for houses and life
the coherent equipment
the help data
the review of the radio amateur circuits in magazines
ACCOUNT of the POWER TRANSFORMER
In radioamateur practice sometimes there is a necessity for manufacturing the transformer with non-standard values of a voltage and current.
It is good, if it is possible to pick up the ready transformer with the necessary windings, otherwise transformer should be made independently.
This page is devoted to manufacturing of the power transformer by the forces. In industrial conditions account of the transformer - rather lab our - consuming work, but for the radiofans the simplified techniques of account are created. From one of such techniques I also want you to acquaint.
Before the beginning of account we need to be defined with the target data of the future transformer.
First - rated power (P). The capacity of the transformer is defined as the sum of capacities of all secondary windings. Capacity any of secondary windings is determined from product of a voltage on a secondary winding and output of a current (voltage) for account we take in Volt, and current - in Amper).
Proceeding from received rated power of the transformer it is possible to calculate the minimal section of the core (S) (is measured in square centimeters). At a choice of the core are guided by width of the central plate of the core and thickness of a set. The area of section of the core is defined as product of width of a plate on thickness of a set.
S ferrum = L*T (all sizes undertake in Centimeters!)
S of a window = h*b
Also it is useful at once to calculate the area of a window of the core, chosen by us. This size will be used for check of factor of filling of a window (easier speaking - all windings on the given transformer, whether or not) will be placed.
Further - we begin calculation of factor N. This factor shows, how many coils are necessary to wind for reception of a pressure on a winding in 1 volt.
The further account is reduced to multiplication of a pressure on a winding on it factor (N). This procedure is identical to all windings.
Further - the working current in a network winding proceeding from capacity of the transformer and mains voltage is considered.
The diameter of a wire in windings pays off under the given formulas (current undertakes in MilliAmp!).
At the end of account we check factor of filling of a window by windings. If this factor does not exceed 0,5 - all in the order - it is possible to begin winding, otherwise it is necessary to use the core with the greater area of section and to make all account anew...
If you will have a ready power transformer with rated power not below, than it is necessary, it is possible a network winding to not rewind, and to be limited to account only of secondary winding.
For an example: to us the power transformer for charge of the automobile accumulator with rated current to charge5 Amp is necessary.
Thus - the capacity of such transformer should be not less than 90 WA (18 volts multiplied on 5 Amp).
In this case it is possible to use the power transformer such as TS180 from the lamp black-and-white TV set. The alteration of such transformer is reduced only to rewind of a secondary winding. The given transformer is made with application so-called "Î" - figurative core and has two coils. All windings of such transformer are shared half-and-half and are reeled up on both coils. For alteration we assort accurately core (previously having marked one of the parties of the core, as parts at assembly of the transformer are adjusted to each other), we take up all windings, except for marked in the figures 1-3. During taking - up to warm up of a winding she is reeled - up by the thickest wire) it is necessary to count number of coils. The received number of coils is divided on 6,5 - we receive quantity of coils of a winding of the given transformer on 1 volt. Then we multiply this number on 18 and is received the necessary number of coils of a secondary winding. Under the formula we consider a diameter of a wire of a secondary winding. At the given current of a winding the diameter of a wire should be not less, than 1,42 millimeters. If you will find such wire, the secondary winding needs to be shared into 2 parts and to reel up on each skeleton then to connect windings consistently. It is possible to use a wire of a smaller diameter (for example 1,0 millimeters). In this case on each skeleton is reeled up complete number of coils and winding is connected in parallel.