What is the meaning of the star junction between the primary and secondary sides of the transformer?

The meaning of the star junction angle connection between the primary and secondary sides of the transformer is that the high voltage is y (star connection), the low voltage is y connection (also star connection), and n means that there is a neutral line leading out. The line voltage of the low voltage is 380V (400V at no load), which means 380V between the three live wires.

A transformer is a device that uses the principle of electromagnetic induction to change the alternating voltage, and the main components are the primary coil, the secondary coil and the iron core (magnetic core). The main functions are: voltage conversion, current conversion, impedance conversion, isolation, voltage regulation (magnetic saturation transformer), etc.

According to the use, it can be divided into: power transformer and special transformer (electric furnace transformer, rectifier transformer, power frequency test transformer, voltage regulator, mining transformer, audio transformer, intermediate frequency transformer, high frequency transformer, impact transformer, instrument transformer, electronic transformer, reactor, transformer, etc.). Circuit symbols often start with t.

Example: T01, T201, etc.

You said a three-phase transformer.

The star connection is that the three phases of the three-phase generator are connected to the original edge of the transformer, and the three-phase circuit shares a line, which can also be called the center line, and the current on the center line is zero when the load on the three phases is equal.

The middle line is generally omitted, and the secondary corner connection is equivalent to connecting three resistors on the secondary side of the transformer, and these three resistors are connected in order to form a triangle, and the three that are drawn from the secondary side of the transformer.

The root line is connected to the three vertices of this triangle separately, which is called"Corner joints"

A star connection is equivalent to one end of three resistors connected together, and the other three ends are connected to three wires drawn from the secondary side of the transformer.

Type Y is mostly used to provide grounding for the high-voltage side because it has a neutral point that can be grounded, that is:

The triangle (d) connection is to connect the three-phase load (or coil) end to end to form a closed triangle, which leads from the three vertices of the triangle.

The star (Y) connection is to connect the three ends of the three-phase load (or coil) together to make the neutral point (the neutral point can also be drawn out), and the three heads are led out.

When connected in a triangle, the phase voltage is equal to the line voltage, and the line current is equal to 3 times the root number of the phase current.

When the star is connected, the line voltage is equal to 3 times the root number of the phase voltage, and the line current is equal to the phase current.

The coils of a transformer are divided into heads and tails.

The star connection method is that the three coils are connected together, and the lead wire is the neutral line, that is, the neutral wire. The lead-out wires of the three heads are the ABC three-phase.

The triangular connection method is that the three coil heads and tails are connected into a triangle, and the lead wire of the three corners is the ABC three-phase, and there is no zero line in this connection.

Generally, the high-voltage side of the transformer is connected by triangle or star, and the low-voltage side (381 220V) is connected by star. Hope the above is helpful to you.

If the input voltage is 380V angular type, then after changing the 660V voltage input, it will become a star type.

It's just that the input method is different, the phase voltage is different, and the star connection and triangle connection are different.

Voltage vs. number of turns of the coil:

u1/u2＝n1/n2

U1 Primary Side Voltage, U2 Secondary Side Voltage, N1 Primary Side Turns, N2 Secondary Side Turns) Relationship between Current and Turns (Voltage).

i1/i2＝n2/n1＝u2/u1

Or: i1 u1 i2 u2

i.e.: p1 p2

P1 primary power, P2 secondary power).

The voltage ratio is inversely proportional to the current ratio and directly proportional to the number of turns.

1. The characteristics of the star connection are that there are fewer coils and the current is large, and the characteristics of the corner connection are that there are many coils and the current is small. Because of the high voltage on the high-voltage side of the large transformer, the number of angular coils will be more, increase the coil production time, and reduce the number of coils with star connection, although the current increases, but the high-voltage current is small, and it does not increase much; The current on the low-voltage side is large, and the corner connection is used to reduce the current, reduce the cross-sectional area of the wire, and facilitate the processing and production of the coil.

2. The high-voltage side of the large transformer is above 110kv, and the neutral line is grounded in the mode of operation, and the star connection is used to facilitate the grounding of the neutral line (neutral wire); The low-voltage side of the large transformer is 35kV or 10kV, in order to improve the reliability of power supply, the neutral point is not grounded to operate, and the angle shape is selected, which can save materials.

