Delta connection: features and advantages of the circuit, star connection

Connection diagrams of power supplies and windings of consuming devices are used for different purposes. With their help, the power of voltage transmission is increased, drops and failures are reduced. And also they allow not to use a large number of wires to connect the load to the network. In physics, several methods of connecting resistors are used: parallel, series, combined, delta and star connection.

Features of the schemes

Series, parallel and mixed connection are most often used for a single-phase network. The windings of consumer devices and a power source in a three-phase network are connected in a star or delta. Chains differ in load on electricity, so before use, you need to find out the strengths and weaknesses of each type of connection.

In parallel circuits, the start and end of the resistors are tied to different points, and a separate current flows through each component.

With a serial connection, the components are on the same line, the beginning of the second component is connected to the end of the first. In mixed circuits, both types of connection are used. But separately it is necessary to disassemble the features of triangular circuits.

Star and triangle

Resistors in a star circuit are connected to one point - zero or neutral. It is connected to the same point on the power supply. But such a connection is not always possible. The circuit is called four-wire if connection is possible, and three-wire if the automatic current feeder does not have a neutral point.

When connected in the form of a triangle, the ends of the resistors are not combined at one point, but are connected to the ends of other windings. The circuit looks like an equilateral triangle, and the components in it are connected in series.

The main difference from the star-shaped scheme is the absence of a zero point. Therefore, the circuit is three-wire.

In three-phase networks, two types of voltage and electricity are distinguished - linear and phase. The latter type is calculated as the difference between the end and the beginning of the consumer phase. This current flows only in one phase of the device. Features of quantities in different circuits:

• phase voltages in the star - Ua, Ub, Uc;
• phase power of electricity - Ia, Ib, Ic;
• voltages when using a delta circuit - Uab, Ubc, Uca;
• current indicators - Iab, Ibc, Ica.

Between the beginnings of the phases or linear conductors, there are corresponding quantities. Electricity flows in components between the load and its source. In the star circuit, the currents are equal to the phase currents, and the line voltages are equated to Uab, Ubc, Uca. In a triangular circuit, the opposite is true: phase voltages are equal to values ​​of a different type, and electricity is Ia, Ib, Ic.

It is also necessary to take into account the electromotive force of the voltage, since without it it will not be possible to carry out calculations and analysis in a three-phase network. This value affects the vector ratio in the diagrams.

Chain advantages

Both schemes have significant differences and are applied in different ways in practice. When the electric motor is started, the current will be greater than its rated value. The protection may not turn on if the mechanism has a low power level. Otherwise, the protective device will work, but the power will be cut off, the voltage will drop, and some fuses will burn out. Because of so many problems, it is necessary to reduce the amount of electricity.

To do this, a choke, transformer or rheostat are connected to the electric motor. Additionally, you can change the connection diagram of the rotor resistors, which is quite simple to implement in practice. It will be effective to switch circuits to a star or triangle. That is, when the motor is turned on, the resistors will be connected in the form of the first figure, and after a set of revolutions, the connection is changed to a triangular one. In an industrial environment, the change in connections occurs automatically.

Both types of chains can be used at the same time. A zero of the electrical network is connected to the neutral point of the motor. This protects against the risk of imbalances in phase amplitudes. The power supply neutral restores the asymmetry caused by the different inductive reactances of the resistors.

The star schema has several advantages:

• the motor starts smoothly;
• the engine works with the power that is stated in its passport;
• the operating mode is maintained during voltage drops or overloads;
• the body of the device does not overheat during operation.

The triangle allows you to squeeze the maximum possible power out of the electric motor. But the modes must be maintained according to the operating conditions. The use of this chain allows the motor's capabilities to be increased three times compared to the star. Different connections of the ends of the resistors make it possible to obtain two voltage ratings. The electrical load when starting the appliance is reduced by switching the connections.