CN110045307B - Magnetic core material hysteresis loop measuring method - Google Patents
Magnetic core material hysteresis loop measuring method Download PDFInfo
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- CN110045307B CN110045307B CN201910450042.8A CN201910450042A CN110045307B CN 110045307 B CN110045307 B CN 110045307B CN 201910450042 A CN201910450042 A CN 201910450042A CN 110045307 B CN110045307 B CN 110045307B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
- G01R33/14—Measuring or plotting hysteresis curves
Abstract
The invention relates to a magnetic core material hysteresis loop measuring method, which provides a magnetic core material hysteresis loop measuring device and measures the magnetic core material hysteresis loop according to the following method: 1) calculating initial voltage or initial frequency required by demagnetization, and then demagnetizing the tested magnetic part; 2) after demagnetization is finished, the direct current source device charges the capacitor of the RLC oscillation circuit, and the voltage is delayed until the RLC oscillation circuit is stably disconnected; 3) the inductor, the capacitor and the resistor of the RLC oscillation circuit generate damping oscillation; 4) data of a voltage sensor and a current sensor used for measuring the voltage and the current of the measured magnetic element are collected through a data acquisition card, after filtering processing is carried out, the magnetic field intensity H and the corresponding magnetic flux density B at each moment are calculated, a group of magnetic hysteresis loops of the measured magnetic element are obtained, and the basic magnetization curve is obtained by connecting the vertexes of the magnetic hysteresis loops. The method can measure a group of limit hysteresis loops of the magnetic piece without a high-power excitation source and obtain the magnetization curve of the measured magnetic piece at the same time.
Description
Technical Field
The invention relates to the technical field of electromagnetic element design, in particular to a magnetic core material hysteresis loop measuring method.
Background
In the design of electromagnetic components, hysteresis loops of the core material are required to obtain relevant magnetic properties, such as: magnetic conductivity, remanence, coercive force, saturation magnetic density and the like. The basic principle of the existing measuring instrument for hysteresis loop or magnetic characteristics is to apply sinusoidal AC excitation to a measured magnetic part, sample the primary or secondary voltage and primary excitation current of the measured part, and use a formula
And H ═ Nxi (t)/lgRespectively calculating corresponding magnetic flux density B and magnetic field strength H to obtain hysteresis loop under excitation, and changing peak magnetic field HmThe size of the magnetic core can obtain a group of magnetic hysteresis loops with different area sizes, and the connection line of the tops of the magnetic hysteresis loops is the basic magnetization curve of the magnetic core material. Due to the limitation of the power of an excitation source, the method is only suitable for the measurement of the small-power magnetic piece with small volume and low saturation magnetic density, and a group of magnetic hysteresis loops and magnetization curves cannot be obtained simultaneously through one-time measurement. For magnetic components in large volume, high power or high magnetic density applications (such as locomotive traction transformers or inductors used in high power photovoltaic systems), the limit hysteresis loop cannot be measured due to the limitation of the power of the excitation source.
Disclosure of Invention
The invention aims to provide a magnetic core material hysteresis loop measuring method, which can measure a group of limit hysteresis loops of a magnetic piece without a high-power excitation source and obtain a magnetization curve of the measured magnetic piece at the same time.