Reduced insulation requirements and reduced harmonics.

For large transformers, there is a difference, and the triangle connection can give the third harmonic.

The wave provides a loop path to avoid unnecessary troubles caused by the closure of the third harmonic through the structural parts. There is no difference for such a small transformer, but it should be noted when designing that the star wiring current is equal to the phase current, and the line voltage is a multiple of the phase voltage.

Mainly from different sources of output voltage: when the star-shaped BAI method is used, the output voltage is equal to the phase voltage of the transformer (if the phase voltage is 220V, then the DAO output voltage is 220V); When the delta connection method is used, the output voltage is equal to 3 times the phase voltage of the transformer (if the phase voltage is 220V, then the output voltage is 380V).

Characteristics of the star connection (Y) connection method:

1. There can be a neutral point to elicit.

2. The second harmonic and zero sequence current cannot circulate internally.

3. The line current is equal to the phase current.

4. The line voltage is 3 times the root number of the phase voltage.

Characteristics of the triangular connection (D) joint:

1. The second harmonic and zero sequence current can flow in the triangle and have no effect on other coils.

2. There can be no neutral point to eliminate.

3. The line voltage is equal to the phase voltage.

4. The line current is 3 times the root number of the phase current.

The star connection is 3 times the root of the angular connection.

There are two connection methods for three-phase alternating current, which are divided into star connection and angular connection.

Star connection - it is a connection method in which the three ends of the three-phase load are connected together as the common end, and the three heads lead to the connection of three live wires. (For example, phase A load is represented by ax, phase B load is represented by by, and phase C load is represented by CZ, that is, X and Y and Z are connected together to lead to three wires A, B and C) The voltage borne by each phase coil of the load is 220 volts, that is, the voltage between the live wire and the neutral line (neutral wire) is 220V.

Angular connection - is the connection method that connects the beginning and end of each phase of the three-phase load in turn. (For example, phase A load is represented by AX, phase B load is represented by by, and phase C load is represented by CZ, that is, X is connected to B, Y is connected to C, Z is connected to A, and the three wires drawn out are BX, CY, and AZ) The voltage borne by each phase load is 380 volts, that is, the voltage between the live wire.

The three-phase winding of the motor is completely connected to the end cover, there are six heads in the end cover, the three heads below are connected together, and the three heads above are connected with three wires respectively; The upper and lower heads are connected vertically, and the three lines are drawn out separately is a triangular connection.

Phase voltage - the voltage at both ends of each phase winding, called phase voltage.

Line voltage – The voltage between any two live wires is called line voltage.

Phase current – The current flowing through each phase load is called phase current.

Line current – The current flowing through each phase line is called line current.

In the star connection: U line = phase I phase = i line.

Triangle connection: In a triangle connection, you phase = u line and i line = phase.

If the power transformer you are referring to is the transformer that supplies power to civil electricity in the power system, then you are right, the user side of the general civil transformer is connected to the star wiring. This is because this wiring method can meet the user requirements of 380V voltage, and can also meet the user requirements of 220V voltage, and the star wiring can lead out the zero line from its center point, and the safety of the civil power system can be guaranteed after being connected with the grounding network.

But if it is a transformer used in industry, its user side is not necessarily a star wiring. Because most of the industrial electricity is 380V, so the user side of some industrial transformers is connected to the triangle wiring, the advantage of this wiring method is that the third and third multiples of the higher harmonics circulate inside the triangle wiring, so that the output voltage quality is better.

If the YD11 type has a triangular connection on the low-voltage side of the transformer, if it is dy11 or the low-voltage side of YYNO, it is star-shaped, and 380V and 220V can be produced, as mentioned above.

In some low-voltage systems, such as user lighting, etc., the power transformer user side uses a star connection, which can meet the needs of users of different voltage levels.

It is generally a star type. The triangle only appears in a 10kV transformer that needs to be connected to a 6kV system.

It can be either a triangle or a star.