# On-line calculation of step-up transformer. Calculation and manufacture of power transformers.

### On-line calculation of step-up transformer. Calculation and manufacture of power transformers.

The most responsible and expensive part of the power supply for radio equipment powered by AC mains is the power transformer. An example of a transformer concept is shown in Figure 4. 1. The transformer has cores assembled with transformer plates. The transformer windings are made of insulated copper wire on the press frame.

The transformer core is assembled into two types of plates, L-shaped and W-shaped. The type of plate determines the design of the transformer, as shown in Figure 1. 2

In the core core (L-shaped plate), the transformer windings are evenly distributed on both loads (Figure 2a). For example, the basic (network) winding and step down for heating the lamp are placed on one rod and the secondary step (high pressure) windings on the other rod. In this type of plate, the windings are often placed on one core of the core.

In the external core (W-type plate), all windings are placed in the middle bar (Figure 2, b).

When the primary winding I of the transformer is connected to the AC power (Figure 3), an alternating current flows and an AC flux is generated in the core. Since the secondary winding II is located at the second terminal of the transformer, the alternating magnetic flux traverses the windings of the secondary winding resulting in electromotive force (EMF) induced by the law of electromagnetic induction. When the unit (voltmeter) is turned on in parallel with the secondary winding, the magnitude of the induced voltage is displayed.

To reduce the voltage on the electrical network, the secondary winding must have fewer windings than the network and must be larger than the primary (network) winding to increase the voltage.

To supply power to the radio equipment, different voltages are required: two small ones to power the glow circuit of the lamp when used in a rectifier, and an anode circuit of the lamp's screen grid and a grid to power the grid A separate voltage is required for the high (followed by commutation) and senotron heat, which can be powered from the common winding of the column.

Due to the loss of the cores and windings of the secondary winding of the transformer, the same power as that supplied to the primary winding can not be obtained. Therefore, there is a concept of efficiency (efficiency) of the transformer. A self-transformer is calculated according to a simplified formula of what is fabricated in an ordinary transformer steel and usually has efficiencies higher than 70-80%.

To obtain a filament power amplifier that requires a transformer, a filament current amplifier, or an AC kenotron 5TS4S rectifier, assume that the circuit receiver must consume 100mA of anode current at 250 V, the current of the heater circuit (2) at a voltage of 6.3 V. 2 And at a voltage of 5V (using their reference data to determine the current consumed by the electrodes of a particular lamp).

Therefore, the auxiliary winding 250V and the current of the lamp filament of 100mA (0.1 A), the winding voltage should be designed 6.3V, ignoring the voltage drop of the internal resistance of the winding inductor (filter inductor kenotron) and the current is 2 A, The filament winding is 5 V and the current is 2A.

Where U is volts and I is amperes. Therefore, P1 = 250 * 0.1 = 25W, P2 = 5 * 2 = 10W, P3 = 6.3 * 2 = 12.6W.

P sat = P 1 + P 2 + P 3 ... W (2)

The power of all three secondary windings is:

P sat = 25 + 10 + 12.6 = 47.6 watts.

If the efficiency of a transformer manufactured in an amateur state is taken as 80% or less,

P lane = 1.2 * P sat. (3)

In our case, the power consumed in the network

RCR = 1.2 * 47.6 = 57.12 watts.

The next step in the calculation is to determine the cross-sectional area, t, e, of the core in square centimeters - Q cm 2. Calculated by formula.

Qcm2 = 1.2 * P / 0.5 = 0.5. (4)

Since the cores are assembled to one another in an insulating thin plate, they are input to the formula element with the charge of 1.2 consideration core. Therefore, our transformer core part is the same

Q cm2 = 1 * 2 57,12 0,5 = 9,07 cm 2

(Considered to be 9.0 cm 2 rounded).

After that, the thickness set in cm (for plate W) cm. By multiplying these values, the width of the intermediate bar for determining the cross-sectional area of the rod must be determined. Since the calculation of the geometric dimensions of the core (thickness and width of the window zone setting plate) beginner ham - rather complicated it can be regarded as a thickness ratio plate thickness ratio, which is simply set to be the same as 2 1.

Table 1

You can use this ratio to ensure that the number of turns from the additional calculations is correct for the core window. At the table. 1 data is 9 cm 2: 2.5 cm = 3.6 cm and 3.6: 2, so choose a plate W-25 with a panel thickness of 3.6 cm and an aspect ratio of 1.44. 5 = 1.44.

n0 = (45 - 60) / Q = turn, (5)

Where Q is the cross-sectional area (in cm) of the core. If you have a good quality transformer steel plate, if the steel is bad, replace the number (45) in the molecule. - Calculate that you are shooting at plants in the core transformer with the same number of revolutions per 60 volts.

Further calculations of the winding no longer indicate difficulty, and it is necessary to multiply the number of windings per volt per set voltage of one or the other winding. Using the voltage at base 127, the included winding 250 in the network must be increased P1 = 127h5 = 635 rotations - P3 = 5 × 5 = 25 and winding filament lamp 6,3 - P2 = 250h5 = 1250 filament kenotron 5 side B - P4 = 6.3x5 = 31.5 turns (up to 32 turns).

Final phase winding calculation - Determine the diameter of the winding by providing a long interruption load transducer with a current density (intensity) per square mm of wire cross section taken less than 2 amps

d = 0.8 * I0.5 = mm, (6)

Where d is the diameter of the wire in millimeters and I is the current in amps.

In our case, d2 = 0.8 * 0.1 0.5 = 0.8x0.316 = 0.25mm; d3 = d = 0.8 * 2 0.5 = 8x1.41 = 1.1 mm (rounded).

I1 = 57.12 / 127 = 0.45 A (rounded),

Therefore d1 = 0.8 * 0.45 0.5 = 0.54 mm or 0.55 mm rounded.

In order to have confidence, we can check that the winding is in the window of the core we chose. You can do this. In the tab. Figure 1 shows that the core plate has a window length of 6 cm and a width of 2.5 cm. However, since windings are wrapped around the frame that takes up a lot of space in the window, it should be reduced according to the thickness of the frame and the thickness of the sleeve. As a result, the window is about 5.2 cm long and 2.2 cm wide. 2, we found that the enamel insulator winding had the following outer diameter: d1 = 0.59 mm, d2 = 0.27 mm, d3 = d4 = 1.15 mm.

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