CN109102999B - Method for selecting magnetic core according to structure size - Google Patents

Method for selecting magnetic core according to structure size Download PDF

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CN109102999B
CN109102999B CN201810965860.7A CN201810965860A CN109102999B CN 109102999 B CN109102999 B CN 109102999B CN 201810965860 A CN201810965860 A CN 201810965860A CN 109102999 B CN109102999 B CN 109102999B
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magnetic core
formula
transformer
winding
turns
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CN109102999A (en
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刘飞翠
冉瑞刚
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SHENZHEN SIKES ELECTRIC Co.,Ltd.
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/30—Circuit design
    • G06F30/36—Circuit design at the analogue level
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
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  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Manufacturing & Machinery (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Coils Of Transformers For General Uses (AREA)

Abstract

The invention discloses a method for selecting a magnetic core by a structural size, which is characterized in that an expression of the structural size Kg of the magnetic core is deduced step by taking winding loss as a design parameter, wherein,
Figure DDA0001774957010000011
resistivity, copper 1.724 x 10 at 20 ℃‑6(Ω/cm2)、P0Output power (W) of the transformer: duty cycle, P, of the circuit topologyCUTransformer total copper wire loss (W), η: transformer operating efficiency, Bm: magnetic induction (T), f) of the transformer during operation: the working frequency (Hz) can be suitable for switching power supply transformers with various topological structures, and then the magnetic core with corresponding specification can be selected corresponding to the inherent structural size coefficient Kg of the magnetic core. The design of a rough transformer which depends on experience is avoided, and the calculation is more refined.

Description

Method for selecting magnetic core according to structure size
Technical Field
The invention relates to the technical field of transformers, in particular to a method for selecting a magnetic core according to the structure size.
Background
A Transformer (Transformer) is a device that changes an ac voltage using an electromagnetic induction principle, and when a Transformer engineer initially designs a product, it is usually considered to select a corresponding magnetic core according to a topology structure and a load capacity of a circuit, and usually, most of the magnetic cores are selected according to experience or an existing power table, which is limited, and when a capacity or a required parameter exceeds the experience and the power table, it is not easy to select a relatively appropriate magnetic core.
Therefore, further research into a method of selecting a magnetic core is necessary.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method for selecting a magnetic core according to the structural size, which is applicable to switching power supply transformers with various topological structures. The method can quickly select the magnetic core with corresponding power according to related original circuit parameters.
Firstly, calculating the required size coefficient Kg of the magnetic core structure according to the topological parameters of each circuit,
Figure BDA0001774951000000011
and then selecting the magnetic core with the corresponding specification corresponding to the inherent structural size coefficient Kg of the magnetic core.
The derivation steps of the magnetic core structure size factor Kg are as follows:
as is known, a transformer has two primary and secondary windings, and its loss is expressed as:
PCU＝IP 2RP+IS 2RS(W)-----------------------------------(1)
in the formula, PCUCopper wire loss (W); i isP、ISA current (A) through the primary and secondary windings; rP、RSResistance (omega) of the primary and secondary windings.
Resistance of winding
Figure BDA0001774951000000012
Wherein rho is resistivity, and the copper is 1.724 x 10 at 20 DEG C-6(Ω/cm2)；l0Winding average turn length (cm); l: total length (m); a. theWA lead sectional area (cm); n: the number of winding turns.
As a result of this, it is possible to,
Figure BDA0001774951000000021
wherein K is the window duty factor; wa magnetic core Window area (cm)2)。
Substituting formula (3) into formula (2) to obtain:
Figure BDA0001774951000000022
setting a half window for each of the primary winding and the secondary winding, and calculating the copper loss formula of the primary winding and the secondary winding as follows:
Figure BDA0001774951000000023
the position of two parameters of the transformation formula (5),
Figure BDA0001774951000000024
the relationship that the ampere turns of the primary and the secondary of the transformer are equal, and the relationship between the effective value of the current and the peak value are as follows:
Figure BDA0001774951000000025
in the formula, NP、NS: primary and secondary winding turns; : duty cycle
Substituting the formula (7) into the formula (6),
Figure BDA0001774951000000026
according to faraday's law, the expression for a magnetic core is,
Figure BDA0001774951000000028
wherein E is a voltage (V); t is ton: on-time (μ s); n: the number of winding turns; bm: magnetic induction (T); f: frequency (Hz).
The structural dimension Kg of the core is (intrinsic parameters of the core),
Figure BDA0001774951000000027
wherein Kg is the structural size (cm) of the magnetic core5) (ii) a Ae: cross sectional area (cm) of magnetic core2)。
The formula (8) and the formula (9) are replaced by the formula (10) to be simplified,
Figure BDA0001774951000000031
output power P of transformer0It can be written as follows,
P0＝EIPη(W)-------------------------------------(12)
wherein η is efficiency.
Substituting the formula (12) into the formula (11) to finally obtain the relation between the structure size of the magnetic core and each parameter of the circuit as follows:
Figure BDA0001774951000000032
the invention has the beneficial effects that: the invention provides a method for selecting a magnetic core according to the structure size, which is characterized in that a required magnetic core structure size coefficient Kg is calculated according to each circuit topological parameter, and then the magnetic core with a corresponding specification can be selected according to the inherent structure size coefficient Kg of the magnetic core. The design of a rough transformer which depends on experience is avoided, and the calculation is more refined.
Detailed Description
The invention is further described with reference to the following examples.
Example of the implementation
In the existing single-ended flyback topology, the output power Po is 70W, and the minimum direct-current voltage U is inputMin230V, duty cycleMaxThe operating frequency f is 22kHz, the transformer efficiency η is 0.85, B is 0.11T, the window utilization factor K is 0.3, the copper loss is 4.6W, and the secondary output is 24V/2.9A. The corresponding core is selected by trial.
And substituting the corresponding parameters into the formula (13) to obtain the required magnetic core structure size coefficient as follows:
Figure BDA0001774951000000033
inquiring the data of the magnetic core manufacturer EI30, the window area Wa is window width, window height is 4.4, 16.3 is 0.72cm2The cross-sectional area Ae of the core is 1.1 × 1.1 ═ 1.21cm2Average turn length of winding l0The obtained data was substituted into formula (10) at 6.2cm, and the intrinsic parameters of the magnetic core were determined
Figure BDA0001774951000000034
An EI30 magnetic core may be selected.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims (1)

