Abstract: Determination of enameled round wire by constant temperature life and dynamic thermogravimetric test
The method of thermal life and temperature index, as the choice for evaluating the insulation structure of electrical equipment
The basis for choosing enameled wire. After many years of use, this method has
The point plays an obvious role in guiding the actual production process, and has a certain precision
Spend.
Key words: temperature index; constant temperature life; dynamic thermal gravity; thermal aging
0 Preface
In the 1960s, my country began to study “measurement” according to IEC60172.
Test Method for Temperature Index of Enameled Winding Wires”, found that the test cycle of this method was too long
It has certain restrictions on product development and scientific research work. Therefore, in 70 years
On behalf of the project researched “the rapid test method for measuring the temperature index of enameled winding wire
Law”, and developed as the industry standard JB2804-1979. After many years of use, this method
The method plays a significant role in guiding the actual production process due to its rapidity and simplicity.
effect. As a rapid test method for the determination of temperature index, the method simultaneously reaches
to a certain accuracy requirement. Therefore, it is necessary to test methods for winding wires in countries
Add “GB/T4074.8-2009” winding wire test method Part 8 to the standard:
Test Methods for Determination of Temperature Index of Enameled Winding Wires “Quick Method”. This standard is
The scientific research results of our own research and development, aiming to complete the enameling in a short time
Determination of temperature index of winding wire, this method is a method for determining the thermal life and temperature index of enameled round wire in atmospheric air by constant temperature life and dynamic thermogravimetric test,
The test results can be used as the basis for selecting enameled wires when evaluating the insulation structure of electrical equipment.
according to.
- The principle of the fast method for measuring the temperature index of enameled winding wires
It has been recognized that many organic insulators have a
Among them, L is the insulation life, T is the absolute temperature, A and B are the fixed values of each insulator
Some constants, e is the base of natural logarithm) method of thermal aging. “Determination of enameled
The test method of winding wire temperature index “quick method” is to use this law to pass
By measuring the weight loss of the paint film at the specified weight loss at three different heating rates
temperature to calculate activation energy to determine the linearity in the thermal aging curve of the enameled wire
slope. Then select the aging of the paint film at a high temperature point to determine the aging
The life at the chemical temperature is determined, and then the aging curve is determined by the “point slope method”.
The line is extrapolated to the temperature (expressed in degrees Celsius) with a lifetime of 20000h, which is the
Test the temperature index of the enameled winding wire.
- Scope of application
“Quick Test Method for Determination of Temperature Index of Enameled Winding Wires”
Determination of enameled round wire in atmospheric air by constant temperature life and dynamic thermogravimetric test
The thermal life and temperature index methods in the electrical strength change as failure
Criterion, the test results can be used as the selection of enameled circles when evaluating the insulation structure of electrical equipment
line basis.
Scope of application: Determination of enameled round wire (including self-adhesive enameled round wire and composite
Enameled round wire) thermal life and temperature index, study two or more composite enameled
line compatibility.
- Introduction to the test procedure
Prepare more than 20 enameled wires that comply with GB/T6109-2008
of twisted pairs, subject the specimens of the twisted pairs that meet the specification to a test cycle
test. This test cycle includes an aging period followed by a room temperature withstand voltage test. Heavy
Repeat such test cycles until a sufficient number of specimens fail. Computational failure
time, weigh and record the initial mass, post-failure mass, and loss of each specimen.
The total mass of the bare conductor of the effective sample.
Remove the paint film on the same enameled wire as the twisted pair using an appropriate method. Will
The paint film that meets the requirements is divided into three parts, each part is about 15mg, and placed in a platinum crucible. by
Three different heating rates less than 6°C/min were heated in an air atmosphere.
The weight loss curve was obtained by weight test, as shown in Figure 1.
Then calculate the activation energy, and calculate the temperature at which the lifetime is 20000h (in terms of
Degrees) represents the temperature index of the tested winding wire.
- Test steps
- Preparation of Specimen
The nominal diameter of the sample conductor should be 0.800mm~1.500mm. Nominal with conductor
Enameled round wire with a diameter of 1.000mm thick paint film is the most suitable sample. make 20
The above twisted pair samples.
Different from the conventional aging method, the rapid method only performs aging at a high temperature point. Depend on
Due to the high temperature, the dispersity of the failure time of the sample is also large, and the requirements for the preparation of the line sample are also large.
very high. If the wire sample is subjected to too much force during the preparation of the twisted pair, it will be easily damaged.
Specimen failure time is shorter when aged at high temperature;
If the force of the center wire sample is too small, there will be gaps between the twisted pairs, and the sample will lose its value when it is aged at high temperature.
The effective time is longer, and the data dispersion is too large, which will affect the test results. Simultaneous
The prepared strands should be fixed on the sample holder, as shown in Figure 2, to prevent
It loosened during the test.
- Preparation of paint film
The preparation of the paint film is crucial in this test method, and the enameled wire paint film has a good
Good flexibility, cannot be ground, and this method requires the paint film to be made into a fineness of 40
Purpose Fragments. Usually, the paint film can be scraped directly from the enameled wire, and then sieved.
pick. Note that any impurities should be prevented from being incorporated during the preparation of the paint film to ensure that
The purity of the sample, especially the copper chips, otherwise has a great influence on the test results, and a very small amount
The oxidation of the copper chips during the test may lead to a weight loss curve exceeding 100%. paint
The fineness and dispersion of the film have a significant effect on the results of the thermal weight loss test, such as the fineness of the paint film.
If the dispersion is large, the thermogravimetric diagram obtained by the test is not smooth and fluctuates, so it cannot be used.
Before each test, the sample needs to be placed in a shallow pan and spread out at 125°C ± 5°C.
The thermal cycle drying box is pre-baked for 2 hours and then stored in the dryer to avoid moisture absorption.
Under the influence of the test results, when the heating rate is too fast, the weight loss of the smaller paint film and the larger paint film
due to differences. When this happens, you need to reduce the heating rate and try again
test.
- Data processing
- Data processing of constant temperature life test
