3-PHASE DELTA CIRCUITS

One distinct advantage of a delta-connected system is its lack of a neutral wire. With a star-connected system, a neutral wire was needed in case one of the phase loads were to fail open (or be turned off), in order to keep the phase voltages at the load from changing. This is not necessary (or even possible!) in a delta-connected circuit. With each load phase element directly connected across a respective source phase winding, the phase voltage will be constant regardless of open failures in the load elements.

Perhaps the greatest advantage of the delta-connected source is its fault tolerance. It is possible for one of the windings in a Δ-connected three-phase source to fail open without affecting load voltage or current!

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Thank you and good night

One distinct advantage of a delta-connected system is its lack of a neutral wire. With a star-connected system, a neutral wire was needed in case one of the phase loads were to fail open (or be turned off), in order to keep the phase voltages at the load from changing. This is not necessary (or even possible!) in a delta-connected circuit. With each load phase element directly connected across a respective source phase winding, the phase voltage will be constant regardless of open failures in the load elements

Dear Snake mike,

Thanks for the reply!! Pls elaborate on my 1st query.

Regards,

Harshvardhan

All the answers are in-front of you of what snake-mike has replyed too?

try this web site -- http://www.wisconsinpublicservice.com/business/phase.asp

below is some of the info they offer, there is more. Check it out. Time to blow a fuse will also depend on the type of fuse you choose. Not sure which is best for any particular application.

What Is Single-Phasing?

Loads using three-phase power sources are subject to loss of one of the three phases from the power distribution system. This condition is known as "single-phasing." The loss of a single phase on a three-phase line may be due to a downed line or a blown pole top fuse on the utility system. Loss of a single phase may also result from a single-phase overload condition causing one fuse to blow, or an equipment failure within the end-user's facility.

The loss of one phase, or "leg," of a three-phase line causes serious problems for induction motors. The motor windings overheat due primarily to the flow of negative-sequence current, a condition that exists anytime there is a phase voltage imbalance. The loss of a phase also inhibits the motor's ability to operate at its rated horsepower.

If single-phasing occurs when a motor is rotating, the torque produced by the remaining two positively rotating fields continues to rotate the motor and develop the torque demanded by the load. The negatively rotating field, the field associated with the lost phase, produces currents in inductive loads resulting in voltages in the faulted leg of the three-phase supply. These voltages may be nearly equal to the phase voltage that was lost. Therefore, detecting a single-phasing condition by measuring the voltages at the motor terminals is usually unproductive.

Three-phase motors may continue to run, but they are not capable of starting on a single phase. If after the overload devices on the energized phases isolate the motor, the motor is not then isolated from the lost phase, later attempting a restart on that single-phase supply will cause the motor to draw locked rotor current.

yes there will be a phase change/ripple. The angle is dependant upon the unity so that if one changes, the ripples occur.