voltage V P = 120V, the angular frequency ω = 2π×10 5 rad / s; the inductance of the primary coil L P = 50μH; the inductance of the secondary coil L S= 6.125 μH; coupling coefficient k = 0.7; capacitance value C of the primary capacitor P = 99 nF; inductance C of the secondary coil S = 207 nF. Considering the total internal resistance of 300 mΩ for the primary coil and primary capacitor, 5 mΩ for the secondary coil internal resistance, and 20 mΩ for the secondary capacitor internal resistance, simulation is carried out using PSIM software, and the results are as Figures 2 - 6 shown.

[0059] Figure 2 is the relationship curve between the magnetic flux phase difference and the load resistance. The theoretical calculation results are in agreement with the simulation results, proving the correctness of the above text. Figure 3 is the relationship curve between the voltage transformation ratio and the load resistance. In the full load range, the voltage transformation ratio adjustment rate does not exceed 8%, which is caused by the internal resistance of the device and there is still room for optimization. Figure 4 is the relationship curve between the voltage transformation ratio and the output power. From no-load to 1.5 kW heavy load, the voltage transformation ratio adjustment rate does not exceed 4%, fully meeting the adjustment rate requirements of traditional iron-core transformers. Figure 5 is the relationship curve between the efficiency and the output power. The maximum efficiency reaches 97.68% at an output power of about 540 W, and the efficiency can reach 96.14% at the maximum output power of 1.5 kW. Figure 6 is the primary coil current I when the load resistance is equal to 50 Ω P and the secondary coil current I LS waveform diagram.

[0060] Based on the above analysis, the series-parallel type coreless transformer provided by the present invention based on the principle of maximizing magnetic flux can completely replace the traditional iron-core transformer. The advantages of the present invention are obvious and worthy of promotion.

[0061] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A series - parallel type coreless transformer based on the principle of maximum magnetic flux linkage, characterized in that: It includes a primary side circuit and a secondary side circuit; the primary side circuit includes a primary side capacitor, a primary side coil, and a sinusoidal voltage source that supplies energy to the transformer, and the sinusoidal voltage source, the primary side capacitor, and the primary side coil are connected in series; the secondary side circuit includes a secondary side capacitor, a secondary side coil, and a load resistor, and the secondary side capacitor, the secondary side coil, and the load resistor are connected in parallel; there is no iron core connection between the primary side coil and the secondary side coil; among them, the primary side capacitor and the secondary side capacitor need to meet the following maximum magnetic flux condition: ； Wherein, is the capacitance value of the primary side capacitor, is the capacitance value of the secondary side capacitor, is the inductance value of the primary side coil, is the inductance value of the secondary side coil, is the coupling coefficient between the primary side coil and the secondary side coil, is the angular frequency of the sinusoidal voltage source.

2. A series - parallel type coreless transformer based on the principle of maximum magnetic flux as claimed in claim 1, wherein: The variation law of the tangent of the phase difference of the magnetic flux satisfies the equation: ； In the formula, is the phase difference of the magnetic fluxes generated by the primary side coil and the secondary side coil, is the resistance value of the load resistor, is the secondary side impedance, , is the mutual inductance coefficient.

3. A series-parallel type coreless transformer based on the principle of maximum magnetic flux as claimed in claim 1, wherein: The voltage transformation ratio of the sine voltage source and the load resistor satisfies the relation: ； Wherein, is the voltage across the sinusoidal voltage source, is the voltage across the load resistor.

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