Why Motor Start in Star and Run in Delta| Star delta Starter| Why Motor Connected in Delta

Electrical With Abhishek Joshi

14 Jul 202405:56

Summary

TLDRThe video script discusses the concept of using a star-delta starter for electric motors, addressing a viewer's question about the logic behind running the motor in delta configuration after starting in star. It explains that starting a motor in star reduces the high starting current, protecting the motor and electrical system from damage. However, after the initial start, the motor is switched to delta for the required high starting and running torque, ensuring the motor can handle the load effectively. The explanation aims to clarify the benefits and necessity of this switching mechanism in electrical engineering applications.

Takeaways

😀 The video discusses the concept of using a star-delta starter for electric motors and the logic behind changing from star to delta configuration.
🔧 When starting a motor through star-delta starting, the starting current is significantly reduced compared to full-load current, which can be six to seven times higher.
⚡ The high starting current in a direct start can cause the motor's circuit breaker to trip due to overcurrent, and it can also affect other feeders due to voltage drop.
🌟 Star-delta starters are used to avoid these issues by applying reduced voltage during the starting phase, thus controlling the inrush current.
📐 In star configuration, the phase voltage is approximately 1.3 times the line voltage, which means starting with reduced voltage compared to the full line voltage.
🔄 The transition from star to delta configuration is necessary because star configuration does not provide the high starting and running torque required by some applications.
🛠 High starting torque is essential for applications that need the motor to overcome high inertia during startup, ensuring the motor can start effectively.
🔄 High running torque is necessary for the motor to handle the load effectively and maintain rotation under the required torque conditions.
⏱ The changeover from star to delta usually occurs after a short period, typically 8 to 10 seconds, to provide the motor with high starting and running torque.
🔌 The script mentions that if the motor is not switched to delta configuration, it may not meet the required torque demands, leading to potential tripping of the motor.
🔧 The video aims to clarify a common question about why motors are not run continuously in star configuration and the necessity of the changeover to delta for meeting torque requirements.

Q & A

What is the main purpose of using a star-delta starter for motors?
-The main purpose of using a star-delta starter is to reduce the inrush current during the starting phase of the motor, thereby preventing damage to the motor and electrical system due to high starting torque.
Why is the motor not allowed to run continuously in star configuration?
-The motor is not allowed to run continuously in star configuration because it does not provide the high starting and running torque required by certain applications, which can lead to the motor not being able to handle the load properly.
What is the relationship between line voltage and phase voltage in star configuration?
-In star configuration, the phase voltage is related to the line voltage by the formula V_phase = V_line / √3, which means the phase voltage is approximately 1.3 times less than the line voltage.
How does the starting current of a motor compare to its full-load current during a direct start?
-During a direct start, the starting current of a motor can be six to seven times higher than its full-load current, which can lead to significant electrical stress on the motor and the electrical system.
Why might the panels around a large motor trip due to under-voltage when starting?
-When a large motor draws a high starting current, it can cause a significant voltage drop in the system, leading to under-voltage conditions that may trip the panels around it.
What is the function of a reduced voltage starter like the star-delta starter?
-A reduced voltage starter, such as the star-delta starter, is used to apply reduced voltage across the motor terminals during the starting phase, which in turn reduces the starting current and torque.
Why is it necessary to switch from star to delta configuration after a few seconds of motor operation?
-Switching from star to delta configuration after a few seconds is necessary to provide the motor with the required high starting and running torque to handle the load effectively and prevent motor trip due to insufficient torque.
What are the disadvantages of running a motor in star configuration for an extended period?
-Running a motor in star configuration for an extended period can result in insufficient starting and running torque, which may not meet the application requirements and could cause the motor to trip.
How does the star-delta starter help in avoiding the issues related to high inrush current?
-The star-delta starter helps in avoiding issues related to high inrush current by initially starting the motor with reduced voltage in star configuration, which significantly lowers the inrush current, and then switching to delta configuration to provide full torque.
What is the typical time frame for the switch from star to delta configuration in a star-delta starter?
-The typical time frame for the switch from star to delta configuration in a star-delta starter is between 8 to 10 seconds after the motor starts.
Why is high running torque important for certain applications?
-High running torque is important for certain applications because it ensures that the motor can handle the load effectively and maintain smooth operation, preventing the motor from tripping due to overload.

Outlines

00:00

🔧 Understanding Star-Delta Starter Configuration

The first paragraph discusses the concept and necessity of using a Star-Delta starter for electrical motors. It explains that when a motor is started using a dual starting method, the starting current can be six to seven times higher than the full load current, which can lead to issues like tripping of circuit breakers and under-voltage on other feeders. To avoid these problems, a Star-Delta starter is used, which applies reduced voltage to the motor during startup, thus controlling the starting current. The explanation includes the technical aspects of voltage and current transformation in Star and Delta configurations, emphasizing the benefits of reduced starting torque and the eventual transition to Delta configuration for high running torque as required by the application.

