Question 1 of 10
What does kVA stand for?
kVA stands for kilovolt-amperes, a unit of apparent power.
Question 2 of 10
In a single-phase system, what is the formula to calculate current (I) in amperes from kVA and voltage (V)?
The formula is derived from the apparent power formula: S = V * I. Therefore, I = S/V where S is expressed in VA (kVA * 1000)
Question 3 of 10
In a three-phase system, using line-to-line voltage (VL-L), what is the formula to calculate current (I) in amperes from kVA and voltage?
This formula accounts for the phase relationship in a three-phase system.
Question 4 of 10
What is the square root of 3 (?3) approximately equal to?
The square root of 3 is a constant used in three-phase calculations.
Question 5 of 10
In a three-phase system, using line-to-neutral voltage (VL-N), how do you calculate the current (I) in amperes from kVA and voltage?
Line-to-neutral voltage requires the use of the 3 factor in the formula.
Question 6 of 10
What additional information is needed to calculate the current if the apparent power (kVA) is known in a single-phase system?
The voltage is needed as it is part of the apparent power formula S=V*I
Question 7 of 10
What is the current in a single-phase circuit if the transformer is rated at 5 kVA and the voltage is 240V?
Using the formula I = (kVA * 1000) / V; I = (5000)/240 = 20.83 A
Question 8 of 10
What is the current in a three-phase circuit if the transformer is rated at 75 kVA and the line-to-line voltage is 480 V?
Using the formula I = kVA * 1000 / (?3 * VL-L); I = (75000) / (1.732 * 480) = 90.1 A
Question 9 of 10
What unit is used to measure current?
Current is measured in amperes (A).
Question 10 of 10
Why is the square root of 3 used in three-phase calculations involving line-to-line voltage?
The square root of 3 (?3) is used because of the phase difference (120 degrees) in a balanced 3-phase system.
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