In order to achieve the purpose, the technical scheme of the invention is as follows: the magnetic core material magnetic hysteresis loop measuring method comprises an output-adjustable direct current source device, an RLC oscillation circuit, a demagnetizing device, a voltage sensor, a current sensor, a data acquisition card and upper computer software, wherein the direct current source device is electrically connected with the RLC oscillation circuit through a switch SW1 and a current-limiting resistor R, the RLC oscillation circuit mainly comprises a switch SW3, a resistor Rs, a capacitor C and a measured magnetic element L, the demagnetizing device is electrically connected with a secondary winding of the measured magnetic element through a switch SW2, the output ends of the current sensor and the voltage sensor are electrically connected with the data acquisition card, a network interface of the data acquisition card is connected to a PC through a network, the upper computer software on the PC sends a control signal to the data acquisition card through the network, and the data acquisition card receives the control signal and controls the switch SW1, the switch is connected with a digital output port, The triggering signals of SW2 and SW3 control the working state of each switch through the triggering signals;
the magnetic core material magnetic hysteresis loop measuring device measures the magnetic hysteresis loop of the magnetic core material of the magnetic element to be measured according to the following method:
1) the upper computer software calculates initial voltage or initial frequency required by demagnetization, and then sends a trigger signal to close the switch SW2 to demagnetize the tested magnetic piece;
2) after demagnetization is finished, the switch SW2 is switched off, then the switch SW1 is controlled to be switched on, so that the direct current source device charges the capacitor C through the current-limiting resistor R, and the switch SW1 is switched off after voltage stabilization is delayed;
3) sending a trigger signal to turn on the switch SW3, and generating damping oscillation by the inductor L, the capacitor C and the resistor Rs;
4) the data acquisition card is used for acquiring data of a voltage sensor and a current sensor for measuring the voltage and the current of the measured magnetic part, filtering the acquired data, and calculating the magnetic field intensity H and the corresponding magnetic flux density B at each moment according to the formulas (1) and (2):
H＝N×i(t)/lg (1)
wherein N represents the number of turns of the primary side of the measured magnetic element, i (t) represents the current flowing through the primary side of the measured magnetic element, and lgShowing the effective magnetic path length of the magnetic member to be measured, u (t) showing the terminal voltage of the magnetic member to be measured, AeRepresenting the cross section of the magnetic core of the magnetic piece to be measured;
and obtaining a group of limit hysteresis loops of the measured magnetic element in the whole oscillation process, and connecting the vertexes of the hysteresis loops to obtain a basic magnetization curve.
Further, the resistance Rs in the RLC oscillation circuit satisfies
Wherein Ls is the inductance value of the measured magnetic element when the measured magnetic element is saturated, and the inductance value when the measured magnetic element is saturated is the minimum inductance value of the measured magnetic element.
Further, the demagnetizing device performs automatic demagnetization based on the inverter, outputs the direct-current voltage output by the adjustable direct-current source device, is inverted into a sinusoidal power supply through the inverter, and acts on a primary winding or a secondary winding of the measured magnetic part, according to the formula (3):
wherein, BmRepresents the maximum magnetic flux density, u represents the effective value of the demagnetization voltage applied to the measured magnetic element, and f represents the frequency of the demagnetization voltage applied to the measured magnetic element;
the demagnetizing device realizes demagnetization by one of the following two methods: firstly, under the condition that the demagnetization excitation voltage applied to the tested magnetic piece is not changed, the magnetic flux density is reduced by continuously increasing the demagnetization excitation frequency, and finally the magnetic flux density approaches zero; secondly, on the premise that the demagnetization excitation frequency is fixed, the duty ratio of the PWM wave output by the output controller is changed, so that the voltage amplitude of the sine wave generated by inversion (namely, the demagnetization excitation applied to the tested magnetic part) is continuously reduced until the voltage output by the inverter is zero, and automatic demagnetization is realized.
Furthermore, a plurality of voltage sensors and current sensors with different ranges are adopted for measurement, and data measured by the voltage sensors and the current sensors with the different ranges are fused into required voltage and current data, so that high-precision measurement data are provided for measurement of the hysteresis loop.
Further, the voltage sensor is composed of a voltage dividing circuit including resistors R0 and R1 connected in series and capacitors C0 and C1 connected in parallel to the resistors R0 and R1, respectively, and when the signal frequency of the induced voltage is low, the induced voltage u is calculated using equation (4), and when the signal frequency of the induced voltage is high, the induced voltage u is calculated using equation (5):
u＝u0×(R0+R1)/R0 (4)
wherein u0 is the divided voltage of the resistor R0 and the sampling voltage input to the data acquisition card, and 1/j ω C0 and 1/j ω C1 are the impedances of the capacitors C0 and C1 respectively.
