The star (Y) connection of a motor, also known as the star connection or Y-type connection, is a common connection method in motor windings.
The first type is the star (Y) connection, as shown in the figure. The Z, X, and Y terminals of the three-phase stator windings inside the motor are connected together to form a common point O. Then, three terminal lines are led out from the starting ends A, B, and C. In the junction box, three-phase AC power (380V) of UVW is respectively supplied to provide the motor with operating power. This type is suitable for three-phase asynchronous induction motors of 3KW and below.
Schematic diagram of two wiring methods inside the motor junction box
Definition and Principle:
A star connection connects the starting points (or ending points) of the three stator windings of a motor together to form a common point, often called the star point or neutral point. Then, the other end (or starting point) of each winding is connected to the three phase lines of a three-phase power supply. This connection method forms a shape similar to the letter "Y," hence the name.
Features and advantages:
High voltage: Star connection can provide higher voltage and is suitable for some applications that require high voltage power supply.
Low current: Due to the series effect of the windings, the star connection helps to reduce the current and reduce line losses.
Good balance: The star connection ensures that the current is evenly distributed among the three phases, and the voltage and current waveforms are relatively stable, which is beneficial to the stable operation of the motor.
Low torque: Compared to the delta connection, the star connection produces a smaller initial torque, making it more suitable for applications with less demanding load requirements.
Scope of application:
Star connection is mainly used for motors with a rated voltage of 380V and a rated capacity of less than 15kW. For motors with higher power, a Y-Δ reduced voltage starting method can be used during light load starting. That is, the motor is first connected in star connection to reduce the starting current, and then switched to delta connection after the motor starts to operate normally.
The wiring method of the motor should be selected according to its rated voltage, rated capacity and actual load conditions.
The delta (△) connection of a motor is a common way to connect motor windings. Its characteristic is that the windings of each phase are connected end to end to form a closed delta circuit.
The second method is the delta (△) connection, where the start and end of the three-phase stator windings are connected correspondingly. As shown in the diagram, connecting the A end of the first phase winding to the Z end of the third phase winding can be considered the U phase; connecting the B end of the second winding to the X end of the first winding can be considered the V phase; and connecting the C end of the third winding to the Y end of the second winding can be considered the W phase. These three wires are then connected to a junction box, supplying a three-phase AC power supply (380V) to the U, V, and W phases to power the motor. This method is suitable for three-phase asynchronous induction motors of 4kW and above. However, the wiring method for the motor should be based on the actual nameplate wiring.
Simple wiring diagram of an electric motor
Definition and Principle:
A delta connection in motor configuration involves connecting the three stator windings of the motor end-to-end in sequence to form a closed delta circuit. Specifically, one end of each winding is connected to one end of the adjacent winding, forming a closed loop. This connection method ensures that each winding is directly connected to the other two windings, forming an equilateral triangle structure.
Features and advantages:
High starting torque: The delta connection can provide high starting torque, making it particularly suitable for heavy-load starting and high-load operation.
Current characteristics: In a delta connection, the phase current and line current of the motor windings are numerically equal. Because the windings are directly connected, current can flow freely between the coils, resulting in a larger current.
Voltage characteristics: In a delta-connected circuit, the phase voltage of the load is equal to the line voltage of the power supply. This means that the motor can fully utilize the power supply voltage, thereby increasing the motor's output power.
Efficiency and stability: By changing the phase relationship and circuit structure of the motor, the delta connection helps to improve the efficiency and stability of the motor.
Scope of application:
Delta connection is typically suitable for motors with a rated voltage of 380V or higher and a large rated capacity. It is particularly suitable for applications requiring high torque and stable operation, such as wind turbine generators, compressors, and centrifugal pumps.
Precautions:
When selecting the motor connection method, the motor's rated voltage, rated capacity, and actual load conditions should be comprehensively considered. Incorrect connection may lead to motor overheating, damage, or performance degradation.
