CN115407155A - Explosion-proof electrical temperature rise evaluation system and method - Google Patents

Explosion-proof electrical temperature rise evaluation system and method Download PDF

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CN115407155A
CN115407155A CN202211061348.2A CN202211061348A CN115407155A CN 115407155 A CN115407155 A CN 115407155A CN 202211061348 A CN202211061348 A CN 202211061348A CN 115407155 A CN115407155 A CN 115407155A
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explosion
temperature rise
proof
proof electric
temperature
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张红奎
单大阔
马云龙
李桐喆
王帅
鞠哲
孙瑞
王艳鹤
杨帆
李骁洋
吕祥鹏
朱剑锋
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Fushun China Coal Science & Engineering Testing Center Co ltd
Shenyang Research Institute Co Ltd of CCTEG
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Fushun China Coal Science & Engineering Testing Center Co ltd
Shenyang Research Institute Co Ltd of CCTEG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/003—Environmental or reliability tests
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/05—Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts
    • G05B19/054—Input/output

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Abstract

The invention provides an explosion-proof electrical temperature rise evaluation system and method, and relates to the technical field of explosion-proof electrical temperature rise evaluation. The system comprises a PLC controller, a direct current bridge, a stabilized voltage power supply, a temperature sensor, a temperature adjusting device, a gauss meter and an experimental power supply; the voltage-stabilized power supply provides a working power supply for the PLC and the direct current bridge; the direct current bridge is used for testing the resistance of the explosion-proof electrical loop and transmitting the resistance into the PLC; the temperature sensor is used for testing the temperature of the explosion-proof electric operation environment and transmitting the temperature to the PLC; the temperature adjusting device is connected with the PLC and used for adjusting the temperature of the testing environment; the gaussmeter is connected with the PLC and used for testing the intensity of the explosion-proof electric magnetic field; the experiment power supply provides power for the explosion-proof electricity. According to the method, the temperature rise estimation value of the explosion-proof electric appliance is obtained through the resistance of the explosion-proof electric loop measured by the direct current bridge, the magnetic field intensity of the explosion-proof electric appliance measured by the gaussmeter and the relationship between the heating power and the heat dissipation power during temperature rise estimation of the explosion-proof electric appliance.

Description

Explosion-proof electrical temperature rise evaluation system and method
Technical Field
The invention relates to the technical field of explosion-proof electrical temperature rise evaluation, in particular to an explosion-proof electrical temperature rise evaluation system and method.
Background
The explosion-proof electric appliance refers to electric equipment such as an explosion-proof electromagnetic starter, an explosion-proof high-voltage distribution device, an explosion-proof junction box, an explosion-proof illumination comprehensive protection device and the like used in explosive places, and is widely applied to inflammable and explosive places such as coal mines, chemical engineering, petroleum and the like. The explosion-proof type shell structure not only prevents electric sparks in the explosion-proof electric appliance from igniting external explosive gas, but also prevents the explosion of external environment from damaging the explosion-proof electric appliance, and ensures the safe operation of the explosion-proof electric appliance in an explosive place. However, the movement capability of the explosion-proof electric apparatus is limited due to the large weight of the explosion-proof shell structure, and the heat in the explosion-proof electric apparatus cannot be transferred in time, so that the temperature of the explosion-proof electric apparatus is far higher than that of the same-grade electric apparatus on the ground. The temperature rise test is an important type test project of the explosion-proof electric appliance, and the national standard and the industrial standard make clear regulations on the temperature rise value of the explosion-proof electric appliance. At present, no evaluation method for explosion-proof electrical temperature rise exists at home and abroad, the temperature rise capability needs to be actually verified through a product prototype, and the temperature rise capability verification period is long.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art, and provides an explosion-proof electrical temperature rise evaluation system and method.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
