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Small transformer design

Small transformers are 2kva power transformers and audio transformers below. Small transformers in the design of a certain skill.
 
1.determine the size of the transformer cross-sectional area.
In general, the core cross-sectional area a is determined according to the total transformer power P. Design time, if the load is basically the same, the corresponding cross-sectional area of the core can usually take the theoretical value of a = 1.25. If the load changes greatly, such as some equipment, some audio, power amplifier, etc., then the cross-sectional area of the transformer should be properly larger than the normal theoretical calculations, so as to ensure sufficient power output capability.
 
2. transformer determine the number of turns per second.
The number of turns of the transformer is mainly based on the cross-sectional area of the core and the quality of the silicon steel. Experiments show that the number of turns per volt should be booked to give the value of the formula to reduce the value of 10% to 15%. For example, a 35w power transformer, but the actual only 6 turns per volt on it, so after the winding transformer no-load current around 25ma. Usually reduce the number of turns, the winding out of the transformer can not only reduce the internal resistance, but also to avoid the usual specifications of the silicon steel often does not cause trouble around, but also saves costs, thereby increasing the cost.
 
3. enameled wire diameter to determine.
Wire diameter should be based on the load current to determine, as the current enameled wire in different environments, a larger gap, so to determine the magnitude of larger diameter. General cooling conditions are not ideal, when the ambient temperature is relatively high, the current density of the enameled wire should take 2a / mm2 (diameter). If the transformer continuous working load current remains the same, but its own cooling conditions better, coupled with the ambient temperature is not high, so enameled take current density 2? 5a / mm2 (diameter), if the transformer current only has the maximum operating current Of the 1/2, such enameled take current density 3 ~ 3.5a / mm2 (diameter). Audio transformer enameled wire current density of 3 ~ 5 ~ 4a / mm2 (diameter). In this way, quality can be assured and the cost can be greatly reduced.
 
In summary, in order to design a high cost of transformers, the core cross-sectional area can only be small; appropriate to reduce the number of turns per volt; detailed analysis of load conditions; reasonable use of enameled wire specifications. Only through repeated practice careful consideration, can really grasp the design principles and skills of transformers.