Star Delta Connection

 Star Delta Explanation:

In the operation of the engine, we find that we are obliged to start the engine at the beginning of its rotation by connecting it (Star) and then after a short period of time, the connection is automatically transferred to the (Delta) connection.

Star connection:

The ends of the files are connected together to be in the end as a single file, and the end of each file is connected to a source terminal.

Line Voltage = Root (3) * Phase voltage

Line Current = Phase Current

Delta connection:

The beginning of each file is connected to the end of the previous file, then the three ends of the source are connected to the ends of the files.

Line Current = Root (3) * Phase Current

Line Voltage = Phase Voltage

The motor is connected to a delta star connection, meaning that the motor at the beginning of its movement is in star mode and it lasts for about 10 seconds, then

Moves to delta mode: (why???)

The motor starts its movement from idleness to move, and very high values ​​of current are drawn, and what is called the starting current of the movement, and it may reach 5 times

The value of the highest ampere recorded on the motor (Rated Current).

what does that mean ???

We put the engine in a star mode and it is connected to the delta volt, so the engine works at about half its capacity, so the drawn start current is as low as possible.

electrical circuit:

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

Now let's get acquainted with a device called (Megger):

A device used to detect the insulation of electrical coils or the Islam of electrical devices.

A very, very high amount of volts comes out of it, the value of which is from 500 to 1000 volts, through which we can feel any connection between the coils and the body of the device or the coils with each other.

• If the engine is healthy, its readings for the R S T valves are equal (at low voltages).
• But if the readings are zero or relatively small, then it is in shortcomings (at low voltages).
• The readings are expected and have a difference (in high voltages).

The necessary tests to ensure that the engine files are intact:

Using the voltmeter, it is set to the ohm (Ohm) position and by opening the motor shaft, it is known that there are 6 pins inside the nozzle

If the engine is a Star:

So I put the end of the voltmeter on one end and move the other end on the three ends of the motor. If the values ​​are equal, the motor is intact, and if they are not equal and there is a spacing between the values, the motor is burnt out, which is damaged.

If the engine is Delta:

 I have 3 parties. I put the two ends of the voltmeter between each two ends and measure the values ​​between them. If they are equal, the motor is fine, and if they are not equal, the motor is damaged.