on one hand, the invention provides an explosion-proof electrical temperature rise evaluation system which comprises a PLC (programmable logic controller), a direct-current bridge, a voltage-stabilized power supply, a temperature sensor, a temperature adjusting device, a gaussmeter and an experimental power supply; the signal output end of the direct current bridge is connected with the signal input end of the loop resistance of the PLC, and the test end of the direct current bridge is electrically connected with the test end of the loop resistance of the explosion-proof electric bridge and used for testing the loop resistance of the explosion-proof electric bridge and transmitting the loop resistance into the PLC; the voltage output end of the voltage-stabilized power supply is respectively and electrically connected with the power input ends of the PLC controller and the direct current bridge and is used for providing working power supply for the PLC controller and the direct current bridge; the temperature signal output end of the temperature sensor is electrically connected with the temperature signal input end of the PLC controller and used for testing the temperature of the explosion-proof electric operation environment and transmitting the temperature to the PLC controller; the control end of the temperature adjusting device is electrically connected with the temperature control signal output end of the PLC controller and is used for adjusting the temperature of the testing environment; the magnetic field intensity signal output end of the gaussmeter is electrically connected with the magnetic field intensity signal input end of the PLC controller and is used for testing the explosion-proof electric magnetic field intensity and transmitting the explosion-proof electric magnetic field intensity to the PLC controller; the control signal input end of the experiment power supply is electrically connected with the experiment power supply control signal output end of the PLC, and the voltage output end of the experiment power supply is electrically connected with the wiring terminal of the explosion-proof electric wire.
Preferably, the system further comprises a touch screen, a signal communication port of the touch screen is electrically connected with a signal communication port of the PLC controller and used for setting parameters of the explosion-proof electrical temperature rise evaluation system, and a power input end of the touch screen is electrically connected with a voltage output end of the voltage-stabilized power supply.
On the other hand, the invention also provides an explosion-proof electrical temperature rise evaluation method, which comprises the following steps:
step 1, starting a stabilized voltage supply, electrifying each device of an explosion-proof electric temperature rise evaluation system, and setting system parameters through a touch screen; the system parameters comprise skin effect coefficient, current frequency, eddy current resistance and resistance temperature coefficient at 20 ℃;
step 2, testing the operating environment temperature of the explosion-proof electric air temperature through a temperature sensor and transmitting the operating environment temperature to a PLC (programmable logic controller), judging whether the environment temperature reaches 20 ℃ or not by the PLC, if the environment temperature does not reach 20 ℃, controlling a temperature adjusting device to start by the PLC, controlling the temperature adjusting device to stop working by the PLC when the environment temperature reaches 20 ℃, and executing step 4 to evaluate the temperature rise of the explosion-proof electric air;
step 3, connecting the direct current bridge to an anti-explosion electrical loop resistance testing end, testing the anti-explosion electrical loop resistance, and sending a testing result to the PLC;
step 4, starting an experimental power supply, and obtaining the intensity of the explosion-proof electric magnetic field through gauss meter test;
step 5, the PLC carries out operation according to the resistance of the explosion-proof electric loop measured by the direct current bridge, the magnetic field intensity of the explosion-proof electric measured by the gauss meter and the relationship between the heating power and the heat dissipation power when the temperature rise of the explosion-proof electric is evaluated, so as to obtain an estimated value of the temperature rise of the explosion-proof electric;
and 6, the PLC sends the explosion-proof electrical temperature rise estimated value to the touch screen for displaying.
