Star and Delta Configurations

What produces an alternating current in a three-phase system?

• Rotating a coil in a magnetic field

• A constant magnetic field

• A single-phase power supply

• Direct current

How many degrees out of phase are the currents in a three-phase system?

• 180°

• 120°

• 360°

• 90°

What is the relationship between line voltage and phase voltage in a star connection?

In a delta connection, how does the line current compare to the phase current?

What is the phase voltage of a star connected transformer with a line voltage of 520 volts?

• 260 volts

• 900 volts

• 520 volts

• 300 volts

What is the phase current in a delta connected load with a line current of 13.86 amps?

• 8 amps

• 13.86 amps

• 4.62 amps

• 20.79 amps

How is the neutral current calculated in an unbalanced three-phase system?

• By summing the phase currents

• By using a specific formula involving the square and product of phase currents

• By using a phasor diagram

• By subtracting the highest phase current from the total

What is the ideal condition for the neutral current in a balanced three-phase system?

• Equal to the highest phase current

• Zero

• Equal to the sum of all phase currents

• Cannot be determined

What voltage supply is suitable for domestic consumers in Great Britain?

• 520 volts

• 11kV

• 230 volts

• 400 volts

What is the resistance of a delta connected resistive load supplied at 400 volts and drawing 8 amps?

• 25 ohms

• 50 ohms

• 100 ohms

• 75 ohms