CN101788512B - Device and method for measuring heat effect of magnetic material in alternating magnetic field - Google Patents

Abstract

The invention relates to a device and method for measuring the thermal effect of magnetic materials in an alternating magnetic field. The device includes an alternating magnetic field generating device, a constant temperature device and a temperature measuring element. The method is to place a sample to be tested in a sample cup filled with a measuring medium In the process, adjust the temperature of the measuring medium to a predetermined value, put it in a constant temperature chamber, and after the thermal balance is stable, pass an alternating current, apply an alternating magnetic field, and use a temperature measuring element to monitor the temperature of the measuring medium in the sample cup within a certain time interval The heating power of the sample to be tested can be determined. The measuring device and method have the characteristics of continuously adjustable alternating magnetic field intensity, adjustable magnetic field alternating frequency and measuring temperature, and simple structure. The screening of magnetic materials for ice coating is of great significance.

Description

Device and method for measuring thermal effect of magnetic material in alternating magnetic field

technical field

The invention belongs to the field of thermal effect measurement, in particular to a device and method for measuring the thermal effect of magnetic materials in an alternating magnetic field. Screening of magnetic materials for icing.

Background technique

Line icing is one of the natural disasters that seriously threaten the safe operation of power systems. According to incomplete statistics, from December 1954 to the end of 2006, there were more than 1,000 various icing disasters in power grids (including transmission lines and substations) with a voltage level of 6,000 volts and above in various parts of China, of which 35,000 There are more than 86 icing disasters with a large scale of 10 volts or above and causing serious faults in the power grid. Especially at the beginning of 2008, the most serious freezing disaster occurred in most parts of southern my country and the eastern part of Northwest China, which caused serious damage to the power grid. The direct economic loss exceeded 60 billion yuan, and the indirect loss reached more than 300 billion yuan. Therefore, how to prevent transmission lines from icing has become an important issue to ensure the safe operation of power systems.

Extensive and in-depth research has been carried out at home and abroad on the deicing methods of ice-covered lines, and a variety of deicing methods with different mechanisms have emerged. Among them, the low Curie point magnetic material deicing method has attracted widespread attention due to its excellent characteristics focus on. By selecting a magnetic material with a lower Curie temperature, it is coated on the surface of the power transmission wire. When the ambient temperature is lower than the Curie temperature of the magnetic material, the material is in a ferromagnetic state. Due to the action of the alternating magnetic field, the magnetic material has a thermal effect due to hysteresis loss, eddy current loss and residual loss. This part of the energy loss is the fusion The main source of energy needed by ice. When the ambient temperature is high, the magnetic material is in a paramagnetic state, and the loss and heat generation is significantly reduced, thereby reducing unnecessary energy loss.

For practical applications, two indicators are mainly concerned in the process of selecting anti-icing magnetic materials, one is the Curie temperature of the magnetic material, and the other is the thermal effect of the magnetic material in the alternating magnetic field. The measurement of Curie temperature can be done with existing equipment. However, how to evaluate the thermal effect of magnetic materials in alternating magnetic fields, there is no unified test method and ready-made test means. Therefore, this patent proposes a magnetic material in the Method and device for measuring thermal effect in alternating magnetic field.

Contents of the invention

In order to overcome the defect that the thermal effect of magnetic materials in the alternating magnetic field cannot be measured in the prior art, the present invention proposes a device and method for measuring the thermal effect of magnetic materials in the alternating magnetic field based on the temperature rise method. Magnetic field and ambient temperature change, measure the calorific value of magnetic materials in a certain intensity alternating magnetic field, and use it as an index to judge the ice-melting ability of magnetic materials, and provide a basis for the screening of anti-icing magnetic materials.

One of the objectives of the present invention is to provide a device for measuring the thermal effect of magnetic materials in an alternating magnetic field, which includes an alternating magnetic field generating device, a constant temperature device and a temperature measuring element. The sample cup is equipped with a measuring medium; the alternating magnetic field generating device passes an alternating current to the sample to be tested in the constant temperature device and applies an alternating magnetic field; the temperature measuring element extends into the constant temperature In the device, it is used to monitor the temperature change of the measuring medium.

