? R-core transformer
Since 1990, R-type transformers in China have been in operation for more than fifteen years. In the meantime, through the introduction of technology, independent research and development of equipment, taking the road of localization, it has been widely promoted in the domestic transformer industry. R-type transformer products have been widely used in many industrial equipment, instruments and meters, medical equipment, broadcast audio and various power products.
R-type transformer series has developed from single-phase 1KW or below 10 or above to single-phase transformer series. The power of R-type transformer has reached 50KW, and the specifications have reached more than 30 kinds. What's more, we independently developed a three-phase R-type transformer with a power of 500KW and more than 20 specifications. R-type transformer products have been mainly used in the electronics industry in the past, and now they have entered the power industry.
After fifteen years of R-type transformer development, we have accumulated rich transformer design and technical experience. As a new and reasonable transformer, R-type transformer is different from E-type and C-type transformers in structure. Therefore, the transformer design needs to be optimized according to its own characteristics in order to fully realize its? Less magnetic leakage, low temperature rise, small volume, light weight and no noise.
I will sort out the optimal design of R-type transformer according to my years of accumulated R-type transformer design experience and R&D, so as to attract more attention.
General idea of optimal design of R transformer
1, according to the purpose of the product, determine different transformer standards.
R transformer has been promulgated by the Ministry of Information Industry as the standard of single-phase R-core power transformer-SJ/T11245-1. Single-phase r transformer core standard-SJ/t11244-1.
Because of the different uses of R-type transformers, all walks of life also have specific technical requirements. Therefore, it is necessary to understand the relevant standards and requirements before design, and only according to the characteristics of R type can we design qualified products that meet the needs of the whole machine. For example:
A. transformers for civil products
Considering that this product is used in thousands of households, many users lack electrical knowledge. Therefore, the transformer must be safe. Its compressive strength is required to be greater than 3750 volts/minute. For the primary interstage skeleton, insulation should be strengthened to prevent the transformer from leaking due to breakdown.
B. transformers for industrial equipment
Generally, the withstand voltage of transformer is required to be twice the working voltage plus 1000V, mainly to ensure durability.
C. transformers for medical equipment
Medical equipment especially used for contact with patients' bodies shall meet the technical requirements of transformers in GB 9706, 1- 1995 medical electrical equipment standard. The voltage withstand requirement of its transformer is greater than 4000V/ min. At the same time, there are clear requirements for transformer insulation thickness, creepage distance, overheating, overload protection and electrostatic shielding width. Therefore, the design process must be designed and manufactured in strict accordance with specific standards.
D. transformers for ship equipment
Working at sea and under load for a long time requires that the transformer has large power margin, moisture resistance, corrosion resistance, heat resistance, long service life and low noise.
E. mine transformer
Working in harsh environment, the transformer is not allowed to have creepage, arcing, tip discharge and other phenomena. Therefore, the transformer adopts epoxy casting or end sealing to meet the requirements of explosion-proof and flameproof.
F. Spacecraft transformers
It requires stability, small size, light weight, shock and vibration resistance, anti-interference and so on.
A transformer for electronic instruments and equipment
Require small magnetic leakage, small interference, high precision and low temperature rise.
Several industries listed above have specific requirements for transformers. R transformer is widely used because of its unique advantages.
2. According to different use conditions and environments, correctly select the specifications and parameters of R-type transformer core.
A. grid voltage stability
Because the magnetic circuit of R-type iron core is a closed loop, the transformer has a large surge current at the moment of closing. Generally, the magnetic flux density parameter is lower than that of C-type iron core, so as to avoid the phenomenon of fuse blowing due to overcurrent. For a small R-shaped iron core, the magnetic flux density can be higher because of its larger impedance. For the large R-shaped iron core, its own impedance is small, and the magnetic flux density should be lower.
Such as R5——R50? The value of b can be 1.7T gauss.
R80——R 160？ The value of b can be 1.65T gauss.
R260？ ——R 1000？ The value of b can be 1.62T gauss.
Exceeding R 1000? The value of b can be 1.60T gauss.
b.？ Transformer operating environment temperature
For applications with high ambient temperature, in addition to reducing the magnetic flux density and current density, a larger iron core is selected to reduce the temperature rise of the transformer, and high-temperature resistant insulating materials and enameled wires can also be selected to improve the temperature resistance of the transformer.
C. Length of service time of transformer
For transformers working under long-term load, it is necessary to enlarge the iron core specification appropriately; The transformer used for short-time shutdown operation can appropriately reduce the iron core specification.
D. high voltage transformer
Considering that insulation should be added between windings and between layers, isolation insulation should be added to increase the creepage distance. Therefore, it is necessary to increase the iron core specifications according to the actual situation.
3. Determine the reasonable winding structure according to the transformer output winding.
A. Power balance distribution method
The primary winding of transformer must be evenly distributed on the left and right windings in series or parallel according to the current, and the secondary main winding must also be evenly and symmetrically distributed on the left and right windings.
The above purpose is to make the left and right magnetic circuits in a balanced working state, achieve power balance, and tightly couple the primary windings, thus reducing the magnetic leakage of the transformer.
