The equivalent transformer model represents the transformer in terms of what kind of equivalent circ

The equivalent transformer model is represented by an equivalent circuit.

1. The equivalent parameter is related to the change ratio and has no actual physical significance.

2. YT in the model is not the transformer excitation branch admittance.

3. The transformer parameters should generally be attributed to the low-voltage side, because there is only one tap on the low-voltage side, and the transformer parameters attributed to the low-voltage side do not change with the change of the transformer ratio.

4. The transformer adopts the type equivalent model, the line parameters do not need to be calculated, and the voltage of each node in the equivalent circuit is the actual voltage.

5. When considering the excitation branch, it is usually connected to the side away from the ideal transformer.

6. It is suitable for computer calculation, and there is no need to calculate the voltage level.

Compare the difference between transformer-type equivalent circuits and type-equivalent circuits: different meanings, different properties.

First, the meaning is different:

The equivalent circuit of the transformer is only different from single-phase and three-phase, and then the equivalent resistance and inductance are different. The choice of what type of equivalent circuit is relevant to the purpose of the analysis and, of course, to the simulated object. Equivalent circuits of medium length lines may need to choose different models for different analysis purposes or collapses, not just for pig-shaped equivalent circuits.

In general, the steady-state calculation is relatively simple to choose a flat equivalent circuit.

Second, the nature is different:

in alternating current. In addition to the resistance that hinders the current, capacitors and inductors also hinder the flow of current, which we call reactance.

The reactance of capacitance and inductance is called capacitive reactance, respectively.

Inductive resistance. Its unit of measurement is the same as resistance in ohms.

The higher the frequency, the smaller the capacitive resistance and the greater the inductive resistance, and the lower the frequency, the greater the capacitive resistance and the smaller the inductive resistance.

Brief introduction. The frequency range of the resonant transformer is 1 50kHz, which can be used with the intermediate frequency electric furnace, intermediate frequency power supply, and ultra-audio power supply, and is used for diathermy of workpieces, quenching and annealing of metal workpieces, heating of intermediate frequency transformers, and diffusion welding of metals [brazing] and other process equipment. The core of the multi-turn ratio intermediate frequency transformer is made of oriented and high magnetic permeability cold-rolled silicon steel sheet.

It is composed of stacks and is processed and assembled by special technology. The maximum number of turns is 23 turns, which can also be varied according to the capacity and frequency of mass destruction. The resonant transformers are cooled by water.

Because the number of turns of the primary and secondary windings of the transformer is not slow to guess, etc., and even the difference is very large, and the primary and secondary windings are not directly connected with each other, and are only connected by electromagnetic induction, so the calculation is very cumbersome and inconvenient, and the accuracy is reduced.

In order to use a pure circuit with circuit relationship and electromagnetic coupling to calculate, it is necessary to use the method of attribution, one side of the transformer is calculated to the other side, and the two sides are combined, so that the transformer becomes a pure circuit, and this circuit is called the equivalent circuit of the transformer disturbance type. The conditions for the calculation are: the magnetic potential equilibrium relationship and various energy relationships before and after the calculation should remain unchanged.

Brief introduction. A transformer is a static electrical equipment used to convert AC voltage and current and transmit AC electric energy. It is based on the principle of electromagnetic induction to achieve the transfer of electrical energy.

Transformers can be divided into power transformers, test transformers, instrument transformers and special-purpose transformers according to their uses: power transformers are necessary equipment for power transmission and distribution, and power user distribution.

Test transformer equipment for withstand voltage test of electrical equipment; The instrument transformer is used for electrical measurement and relay protection of the distribution system; Special-purpose transformers include smelting furnace transformer and rotten voltage transformer, electric welding transformer, electrolytic rectifier transformer, small voltage regulating transformer, etc.

The above content reference: Encyclopedia - Power Transformer.

Answer] In the equivalence model of the :d power system, the transformer mode is usually represented by a conformal equivalent circuit with centralized parameters.

Answer] In the equivalence model of the :d power system, the transformer mode is usually represented by a conformal equivalent circuit with centralized parameters.

Yes. The equivalent transformer model is a simplified model for the use of the verbecillated car in the power system, which is used to calculate and analyze the transmission characteristics of the transformer in the power system. The model is based on a number of assumptions and approximations, so in some cases there may be some deviations from reality.

However, in most practical power systems, the equivalent transformer model has been widely used and has been proven to be effective in practice.

