LE1D09Q7 | SCHNEIDER ELECTRIC Engine starter

What are star connections and triangle connections?

Star connection and delta connection are two different methods of connecting the windings of a three-phase electric motor. Each method has distinct characteristics that influence engine behavior and performance.

Star connection

In a star connection, the starting ends of the three windings are connected together at a central point, called the neutral point or common point. This point is usually grounded. The other three ends of each winding are connected to the phases of the electrical network.

A star connection produces a lower line-to-line voltage compared to a delta connection, because each winding receives only the simple voltage from the network. Thus, the current in each winding is also reduced, resulting in reduced power consumption and better efficiency.

Triangle connection

In a triangle connection, the windings are connected end to end to form a closed circuit in the shape of a triangle. Each connection at the ends of the windings is connected to a phase of the electrical network.

In this configuration, each winding receives the line-up voltage from the network, resulting in a higher voltage and current in each winding compared to a star connection. This results in higher power consumption and potentially less efficient engine operation.

Which motor for star-delta starting?

The choice of a motor suitable for star-delta starting depends mainly on the specific needs of the application in question. However, there are some key features to consider when selecting an engine.

Motor with suitable windings

For a motor to be compatible with star-delta starting, it must have windings that can be connected in star and delta. Many three-phase motors are designed to work with both of these configurations. It is therefore necessary to check the motor nameplate or consult the manufacturer's documentation to ensure compatibility with star-delta starting.

Power and torque

Choosing a motor must also take into account the power and torque needed for the application. In star-delta starting, the change from star to delta configuration is generally accompanied by an increase in torque and power. It is crucial to choose a motor that can provide the required performance while maintaining good reliability and long life.

Operating voltage range

Also make sure that the motor can operate smoothly within the range of supply voltages intended in your application. A star-delta start has different voltage and current characteristics between the initial (star) and final (delta) phases, so it is important to select a motor that can tolerate these fluctuations.

The advantage of star-delta starting

Star-delta starting is widely used in various industrial applications due to its many advantages, including reliability, performance and equipment protection.

Reduction of overcurrent at start-up

One of the main advantages of star-delta starting is that it significantly reduces the overcurrent that occurs when starting the motor. By first connecting the star windings, the starting current is reduced by approximately 30% of the value that would be obtained with direct connection. This helps protect the motor and associated equipment from current surges and prevents potential damage.

Soft start

With star-delta starting, the motor gradually starts in the star configuration before switching to delta mode once it reaches its rated operating speed. This method eliminates mechanical shocks to the system and gives the installation more time to adapt to the load imposed by the motor.

Optimization of energy use

By modifying the connection of the windings during the starting phase, star-delta starting makes it possible to optimize the use of the electrical energy consumed by the motor. By avoiding wasting energy in the form of heat or excessive vibration, this method helps improve overall system performance and reduce long-term operating costs.

Star-delta starting offers many advantages for three-phase electric motor systems. Understanding the differences between these configurations and choosing a motor suited to your specific application can help you take full advantage of these benefits and improve the overall performance of your industrial equipment.

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