DOL – Star-Delta Starter

In this tutorial, I am going to show you how to start a 3 phase motor > 5HP.

This is the simplest circuit for this type of method and here I will show you the simulation carried out in the Cade-Simu.

This tutorial can be a good kickstart for future development skills in the area of electromechanical, you can see this simple starter system in industrial manufacturing.

The method of DOL Star Delta Starter is used to start higher rating 3 phase motors, a star-delta (Y-Δ) starter is used. Delta-wye (Y-Δ) starter is useful where all six terminals of the motor are accessible.

DOL Star-Delta Starter essentially operates as a basic stop/start switch for an electric motor and is often fitted with overload protection devices to prevent short circuits and overheating.

Parts Required

  • Software Cade-Simu 4.0 (for electrical simulation).

DOL Working

To start the engine, start button S1 (13-14) is activated.

This excites the coil of KM3, KM1, and of the Timer KA1 so that it closes all its contacts offered due to the magnetic force and the voltage reaching the motor. Starting only in Star, (see circuit) so that it starts momentarily.

Even if S1 is released, the motor continues to rotate due to the auxiliary contacts (KM1 13-14) and contact (KM3 13-14) of the contactors (see control circuit), which is closed because its coil is energized, that is, the auxiliary contacts (KM1, KM3) serves to make a feedback to the contact (S1).

After that, as a general rule, the amount of time needed to transition from star to triangle is 5 seconds.

Therefore the motor is working in star start and the timer counts for 5 seconds, after that it opens its auxiliary contact KA1(95-96) the coil KM3 switches off and closes the auxiliary contact KM3(11-12).

After that, it excites the coil KM2 that will supply the Start Delta, with we saw the entire operation of the DOL Star-Delta Start.

Press S2 (11-12) to stop the motor, which interrupts the coil and opens the contactor.

If the engine is running and an overload occurs, the Motor-circuit breaker (Q1) opens its power contacts, and interrupts the motor, in turn, the same occurs in the control circuit which interrupts all power from the auxiliary contact (Q1 13-14).

Power Circuit Diagram

The power circuit supply is a three-phase 400 VAC (can be another electrical voltage value depending on the country of operation), then it is supplied with a motor-circuit breaker (Q1), which is the most used in the industry today. It is connected with a contactor (KM1) and 2 contactors that make the Star Delta (KM2, KM3) that will supply the motor (M1).

Control Circuit Diagram

The control circuit is powered by 24VDC for this we use a power supply (PS1) that is powered by 230v, a phase and neutral protected by a Gg fuse (F1), and its output is 24VDC protected by a fuse as well Gg (F2).


Contactors KM1, KM2, KM3 – The contactor is an electromechanical device (as well as a relay) that allows the activation of loads from the polarization of a coil.

Timer KA1 – when energizing the relay, the timing starts, when the time is reached, the output contact will switch, when the relay runs out of energy, it resets the contact to its initial position, this is called work timer.

Motor Circuit-Breaker Q1 – is a device that combines protection and control for electric motors. It was developed especially for the activation and protection of electric motors. The great advantage of this circuit breaker is that it can combine fuse, thermal relay, and contactor functions in a single device.

Push buttons S1 – the pushbutton S1, is a start button containing an NO 13-14 contact that will close when activated.

The pushbutton S2 is a stop button containing an NC 11-12 contact that will close when activated.

1 thought on “DOL – Star-Delta Starter

Leave a Reply

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

Ads Blocker Image Powered by Code Help Pro

Ads Blocker Detected!!!

We have detected that you are using extensions to block ads. Please support us by disabling these ads blocker.

Powered By
100% Free SEO Tools - Tool Kits PRO