Where can we use star connection and where can we use delta connection in a power network?
Answer:
Either star or delta can be used in most situations. The star or wye (y) connection must be used if it is necessary to provice connection access to both the line-to-line and the line-to-neutral voltage.
In power distribution transformers, a wye connection not only provides a neutral connection but also provides a grounding point. A "corner" of a delta can be grounded, but it is usually preferable to ground the center point of a wye so that the circuit voltage to ground is lower and symetrical.
Motors can be internally wye or delta connected or arranged to start in the wye connection and run in the delta connection. So that less than full voltage is initially connected to the windings. It is more common for motors to be only wye connected.
well if you are talking about a delta wye selection, your power network determines that. Most of the areas i deal with are Wye systems. the neutral is rarely used in running three phase motors.
the purpose of the neutral on a wye system is to carry load imbalance. therefore, as long as your load is balanced, you are ok.
In other real simple terms...3 phase motors. anything on 480 volt operating as long as you maintain load balance.
The phase-to-phase voltage difference is less in a delta cofiguration than the phase-to-ground in a star. That voltage reduction through the coils has to reduce the current. Hence motors start with a Delta and run with a Y or star!
normally delta transformer design with the intention of line voltage equals to phase voltage, line current equals to phase current but no neutral ground return.
wye transformer design involving the factor root 3 but with neutral ground return.
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