The transformer 220 to 36 volts is ideal for powering the lighting circuit in baths, saunas, bathrooms, basements. Safety requirements impose some restrictions on the use of AC voltage of 220 volts in rooms with high humidity. Therefore, the ideal way out of this situation is the use of AC voltage of 12, 24 or 36 volts. If a person comes into contact with the electric network, he will feel only a slight blow. It will not do any harm to the human body.
Transformer design
Like any other, a step-down transformer from 220 to 36 volts consists of three main components:
- Primary winding.
- Secondary winding.
- Magnetic circuit.
Both the primary and secondary windings consist of a certain number of turns of copper wire. Usually they use copper wire in varnish insulation, since it is much better in its characteristics than aluminum. If you use aluminum, it will require several times more, which significantly increases the dimensions of the transformer. True, aluminum wires in varnish insulation were previously used in voltage stabilizers. The magnetic circuit can be made of transformer steel or of a ferromagnet. This is a material that is significantly better than any metal.
Power and Transformation Ratio
You can even visually assess the power of any transformer - the larger the dimensions, the higher it is. But for the exact calculation of power it is necessary to use special formulas. The simplest method for calculating the power of a transformer is to multiply the voltage of the secondary winding by the current strength in it. Get the real power value of the investigated transformer. To work on creating and designing such a device, you will need to know one more main parameter characterizing the transformer.
This is nothing but a transformation ratio. It is the ratio of the number of turns of the secondary winding to the primary. The same value can be obtained if we separate I2 / I1, as well as the voltage U2 / U1. In any of these three cases, you get the same value. You may need it when you independently calculate the exact number of turns for the primary and secondary windings.
Transformer Calculation
If it is necessary to make a transformer 220 by 36 volts (1000 watts), it is advisable to use the formula for calculating the power in the secondary winding. It was mentioned above, power is equal to the product of current strength by voltage. In this case, there are two parameters that are known to be known - this is directly the power of P2 (1000 W) and the voltage in the secondary circuit U2 (36 V). From this formula it is now necessary to calculate the current that flows through the primary circuit.
One of the important parameters is the efficiency, which for transformers does not exceed 0.8. It shows how much power consumed directly from the network goes into the load connected to the secondary winding (in this case it is only 80%). The difference in power goes to heating the magnetic circuit and windings. It is lost, and irrevocably. The power that is consumed from the AC network is equal to the ratio of P2 to the efficiency.
Transformer magnetic core
All power passes from the primary to the secondary by means of a magnetic flux, which is created in the magnetic circuit (core). The cross-sectional area of the core S depends on the power P1. Most often, a set of plates in the shape of the letter “Sh” is used for the core. Moreover, the cross-sectional area is equal to the product of the square root of P1 by a factor of 1.2. Knowing the value of the area, it is possible to determine the number of turns W per 1 V. For this, 50 need to be divided by area.
Voltages in the primary and secondary windings are known - these are 220 and 36 volts. The number of turns for each of the windings is determined by multiplying the voltage by W. If decimal values are obtained, it is necessary to round them up. It should also be borne in mind that when a secondary circuit load is connected, a voltage drop occurs . For this reason, it is desirable to increase the number of turns by about 10% of the calculated one.
Winding wires
And now you need to calculate the current in the primary and secondary windings. The current is equal to the ratio of power to voltage. If a transformer 220 for 36 volts (500 watts) is manufactured, then a current equal to the ratio 500/36 = 13.89 A will flow in the secondary circuit. The power in the primary circuit will be 625 W, and the current strength will be 17.36 A.
Next, the current density is calculated. This parameter indicates what value of current falls on each square millimeter of the cross-sectional area of the wire. Typically, transformers take a current density of 2 A / sq. mm The diameter of the wire required for winding can be determined by a simple formula: the efficiency multiplied by the square root of the current strength. Therefore, in the secondary circuit it is necessary to use a wire whose diameter will be equal to the product of 0.8 by 3.73 - this is 2.9 mm (round up to 3 mm). In the primary winding, you need to use a wire whose diameter will be 3.33 mm. In the event that you do not have wires with the right diameter, you can use a simple trick. Win at the same time with several wires connected in parallel. In this case, the sum of the cross sections must be no less than that calculated by you. The cross section of the wire is equal to the ratio of efficiency to the square of the diameter.
Conclusion
Knowing all these simple formulas, you can independently make a reliable transformer that will work in perfect mode. But you still need to know how to connect a transformer 220 to 36 volts. There is nothing complicated in this, it is enough to connect the primary winding to an alternating current network of 220 V, and the secondary to the load, the lighting system, for example. At the first start, try to connect the transformer with the maximum power load to determine if the core and windings are overheated.