What do you know about st

ar and delta

connection

?

Q1: 380-V, 60 Hz, 9kw three-phase induction motor is connected delta star at 0.8 PF calculate the current in and delta also calculate the starting current and

power developed in star?

1 )IL∆=P/√3*cos6*103√/3*380*0,9=10.12A

2 )Ip∆= IL/√3 10.12A/√3=5.84A

3 )Z=Vp/Ip 380V/5.84=65.06Ω

4)Vph=Vl/√3 380√/3=219.34V

5 )IL=Ip=vp/Z 219.34/65.66=3.37A

6 )Is=7*IL 7A*3.8=23.6A

7 )p=√3*VL*Ic*cos √= 3*380*0.9*3.37=2KW

1-How to connect the motor ?

Star – Delta

2-why we connect star-delta?

To avoid damage to the motor and an increase in energy consumption.

3-when we convert to delta?

After the speed up to about 75% of the speed of your connection is converted to Delta.

4-why we connect the delta?

Because Delta can bear loads in excess of the motor.

1 )what different between star and delta?

Star has high voltage and low current and Delta has low voltage and high current.

2 )why we start motor in the beginning in star?

Because the star has high voltage ,so we need high-torque to starting the motor.