Star Delta Starter Working Principle | Types of Star Delta Starter | Star Delta Starter Theory

Star Delta Starter Working Principle

The star-delta starter is usually used to start an induction motor. Initially, when the motor starts it rotates in star connection and once it reaches a fixed speed it converts to the delta.

3 methods have been used to start the induction motor. One of them is the DOL starter i.e. direct online starter but the use of this starter is limited only a small horsepower motor can be operated by this. But for large class motors, semi-automatic star delta starter, fully automatic star delta starters has been used. In which 6 terminals are used.

In this article, we will see which parts are used in this way. He has a theory. And discuss its diagram and its working method.

The star-delta starter is designed to reduce the initial flow of the induction motor. This starter is used for all types of induction motors. Which are usually delta connected.

Thus a decrease in starting torque is observed due to the reduction of high current. This flow is perfect for Star Delta start drives. After the arrival of such a starter, there is no question of overload. Thus, the initial time is long.

Large horsepower motors require a reduced voltage starter to control the starting current to operate the motor. A star-delta starter is a reduced voltage starter that applies 1 / √3 voltage during the initial time.

Also Read: Star to Delta Conversion and Delta to Star Conversion

Types of Star Delta Starter:

Sr. No. Types of Star Delta Starter
#1. Semi-automatic star delta starter
#2. Manual Star Delta Starter
#3. Fully Automatic Star Delta Starter (Y-Delta)

Working Process of Star Delta Starter:

#1. Star Connect State:

Star connected motor terminals star delta starter
current and voltage in star connection star delta starter

The star stays close to the contactor and the star contactor at the beginning of the delta and completes the full power circuit.

The motor is initially connected to the star after supply. The connected state voltage on the star is applied to the motor, reducing up to a third of the winding voltage. When the motor operates at its full load. Then the full circuit is connected and 90% of the timer is activated. Which causes the star to leave the connector and convert to the delta. This means it’s about to be the most delusional time of the year, as well.

#2. Open position:

The circuit opens when the motor is rotated from star to delta. And the time motor neither stays in the star nor in the delta from this situation is called an open transition state.

#3. Delta State:

delta connected motor winding star delta starter
Current and voltage in delta state

After activation of the timer, the motor is switched from star to delta. In the case of delta connection, phase voltage and line voltage are equal. So the line voltage is applied across the winding of the motor so the motor starts working across its full load.

Star Delta Starter Control Diagram:

The control circuit wiring diagram in Star Delta Starter uses a push-button for the timer, start and stop.

Star delta starter control diagram

After pressing the push button at the beginning, the single-phase supply turns on the timer which causes the timer contact to be closed 17-18. And normally the contact starts.

This type of process causes the star contactor to turn on and the motor to turn into a star. After a while, the motor converts from star to delta after reaching 90% of it. Due to this line voltage is applied to the motor and the motor starts rotating at full power.

Components of Star Delta Motor Starter:

Sr. No. Components of Star Delta Motor Starter
#1. Timer
#2. Overload relay (OLR)
#3. Contactor
#4. MCB
#5. Fuse unit
#6. Normally Open Push-button start (NO)
#7. Normally Close Stop push button (NC)

Star Delta Starter Power Diagram and Principle:

star delta starter power circuit diagram

The Theory of working is as follows:

  •  At the beginning of the star-delta starter, 2 contactors remain in the closed position.One Main contactor to delta contactor.
  •  3 If the contactor is a star contactor and it splits at the start of the motor when the motor is turned on.
  •  The current in the star state is 1/3 of the current in the delta state. So the contactor rating is one-third of the motor rated current
  • The star connector is closed when starting the main contactor.
  • After a while, the timer in the circuit is activated, it closes the star contactor, opens the delta contactor. This causes the motor to operate at full load.

Advantages of Star Delta Starter:

  • It is very popular because of its low price.
  • Does not generate any kind of heat. A tap change device is used so it gives more efficiency.
  • The starting current reduces the direct starting line to 1/√3 of the starting current.

Disadvantages of Star Delta Starter:

  • This starter can only be used for 6 terminals.
  • Starting torque reduces the full load to one-third of the full power of the torque.
  • Can only be used for certain types of motors.

Frequently Asked Questions (FAQs):

Frequently Asked Questions

1. What is the star delta starter?

The Star Delta Starter is used to start a three-phase induction motor which is the most popular method in the market. Starting an induction motor in the Star Delta connects to the Star Connection throughout the period. And we use this starter to reduce the initial flow of any external tool or device except the work

2. Why is the star delta starter used?

The star-delta starter is the most common reduction voltage starter. It is used in an attempt to reduce the initial current applied to the motor at start-up as a means of reducing interruptions and interference to the power supply.

3. Which is faster Star or Delta?

The speed of the motors in the star connection is slow as they receive 1/√3 voltage. In delta connection, its speed is higher as each phase gets full load voltage. The motor receives the highest output in a delta connection. In a star connection, the phase voltage is less than 1/√3 of the line voltage.

4. Can we run Delta motor in Star?

The Delta connection motor will draw 1.732 times higher current when connected into a star connection mode.

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Hey, I am Vishnu Patil and I'm an Electrical Engineer and Electrical maestro. I have more than 10 years of experience with electricals. Through ElectricalGang I want to spread my knowledge with everyone else.

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