The specific method of the step 5 comprises the following steps:
step 5.1, determining the heating power during the temperature rise evaluation of the explosion-proof electric appliance;
the anti-explosion electric temperature rise evaluation heating power consists of three parts, namely resistance loss heating power, eddy current loss heating power and hysteresis loss heating power, and is shown in the following formula:
P＝P d +P w +P c (1)
wherein, P d The heating power is lost for the resistance; p w The heating power is lost for eddy current; p c Heat power is lost for magnetic hysteresis;
the resistance loss is the loss generated by current passing through the explosion-proof electric apparatus, and the heating power of the resistance loss is shown as the following formula:
P d ＝I 2 R (2)
wherein I is loop current in explosion-proof electrical temperature rise evaluation; r is the total resistance of the circuit during the evaluation of the explosion-proof electrical temperature rise;
setting the total resistance R of the circuit when the temperature rise of the explosion-proof electric is evaluated to be equal to the maximum allowable temperature R of the explosion-proof electric t It is calculated from the loop resistance at 20 ℃, as shown in the following formula:
R t ＝K s R 20 [1+α 20 (T-20)] (3)
wherein R is t The resistance of the circuit at the highest allowable temperature of the explosion-proof electric is used; k s The skin effect coefficient; r 20 Loop resistance at 20 ℃; alpha is alpha 20 A temperature coefficient of resistance at 20 ℃; t is the maximum temperature allowed by explosion-proof electricity;
the explosion-proof electric eddy current loss heating power is shown in the following formula:
Figure BDA0003826349580000031
wherein f is the current frequency during the temperature rise evaluation of the explosion-proof electric appliance; b is m The magnetic field intensity is used for evaluating the temperature rise of the explosion-proof electric appliance; r w Is an eddy current resistor;
the explosion-proof electrical hysteresis loss heating power is shown as the following formula:
Figure BDA0003826349580000032
wherein eta is a hysteresis coefficient;
substituting the formulas (2), (4) and (5) into the formula (1) to obtain the heating power during the temperature rise evaluation of the explosion-proof electric device, wherein the formula is as follows:
Figure BDA0003826349580000033
step 5.2, determining the heat dissipation power during the temperature rise evaluation of the explosion-proof electric appliance;
setting the equal heat dissipation positions of the explosion-proof electrical surface, and multiplying two sides of the Newton's cooling law by the heat dissipation surface area A of the explosion-proof electrical surface simultaneously to obtain the heat dissipation power when the temperature rise of the explosion-proof electrical surface is evaluated, wherein the heat dissipation power is shown in the following formula:
Figure BDA0003826349580000034
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003826349580000035
the heat dissipation power is the heat dissipation power in the explosion-proof electrical temperature rise evaluation; k T Is an explosion-proof electrical heat dissipation coefficient; tau is w The temperature rise value of the explosion-proof electric appliance; q is the total heat dissipation capacity in the explosion-proof electrical temperature rise evaluation; q is the heat dissipation capacity per unit area in the explosion-proof electrical temperature rise evaluation; t is time;
step 5.3, determining the temperature rise value of the explosion-proof electric appliance according to the relation between the heating power and the heat dissipation power when the temperature rise of the explosion-proof electric appliance is evaluated;
when explosion-proof electric temperature rise is evaluated, the heating power is equal to the heat dissipation power, namely:
Figure BDA0003826349580000036
obtaining the temperature rise value of the explosion-proof electric according to the formulas (6) and (8), wherein the temperature rise value is shown as the following formula:
Figure BDA0003826349580000037
adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the anti-explosion electric temperature rise evaluation system and method provided by the invention, the anti-explosion electric temperature rise evaluation system is designed by utilizing the PLC, the temperature rise capability is evaluated through test data, the temperature rise inspection period is shortened, the electric power resource is saved, a test verification technical support is provided for material and part selection in the research and development process of an anti-explosion electric new product, the quality of the anti-explosion electric product is ensured, and the detection and inspection and the continuous and healthy development in the field of electric appliances are promoted.
