When designing a homemade power supply with a certain difficulty causes winding of the mains transformer, especially in the absence winding of the machine. You can buy a transformer, but it does not always provide the required parameters of the power supply. The most time-consuming to manufacture primary the winding.
Offer the option of transformer design, which already has a primary the winding. You need an appropriate size standard magnetic starter, for example, PMI and others Such actuators are widely used in industrial the electrical equipment. They can be from faulty contact, broken body, but always with a healthy retractor coil.
The starter should be disassembled, remove the coil and both halves of the magnetic core. On the coil has enough space to accommodate the secondary winding to fill the window magnetic circuit With the primary winding is used as a primary and enabled in the electrical network. Data to calculate the number of turns of the secondary winding there are on the spool starter On it shows the nominal voltage, frequency, number of turns, mark and wire diameter For example, U=220 V 50 Hz W=4100 Vit sew-2 O 0.14 mm. Based on these data, calculated the number of turns of the secondary winding depending on the required voltage at its output.
The calculation is made according to the formula WII = WIUII /UI WII where is the number of turns of the secondary winding; WI is the number of turns of the primary winding; UI is the voltage on the primary the winding; UII - voltage on the secondary winding. The calculated number of turns the secondary winding should be increased by 10 - 15%. The diameter of the wire is taken in depending on load and conditions populate the window of the magnetic circuit. After winding the secondary winding must be isolated by any insulating material.
On one of the sides of the magnetic circuit are short-circuited copper coils. In I have mentioned magnetic starter PME two of them. These coils need to be removed, you can just open. This reduces the consumption of network magnetizing current (idling current) and decreases heating of the transformer.
After checking the settings are wound transformer, the ends of the magnetic core need glued together. For this purpose the ends of both halves of the magnetic core need clean away dirt, oil and grease with solvent (acetone, etc.). Then lubricate the ends of the epoxy paste the two halves into the coil and slowly tighten in the grip. After curing of the adhesive (24 h at normal temperature) the transformer is ready. Made in the described way a transformer works noiselessly.
Author: E. Kolesnikov, C. Gavrilis Voronezh region.