ControlElectrical DesignElectrical WiringHow ToMotors

STAR-DELTA Starter Motor Starting Method Without Timer

Starting & Controlling of 3-Phase Motor using Semi-Automatic Star-Delta Starter Without Timer

Electric motors are essential components in various industrial applications and play a vital role in powering machines, pumps, compressors, and other equipment. However, when it comes to starting large motors, the initial inrush current can be significantly high, leading to voltage drops and potential damage to the motor windings. That’s why do we need a PLC, VFD, or a motor starter such as a Star-Delta Starter.

To overcome this challenge, engineers have developed various motor starting methods, and one such method is the “Star-Delta Starter.” As we have explained the automatic star-delta starter using timer in the previous post, In this article, we will explore the power and control diagram, working principle and applications of semiautomatic or manual star-delta starter without using a timer.

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Introduction to Star-Delta Starter

A star-delta starter is a widely used method for starting three-phase induction motors. It allows for a gradual reduction of the starting current, reducing the impact on the power supply and the motor itself. Typically, an automatic star-delta starter uses a time delay relay to switch between the star and delta connections of the motor windings. However, in some cases, the use of a timer may not be necessary or practical, especially in applications where simplicity and cost-effectiveness are crucial.

Working Principle of Star-Delta Starter without Timer

The star-delta starter without timer follows a basic principle: the motor starts in a star configuration, and after a predefined time, it switches to the delta configuration. This methods uses when a time delay timer is faulty or not available during the emergency operation of large motors.

Unlike the conventional star-delta starter, this method does not use a time delay relay. Instead, it relies on manual control for the switching process e.g. using push button switches for manual operation for transferring the mains connection from Star to Delta.

Star Connection

During the starting process, the motor windings are initially connected in a star (Y) configuration. In the star connection, each winding receives the full line voltage (VL) across them. This configuration allows the motor to draw reduced current compared to a direct-on-line start.

Delta Connection

After a specific period (usually a few seconds) of running in star mode, the motor windings are switched to a delta (Δ) configuration. In the delta connection, each winding receives the line voltage divided by the square root of 3 (√3) across them. This results in an increase in the current but provides higher torque, allowing the motor to reach its full speed.

Related Posts:

Wiring, Power & Control Diagrams of Star-Delta Starter

Power Diagram:

Power Diagram of STAR - DELTA Starter

Schematic Wiring Diagram:

Schematic Wiring Diagram of STAR - DELTA Starter

Control Circuit Diagram:

Control Circuit Diagram of STAR-DELTA Starter without using Timer

Control Wiring Diagram:

Control Circuit of Star - Delta Starter without Timer

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Manual Control Procedure

The manual control procedure for the star-delta starter without timer is relatively simple. It involves the following steps:

  1. Initial State: The motor is at rest, and the windings are disconnected.
  2. Star Connection: Press the “Start” button or close the start contactor. This connects the motor windings in a star configuration.
  3. Star Mode Operation: The motor runs in the star configuration for a predetermined time to reduce the starting current.
  4. Delta Connection: After the time delay (manually measured or estimated), press the “Changeover or pushbutton” button or close the changeover contactor. This switches the motor windings from star to delta configuration.
  5. Delta Mode Operation: The motor runs in the delta configuration, reaching its full speed and providing the necessary torque for the intended load.
  6. Stopping the Motor: To stop the motor, press the “Stop” button or open the main contactor.


The Star-Delta Starter without Timer offers several advantages:

  • The absence of a time delay relay simplifies the control circuit. It reduces the chances of timer-related failures and eliminates the need for adjusting the timer based on motor size and specifications.
  • The removal of the timer component reduces the overall cost of the starter. This makes it an attractive option, especially for small to medium-sized motor applications, where cost plays a significant role in equipment selection.
  • With fewer components involved, the star-delta starter without timer improves the overall reliability of the motor starting process. The manual control procedure is straightforward and less prone to electronic or electrical malfunctions.
  • The simplified design reduces maintenance efforts and costs. Technicians can easily troubleshoot and replace faulty components if necessary, without dealing with intricate timer circuits.


The Star-Delta Starter without Timer finds application in various industries, including:

  • Agriculture: Irrigation pumps and agricultural machinery.
  • Manufacturing: Fans, blowers, conveyors, and compressors.
  • Mining: Crushers and large conveyor systems.
  • Oil and Gas: Pumps and compressors for fluid transportation.
  • Water Treatment: Water pumps and purification systems.