1. Part of the alternating magnetic field generator:

The alternating magnetic field generating device includes an alternating power supply, an alternating current meter, a rheostat and a solenoid, one outlet end of the alternating power supply is connected with an alternating current meter and a rheostat, and the other outlet end of the alternating power supply is connected to the rheostat. Connect the solenoid between the outgoing ends.

The alternating length measurement generating device uses a solenoid for magnetic field loading, which is specifically divided into the following two types:

(1) The solenoid uses a long straight solenoid to load the magnetic field

The size parameters of the long straight solenoid are shown in Figure 1, and the enamelled copper wire is used for single-layer dense winding. When the ratio of the length to diameter of the solenoid (hereinafter referred to as the aspect ratio) L/2r is greater than 2, the axial magnetic field in the solenoid is uniform within a certain range in the central area, which can meet the requirements of different shapes and sizes. Sample measurement requirements.

When using the long straight solenoid magnetic field loading method, in order to reduce the influence of the demagnetization field of the sample itself, it is preferable to use a cylindrical sample to be tested with a large aspect ratio and it is best placed in the central part of the long straight solenoid axis , it is specially stipulated that the aspect ratio L/D of the sample to be tested is > 10, and the longitudinal axis of the sample to be tested is kept parallel to the magnetic field of the long straight solenoid during the measurement process.

(2) The solenoid uses a ring solenoid to load the magnetic field

The size parameters of the annular solenoid are shown in Figure 2, and the enamelled copper wire is used for single-layer dense winding, preferably an annular sample to be tested, and the annular solenoid is uniformly and densely wound on the annular sample to be tested. Since the magnetic circuit of the annular sample to be tested is closed, there is no influence of the demagnetizing field. In order to ensure that the magnetization field is evenly distributed along the radial direction of the sample to be tested, the ratio of the radial thickness to the average diameter of the ring is required to be as small as possible, and the ratio of the radial thickness h to the average diameter of the annular sample to be tested is preferably not greater than 1/6 .

For the above two magnetic field loading methods, the intensity of the alternating magnetic field changes with the intensity of the alternating current in the solenoid. By adjusting the intensity of the alternating current, the intensity of the alternating magnetic field can be adjusted to meet the needs of thermal effect measurement under different magnetic field intensities. The changing frequency of the alternating magnetic field depends on the frequency of the alternating current. By changing the frequency of the alternating current, the alternating frequency of the magnetic field can be changed to meet the measurement needs from power frequency to high frequency. For the magnetic materials used for anti-icing of transmission wires, special attention should be paid to the thermal effect under the power frequency alternating magnetic field.

2. The part of constant temperature device:

The constant temperature device includes a constant temperature chamber with a sample cup inside and a circulation device, and the circulation device is connected with the constant temperature chamber. The thermostatic chamber includes a main body composed of a thermal insulation layer, and a cooling channel is provided outside the thermal insulation layer. The circulation device includes a circulation medium tank filled with a circulation medium and a circulation pump. The circulation medium tank passes through the water inlet pipe and the water outlet pipe. It communicates with the cooling channel of the thermostatic chamber, and the water inlet pipe is provided with a circulation pump.

The thermostatic chamber is equipped with a sample cup, and the temperature in the thermostatic chamber can be controlled by adjusting the temperature of the circulating medium in the circulation device to provide the temperature conditions required for the measurement. The constant temperature range of the thermostatic chamber can be changed between 0°C and 50°C.

When measuring, first weigh a certain mass of liquid medium with known specific heat and put it into the sample cup, and immerse the sample to be tested in it as a whole, and then put them together in the constant temperature room. After the heat balance is stable and the required temperature is reached, that is, An alternating magnetic field can be applied to measure thermal effects.

The liquid medium with known specific heat mentioned here can be pure water, absolute ethanol, kerosene, castor oil and other organic or inorganic liquids.

3. Temperature measuring element:

This measuring device is mainly based on the basic principle of the temperature rise method to measure the thermal effect. The loss and heat generation of the sample to be tested in the alternating magnetic field causes the temperature of the measuring medium in the sample cup to rise. The temperature change within a certain time interval is measured by the temperature measuring element, that is The heating power of the sample material to be tested can be determined.

