Three-phase basics

In a DELTA connected balanced load, which relationship is true:

• V_P = √3 V_L

• I_L = I_P

• I_P = √3 I_L

• V_L = V_P

In a STAR connected balanced load, which relationship is correct:

• I_L = 3 I_P

• V_P = V_L ÷ √3

• I_P x √3 = I_L

• V_L = V_P ÷ √3

The line current drawn by a balanced three-phase load is given by:

• I_P = P ÷ (3 V_P cos Φ)

• I_L = P ÷ (3 V_L cos Φ)

• I_L = P ÷ (√3 V_L cos Φ)

• I_L = P ÷ ( V_L cos Φ)

If the RMS line voltage in a three-phase four-wire system is 11,000 V:

• the RMS voltage between any two LINE conductors is approximately 6351 V

• the peak line voltage is 31.11 kV

• the line-to-neutral RMS voltage is 11,000 V

• the peak-to-peak phase voltage is approximately 17.96 kV

The line currents in a three-phase load are:

(2∠0^∘) A, (2∠-120^∘) A and (2∠120^∘) A. Which statement about the loads is correct?

• The loads are resistive and inductive.

• The loads are resistive and capacitive.

• The loads are resistive and unbalanced.

• The loads are resistive and balanced.

The line currents in a three-phase four-wire load are:

(2∠0^∘) A, (2∠-90^∘) A and (2∠90^∘) A. Which statement below is correct?

• The loads are balanced.

• The power factor is 0.866 in each load.

• The neutral current is zero.

• The neutral current is (2∠0^∘) A.

A three-phase motor is connected in delta to a three-wire 400 V supply. It draws a line current of 18.76 A and absorbs 12 kW. Select the correct statement:

• The reactive power absorbed is 5 kVAr.

• The reactive power absorbed is 13 kVAr.

• The apparent power developed is 7504 VA.

• The active power = the reactive power.

Select the correct statement regarding a three-phase delta-connected unbalanced load.

• The line currents will be equal in magnitude.

• The phase currents will be equal in magnitude.

• The line currents will be unequal in magnitude.

• The phase voltages will be unequal in magnitude.