Phasor Diagram and Phase Shift Example

Fill in the blank: Power in VARs in lagging phase angle is associated with ______ load.

• lagging

• leading

• resistive

• capacitive

Using the formula P = E_LL * I * √3 * cos θ, calculate the power if E_LL = 400V, I = 10A, and θ = 30 degrees.

• 2000 W

• 3464 W

• 4000 W

• 6000 W

What type of transformer connection is shown in the diagram?

• Delta on the low side

• Delta on the high side

• Wye on the high side

• Wye on the low side

Answer explanation

The answer is on PHASOR DIAGRAM AND PHASE SHIFT EXAMPLE

Fill in the blank: A phase shift of ___ degrees, current on the delta (high side, Ia) side leads current on the wye (low side, IA) side of the transformer.

• 30

• 15

• 45

• 60

What is the phase angle relationship across a delta-wye transformer bank?

• 0 degrees

• 30 degrees

• 60 degrees

• 90 degrees

What is the formula for calculating power (W) using current (I) and voltage (V)?

• P = I × V

• P = V / I

• P = I / V

In a DC series circuit, how is the total resistance (R_T) calculated?

• By summing up all the individual resistances

• By multiplying all the individual resistances

• By taking the reciprocal of the sum of the reciprocals of all individual resistances

• By subtracting the smallest resistance from the largest resistance

What is the formula for inductive reactance (X_L)?

• The formula for inductive reactance (X_L) is X_L = 2πfL, where f is the frequency in hertz and L is the inductance in henries.

• The formula for inductive reactance (X_L) is X_L = f/L, where f is the frequency in hertz and L is the inductance in henries.

• The formula for inductive reactance (X_L) is X_L = L/2πf, where f is the frequency in hertz and L is the inductance in henries.

• The formula for inductive reactance (X_L) is X_L = 1/2πfL, where f is the frequency in hertz and L is the inductance in henries.

Which of the following is the correct formula for capacitive reactance (X_C)?

• X_C = 2πfC

• X_C = 1/2πfC

• X_C = 2πfL

• X_C = 1/2πfL

In a DC parallel circuit, how is the total voltage (V_T) related to the individual voltages (V_1, V_2, V_3)?

• The total voltage (V_T) in a DC parallel circuit is equal to the individual voltages (V_1, V_2, V_3), meaning V_T = V_1 = V_2 = V_3.

• The total voltage (V_T) is the sum of the individual voltages, meaning V_T = V_1 + V_2 + V_3.

• The total voltage (V_T) is the average of the individual voltages, meaning V_T = (V_1 + V_2 + V_3) / 3.

• The total voltage (V_T) is zero if any of the individual voltages is zero.