05:01

🛠 Transition from Star to Delta Configuration

The second paragraph elaborates on why it is necessary to transition a motor from Star to Delta configuration after starting it with reduced voltage. It highlights the need for high running torque as per the load requirements. If the motor is not provided with the necessary torque conditions, it may not be able to handle the load, leading to poor performance and potential motor trips. The paragraph clarifies that while the Star configuration helps in reducing the starting current, it does not provide the high starting and running torques that some applications demand. Therefore, after a brief period, typically 8 to 10 seconds, the motor is switched to Delta configuration to deliver the required torque and ensure smooth operation under load. The speaker encourages viewers to ask more questions in the comment section and subscribes to the channel for more informative content.

Mindmap

Keywords

💡Star Delta Starter

A Star Delta Starter, also known as a wye-delta starter, is an electrical device used to start three-phase induction motors. It is relevant to the video's theme as it discusses the use of this starter to reduce the high inrush current during motor startup. In the script, it is mentioned as a device that starts the motor in star configuration and then switches to delta configuration to provide high torque.

💡Electrical Engineering

Electrical Engineering is the technical field that the speaker, Abhishek Joshi, is associated with. It is the branch of engineering that deals with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. In the video, the speaker uses his expertise in this field to explain the concept of the Star Delta Starter.

💡Motor

A motor is an electrical machine that converts electrical energy into mechanical energy. In the context of the video, the motor is the device that is being started using the Star Delta Starter. The script discusses the challenges of starting large motors and the benefits of using reduced voltage during startup to manage the inrush current.

💡Inrush Current

Inrush current is the initial surge of electric current that flows through an electrical device when it is turned on. The video explains that starting a motor through a direct start can lead to an inrush current that is six to seven times higher than the motor's full-load current, which can be problematic and is mitigated by using a Star Delta Starter.

💡Full-Load Current

Full-Load Current refers to the current drawn by an electric motor when it is operating at its rated load. The script uses this term to contrast with the high inrush current during startup, explaining that the Star Delta Starter reduces the initial current to protect the motor and electrical system.

💡Star Configuration

Star Configuration, also known as wye connection, is a method of connecting electrical loads in which one end of each load is connected together at a common node, and the other ends are connected to the power source. In the video, the motor is initially started in star configuration to reduce the voltage and current during startup.

💡Delta Configuration

Delta Configuration, also known as mesh or delta connection, is an arrangement where each electrical load is connected end-to-end and the other ends are connected to the power source. After the initial star start, the video mentions that the motor is switched to delta configuration to provide the necessary high torque for operation.

💡High Starting Torque

High Starting Torque is the torque required by a motor at the beginning of its operation to overcome the static friction and get the machine moving. The video explains that after the initial star start, the motor is switched to delta to provide the high starting torque needed for certain applications.

💡High Running Torque

High Running Torque is the torque required by a motor during its normal operation to maintain the speed and overcome the load. The script mentions that switching to delta configuration after startup also provides the high running torque necessary for the motor to handle its load effectively.

💡Voltage Drop

Voltage Drop is the reduction in voltage that occurs as electric current passes through a resistance. The video discusses how the high inrush current during startup can cause a voltage drop, potentially leading to other equipment tripping due to under-voltage conditions.

💡Overcurrent Trip

Overcurrent Trip is a safety mechanism in electrical systems that causes a circuit breaker to open and stop the flow of electricity when the current exceeds a safe level. The script explains that the high inrush current during motor startup could potentially cause the motor's circuit breaker to trip, which is prevented by using a Star Delta Starter.

Highlights

Abhishek Josh from Electrical Engineering Block Group discusses the concept of a Star Delta Starter.

The logic behind starting a motor on Star configuration and then changing over to Delta.

High starting current of a motor during Delta Starting can be six to seven times the full load current.

The risk of circuit breakers tripping due to high starting current in Delta configuration.

Use of Star Delta Starter to avoid high starting current and reduce torque.

Explanation of Reduced Voltage Starter and its application in Star configuration.

Conversion from Star to Delta is necessary to meet high starting and running torque requirements.

The Star Delta Starter is used to control the high starting current of large motors.

Star configuration provides reduced voltage, thus controlling the starting current.

Delta configuration is used for running the motor to provide high torque for the load.

The changeover from Star to Delta occurs after 8 to 10 seconds to ensure motor stability.

Importance of high starting torque for applications that require it.

The necessity of high running torque for the motor to handle the load effectively.

Star Delta Starter helps in avoiding trips due to overcurrent and undervoltage conditions.

The video provides a detailed explanation of the Star Delta Starter's working principle.

The video is an educational resource for understanding motor starting methods in electrical engineering.

Invitation for viewers to ask more questions in the comment box and subscribe to the channel for more topics.

The video concludes with a reminder to stay tuned for the next interesting topic next week.