Another object of the present invention is to provide a method for measuring the thermal effect of a magnetic material in an alternating magnetic field, comprising the steps of:

A) Place the sample to be tested in a sample cup filled with a measuring medium, adjust the temperature of the measuring medium to a predetermined value, and then put it in a thermostatic chamber, and at the same time, adjust the temperature of the circulating medium to a predetermined value (here the predetermined value It is equal to the preset value in "adjusting the temperature of the measuring medium to the preset value" mentioned above), and the circulation device is turned on to keep the thermal balance inside and outside the heat insulation layer of the thermostatic chamber;

B) After the thermal balance is stable, turn on the alternating current and apply the alternating magnetic field to the solenoid to adjust the current to the required value;

C) Using the temperature measuring element to monitor the temperature change of the measuring medium in the sample cup within a certain time interval, so as to determine the heating power of the sample to be tested.

When the solenoid adopts a long straight solenoid, the specific calculation method for measuring the heating power of the sample to be tested is as follows:

Considering the sample to be tested, the sample cup and the measuring medium as a whole, the total thermal effect can be obtained by formula (1) as

Among them, m _cup -sample cup mass, unit g, c _cup -sample cup wall material specific heat, unit J/g℃

m- _sample -sample mass, unit g, c- _sample -sample specific heat, unit J/g℃

m _medium - the mass of the measuring medium, in g, c _medium - the specific heat of the measuring medium, in J/g°C

T ₀ - the initial temperature of the system, in °C, T - the final temperature of the system, in °C

t ₀ - measurement start time, unit s, t - measurement end time, unit s

In order to facilitate the comparison of the properties of different magnetic materials, it is stipulated that the heating power per unit mass is uniformly used, referred to as the single heating value, and the heating power of the sample to be tested can be divided by its mass by formula (2).

This is the single calorific value of the sample to be tested in a certain intensity alternating magnetic field.

When the solenoid adopts an annular solenoid, the specific calculation method for measuring the heating power of the sample to be tested is as follows:

Considering the sample cup, the sample to be tested, the copper wire of the toroidal coil and the measuring medium as a whole, the total thermal effect can be obtained by formula (3) as

Among them, m _cup -sample cup mass, unit g, c _cup -sample cup wall material specific heat, unit J/g℃

m- _sample -sample mass, unit g, c- _sample -sample specific heat, unit J/g℃

m _medium - the mass of the measuring medium, in g, c _medium - the specific heat of the measuring medium, in J/g°C

m _copper -the mass of copper wire used in the ring coil, g, c _copper -copper specific heat, unit J/g℃

T ₀ - the initial temperature of the system, in °C, T - the final temperature of the system, in °C

t ₀ - measurement start time, unit s, t - measurement end time, unit s

Let the mass of the sample to be tested in the formula (3) be zero, that is, m _sample = 0, then the calculation formula (4) of the thermal effect of the empty coil can be obtained

Therefore, using formula (5), the heating power of the sample to be tested can be obtained as

P _sample = P _total - P _coil (W) (5)

In order to facilitate the comparison of the properties of different magnetic materials, it is stipulated that the heating power per unit mass is uniformly used, referred to as the single-weight heating value, and the heating power of the sample to be tested is divided by its mass by formula (6).

This is the single calorific value of the sample to be tested in a certain intensity alternating magnetic field.

The measuring medium adopts pure water, absolute ethanol, kerosene, castor oil and other organic or inorganic liquids.

The beneficial effects of the present invention are: the present invention provides a simple and feasible method and measuring device for evaluating the thermal effect of the anti-icing magnetic material of the transmission wire in the alternating magnetic field. Adjustable, adjustable magnetic field alternating frequency, adjustable measurement temperature and simple structure, the operation is very simple, and the measurement data is true and reliable, the repeatability is good, and the operation cost is low, which is of great significance for the screening of anti-icing magnetic materials .

