Star delta starting of three-phase motor

Three-phase electric motors have several ways of connecting to guarantee correct operation within the characteristics of the machine, the first that we can find is direct connection to the three-phase network through a power circuit and a maneuver, which would be a simple start-stop. A rotation inverter can be added to this start-stop.

Other ways to control the operation of the motor would be with a soft starter or with frequency inverters, this type of start is usually ideal for the motor to protect it, although it is often not necessary to make this additional investment, being able to solve the start of the motor with a timed circuit of contactors.

These types of starts are used to prevent electric motors from having a high current peak when starting them up, as happens with direct starting, to avoid this current peak at the time of acceleration to full load, until the reaches the desired operating speed. Star starting has a torque limitation, so it is not suitable for motors that have to start at full load with all the torque that the motor allows.

Advantages and disadvantages of star delta starting:

– Consumption is lower in star-delta starting than in direct starting.

– The star-delta circuit is simple and economical, requiring three contactors and a timer.

– The motor windings suffer less as they do not receive the intensity peak as it happens in the direct start, extending the useful life of the motor.

– The motor winding must be suitable for the three-phase voltage of the installation, and the installation voltage must be equal to that indicated in the delta connection of the motor specifications.

– The motor terminal block must have both ends of the coils accessible, leaving it without the 3 connection plates, placing a cable on each coil terminal directly to the power circuit panel.

triangle star outline

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