  • R ,Y, B = Red, Yellow, Blue or Brown, Black, Gray ( 3 Phase Lines L1, L2, L3)
  • C.B & MCCB = General Circuit Breaker & Molded Case breakers
  • Mains = Main Supply
  • Y = Star
  • Δ = Delta
  • O/L = Over Load Relay
  • NO = Normally Open
  • NC = Normally Closed K1 = Contactor (Contactor coil) K1/NO = Contactor Holding Coil (Normally Open)
  • K1 , K2, K3 = Contactors

Related Tutorials and Resources used in Power & Control Wiring Diagrams for Motors



  1. Stephen musyoka says:

    Very educative and important information. Keep it up. Thank you.

    1. Emori Maurice enya says:

      I like it and will love more of it

  2. Mustak khan says:

    Sir m new to this site plz. Tell me the hole table of circuit breakers acc. and There range of use.

    1. Monu Kumar says:

      Okk don’t worry we will give you whole knowledge about this in next article

  3. Special thanks to wasim khan.very educative and important information.keep it up.

    1. Electrical Technology says:

      Dear K.Mark. Thanks for appreciation . =D

      1. mengistu yihunie says:

        i like it God bless you

  4. Can anyone please help…
    I have a 3 phase grain mill for grinding corn etc (farming implications) but only have a single phase supply. Can I get the mill to work on the single phase and HOW ?
    All replies much appreciated.

    1. SALIM KHAN says:

      There must a 3 phase motor inside,disconnect its wires and give supply through a separate connections from a VFD drive of any good brand, VFD drives capable to run three phase motors from single phase supply.

  5. Eunjiro Domingo says:

    How it works it real life w/o a timer, it that means that you’ll operate it manually to change from delta to wye?

    1. Ibrahim Atta says:

      yes that is what it mean, and you can do that with the configuration of another button.

  6. leonard kasambala says:

    Your a special teacher! I`ll disturb 4 this things myn!

  7. hi thanks for help me so now i ask you same questions what about on control citric you use two line means L1 AND L2 YOU SAY L2 IS NEUTRAL OR NOT

  8. ch waheed says:

    Nice dear buhat achy

  9. quadir hussain says:

    Please add me

  10. mridul nandan says:

    Star delta diagram

  11. please explain me how that control circuit works

  12. Md Mozahid says:

    i am electric engg from GRD Jharkhand

  13. This means that we stil ned to manualy pres a swetch to change d comection to delta ryt?

  14. santosh hangirkar says:

    Dear friends,
    I need to run the motor on vfd with star delta circuit pls suggest me circuit.

  15. Anthony Christopher says:

    please i need a help. i operate an Ingersollrand air compressor that is controlled by a star delta starter. the motor runs for some minutes and the control circuit will trip but starts when start push button was pressed. also, the timer relay just went off after the compressor ran for 4 cycles. what should i do because one component keeps going off after another. Please advice me. my email is Thanks

  16. Muhammad shahid says:

    thanks sir , very educative information for us ,, so plz next time give us a star delta control circuit with timer

    1. Electrical Technology says:

      We have already added this post… Search in the above links….

  17. Bhai Thnxs For This Butt Tell me about Timer yar How to Attach time with star and delta

  18. syed Iqbal Hussain says:

    pls add me

  19. Sheriff adam says:

    Need update always

  20. Dear Sir please let me know how to make connotation for star delta with VFD control use for chiller water pump thank you

  21. This doesn’t work , motor first starts in delta according to this connection then it will work on star , that is un acceptable solution


  23. Asad Qayyum says:

    sir I want to know that if we are going to connect a motor directly in star or delta connection without a stater thaen how we can make sure that which connection is suitale for the motor star or delta? if star why? if delta why? explain the reason also and explain it for havey motor and also for normal 75 w 3 phase motor


    Dear I need easy wiring dia gram 220 to 380 we are using Stamford alternator pls send me any I always burned AVR

  25. Aslam Khan says:

    Dear Leeman you may use capacitor for Three Phase motor.phase sequence will change

  26. very useful topic ……………..

  27. nsofwa mungulube says:

    i want to be receiving news letters

  28. Christopher marufu says:

    Can i have the operation please and a typical example where this can be used

  29. Ansab ali says:

    sir tell me s1 and s2

  30. kinzang gyelpo says:

    since i hv new 3phase induction motor .i need ur help to do connection with power & control circuit with push bottom but without timer.

  31. kinzang gyelpo says:

    can u show the power and control diagram for 3phase induction motor with push bottom but without timer

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