Most household amplifiers are powered by toroidal transformers. Ring transformer has the characteristics of small magnetic leakage, high conversion efficiency and wide frequency response, which can improve the sound quality of power amplifier. If the ring transformer is burnt out, you can't buy the original model to replace it, so you can only copy it by hand. Here is the manual winding method.
Brief introduction of ring transformer:
Ring transformer is a main type of electronic transformer, which is widely used in household appliances and other electronic equipment with high technical requirements. It is mainly used as a power transformer and an isolation transformer. Ring transformers have a complete series abroad, which are widely used in computers, medical instruments, telecommunications, instrumentation and lighting. ? In recent ten years, ring transformers have grown from scratch in China, and have formed a considerable production scale, which not only meets domestic demand, but also exports in large quantities. Mainly used for audio equipment and automatic control equipment of household appliances and quartz lamp for lighting. ? Ring transformer has excellent cost performance, good output characteristics and anti-interference ability, and is a very competitive electronic transformer. This paper intends to introduce its characteristics.
Product characteristics
The iron core with high electric efficiency has no air gap and the stacking coefficient can be as high as 95%.
Small vibration noise The iron core has no air gap, which can reduce the induced vibration noise of the iron core, and the winding evenly and tightly wraps the annular iron core, effectively reducing the "buzzing" sound caused by magnetostriction.
Low operating temperature Because the iron loss can reach 1. 1W/kg, the iron loss is very small, and the temperature rise of the iron core is low, so the temperature rise of the transformer is low.
There is only one mounting screw in the center of the ring transformer, which is easy to install, so it is especially easy to install and disassemble quickly in electronic equipment.
product classification
According to foreign literature, toroidal transformers can be divided into three types: standard type, economical type and isolated type. The characteristics of each type are as follows:
Standard power transformer products
This series has a capacity of 8 ~ 8~ 1500VA, a small voltage regulation rate, a full-load operation temperature rise of only 40℃, short-term overload operation is allowed, and it is suitable for demanding use occasions. The primary winding is insulated with B-grade (130℃) polyester film, which requires at least three layers of insulating tape and can withstand AC withstand voltage test of 4000V and 1min.
Economical power transformer products
The capacity of this series is 50 ~ 50~ 1500VA, and the cost is reduced on the basis of ensuring performance. It is suitable for continuous operation without overload. When the working temperature rises to 60℃, the insulation material grade is A (105℃), and the output voltage error is less than 3% when fully loaded.
Isolation transformer product series
The capacity is 50 ~ 50~ 1000VA, which is divided into two series: industrial and medical equipment. Isolation transformer focuses on its insulation performance. At least four layers of polyester film with class B insulation are wrapped between the primary and secondary, and the breakdown voltage is greater than 4000V V V. All primary leads must adopt double insulated wires. The maximum temperature rise of transformer is lower than 45℃.
Medical isolation transformer
In addition to the above requirements, the medical isolation transformer should also meet the UL544 standard, that is, the primary and secondary windings should be thermally protected, and the distance between the windings and the grounding copper shield should be greater than13 mm.
1. Remove the old winding.
After cutting the insulating paper with scissors, the secondary winding of the transformer is exposed. The wire diameter of secondary winding is usually thick, and it is rarely burned out in actual maintenance. Because there are not many laps, you can take them down one by one and count them. Multiple secondary windings can be disassembled and counted in a similar way. The primary winding has small wire diameter and common burning loss. Because the number of turns in the primary winding is more than 1000 turns, and the insulating material is attached to the turns after melting, it is obviously troublesome to count the number of turns with the above method. The quick processing method is: use scissors to cut off the primary coil layer by layer along the center line of the circumference, then peel off the cut coil from the iron core and count it to get the total number of turns. The cutting method is shown in the figure.
2. Insulated annular iron core.
The iron core of toroidal transformer is usually made of silicon steel sheet with high quality and high permeability. When the primary coil is burnt out, the insulating layer of the annular iron core impregnated with insulating paint will be damaged to varying degrees at the same time, so it should be dipped in paint before rewinding the coil. The method is: soak the annular iron core in insulating paint, take it out for a few minutes to dry, and then put it in an oven to dry. Then stick a layer of adhesive tape on the inner and outer circumferences, cut cellophane into strips about 2cm wide, wrap a layer on the iron core, and stick the joint with double-sided tape.
Step 3 make a thread shuttle
In order to facilitate manual operation, special winding edges must be made. I designed an I-shaped thread shuttle, as shown in Figure 2. It can be made of plastic sheet or stainless steel sheet, which can be about 8 times the circumference of a single turn, and its width is about 2cm smaller than the inner diameter of the annular core. This kind of wire core is not only convenient to thread, but also can reduce the number of threads. Obviously, the length of the enameled wire wound on the bobbin is 8×2= 16 times of the circumference of a single wire turn. If double-stranded winding is adopted, each winding of enameled wire on the bobbin can be wound on the annular iron core for 32 times. Taking Emperor AV-228 professional power amplifier as an example, the primary winding of its ring transformer is 1068T. Double parallel winding of 534T, winding of 534÷I6≈34 turns of enameled wire on the bobbin is enough.
4. Winding coil
First, wind the winding once, take high-quality and high-strength enamelled wire with a diameter similar to the original wire, and wind the double-stranded wire in parallel on the I-beam, and cut it after the number of turns meets the requirements. Stick the end of the double thread on the outer circumference of the annular core with double-sided tape, so that the thread shuttle can be wound in the inner hole of the annular core, as shown in Figure 3. After winding the first layer of coil, brush a layer of insulating paint (which is beneficial to the positioning and insulation of turns), wrap a layer with cellophane, and then wind the second layer of coil. After winding, the head and tail of the two coils are connected in series, and the other two ends are welded and insulated with soft leather wires. Before winding the secondary winding, a layer of interlayer insulating paper is added to the primary system, and the winding method is similar to that of the primary winding.
When all windings are wound, put the ring transformer into a constant temperature box and bake for a period of time to dry the insulating paint. Then wrap a thick layer of insulating paper on the outermost layer, and the toroidal transformer is completed.
The above is the introduction of all the production methods. It seems complicated, but as long as you follow the required steps, it is still very simple. First of all, we should see the main points and operating procedures clearly and understand the principle, and then choose different production methods according to different needs and conditions. Each production method has its own uniqueness. I believe these methods can meet everyone's needs. I believe that I will be very excited when I successfully make a toroidal transformer myself.
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