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Explanation of how to bind star delta:
A complete and detailed explanation of the power and control circuit of the Star Delta engine.
The Star Delta method is one of the most important ways to start the Three Phase Induction Motor for the following reasons:
One of the cheapest ways
Suitable for high power engines
- Easy to install and maintain
In this method, the motor is initially started with a curtain connection until it takes its speed (after about 10 seconds) and then is transferred to the delta connection so that the motor works in a normal way.
It is known that in its connection there is a curtain: the ends of the files are connected together to form one point, and the ends of each file are connected in ways from the source
line voltage = root(3) *phase voltage
and line current = phase current
If at the beginning of the operation, the voltage applied to the phase is less than the line voltage, so the drawn current decreases, so the coils bear the starting current
And in the delta connection: the beginning of each file is connected to the end of the previous file, and the three source terminals are connected to the three terminals of the coils
line voltage = phase voltage
and line current = root(3) *phase current
If at first the drawn current is low, the motor is protected from high starting current ... Then, after switching to the delta connection, the motor pulls the total current I rated
Now the power and control circuit used
Items required to make a star delta circle
- 3 contactors
- 1 automatic three phase circuit breaker
- 1 timer type on delay
- 1 push button switch of type NC and another of type NO
- 1 thermal overload to protect the engine
- To operate the star motor, the contactor km2 and the contactor km1 must work until its connection represents a star where the ends of the motor coils are collected in one point
- To run the delta motor, the contactor km2 and the contactor km3 must work until it represents a delta connection where the end of each coil is connected to the beginning of the next coil
We note that the km2 contactor works throughout the engine life, whether the connection is delta or star
So the contactor km2 and km1 must work initially and for about 10 seconds (an estimated period that increases with increasing engine power), then the contactor km1 is turned off and the contactor km3 is turned on
And that is what the control circuit should do, as we shall see
Note: the overhead is set to 1.1 * total motor current / root 3
Star Delta Motor Control Circuit
There is more than one control circuit that can be designed, but the most suitable and safest circuit will be explained
When you press the power key S2 and it is of type NO
The contactor km1 will work and its open points will be closed, so the contactor km2 will also work (the main contactor)
Also, the timer file T1 of type on delay will work (this timer is set to about 10 seconds).