Description of drawings

Fig. 1 is a schematic diagram of the structure of a long straight solenoid;

Fig. 2 is a structural schematic diagram of an annular sample to be tested and an annular solenoid wound on the annular sample to be tested;

Fig. 3 is a schematic diagram of the test device of the present invention (long straight solenoid plus field);

Fig. 4 is a schematic diagram of the testing device of the present invention (annular solenoid adds field);

Among them, 1-alternating power supply, 2-AC ammeter, 3-varistor, 4-long straight solenoid, 5-circulating medium, 6-cylindrical sample to be tested, 7-measuring medium, 8-sample cup, 9- Sample cup cover, 10-heat insulation layer, 11-temperature measuring element, 12-circulating medium box, 13-circulating pump, 14-cooling channel, 15-water inlet pipe, 16-water outlet pipe, 17-ring solenoid, 18- Ring the sample to be tested.

Detailed ways

The measuring device and measuring method of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Example 1

As shown in FIG. 3 , the sample to be tested in this example is a cylindrical sample to be tested 6 , and the solenoid is a long straight solenoid 4 .

The measuring device described in this example is mainly composed of an alternating magnetic field generating device, a constant temperature device and a temperature measuring element 11 . The alternating magnetic field generating system includes an AC power source 1, an AC ammeter 2, a rheostat 3 and a long straight solenoid 4. The AC power source 1 is connected to a 220V voltage, and one outlet end of the AC power source 1 is connected to an AC ammeter 2 and a rheostat 3 in sequence. A long straight solenoid 4 is connected between the other outlet end of the power supply 1 and the outlet end of the rheostat 3, and the long straight solenoid is evenly wound around the outside of the thermostatic chamber, and the AC ammeter 2 is used to observe the current situation in the device in real time , the rheostat 3 is used to change the current intensity in the circuit; the constant temperature system includes a thermostatic chamber and a circulation device, the thermostatic chamber includes a main body made of a thermal insulation layer 10 (such as polyurethane foam), and the outside of the thermal insulation layer is provided with a cooling channel 14; the circulation device includes A circulating medium tank 12 and a circulating pump 13 filled with circulating medium, the circulating medium tank 12 is connected to the bottom inlet of the cooling channel 14 through the water inlet pipe 15, and the circulating medium tank 12 is connected to the top water outlet of the cooling channel 14 through the water outlet pipe 16 , The water inlet pipe 15 is provided with a circulation pump 13 . The cylindrical sample to be tested 6 is placed in a sample cup 8 equipped with a measuring medium 7. The sample cup 8 is provided with a sample cup cover 9 for sealing, and then the sealed sample cup is put into a thermostatic chamber composed of a heat insulating layer 10 as a whole. Middle; two temperature measuring elements 11 are used, one end of the two temperature measuring elements is inserted into the sample cup 8 and the cooling channel 14 respectively, and the other end is exposed in the air, and the two temperature measuring elements are respectively used to measure the measuring medium 7 in the sample cup temperature and the temperature of the circulating medium 5 in the cooling channel; the temperature measuring element 11 can be a precision thermometer or a temperature sensor and its display instrument, and the measuring medium 7 can be organic or inorganic liquids such as pure water, absolute ethanol, kerosene, castor oil, etc. The circulation medium 5 can adopt liquids such as water, liquid ammonia or liquid nitrogen.

The specific method of measurement is:

When measuring, at first weigh the measurement medium 7 of known specific heat of a certain mass (specific amount so that the sample to be tested is immersed in it as a whole) and put it into the sample cup 8, and immerse the cylindrical sample to be measured 6 as a whole Among them, the temperature of the measuring medium 7 is first adjusted to a predetermined value, and then the whole is put into a thermostatic chamber for heat balance. At the same time, adjust the temperature of the circulating medium 5 to a predetermined value (here the predetermined value is equal to the predetermined value in the aforementioned "adjusting the temperature of the measuring medium to a predetermined value"), open the circulation device, and keep the heat insulation of the thermostatic chamber Temperature balance inside and outside the layer. After the thermal balance reaches a stable state, the AC power supply 1 is turned on, and the long straight solenoid 4 generates an alternating magnetic field, and the current is adjusted to a required value according to the strength of the applied alternating magnetic field. The loss and heat generation of the sample to be tested 6 in the alternating magnetic field causes the temperature of the measurement medium in the sample cup 8 to rise, and the heating power of the sample to be tested 6 can be determined by measuring the temperature change within a certain time interval with the temperature measuring element 11 .

