Star vs Delta - advantages & disadvantages

STAR (WYE) ADVANTAGES
- Y used for high voltage
- common neutral point
- neutral point can be earthed
- availability of single phase at a lower voltage
- ability to spread load between the phases
- good for unbalanced loading
- each phase is a separate circuit
- dual voltage applications (3-phase and 4-wire system)
- star connected alternator requires lesser number of turns than delta for the same voltage
- star connected alternator requires lesser insulation
- star connection can distribute the load evenly



STAR (Y) DISADVANTAGES
- less torque
- construction involves combining 3 single phases into 1
- secondary distribution, light duty applications
- construction cost is more expensive (4 conductors)



DELTA ADVANTAGES
- efficient
- more torque
- simple motor design
- protection is simple and less costly
- construction cost is cheaper (3 conductors instead of 4)
- heavy duty applications
- used in rotatory conveyors
- less current per winding for the same power output
- major applications in power generation, transmission and distribution
- the transformer secondary provides all the 3 phases (if one is lost, you still have 2)



DELTA DISADVANTAGES
- no common neutral point
- detecting earth ground faults is difficult
- low voltage connection




Note 1:
If Power is kept constant,
Delta (parallel) has lower voltage but higher current (amperage) capacity
Star (series) has higher voltage but lower amperes

Note 2:
Some motors are soft started with star and then switched to delta.

Note 3:
Most modern motors have windings connected in delta.
Most 3-phase induction motors are connected in delta.

Fractional HP Approx Fractional KW

1 1/3 HP --- 1 KW

1 HP --- 3/4 KW or 750 W

3/4 HP --- 1/2 KW or 500 W

1/2 HP --- 1/3 KW or 375 W

1/4 HP --- 1/5 KW or 200 W

1/5 HP --- 3/20 KW or 150 W

1/6 HP --- 3/25 KW or 120 W

1/8 HP --- 1/10 KW or 100 W

1/10 HP --- 7/100 KW or 70 W

1/12 HP --- 3/50 KW or 60 W

1/15 HP --- 1/20 KW or 50 W

1/20 HP --- 1/25 KW or 40 W

1/25 HP --- 3/100 KW or 30 W

1/50 HP --- 15/1000 KW or 15 W

1/125 HP --- 6/1000 KW or 6 W