Drawings
Fig. 1 is a block diagram of an explosion-proof electrical temperature rise evaluation system according to an embodiment of the present invention;
fig. 2 is a flowchart of an explosion-proof electrical temperature rise evaluation method according to an embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In this embodiment, an explosion-proof electrical temperature rise evaluation system, as shown in fig. 1, includes a PLC controller, a dc bridge, a voltage-stabilized power supply, a temperature sensor, a temperature adjustment device, a gauss meter, a touch screen, and an experimental power supply; the signal output end of the direct current bridge is connected with the signal input end of the loop resistance of the PLC, and the test end of the direct current bridge is electrically connected with the test end of the loop resistance of the explosion-proof electric bridge and used for testing the loop resistance of the explosion-proof electric bridge and transmitting the loop resistance into the PLC; the voltage output end of the voltage-stabilized power supply is respectively and electrically connected with the PLC controller, the direct current bridge and the power input end of the touch screen and is used for providing working power supply for the PLC, the direct current bridge and the touch screen; the temperature signal output end of the temperature sensor is electrically connected with the temperature signal input end of the PLC controller and used for testing the temperature of the explosion-proof electric operation environment and transmitting the temperature to the PLC controller; the control end of the temperature adjusting device is electrically connected with the temperature control signal output end of the PLC controller and is used for adjusting the temperature of the testing environment; the magnetic field intensity signal output end of the gaussmeter is electrically connected with the magnetic field intensity signal input end of the PLC controller and is used for testing the explosion-proof electric magnetic field intensity and transmitting the explosion-proof electric magnetic field intensity to the PLC controller; a signal communication port of the touch screen is electrically connected with a signal communication port of the PLC and is used for setting parameters of the explosion-proof electrical temperature rise evaluation system; the control signal input end of the experiment power supply is electrically connected with the experiment power supply control signal output end of the PLC, and the voltage output end of the experiment power supply is electrically connected with the wiring terminal of the explosion-proof electric wire.
In this embodiment, an explosion-proof electrical temperature rise evaluation method is implemented based on the above evaluation system, and specifically includes the following steps, as shown in fig. 2:
step 1, starting a stabilized voltage supply, electrifying each device of an explosion-proof electric temperature rise evaluation system, and setting system parameters through a touch screen; the system parameters comprise skin effect coefficients, current frequency, eddy current resistance and resistance temperature coefficients;
step 2, testing the operating environment temperature of the explosion-proof electric air temperature through a temperature sensor and transmitting the operating environment temperature to a PLC (programmable logic controller), judging whether the environment temperature reaches 20 ℃ or not by the PLC, if the environment temperature does not reach 20 ℃, controlling a temperature adjusting device to start by the PLC, controlling the temperature adjusting device to stop working by the PLC when the environment temperature reaches 20 ℃, and executing step 4 to evaluate the temperature rise of the explosion-proof electric air;
step 3, connecting the direct current bridge to an anti-explosion electrical loop resistance test end, testing the anti-explosion electrical loop resistance, and sending a test result to the PLC;
step 4, starting an experimental power supply, and obtaining the intensity of the explosion-proof electric magnetic field through gauss meter test;
step 5, the PLC carries out operation according to the resistance of the explosion-proof electric loop measured by the direct current bridge, the magnetic field intensity of the explosion-proof electric measured by the gauss meter and the relationship between the heating power and the heat dissipation power when the temperature rise of the explosion-proof electric is evaluated, so as to obtain an estimated value of the temperature rise of the explosion-proof electric;
and 6, the PLC sends the explosion-proof electrical temperature rise estimated value to the touch screen for displaying.