Since the long straight solenoid 4 is placed outside the thermostatic chamber, the self-heating of the long straight solenoid 4 is taken away by the circulating medium. Therefore, the temperature change in the sample cup is only caused by the heat loss of the sample itself, and the measured value is the sample The actual heating power, the specific calculation method is as follows:

Considering the sample to be tested, the sample cup and the measuring medium as a whole, the total thermal effect can be obtained by formula (1) as

Among them, m _cup -sample cup mass, unit g, c _cup -sample cup wall material specific heat, unit J/g℃

m- _sample -sample mass, unit g, c- _sample -sample specific heat, unit J/g℃

m _medium - the mass of the measuring medium, in g, c _medium - the specific heat of the measuring medium, in J/g°C

T ₀ - the initial temperature of the system, in °C, T - the final temperature of the system, in °C

t ₀ - measurement start time, unit s, t - measurement end time, unit s

In order to facilitate the comparison of the properties of different magnetic materials, it is stipulated that the heating power per unit mass is uniformly used, referred to as the single heating value, and the heating power of the sample to be tested can be divided by its mass by formula (2).

This is the single calorific value of the sample to be tested in a certain intensity alternating magnetic field.

Example 2

As shown in FIG. 4 , the sample to be tested in this example is an annular sample 18 to be tested, and the solenoid is an annular solenoid 17 .

The measuring device described in this example is mainly composed of an alternating magnetic field generating device, a constant temperature device and a temperature measuring element 11 . The alternating magnetic field generation system includes an AC power source 1, an AC ammeter 2, a rheostat 3 and a ring solenoid 17. The AC power source 1 is connected to a 220V voltage. The two ends of the annular solenoid 17 on the outer layer of the test sample 18 are respectively connected with the other outlet end of the AC power supply 1 and the outlet end of the rheostat 3. The AC ammeter 2 is used to observe the current situation in the device in real time, and the rheostat 3 is used for To change the current intensity in the circuit; the constant temperature system includes a constant temperature room and a circulation device, the constant temperature room includes a main body made of a thermal insulation layer 10 (such as polyurethane foam), and the outside of the thermal insulation layer is provided with a cooling channel 14; Circulating medium box 12 and circulating pump 13, circulating medium box 12 is connected with the bottom inlet of cooling channel 14 through water inlet pipe 15, circulating medium box 12 is connected with the top water outlet of cooling channel 14 through water outlet pipe 16, and water inlet pipe 15 There is a circulation pump 13 on it. The annular sample to be tested 18 wound around the annular solenoid 17 is placed in the sample cup 8 equipped with the measuring medium 7, the sample cup 8 is provided with a sample cup cover 9 for sealing, and then the sealed sample cup is put into the whole by In the thermostatic chamber formed by the heat insulating layer 10; two temperature measuring elements 11 are used, one end of the two temperature measuring elements is inserted into the sample cup 8 and the cooling channel 14 respectively, and the other end is exposed in the air, and the two temperature measuring elements are respectively used for Measure the temperature of the measuring medium 7 in the sample cup and the temperature of the circulating medium 5 in the cooling channel; the temperature measuring element 11 can be a precision thermometer or a temperature sensor and its display instrument, and the measuring medium 7 can be pure water, absolute ethanol, kerosene, castor For organic or inorganic liquids such as sesame oil, the circulation medium 5 can adopt liquids such as water, liquid ammonia or liquid nitrogen.