The main assumption of the equivalent transformer model is that the transformer is considered as an ideal transformer, i.e., the transformer's parameters such as transformation ratio and efficiency are fixed and are not affected by factors such as load current. In addition, the equivalent transformer model ignores nonlinear properties such as electromagnetic coupling and hysteresis inside the transformer, as well as complex factors such as the distribution of resistance and inductance inside the transformer. These approximations and assumptions may lead to some differences between the equivalent transformer model and the actual situation, but this difference is acceptable in the case of the loss of the land tunnel, and will not have a great impact on the calculation and analysis of the power system.

Therefore, the equivalent transformer model is an approximate model, but it has been widely used in practice and can usually provide more accurate calculation results.

The equivalent transformer model is an approximate model used to describe a power transmission system with a transformer in a system. In this model, the transformer is simplified to an ideal transformer, and the voltage on the secondary side is equal to the voltage on the main side multiplied by the transformation ratio, while ignoring the influence of nonlinear components such as resistance, inductance, and capacitive reactance of the transformer itself.

Therefore, the equivalent transformer model is a model that approximates the operation of the transformer, and only has a certain use value when analyzing the overall behavior of the system, while Lu Youchen needs to consider more complex transformer models in the specific design and operation control to ensure the stable operation of the system.

In practice, the equivalent transformer model is often used for static steady-state analysis and power flow calculation of the power system, while more complex models are required for the dynamic response and transient process of the transformer. Therefore, the equivalent transformer model is an approximate description of the actual transformer, which is used to simplify the complexity of power system calculations and analysis, and is not a complete replacement for the actual transformer.

Equivalent circuit 1The three impedances (admittance) in the transformer's equivalent circuit are all related to the transformation ratio; The signs of the impedance (admittance) of the two parallel branches of the type are always opposite.

1. Differences between parameters:

1. Experimental data can be obtained from short-circuit experiments: Short-circuit test: short-circuit one winding on one side, and apply voltage to the other winding, so that the current leakage of the winding on the short-circuit side reaches the rated value.

2. Percentage of transformer short-circuit voltage: refers to the percentage value of the ratio of the voltage drop on the transformer to the rated voltage of the transformer when the transformer passes the rated current in the short-circuit test; No-load test: one side of the winding is opened, and the rated voltage is applied to the other side winding; No-load current percentage:

Refers to the ratio of no-load current to rated current multiplied by 100.

3. Calculation of parameters Finding rt Finding xt xt is determined by the us% obtained from the short circuit test Finding gt: GT is determined by p0 of the open circuit test Finding bt: BT is determined by i0% of the open circuit test Points to note.

2. Differences between each quantity unit:

1. Which side of un is the calculated parameter and equivalent circuit are converted to that side.

2. The voltage ratio of the primary and secondary sides of the three-phase transformer is not necessarily equal to the turns ratio.

3. Regardless of the connection method of the three-phase transformer, the parameters obtained are the one-phase parameters in the equivalent y y connection method 5The excitation branch is placed on the power input side (power supply side, primary side) 2 and 3 winding transformers 2 and 3 winding transformers Equivalent circuit Acquisition of parameters Open circuit test: add un on one side and open circuit on the other side.

4. GT and BT are the same as those of double winding Short circuit test: add low voltage on one side to make the current reach the rated rate, and in the other two sides, one side is short-circuited and one side is open-circuited. Get:

Find R1, R2, R3 For the three windings, the transformer capacity and the winding capacity are not necessarily equal, if the transformer capacity is 100 (%), the winding rated capacity ratio is 50, 100, etc.

3. Difference in capacity ratio:

When the capacity ratio is not equal, such as The following parameters should be noted that the parameters are the parameters under the capacity of the corresponding transformer. The windings with 50% transformer capacity participate in the short circuit test, and can only do the allowable current of 1 2 transformer capacity.

2. In the converted transformer, the capacity ratio between the windings is the current ratio, and the loss is proportional to the square of the current, so the short-circuit test data corresponding to the winding with 50% capacity must be attributed to the transformer capacity. Each measured value is x1, x2, x3 and is set to the corresponding short-circuit voltage us1%, us2%, us3% of each winding.

The physical quantities of the secondary side of the transformer are calculated.

The atducted value of any physical quantity in volts is equal to the original value multiplied by k, the inducted value of any physical quantity in ohms is equal to the original value multiplied by k2, and the attributed value of current is equal to the original value multiplied by 1 k

After calculation, the circuit is equivalent to a T-type.

In omitting simplification.