Three-Phase System Quiz

In a balanced three-phase system-delta load, if we assume the line voltage is VRY = V∠0⁰ as a reference phasor. Then the source voltage VBR is?

• V∠120⁰

• V∠240⁰

• V∠-240⁰

• V∠-120⁰

In a delta-connected load, the relation between line voltage and the phase voltage is?

• line voltage > phase voltage

• line voltage = phase voltage

If the load impedance is Z∠Ø, the current (IR) is?

• (V/Z)∠-Ø

• (V/Z)∠Ø

• (V/Z)∠90-Ø

• (V/Z)∠-90+Ø

A three-phase balanced delta connected load of (4+j8) Ω is connected across a 400V, 3 – Ø balanced supply. Determine the phase current IY.

• 44.74∠183.4⁰A

• 45.74∠183.4⁰A

• 44.74∠-183.4⁰A

• 45.74∠-183.4⁰A

The three impedances Z1 = 20∠30⁰Ω, Z2 = 40∠60⁰Ω, Z3 = 10∠-90⁰Ω are delta-connected to a 400V, 3 – Ø system. Find the line current I3.

• (24.646+j20) A

• (-24.646+j20) A

• (-24.646-j20) A

• (24.646-j20) A

The voltage between __________ and ___________ is called phase voltage.

• line and line

• line and reference

• neutral point and reference

• line and neutral point

In delta-connected system, the currents IR, IY, IB are equal in magnitude and they are displaced by _____ from one another.

• 0⁰

• 60⁰

• 90⁰

• 120⁰

The relation between IL and IPh is in a delta connected system is?

• IL = IPh

• IL = √3 IPh

• IL = 3 IPh

• IL = 3√3IPh

The wattmeter method is used to measure power in a three-phase load. The wattmeter readings are 400W and -35W. Calculate the total active power.

• 360

• 365

• 370

• 375

The wattmeter reading while measuring the reactive power with wattmeter is?

• VL*IL*secØ

• VL*IL*sinØ

• VL*IL*tanØ

• VL*IL*cosØ