Further, switches SW2 and SW3 are both triacs, and switch SW1 is a triac.
Further, the upper computer software calculates the initial voltage or the initial frequency required by demagnetization according to the size, the number of turns and the saturation flux density of the magnetic piece to be detected.
Compared with the prior art, the invention has the beneficial effects that: the method can measure a group of limit hysteresis loops of the magnetic element without a high-power excitation source and simultaneously obtain the magnetization curve of the magnetic element to be measured, and has strong practicability and wide application prospect.
Drawings
FIG. 1 is a schematic diagram showing the structure of a hysteresis loop measuring apparatus for a magnetic core material according to an embodiment of the present invention.
Fig. 2 is a graph of the hysteresis loop and magnetization obtained in the example of the present invention.
Fig. 3 is a schematic diagram of the configuration of a voltage sensor in the embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the figures and the embodiments.
The invention discloses a magnetic core material hysteresis loop measuring method, and provides a magnetic core material hysteresis loop measuring device, which comprises an output-adjustable direct current source device, an RLC oscillation circuit, a demagnetizing device, a voltage sensor, a current sensor, a data acquisition card and upper computer software as shown in figure 1. The direct current source device is electrically connected with an RLC oscillation circuit through a switch SW1 and a current-limiting resistor R, the RLC oscillation circuit is mainly composed of a switch SW3, a resistor Rs, a capacitor C and a winding on a tested magnetic piece L, a demagnetizing device is electrically connected with a secondary winding of the tested magnetic piece through a switch SW2, the output ends of a current sensor and a voltage sensor are electrically connected with a data acquisition card, a network interface of the data acquisition card is connected to a PC through a network cable, upper computer software on the PC sends control signals to the data acquisition card through a network, and the data acquisition card controls the trigger signals of the switches SW1, SW2 and SW3 connected to a digital output port through a digital output port after receiving the control signals and controls the working state of each switch through the trigger signals. The switches SW2 and SW3 are both triacs, and the switch SW1 is a one-way thyristor.
The magnetic core material magnetic hysteresis loop measuring device measures the magnetic hysteresis loop of the magnetic core material of the magnetic element to be measured according to the following method:
1) and the upper computer software calculates initial voltage or initial frequency required by demagnetization according to the magnetic core sectional area, the number of turns and the saturation flux density of the magnetic piece to be detected, and then sends a trigger signal to close the switch SW2 to demagnetize the magnetic piece to be detected. This makes the magnetic hysteresis loop of the magnetic piece to be measured start to measure from the position where the magnetic field intensity and the magnetic flux density are zero points.
2) After demagnetization is finished, the switch SW2 is opened, then the switch SW1 is controlled to be closed, so that the direct current source device charges the capacitor C through the current limiting resistor R, and after the voltage is delayed to be stable, the SW1 is opened.
3) The trigger signal is sent to turn on the switch SW3, and the inductor L, the capacitor C and the resistor Rs generate ringing.
4) The data acquisition card is used for acquiring data of a voltage sensor and a current sensor for measuring the voltage and the current of the measured magnetic part, namely sampling the exciting current of a primary side and the voltage of the primary side or a secondary side, filtering the acquired data, and then calculating the magnetic field intensity H and the corresponding magnetic flux density B at each moment according to the formulas (1) and (2):
H＝N×i(t)/lg (1)
wherein N represents the number of turns of the primary side of the measured magnetic element, i (t) represents the current flowing through the primary side of the measured magnetic element, and lgRepresenting the effective path length of the magnetic member under test, u (t) tableIndicating the terminal voltage of the magnetic member to be measured, AeThe cross-sectional area of the magnetic member to be measured is shown.
And (3) drawing to obtain a group of limit hysteresis loops of the measured magnetic piece in the whole oscillation process as shown in FIG. 2, and connecting the vertexes of the hysteresis loops to obtain a basic magnetization curve.