The specific method of measurement is:

When measuring, at first weigh the measurement medium 7 with known specific heat of a certain mass (specific amount so that the sample to be measured is immersed in it as a whole) and put it into the sample cup 8, first adjust the temperature of the measurement medium 7 to a predetermined value, Then the whole is placed in a thermostatic chamber for heat balance. At the same time, adjust the temperature of the circulating medium 5 to a predetermined value (here the predetermined value is equal to the predetermined value in the aforementioned "adjusting the temperature of the measuring medium to a predetermined value"), open the circulation device, and keep the heat insulation of the thermostatic chamber Temperature balance inside and outside the layer. After the thermal balance reaches a stable state, the AC power supply 1 is turned on, and the annular solenoid 17 generates an alternating magnetic field, and the rheostat is adjusted according to the strength of the applied alternating magnetic field to adjust the current intensity to a required value. Due to loss of heat, the temperature of the measuring medium in the sample cup 8 rises, and the temperature change within a certain time interval is measured by the temperature measuring element 11 .

For the way that the ring solenoid 17 is loaded with a magnetic field, the monitored temperature change is caused by the heat loss of the sample to be tested and the heat generation of the solenoid loss, that is, P _total = P _sample + P _solenoid . Therefore, when calculating the thermal effect of the sample, the influence of the solenoid's self-heating must be deducted. In the specific operation, an empty coil with the same specification and size as the sample to be tested can be used to measure its heating power under the same test conditions, and then deduct it from the total heating power. The specific calculation method is as follows:

Considering the sample cup, the sample to be tested, the copper wire of the toroidal coil and the measuring medium as a whole, the total thermal effect can be obtained by formula (3) as

Among them, m _cup -sample cup mass, unit g, c _cup -sample cup wall material specific heat, unit J/g℃

m- _sample -sample mass, unit g, c- _sample -sample specific heat, unit J/g℃

m _medium - the mass of the measuring medium, in g, c _medium - the specific heat of the measuring medium, in J/g°C

m _copper -the mass of copper wire used in the ring coil, g, c _copper -copper specific heat, unit J/g℃

T ₀ - the initial temperature of the system, in °C, T - the final temperature of the system, in °C

t ₀ - measurement start time, unit s, t - measurement end time, unit s Let the mass of the sample to be measured in the formula (3) be zero, that is, m _sample = 0, then the calculation formula (4) of the thermal effect of the empty coil can be obtained

Therefore, using formula (5), the heating power of the sample to be tested can be obtained as

P _sample = P _total - P _coil (W) (5)

In order to facilitate the comparison of the properties of different magnetic materials, it is stipulated that the heating power per unit mass is uniformly used, referred to as the single-weight heating value, and the heating power of the sample to be tested is divided by its mass by formula (6).

This is the single calorific value of the sample to be tested in a certain intensity alternating magnetic field.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims (10)

