Understanding STAR-DELTA Starter !
star-delta starting must allow a control cabinet connected to a three-phase asynchronous motor to be wired. The diagram results from the knowledge of the coupling at the level of the terminal plate and from the purely electrotechnical study of the star-delta starting.
The conditions to be fulfilled for drawing up a diagram are as follows:
The delta coupling must correspond to the network voltage,
The engine must be started in two stages,
First step: coupling of the star windings and energizing,
Second step: removal of star coupling, immediately followed by delta coupling.
Start-up operation analysis
When starting, the motor is star-coupled. The voltage applied to one phase is reduced, that is, U divide by the square root of three.
The absorbed current (proportional to the applied voltage) is 1/3 of that which the motor would absorb if it started directly in delta. The value of the peak of the intensity generally reaches twice the nominal intensity.
The starting torque (proportional to the square of the applied voltage) and the maximum star torque are reduced to 1/3 of the values obtained in direct starting. The value of the starting torque generally reaches 0.5 times the nominal torque.
Cut-off (star-delta passage):
The passage time between the two couplings must be very short.
Triangle coupling:
A second current draw occurs; it depends on the duration of the star coupling and can reach the peak value of direct start. This short-lived spike arises from the fact that the electromotive forces which remain in the stator during delta coupling are not in phase opposition with the line voltages.
You might have seen that in order to start a high power rating induction motor, a starting technique called star-delta is used. In this video, we will understand why a star-delta starter is needed, and how it is accomplished practically with help of animation.
Understanding STAR-DELTA Starter !
star-delta starting must allow a control cabinet connected to a three-phase asynchronous motor to be wired. The diagram results from the knowledge of the coupling at the level of the terminal plate and from the purely electrotechnical study of the star-delta starting.
The conditions to be fulfilled for drawing up a diagram are as follows:
The delta coupling must correspond to the network voltage,
The engine must be started in two stages,
First step: coupling of the star windings and energizing,
Second step: removal of star coupling, immediately followed by delta coupling.
Start-up operation analysis
When starting, the motor is star-coupled. The voltage applied to one phase is reduced, that is, U divide by the square root of three.
The absorbed current (proportional to the applied voltage) is 1/3 of that which the motor would absorb if it started directly in delta. The value of the peak of the intensity generally reaches twice the nominal intensity.
The starting torque (proportional to the square of the applied voltage) and the maximum star torque are reduced to 1/3 of the values obtained in direct starting. The value of the starting torque generally reaches 0.5 times the nominal torque.
Cut-off (star-delta passage):
The passage time between the two couplings must be very short.
Triangle coupling:
A second current draw occurs; it depends on the duration of the star coupling and can reach the peak value of direct start. This short-lived spike arises from the fact that the electromotive forces which remain in the stator during delta coupling are not in phase opposition with the line voltages.
You might have seen that in order to start a high power rating induction motor, a starting technique called star-delta is used. In this video, we will understand why a star-delta starter is needed, and how it is accomplished practically with help of animation.
No comments:
Post a Comment