The specific method of the step 5 comprises the following steps:
step 5.1, determining the heating power of the explosion-proof electric during temperature rise evaluation;
the anti-explosion electric temperature rise evaluation heating power consists of three parts, namely resistance loss heating power, eddy current loss heating power and hysteresis loss heating power, and is shown in the following formula:
P＝P d +P w +P c (1)
wherein, P d Is the resistive loss heating power in watts (W); p w Is the eddy current loss heating power in watts (W); p c The hysteresis loss heating power is in watt (W);
the resistance loss is the loss generated by current passing through the explosion-proof electric apparatus, and the heating power of the resistance loss is shown as the following formula:
P d ＝I 2 R (2)
wherein I is loop current in ampere (A) when the explosion-proof electric temperature rise is evaluated; r is total resistance of a loop in the explosion-proof electrical temperature rise evaluation, and the unit is ohm (omega);
setting the total resistance R of the circuit when the temperature rise of the explosion-proof electric is evaluated to be equal to the maximum allowable temperature R of the explosion-proof electric t It is calculated from the loop resistance at 20 ℃, as shown in the following formula:
R t ＝K s R 20 [1+α 20 (T-20)] (3)
wherein R is t The resistance of a circuit at the highest allowable temperature of the explosion-proof electric appliance is expressed by ohm (omega); k s The skin effect coefficient (usually 1.1-1.4); r 20 Loop resistance at 20 ℃ in ohms (Ω); alpha is alpha 20 The resistance temperature coefficient at 20 ℃ is in the range of 3.81 multiplied by 10 -3 ℃～4.35×10 -3 DEG C; t is the highest temperature allowed by explosion-proof electricity, and the unit is (DEG C);
the heat power of the explosion-proof electric eddy current loss is shown in the following formula:
Figure BDA0003826349580000052
wherein f is the current frequency in hertz (Hz) when the temperature rise of the explosion-proof electric is evaluated; b m The magnetic field intensity is the magnetic field intensity in Tesla (T) when the explosion-proof electric temperature rise is evaluated; r w Is eddy current resistance, and has the unit of ohm (omega);
the explosion-proof electrical hysteresis loss heating power is shown as the following formula:
Figure BDA0003826349580000051
wherein eta is a hysteresis coefficient and is dimensionless;
substituting the formulas (2), (4) and (5) into the formula (1) to obtain the heating power during the temperature rise evaluation of the explosion-proof electric device, wherein the formula is as follows:
Figure BDA0003826349580000061
step 5.2, determining the heat dissipation power during the temperature rise evaluation of the explosion-proof electric;
setting the heat dissipation positions of the surface of the explosion-proof electric appliance to be equal, and multiplying two sides of the Newton's cooling law by the heat dissipation surface area A of the explosion-proof electric appliance at the same time to obtain the heat dissipation power when the temperature rise of the explosion-proof electric appliance is evaluated, wherein the heat dissipation power is shown in the following formula:
Figure BDA0003826349580000062
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003826349580000063
the unit is watt (W) for the heat dissipation power during the evaluation of the temperature rise of the explosion-proof electric appliance; k T Is an explosion-proof electrical heat dissipation coefficient; tau is w Is the temperature rise value of the explosion-proof electric appliance, and has a unit of Kelvin (K); q is the total heat dissipation capacity in joules during the evaluation of the explosion-proof electrical temperature rise; q is the heat dissipation capacity per unit area in joules/second during the evaluation of the explosion-proof electrical temperature rise; t is time in seconds;
step 5.3, determining the temperature rise value of the explosion-proof electric appliance according to the relation between the heating power and the heat dissipation power when the temperature rise of the explosion-proof electric appliance is evaluated;
when explosion-proof electric temperature rise is evaluated, the heating power is equal to the heat dissipation power, namely:
Figure BDA0003826349580000064
obtaining the temperature rise value of the explosion-proof electric according to the formulas (6) and (8), wherein the temperature rise value is shown as the following formula:
Figure BDA0003826349580000065
finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions and scope of the present invention as defined in the appended claims.