1. A device for measuring the thermal effect of magnetic materials in an alternating magnetic field, characterized in that: the device includes an alternating magnetic field generator, a constant temperature device and a temperature measuring element, and the said constant temperature device is provided with a sample for containing the sample to be tested Cup, the sample cup is equipped with a measuring medium; the alternating magnetic field generating device applies an alternating magnetic field to the sample to be tested in the constant temperature device; the temperature measuring element extends into the sample cup in the constant temperature device, Used to monitor the temperature change of the measuring medium; The thermostatic device includes a thermostatic chamber with a sample cup inside and a circulation device, and the circulation device is connected with the thermostatic chamber; The thermostatic chamber includes a main body composed of a thermal insulation layer, and a cooling channel is provided outside the thermal insulation layer. The circulation device includes a circulation medium tank filled with a circulation medium and a circulation pump. The circulation medium tank passes through the water inlet pipe and the water outlet pipe. It communicates with the cooling channel of the thermostatic chamber, and the water inlet pipe is provided with a circulating pump. 2. measuring device as claimed in claim 1, is characterized in that: described alternating magnetic field generating device comprises alternating power supply, alternating current meter, rheostat and solenoid, and an outgoing line end of described alternating current power supply is connected with alternating current meter and a rheostat, a solenoid is connected between the other outlet end of the alternating power supply and the outlet end of the rheostat. 3. The measuring device according to claim 2, characterized in that: when the solenoid is a long straight solenoid, the sample to be tested is cylindrical, and the cylindrical sample to be tested is placed on the long straight spiral. The central part of the tube axis and its longitudinal axis direction is parallel to the magnetic field of the long straight solenoid. 4 . The measuring device according to claim 3 , wherein the length-to-diameter ratio of the long straight solenoid is greater than 2, and the length-to-diameter ratio of the cylindrical sample to be measured is greater than 10. 5 . The measuring device according to claim 2 , wherein when the solenoid is an annular solenoid, the sample to be tested is annular, and the annular solenoid is evenly and tightly wound on the annular sample to be tested. 6 . 6. The measuring device according to claim 5, characterized in that: the ratio of the radial thickness of the annular sample to be measured to the average diameter is not greater than 1/6. 7. A method for measuring the thermal effect of magnetic material in an alternating magnetic field with the device according to claim 1, characterized in that: comprise the steps: A) Place the sample to be tested in a sample cup filled with a measuring medium, adjust the temperature of the measuring medium to a predetermined value, and then put it in a thermostatic chamber, at the same time, adjust the temperature of the circulating medium to a predetermined value, and turn on the circulation device, Maintain the thermal balance inside and outside the insulation layer of the thermostatic chamber; B) After the thermal balance is stable, turn on the alternating current and apply the alternating magnetic field to the solenoid to adjust the current to the required value; C) Using the temperature measuring element to monitor the temperature change of the measuring medium in the sample cup within a certain time interval, so as to determine the heating power of the sample to be tested. 8. The measuring method as claimed in claim 7, characterized in that: when the solenoid adopts a long straight solenoid, the specific calculation method for measuring the heating power of the sample to be tested is as follows: Considering the sample to be tested, the sample cup and the measuring medium as a whole, the total thermal effect can be obtained by formula (1) as

Among them, m _cup -sample cup mass, unit g, c _cup -sample cup wall material specific heat, unit J/g℃ m- _sample -sample mass, unit g, c- _sample -sample specific heat, unit J/g℃ m _medium - the mass of the measuring medium, in g, c _medium - the specific heat of the measuring medium, in J/g°C T ₀ - the initial temperature of the system, in °C, T - the final temperature of the system, in °C t ₀ - measurement start time, unit s, t - measurement end time, unit s In order to facilitate the comparison of the properties of different magnetic materials, it is stipulated that the heating power per unit mass is uniformly used, referred to as the single-weight heating value, and the heating power of the sample to be tested can be divided by its mass by formula (2).

This is the single calorific value of the sample to be tested in a certain intensity alternating magnetic field. 9. measuring method as claimed in claim 7, is characterized in that: when described solenoid adopts annular solenoid, the specific calculation method of measuring the heating power of the sample to be tested is as follows: Considering the sample cup, the sample to be tested, the copper wire of the toroidal coil and the measuring medium as a whole, the total thermal effect can be obtained by formula (3) as

Among them, m _cup -sample cup mass, unit g, c _cup -sample cup wall material specific heat, unit J/g℃ m- _sample -sample mass, unit g, c- _sample -sample specific heat, unit J/g℃ m _medium - the mass of the measuring medium, in g, c _medium - the specific heat of the measuring medium, in J/g°C m _copper -the mass of copper wire used in the ring coil, g, c _copper -copper specific heat, unit J/g℃ T ₀ - the initial temperature of the system, in °C, T - the final temperature of the system, in °C t ₀ - measurement start time, unit s, t - measurement end time, unit s Let the mass of the sample to be tested in the formula (3) be zero, that is, m _sample = 0, then the calculation formula (4) of the thermal effect of the empty coil can be obtained

Therefore, using formula (5), the heating power of the sample to be tested can be obtained as P _sample = P _total - P _coil (W) (5) In order to facilitate the comparison of the properties of different magnetic materials, it is stipulated that the heating power per unit mass is uniformly used, referred to as the single-weight heating value, and the heating power of the sample to be tested is divided by its mass by formula (6).

This is the single calorific value of the sample to be tested in a certain intensity alternating magnetic field. 10. The measuring method according to claim 7, characterized in that: the measuring medium is an organic or inorganic liquid, and the organic or inorganic liquid is pure water, absolute ethanol, kerosene or castor oil.

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