CARA KERJA STAR DELTA MOTOR 3 PHASE | ALASAN PUTARAN STAR HALUS ? DAN DELTA BERAT ?

Summary

In this video, we explore the difference between Star and Delta motor connections, explaining why motors start smoothly in Star and become heavier in Delta. The Star connection reduces voltage and current, providing a smooth start for light loads like pumps and compressors. In contrast, Delta provides full voltage and current for heavy industrial loads, resulting in higher torque. The video also covers the transition process between the two, using a timer and contactors to ensure a smooth switch once the motor reaches near full speed.

Takeaways

• 😀 The main focus of the video is explaining why motors behave differently during startup in star and delta connections.
• 😀 In Indonesia, the line-to-line voltage is 380V, which is crucial in understanding how motors behave in different configurations.
• 😀 In a delta connection, each winding of the motor is connected to two phases, which results in the motor receiving full voltage (380V), leading to higher current and torque.
• 😀 In a star connection, one end of each winding is connected to a neutral point, which reduces the voltage per winding to approximately 220V, lowering the current and torque during startup.
• 😀 The current in the delta connection is three times higher than in the star connection, making the motor's torque significantly greater in delta mode.
• 😀 Motors in star configuration start with a smoother rotation because of lower voltage and current, making them ideal for light loads like pumps, blowers, and compressors.
• 😀 In the star configuration, the starting current is smaller, which prevents electrical systems from tripping due to overload.
• 😀 The transition from star to delta mode happens after a short delay (typically 5 to 12 seconds) once the motor reaches about 80-90% of its full speed.
• 😀 The motor's torque and speed increase dramatically once it switches to delta mode, making it suitable for full-load industrial applications.
• 😀 Star-delta starting is commonly used to reduce the high starting current, but it’s not compatible with all three-phase induction motors.
• 😀 The video concludes by explaining that star is for smooth startup, while delta is used for full performance after reaching near-normal speed.

Q & A

What is the difference between star and delta connections in a 3-phase induction motor?

In a delta connection, each winding is connected between two phases, allowing the motor to receive the full 380V, which results in a higher current. In a star connection, one end of each winding is connected to the neutral point, which reduces the voltage per winding to approximately 220V, resulting in a lower current and smoother start.

Why does a motor start smoothly in star connection?

In the star connection, the voltage per winding is reduced to 220V, which lowers the current and the torque. As a result, the motor starts gently without high inrush current or heavy mechanical stress.

What is the relation between voltage and torque in an induction motor?

The torque in an induction motor is directly proportional to the square of the voltage. Therefore, a reduction in voltage (like in the star connection) leads to a significant decrease in the torque, making the motor start more smoothly but with less force.

What causes the motor to behave differently when switching from star to delta?

When switching from star to delta, the motor receives the full 380V across each winding, which increases the current and the torque. This leads to a higher mechanical load, making the motor's start heavier with greater force and inrush current.

Why does the motor sound louder and its start become more abrupt in delta connection?

In the delta connection, the motor receives full voltage (380V) and therefore higher current, which results in a stronger torque. This increased torque causes the motor to start abruptly, and the sound is louder due to the higher mechanical stress on the motor.

What is the significance of the motor's transition from star to delta?

The transition from star to delta allows the motor to start with a lower current and smooth motion in star, and then, once it reaches near normal speed, it switches to delta to provide full torque and power for normal operation. This transition is controlled by a timer and contactors to prevent mechanical shock.

Why is the star-delta starting method not suitable for all 3-phase motors?

Not all 3-phase motors are designed to handle star-delta starting. Some motors may not be able to operate efficiently or safely under this method due to their specific design characteristics, such as winding configurations or insulation ratings.

What is the typical delay time when switching from star to delta mode?

The typical delay time when switching from star to delta mode is between 5 to 12 seconds. This delay ensures the motor reaches approximately 80-90% of its normal speed before the switch is made.

How does the current in the motor change when switching from star to delta?

When switching from star to delta, the current increases significantly. In star mode, the line current is around 11 amps, but in delta mode, it rises to about 33 amps due to the higher voltage applied to the windings.

Why is the star connection preferred for light loads like pumps and blowers?

The star connection is preferred for light loads because it provides a lower starting current and smoother operation, making it ideal for applications like pumps and blowers where the load is not heavy and does not require high starting torque.