Claims (7)

1. The utility model provides an explosion-proof electric temperature rise evaluation system which characterized in that: the device comprises a PLC controller, a direct current bridge, a stabilized voltage power supply, a temperature sensor, a temperature adjusting device, a gauss meter and an experimental power supply; the signal output end of the direct current bridge is connected with the signal input end of the loop resistor of the PLC, and the test end of the direct current bridge is electrically connected with the test end of the loop resistor of the explosion-proof electric circuit and is used for testing the loop resistor of the explosion-proof electric circuit and transmitting the loop resistor to the PLC; the voltage output end of the voltage-stabilized power supply is respectively and electrically connected with the power input ends of the PLC controller and the direct current bridge and is used for providing working power supply for the PLC controller and the direct current bridge; the temperature signal output end of the temperature sensor is electrically connected with the temperature signal input end of the PLC controller and used for testing the temperature of the explosion-proof electric operation environment and transmitting the temperature to the PLC controller; the control end of the temperature adjusting device is electrically connected with the temperature control signal output end of the PLC controller and is used for adjusting the temperature of the testing environment; the magnetic field intensity signal output end of the gaussmeter is electrically connected with the magnetic field intensity signal input end of the PLC controller and is used for testing the explosion-proof electric magnetic field intensity and transmitting the explosion-proof electric magnetic field intensity to the PLC controller; the control signal input end of the experiment power supply is electrically connected with the experiment power supply control signal output end of the PLC, and the voltage output end of the experiment power supply is electrically connected with the wiring terminal of the explosion-proof electric wire.
2. An explosion-proof electrical temperature rise evaluation system according to claim 1, characterized in that: the system further comprises a touch screen, a signal communication port of the touch screen is electrically connected with a signal communication port of the PLC and used for setting parameters of the explosion-proof electrical temperature rise evaluation system, and a power input end of the touch screen is electrically connected with a voltage output end of the voltage-stabilized power supply.
3. An explosion-proof electrical temperature rise evaluation method is realized based on the system of claim 1, and is characterized in that: the method comprises the following steps:
step 1, starting a stabilized voltage supply, electrifying each device of an explosion-proof electric temperature rise evaluation system, and setting system parameters through a touch screen; the system parameters comprise a skin effect coefficient, a current frequency, an eddy current resistance and a resistance temperature coefficient at 20 ℃;
step 2, testing the operating environment temperature of the explosion-proof electric air temperature through a temperature sensor and transmitting the operating environment temperature to a PLC (programmable logic controller), judging whether the environment temperature reaches 20 ℃ or not by the PLC, if the environment temperature does not reach 20 ℃, controlling a temperature adjusting device to start by the PLC, controlling the temperature adjusting device to stop working by the PLC when the environment temperature reaches 20 ℃, and executing step 4 to evaluate the temperature rise of the explosion-proof electric air;
step 3, connecting the direct current bridge to an anti-explosion electrical loop resistance testing end, testing the anti-explosion electrical loop resistance, and sending a testing result to the PLC;
step 4, starting an experimental power supply, and obtaining the intensity of the explosion-proof electric magnetic field through gauss meter test;
and 5, the PLC carries out operation according to the resistance of the explosion-proof electric loop measured by the direct current bridge, the intensity of the magnetic field of the explosion-proof electric field measured by the gauss meter and the relationship between the heating power and the heat dissipation power during the temperature rise evaluation of the explosion-proof electric field, so as to obtain an estimated value of the temperature rise of the explosion-proof electric field.
4. An explosion-proof electrical temperature rise assessment method according to claim 3, characterized in that: the specific method of the step 5 comprises the following steps:
determining the heating power during the temperature rise evaluation of the explosion-proof electric appliance according to the resistance loss heating power, the eddy current loss heating power and the hysteresis loss heating power during the temperature rise evaluation of the explosion-proof electric appliance;
determining the heat dissipation power during the temperature rise evaluation of the explosion-proof electric equipment according to the Newton's cooling law and the heat dissipation surface area of the explosion-proof electric equipment;
and determining the temperature rise value of the explosion-proof electric appliance according to the relation between the heating power and the heat dissipation power when the temperature rise of the explosion-proof electric appliance is evaluated.