Wherein a resistance Rs in the RLC oscillation circuit satisfies
Wherein Ls is the inductance value of the measured magnetic element when the measured magnetic element is saturated, and the inductance value when the measured magnetic element is saturated is the minimum inductance value of the measured magnetic element. If the resistance in the RLC second-order circuit can satisfy the formula
The circuit must oscillate when the inductance is greater than Ls.
In this embodiment, the demagnetizing device performs automatic demagnetization based on an inverter, outputs a dc voltage output by an adjustable dc source device, and inverts the dc voltage into a sinusoidal power supply through the inverter to act on a primary winding or a secondary winding of the magnetic component to be measured, according to equation (3):
wherein, BmAnd f represents the frequency of the demagnetization voltage applied to the measured magnetic element.
The demagnetizing device realizes demagnetization by one of the following two methods: firstly, under the condition that the demagnetization excitation voltage applied to the tested magnetic piece is not changed, the magnetic flux density is reduced by continuously increasing the demagnetization excitation frequency, and finally the magnetic flux density approaches zero; secondly, on the premise that the demagnetization excitation frequency is fixed, the duty ratio of the PWM wave output by the output controller is changed, so that the voltage amplitude of the sine wave generated by inversion (namely, the demagnetization excitation applied to the tested magnetic part) is continuously reduced until the voltage output by the inverter is zero, and automatic demagnetization is realized.
The bandwidth of the voltage sensor and the bandwidth of the current sensor are required to meet the measurement requirement, and the sampled induced voltage and the excitation current range are large, so the invention adopts the voltage sensors and the current sensors with a plurality of different ranges to measure, fuses the data measured by the voltage sensors and the current sensors with a plurality of different ranges into the required voltage and current data, and provides high-precision measurement data for the measurement of the hysteresis loop. In this embodiment, as shown in fig. 3, the voltage sensor is formed by a voltage dividing circuit including resistors R0 and R1 connected in series and capacitors C0 and C1 connected in parallel to R0 and R1, respectively, and when the signal frequency of the induced voltage is low, the induced voltage u is calculated by using equation (4), and when the signal frequency of the induced voltage is high, the resistors R0 and R1 at this time take the influence of stray inductance into consideration, and the induced voltage u is calculated by using equation (5):
u＝u0×(R0+R1)/R0 (4)
wherein u0 is the divided voltage of the resistor R0 and the sampling voltage input to the data acquisition card, and 1/j ω C0 and 1/j ω C1 are the impedances of the capacitors C0 and C1 respectively.
The above are preferred embodiments of the present invention, and all changes made according to the technical scheme of the present invention that produce functional effects do not exceed the scope of the technical scheme of the present invention belong to the protection scope of the present invention.
Claims (6)
1. A magnetic core material magnetic hysteresis loop measuring method is characterized by providing a magnetic core material magnetic hysteresis loop measuring device, which comprises a direct current source device with adjustable output, an RLC oscillation circuit, a demagnetizing device, a voltage sensor, a current sensor, a data acquisition card and an upper computer system, wherein the direct current source device is electrically connected with the RLC oscillation circuit through a switch SW1 and a current-limiting resistor R, the RLC oscillation circuit mainly comprises a switch SW3, a resistor Rs, a capacitor C and a measured magnetic element L, the demagnetizing device is electrically connected with a secondary side winding of the measured magnetic element through a switch SW2, the output ends of the current sensor and the voltage sensor are electrically connected with the data acquisition card, a network interface of the data acquisition card is connected to a PC through a network, the upper computer software on the PC sends a control signal to the data acquisition card through a network, and after the data acquisition card receives the control signal, the digital output port on the acquisition card is used for controlling the trigger signals of the switches SW1, SW2 and SW3 connected with the digital output port, and the working state of each switch is controlled by the trigger signals;
the demagnetizing device performs automatic demagnetization based on the inverter, outputs direct current voltage output by the adjustable direct current source device, is inverted into a sinusoidal power supply by the inverter and acts on a primary winding or a secondary winding of the measured magnetic part, and is characterized in that the demagnetizing device performs automatic demagnetization based on the inverter according to the formula (3):
