Star-Delta (Y-Δ) Starter, Power & control wiring

Published by ASHA CHAUHAN on

Star/Delta ( Y – Δ ) is a one types of Starter.

The Y-Δ starting is a type of motor startup at reduced voltage which is useful to start the motor smoothly, without excessive mechanical stress and limiting the start-up currents. It is suitable for with Motors.

Which Type Useful ??

What is benefits of ( Y – Δ ) Starter ???

So Now, Finely Starter Used Mean….. A Motor Starting a Start time Without jerk, Without Starting High current/Over current.

It’s Main used :- For a motor starting Current Limiting.

Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less losses.

  • Star/delta ( Y – Δ ) circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused.
  • The operation of the Star/delta method is simple and rugged.
  • It is relatively cheap compared to other reduced voltage methods.
  • Good Torque/Current Performance.
  • The components require very little space.
  • The most significant advantage of using Star/delta starting is the huge reduction in the starting current of the motor, which will result in a significant cost saving on cables, transformers and switch gear. 

Wiring Diagram of Motor ( Y – Δ ) Starter

Star-Delta Starter

Abbreviations: ( FOR Control Wiring of Three Phase Star Delta Starter with Timer)

  • R , Y, B = Red, Yellow, Blue ( 3 Phase Lines)
  • C.B = General Circuit Breaker
  • Main = Main Supply
  • Y = Star
  • Δ = Delta
  • 1 = Timer
  • C1, C2, C3 = Contactors (For Power & Control Diagram)
  • O/L = Over Load Relay
  • NO = Normally Open
  • NC = Normally Closed
  • K1 = Contactor (Contactor coil)
  • K1/NO = Contactor Holding Coil (Normally Open)

Motor Star-Delta Starter Selection of Component Rating Chart

Star-Delta Starter
Motor Star-Delta Starter Selection of Component Rating Chart

Characteristics & Features of Star-Delta Starter

  • The starting current is 33% of full load current for ( Y – Δ ) starter.
  • The peak starting torque is 33% of full load torque.
  • The peak starting current is 1.3 to 2.6 of full load current.
  • Star-Delta Starter can be used only for low to high power three phase induction motors.
  • It has reduced starting current and torque.
  • The 6 connection cables are needed for motor terminal box.
  • In (Y-Δ) starter, Current peak and mechanical load on Changeover from ( Y – Δ ).

Schematic Diagram of Star-Delta ( Y – Δ ) Starter

star-delta starter wiring diagram.

Applications of Star-Delta Starter

As we know the main purpose of (Y-Δ) starter is to start the three phase induction motor in star connection while run in delta connection.

While keep in mind that (Y-Δ) starter can only be used for low to medium voltage and light starting torque induction motors. In case of direct on line (D.O.L) start, the receiving current at motor is about 33% while the starting torque reduced about 25-30%.

This way, (Y-Δ) Starter can be only used for light load during starting the motor. Otherwise, the heavy load motor wont start due to low torque which need to accelerate the motor to rated speed while converting to the Delta connection.

Now, We are known About this Function.

Thanks For read……..

Get More knowledge of Machine or Electrical related any Information regarding Topic So please comment me and Subscribe this Site for Help of Study Practical and Theory.


  • DOL (Direct Online) Motor Starter - Engineering Tech · October 12, 2021 at 2:40 pm

    […] Starter :- It is very easy circuit, Full form of DOL – Direct online […] · January 29, 2022 at 4:30 pm

    cialis tablets australia

    Nicely put. Thank you!

    Leave a Reply

    Avatar placeholder

    Your email address will not be published. Required fields are marked *