We have designed a brand new video series in PLC programming here at RealPars which can teach you some valuable practical concepts in automation and electrical engineering. In this video series, you’re going to learn how to write a PLC program for a three-phase electrical motor that will utilize a star delta starter.

The star-delta starter is a common method used in starting heavy three-phase motors. Although there are other new ways of starting heavy-duty PLC motors, you can still benefit from learning this popular traditional method as an automation engineer.

Here is the basic idea. When you turn on a three-phase motor, in the first few minutes of starting the motor, it draws up to 4 times more current than the rated current. This huge amount of current can damage the motor windings and also the electrical network.

Wiring a three-phase motor to a PLC

In the star-delta starter, we first run the motor in star connection and then after a few minutes, when the motor gains sufficient speed, we’ll switch the connection to the delta. In star connection, the current that the motor draws is one-third of the rated current so by running the motor in star connection we can reduce the startup current.

Star delta starter wiring diagram

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The RealPars Team