wherein, BmRepresents the maximum magnetic flux density, u represents the effective value of the demagnetization voltage applied to the measured magnetic element, and f represents the frequency of the demagnetization voltage applied to the measured magnetic element;
the demagnetizing device realizes demagnetization by one of the following two methods: firstly, under the condition that the demagnetization voltage applied on the tested magnetic piece is not changed, the magnetic flux density is reduced by continuously increasing the frequency of the demagnetization voltage, and finally the magnetic flux density approaches zero; secondly, on the premise that the frequency of the demagnetization voltage is fixed, the duty ratio of PWM waves output by the output controller is changed, so that sine waveforms generated by inversion, namely the voltage amplitude of the demagnetization voltage applied to the tested magnetic part is continuously reduced until the demagnetization voltage output by the inverter is zero, and automatic demagnetization is realized;
the magnetic core material magnetic hysteresis loop measuring device measures the magnetic hysteresis loop of the magnetic core material of the magnetic element to be measured according to the following method:
1) the upper computer software calculates initial voltage or initial frequency required by demagnetization, and then sends a trigger signal to close the switch SW2 to demagnetize the tested magnetic piece;
2) after demagnetization is finished, the switch SW2 is switched off, then the switch SW1 is controlled to be switched on, so that the direct current source device charges the capacitor C through the current-limiting resistor R, and the switch SW1 is switched off after voltage stabilization is delayed;
3) sending a trigger signal to enable the switch SW3 to be conducted, and at the moment, generating damping oscillation by the magnetic element L to be tested, the capacitor C and the resistor Rs;
4) the data acquisition card is used for acquiring data of a voltage sensor and a current sensor for measuring the voltage and the current of the measured magnetic part, filtering the acquired data, and then calculating the magnetic field intensity H and the corresponding magnetic flux density B at each moment according to the formulas (1) and (2):
H＝N×i(t)/lg (1)
wherein N represents the number of turns of the primary side of the measured magnetic element, i (t) represents the current flowing through the primary side of the measured magnetic element, and lgShowing the effective magnetic path length of the magnetic member to be measured, u (t) showing the terminal voltage of the magnetic member to be measured, AeRepresenting the cross section of the magnetic core of the magnetic piece to be measured;
and obtaining a group of limit hysteresis loops of the measured magnetic element in the whole oscillation process, and connecting the vertexes of the hysteresis loops to obtain a basic magnetization curve.
2. The method as claimed in claim 1, wherein the resistance Rs in the RLC oscillator circuit satisfies the requirement
Wherein Ls is the inductance value of the measured magnetic element when the measured magnetic element is saturated, and the inductance value when the measured magnetic element is saturated is the minimum inductance value of the measured magnetic element.
3. The method as claimed in claim 1, wherein a plurality of voltage sensors and current sensors with different ranges are used for measurement, and the data measured by the voltage sensors and the current sensors with different ranges are combined into the required voltage and current data, so as to provide high-precision measurement data for hysteresis loop measurement.
4. The method as claimed in claim 1, wherein said voltage sensor is formed by a voltage divider circuit including a resistor R0 and a resistor R1 connected in series, and a capacitor C0 connected in parallel to the resistor R0 and a capacitor C1 connected in parallel to the resistor R1, wherein the induced voltage u is calculated by using formula (4) when the signal frequency of the induced voltage is low, and the induced voltage u is calculated by using formula (5) when the signal frequency of the induced voltage is high:
u＝u0×(R0+R1)/R0 (4)
wherein u0 is the divided voltage of the resistor R0 and the sampling voltage input to the data acquisition card, and 1/j ω C0 and 1/j ω C1 are the impedances of the capacitor C0 and the capacitor C1 respectively.
5. The method as claimed in claim 1, wherein switches SW2 and SW3 are both thyristors, and switch SW1 is a triac.
6. The method as claimed in claim 1, wherein the upper computer software calculates the initial voltage or initial frequency required for demagnetization according to the core cross-sectional area, the number of turns and the saturation flux density of the magnetic member to be measured.
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