Star delta starter of induction motor
Today we will learn about star delta starter of induction motor this topic consists of following topics of star delta starters of induction motor:-
- circuit diagram explanation
Introduction of star delta starter of induction motor
Star delta starter of induction motor is most commonly starter used for starting squirrel cage induction motor rated above 05 HP. The motors that are below 05HP started directly with the help of DOL(Direct-On-Line)starter. In the case of star delta starter the motor first started in the star connection and when motor takes up speed of about (75-80%) speed it changes in the delta connection. In this method the starting voltage is reduced to root 3 i.e VL/√3.here VL Line Means Line Voltage. Therefore the starting current is also reduced. Hence motor get protected from overheating of the motor.
Construction of star delta starter of induction motor
Star delta starter of induction motor consists of following parts-
- Push Buttons
There are two push buttons are used in the star delta starter of induction motor
There are three contactors are used in star delta starter of induction motor
- Main contactor
- Overload relay
In the star delta starter of induction motor two push buttons are used
Start (NO) push button are used for starting of the motor. It is of green colour. Stop buttons are used for stop the motor. It is usually of red colour.
contactor of star delta starter of induction motor is an electromagnetic switch which is used to control large amount of current with low input voltage.
Here are three contactors are used one for main contactors,one for the star contactor and other for delta contactor
Timer of star delta starter of induction motor is basically a switch which operates after specific time which is set in the timer. It is used to change the winding connection from star mode to delta mode after set time.
Thermal overload relay of star delta starter of induction motor is used for protection of motor against over voltage, over current, low voltage single phasing etc.
Working of star delta starter of induction motor
when we press the start (NO) switch the main contactor, star contactor and the timer is in On condition and connect the motor in the star mode and timer starts counting time. The time may be in the second, milli second and when time is completed or motor reached their 75-80% of speed the timer change their connection from star to delta mode and motor starts running in the delta mode.
To stop the motor press stop (NC) button.
Related articles to the of star delta starter of induction motor
- Dol starter control diagram
- three phase induction motor
- precaution to take while make connection of star delta starter of induction motor
Circuit diagram explanation of star delta starter of induction motor
When power up the circuit by mcb (Miniature Circuit Breaker) on the voltage reaches up to the start push button and not go forward as it is no. When press start button the voltage reaches up to the star contactor Timer and main contactor and holds these contactor immediately the motor starts running in the star condition.
Here the motor remains in on condition even when we left the start push button because the the voltage reaches up to the contactor by no.
At the same time timer starts counting time.
When timer time has been completed. timer changes it’s contact from NC to NO and holds the delta contactor and motor starts running in the delta mode.
In this circuit the NC contact of the star contactor goes in the delta contactor and the NC contact of the delta contactor goes in the star contactor. This is for interlocking and safety purpose. When delta contactor is in on condition the star contactor will not operate and when star contactor in on condition delta contactor would not operate.
Advantages of the star delta starter of star delta starter of induction motor
On the time of the starting the motor is in star condition and recives the less voltage as compared to the full load voltage. It recives VL/√3 means the motor gets 3 times reduced voltage as compared to the full line voltage and hence starting current is also reduced Therefore the voltage drops at the time of the starting is reduced. This reduced the overheating of the motor. overheating of the motor reduced the life of the motor.
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