TM-250 transformer drawing

Contents

1. Introduction

2. Job for coursework

3. Calculation Plan

4. Preparation of magnetic core measurement data

5. Selection of winding connection circuit

6. Rated power and rated currents in windings

7. Determination of rational magnitudes of magnetic induction in magnetic circuit of transformer

8. Determination of number of turns in windings

9. Selection of main transformer insulation

10. Selection of transformer windings type

11. Transformer Winding Design

12. Calculation of losses in transformer windings

13. Calculation of transformer short-circuit voltage

14. Thermal calculation of transformer

Literature

3 Calculation plan

3.1 Prepare magnetic core measurement data for further calculations.

3.2. Select the winding connection scheme.

3.3 Calculate the rated power of the transformer and rated currents in its windings.

3.4 Perform check calculation of transformer magnetic circuit (determine rational magnetic induction), for that:

3.4.1 Calculate the losses in the magnetic core (idling losses) and compare them with the permissible ones according to GOST for this transformer.

3.4.2 Calculate the idling current and compare it with the permissible one according to GOST and give a conclusion on the selected magnetic load.

3.5 Determine the number of turns in the HV and LV windings of the transformer, check the correctness of calculation for all stages of transformation.

3.6 Select the main insulation of the transformer.

3.7 Select types of HV and LV windings of the transformer.

3.8 Calculate and design HV and LV windings of the transformer:

select winding wire grades, calculate and select their standard sections, select insulation materials, determine winding sizes, check their placement in the magnetic conductor windows (in radial and axial directions), draw sketches of one LV winding turn and winding placement on the magnetic conductor.

3.9 Calculate losses in transformer windings (short-circuit losses) and compare them with permissible ones as per GOST, make a conclusion.

3.10 Calculate the short-circuit voltage of the transformer, compare it with the permissible one as per GOST and give a conclusion.

3.11 Perform thermal calculation of the transformer to determine specific heat transfer of windings and give a conclusion.

5 Selection of winding connection circuit

The main advantages and disadvantages of connection schemes of windings of the given transformers.

Scheme U/D11 Advantages: relatively low consumption of electrical materials during manufacture, simplicity of manufacturing technology, therefore, economical; relatively small distortion of the phase voltage system at uneven phase load; higher reliability of electric network operation.

Disadvantages: distribution and consumption of electric power is carried out at reduced (phase) voltage, which causes increased consumption of wires in the lines, increased losses of electric power in them, since lowering the voltage to phase causes an increase in current to linear

(S=З U I=Const); shortened radius of low-voltage lines; impossibility of operation of such transformers in parallel or in a ring with U/Un0 transformers that have received pre-mining application in electrical networks, since they have 11 winding connection group.

Scheme U/Un0 Advantages: minimum consumption of electrical materials for manufacturing, simplicity of manufacturing technology, therefore, minimum cost of transformer; distribution of electric energy with increased (linear) voltage, consumption at reduced (phase) voltage; relatively increased radius of low-voltage lines and reduced power losses therein; the smallest short circuit losses in the transformer compared to others; easy operation.

Disadvantages: sharp distortion of the phase voltage system at uneven phase load.

Scheme Y/Zn11 Advantages: practical absence of distortion of the si-system of phase voltages at uneven phase load; distribution of electric energy with increased (linear) voltage, consumption at reduced (phase) voltage; relatively increased radius of low-voltage lines and reduced electric power losses in them.

Disadvantages: increased consumption of electrical materials, relatively complex transformer production technology, therefore, increased cost; greater short-circuit losses than in the U/U circuit; impossibility of operation of such transformers in parallel or in a ring with U/Un-0 transformers, which have a dominant application in electrical networks, since they have 11 winding connection group.

Diagram D/N 0 Advantages: reduced distortion of the phase voltage system at uneven phase load compared to Y/N transformers; distribution of electric energy with increased (linear) voltage, consumption at reduced (phase) voltage; relatively increased radius of low-voltage lines and reduced electric power losses in them.

Disadvantages: increased consumption of electrical materials, relatively complex transformer production technology, therefore, increased cost; greater short-circuit losses than in the U/U circuit; impossibility of operation of such transformers in parallel or in a ring with U/Un-0 transformers, which have a dominant application in electrical networks, since they have 11 winding connection group.

The advantages and disadvantages of the winding connection schemes allow us to conclude that with a uniform phase load, the most economical Y/UN connection scheme is the most economical one, since in this case the current of the zero sequence I0 is zero, therefore, and U0 = I0Z0 will also be zero, so there will be no distortion of the phase voltage system. With an uneven phase load, I0 is not zero, then and U0≠0, and therefore, in order for U0 = 0 to be zero or as small as possible, either a circuit capable of compensating for zero sequence flows (Y/Zn, D/Un, Y/D) or some kind of balancing device to the Y/Un transformer, for example [1], is necessary.

From the above main advantages and disadvantages of winding connection circuits, for further calculation we accept the U/Un winding connection circuit.

9 Selection of main transformer insulation

The main insulation of oil transformers is transformer oil, dry - air. Therefore, to obtain the required electrical strength, insulation distances are made, which are filled with the main insulation. Main insulation is performed between windings and magnetic circuit, between windings of different voltages on one rod, between winding-s on adjacent rods.

Minimum insulation distances depend: on the kind of insulation (oil or air), on the voltage class of the windings, on the power of the transformer.

Together with the main insulation, the transformer has longitudinal insulation of windings, by which it means insulation between turns of winding wires, layers of turns and between coils in coil windings. The selection of this insulation is determined by electrical strength at a frequency of 50 Hz and is taken according to the tables. At the same time, insulation between turns is usually provided by its own insulation of the winding wire.

We accept the following data from tables 8 [1] and 9 [1]: l02 = 75 mm; a12 = 27 mm;

δ12 =5mm; lts2=50mm; a22 = 20 mm; δ01=1мм; a01=4mm; l01=15mm.

10 Selection of transformer windings type

The choice of winding type depends on transformer power, voltage class, advantages and disadvantages of winding type and their economy .

Practice for transformers with a capacity of 25 to 630 kVA and voltage up to 35 kV inclusive is recommended:

• for LV windings cylindrical single- and double-layer rectangular wire (with large LV is also suitable for HV windings).

Advantages: simple manufacturing technology, good cooling, cheap.

Disadvantages: low mechanical strength.

• for small HV windings, cylindrical multilayer round wire (with small LV (LV) is also suitable for LV windings).

Advantages: simple manufacturing technology, cheap.

Disadvantages: deteriorated heat transfer and reduced mechanical strength with increased power.

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