STAR DELTA
CHAVES ELÉTRICAS TRIFÁSICAS

USAGE:

When choosing the Star-Delta switch it must be considered that in the start moment in star, the current and the start moment are reduced to roughly ⅓ of its correspondent values at boot time.
This equipament is destinated to the start of three-phase voltage motors with short-circuit rotor. This kind of equipament applies solely to motors in which the rated voltage in delta coincides with the rated voltage between the power suply phases, therefore a 220/380 Y motor can not be turned on with a star-delta switch in a 380 V network between phases. It is crucial for the start that the motor is capable of starting in a dual tension, which means in 220/380V, in 380/660V or 440/760V. The motors must have at least six connection terminals.

The stat-delta starting must be used when the power curve of the motor is high enough to garantee the machine’s acceleration in case of reduced current. In star connection, the current is reducted from 25 to 33% of the start current in delta start. The loads power resistent, can not exceed the start load of the motor and in the moment of changing the start load” for star it cannot have unnaceptable value. There are cases in which this starting system cannot be used.

Motors that have the rated voltage of operation over 660V must have a special isolated system suitable for their conditions.
They are used for three-phase motor starting with the purpose of reducing the starting current to limit the voltage drop in the power suply phase. The usage of this kind of switch is usually demanded by the electricity concessionaire so its energy grade lines are not overloaded, due to the start of higher power electrical motors (consult the electricity concessionaire of the region where the instalation will be made). For security reasons the gauntlet is never locked in the START position.

In some cases the machine’s characteristics forces us to use this kind of switch. They are machines with overestimated steering wheels (all kinds of presses), wire drawing machine, conveyor belts, injection machines, cutters, etc.
Generally the star-delta swicht can only be used machines starting in empty, which means, unladen. Only after reached the nominal speed, the load can be applied.

APPLICATION:

Winches, turning presses, excentric presses, guillotines presses, agricultural machinery and all kinds of machine toO.

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