1. A method for selecting a magnetic core according to the structure size is characterized in that the magnetic core selection method comprises the following steps: firstly, calculating the required size coefficient Kg of the magnetic core structure according to the topological parameters of each circuit,
Figure FDA0002723260140000011
then selecting a magnetic core with corresponding specification corresponding to the inherent structural size coefficient Kg of the magnetic core, wherein rho is resistivity, and copper is 1.724 x 10 at 20 DEG C-6(Ω/cm2)、P0Output power (W) of the transformer: duty cycle, P, of the circuit topologyCUTransformer total copper wire loss (W), η: transformer operating efficiency, Bm: magnetic induction (T), f) of the transformer during operation: operating frequency (Hz);
the derivation steps of the magnetic core structure size factor Kg are as follows:
the winding of the transformer comprises: the loss of the two windings of the primary winding and the secondary winding is expressed as follows:
PCU＝IP 2RP+IS 2RS(W)-----------------------------------(1)
in the formula, PCUTotal copper wire loss (W) of the transformer; i isP、ISIs the current (a) through the primary and secondary windings, respectively; rP、RSResistance (Ω) of the primary winding and the secondary winding, respectively;
resistance of winding
Figure FDA0002723260140000012
Wherein rho is resistivity, and the copper is 1.724 x 10 at 20 DEG C-6(Ω/cm2)；l0Winding average turn length (cm); l: total winding wire length (m); a. theWThe sectional area (cm) of the winding wire; n: the number of winding turns;
as a result of this, it is possible to,
Figure FDA0002723260140000013
where K is the core window duty factor (net utilization); wa magnetic core Window area (cm)2)；
Substituting formula (3) into formula (2) to obtain:
Figure FDA0002723260140000014
when the primary winding and the secondary winding respectively occupy half of the window, the formula for calculating the copper loss of the primary winding and the secondary winding is as follows:
Figure FDA0002723260140000015
the position of two parameters of the transformation formula (5),
Figure FDA0002723260140000021
the ampere-turns of a primary winding and the ampere-turns of a secondary winding of the transformer are equal, and the current effective value and the peak value are equal:
Figure FDA0002723260140000022
in the formula, NP、NS: the number of turns of the primary winding and the secondary winding; : duty cycle of circuit topology
Substituting the formula (7) into the formula (6),
Figure FDA0002723260140000023
according to faraday's law, the expression for a magnetic core is,
Figure FDA0002723260140000024
wherein E is a voltage (V); t is ton: on-time (μ s); n: the number of winding turns; bm: magnetic induction (T); f: frequency (Hz);
the structural dimension Kg of the core is (intrinsic parameters of the core),
Figure FDA0002723260140000025
wherein Kg is the structural size (cm) of the magnetic core5) (ii) a Ae: cross sectional area (cm) of magnetic core2)；
The formula (8) and the formula (9) are replaced by the formula (10) to be simplified,
Figure FDA0002723260140000026
output power P of transformer0Can be written as:
P0＝EIPη(W)-------------------------------------(12)
in the formula, eta is the working efficiency of the transformer;
substituting the formula (12) into the formula (11) to finally obtain the relation between the structure size of the magnetic core and each parameter of the circuit as follows:
Figure FDA0002723260140000027
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CN105060872A (en) * 2015-07-24 2015-11-18 天长市中德电子有限公司 High-impedance low-power-consumption soft magnetic ferrite material and preparation method thereof
CN107735843A (en) * 2014-11-25 2018-02-23 艾普伦 For the magnetic core of the infrastructure component of power transformer magnetic core, including the infrastructure component, the method for the magnetic core and the transformer including the magnetic core are manufactured

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CN101692397A (en) * 2009-08-25 2010-04-07 中国电子科技集团公司第十四研究所 Novel high power magnetic integrated components and preparation method thereof
CN202167993U (en) * 2011-08-15 2012-03-14 天津理工大学 Phase-shifted full-bridge switching power supply converter with lossless snubber circuit
CN104317979B (en) * 2014-08-20 2018-01-30 江苏科技大学 High frequency high voltage transformer design optimization method based on genetic algorithm
CN104410363A (en) * 2014-12-03 2015-03-11 黄河科技学院 Solar battery simulator
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CN107735843A (en) * 2014-11-25 2018-02-23 艾普伦 For the magnetic core of the infrastructure component of power transformer magnetic core, including the infrastructure component, the method for the magnetic core and the transformer including the magnetic core are manufactured
CN105060872A (en) * 2015-07-24 2015-11-18 天长市中德电子有限公司 High-impedance low-power-consumption soft magnetic ferrite material and preparation method thereof

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