5. The explosion-proof electrical temperature rise evaluation method according to claim 4, characterized in that: the specific method for determining the heating power in the explosion-proof electrical temperature rise evaluation comprises the following steps:
the heating power during the temperature rise evaluation of the explosion-proof electric appliance is composed of three parts of resistance loss heating power, eddy current loss heating power and hysteresis loss heating power, and the following formula is shown:
P＝P d +P w +P c (1)
wherein, P d Heating power is lost for resistance; p w The heating power is lost for eddy current; p c Heat power is lost for magnetic hysteresis;
the resistance loss is the loss generated by current passing through the explosion-proof electric apparatus, and the heating power of the resistance loss is shown as the following formula:
P d ＝I 2 R (2)
wherein I is loop current in explosion-proof electrical temperature rise evaluation; r is the total resistance of the circuit during the evaluation of the explosion-proof electrical temperature rise;
setting total resistance R of circuit equal to explosion-proof when evaluating explosion-proof electric temperature riseLoop resistance R at the maximum allowable electrical temperature t It is calculated from the loop resistance at 20 ℃, as shown in the following formula:
R t ＝K s R 20 [1+α 20 (T-20)] (3)
wherein R is t The resistance of the circuit at the highest allowable temperature of the explosion-proof electric is used; k s The skin effect coefficient; r 20 Loop resistance at 20 ℃; alpha is alpha 20 Temperature coefficient of resistance at 20 ℃; t is the maximum temperature allowed by explosion-proof electricity;
the explosion-proof electric eddy current loss heating power is shown in the following formula:
Figure FDA0003826349570000021
wherein f is the current frequency during the temperature rise evaluation of the explosion-proof electric appliance; b is m The magnetic field intensity is used for evaluating the temperature rise of the explosion-proof electric appliance; r w Is an eddy current resistor;
the explosion-proof electrical hysteresis loss heating power is shown as the following formula:
Figure FDA0003826349570000022
wherein eta is a hysteresis coefficient;
substituting the formulas (2), (4) and (5) into the formula (1) to obtain the heating power during the temperature rise evaluation of the explosion-proof electric device, wherein the formula is as follows:
Figure FDA0003826349570000023
6. the explosion-proof electrical temperature rise evaluation method according to claim 5, characterized in that: the specific method for determining the heat dissipation power in the explosion-proof electrical temperature rise evaluation comprises the following steps:
setting the heat dissipation positions of the surface of the explosion-proof electric appliance to be equal, and multiplying two sides of the Newton's cooling law by the heat dissipation surface area A of the explosion-proof electric appliance at the same time to obtain the heat dissipation power when the temperature rise of the explosion-proof electric appliance is evaluated, wherein the heat dissipation power is shown in the following formula:
Figure FDA0003826349570000031
wherein the content of the first and second substances,
Figure FDA0003826349570000032
the heat dissipation power is the heat dissipation power in the explosion-proof electrical temperature rise evaluation; k T Is an explosion-proof electrical heat dissipation coefficient; tau is w The temperature rise value of the explosion-proof electric appliance; q is the total heat dissipation capacity in the explosion-proof electrical temperature rise evaluation; q is the heat dissipation capacity per unit area in the explosion-proof electrical temperature rise evaluation; t is time.
7. The explosion-proof electrical temperature rise evaluation method according to claim 6, characterized in that: the specific method for determining the temperature rise value of the explosion-proof electric appliance according to the relationship between the heating power and the heat dissipation power during the temperature rise evaluation of the explosion-proof electric appliance comprises the following steps:
when explosion-proof electric temperature rise is evaluated, the heating power is equal to the heat dissipation power, namely:
Figure FDA0003826349570000033
obtaining the temperature rise value of the explosion-proof electric according to the formulas (6) and (8), wherein the temperature rise value is shown as the following formula:
Figure FDA0003826349570000034
CN202211061348.2A 2022-08-31 2022-08-31 Explosion-proof electrical temperature rise evaluation system and method Pending CN115407155A (en)

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