Transformer windings with high current are generally connected in parallel; The windings of small current transformers are mainly connected in series.
B. Classification and arrangement methods
For transformer windings with different output voltages, the high and low voltage windings are arranged separately to avoid the high potential winding being sandwiched between the low potential windings. In addition to strengthening the insulation between the high-potential winding and the low-potential winding, insulation isolation belts can be wound at both ends of the framework to increase the creepage distance with other low-potential windings.
The above purpose can reduce the potential difference between the insulation layer and the winding, which is beneficial to improve the compressive strength of the winding.
C. Layout method of fine inside and coarse outside
Generally, thin wire winding is wound in the inner layer, and thick wire winding is wound in the outer layer, with the same wire diameter.
The above purpose can reduce the DC resistance of the thin winding, reduce the resistance voltage drop of the thin winding and reduce the copper consumption of the winding, which is beneficial to the smoothness of winding packaging.
D. Online placement method
For high voltage winding, the potential at both ends of the winding is very high. In order to reduce the potential difference with the primary winding, series connection is often adopted. As shown in the figure below, it is wound around the center of the high-voltage winding first, then around the center of the left and right windings in parallel, and the two ends of the back end are used as leads. This can reduce the potential difference between the primary by half, greatly reduce the potential difference between the windings and help improve the insulation strength of the windings.
e.？ Skeleton anti-winding parallel connection
For transformers with tapped high potential windings, there is still the problem that the high potential head and the low potential head are in the same layer when the left and right windings are symmetrically wound and connected in parallel. In order to solve the insulation problem caused by potential difference, it is necessary to add multi-layer insulation in the same winding, which brings a lot of trouble to the winding, and improper insulation treatment will also lead to short circuit of the winding.
In order to solve the above problems, the left skeleton can be wound in the forward direction, the right skeleton can be wound in the reverse direction, and then wound in sequence. In this way, there is no potential difference when knocking, and the left and right sides are symmetrical and balanced. As shown in the figure below:
F. Cross-connection balance method
As shown in the following figure, when the output has two windings with the same voltage and current, in order to realize the balanced distribution of the two windings on the left and right windings and the same DC resistance, the AC * connection balance method shown in the following figure can be adopted.
3. Design example
3. 1? technical requirement
Input voltage? 220 volts
Power frequency? 50 Hz
Output load? 14V/？ 2A？ 9V/？ 1A？ 100 volt /0.2 amp
Working conditions? Instrument transformer? Conventional requirements
3.2? Design steps
A. Electrical schematic diagram
B. Load power calculation
Choose R-50? δ0.27? The power capacity of iron core has a margin.
C. Preliminary selection of electromagnetic parameters
Magnetic flux density b? Take 1.65T? Core part? 3.72 square centimeters
Current density j? Take 3.3A/mm2? Voltage regulation rate? Take 10%
Length of magnetic circuit of iron core? 2 1.34cm？ Efficiency eta%? Take 90%
D. Calculation of turns per volt
In order to consider the integer number of turns of the secondary low-voltage winding and ensure the correct output voltage, the correction is made.
e.？ Turning calculation
Convert the above electrical schematic diagram into figure B.
Primary series connection
100V/0.2A？ Winding series
Series connection of 9V/ 1A winding
Parallel connection of 14V/2A winding
f.？ Calculation of steel wire diameter
Primary current calculation:
Diameter of main steel wire:
Secondary wire diameter:
g.？ Winding arrangement table
Main skeleton winding width L 1? =4 1mm？ The winding thickness is 3mm, and the secondary winding width is L2? =4 1mm？ Winding thickness? 3 mm
As long as the winding is neat, the above winding is possible.
Because the left and right skeletons are symmetrical, the right skeleton is the same as above, and the data is omitted.
h.？ Calculation of winding parameters
1)? Average turn length of primary winding
Total length of primary winding
DC resistance of primary winding
Copper weight of primary winding
2)? Average turn length of secondary winding 3-3'
Total length of winding 3-3'
DC resistance of winding 3-3'
Copper weight of winding 3-3'
3)? Average number of turns of secondary winding 7-8
Total length of windings 7-8
DC resistance of windings 7-8 and 7'-8'. (parallel)
The windings 7-8 and 7'-8' are heavy copper windings.
4)? The average number of turns of the secondary winding is 5-5'
The total winding length is 5-5 feet.
DC resistance of winding 5-5'
Copper weight of winding 5-5'
Me? Primary induced potential
j.？ Secondary 3-3' induced potential
K. Secondary 3-3' load voltage
According to the calculation, the ratio of v 33'' is rated as 100V? Low? 100-99.67 = 0.33v.
Transformers design is so simple, does this set of data make you see a little dazzling, haha? Don't worry, it will be easy to understand slowly. This is the main content brought to you by Bian Xiao today. In reality, with the appearance of this new thing, our life becomes more convenient. Don't underestimate it! We really can't live without these things. Ok, let's call it a day.
So much for the design of R-type transformer. I hope I can help you!
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