3-Phase Circuit - Line Current Calculation Question

In summary, there is a discrepancy in calculating line current in a 3-phase circuit when given a 3-phase balanced y-source connected to a y-load with equal impedance on each phase and an equal line impedance on each phase. Some examples use only the y-load impedance to calculate line current, while others include the line impedance in the calculation. However, in this scenario, both methods result in the same line current, which is equal to the phase current obtained by adding the line impedance and y-load impedance and dividing the phase voltage by the result.
  • #1
joenooch
1
0
Hello,

While reviewing my professor's notes and my textbook I've run to a discrepancy in regard to how to calculate line current in a 3-phase circuit.

In these particular examples, you are given a 3-phase balanced y-source connected to a y-load with equal impedance on each phase. In addition, there is an equal line impedance on each phase.

The question ask to calculate the line current.

In several of my examples, the line current is calculated using the impedance of the y-load and NEGLECTS the line impedance.

In several other examples, the line current is calculated using both the impedance of the y-load and INCLUDES the line impedance in the calculation.

Which is the correct method?

Thanks!
 
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  • #2
In this case both line current and phase current are the same. So add both line impedance and Y-load(single branch) and divide the phase voltage with the result to get line/phase current.
 

1. What is a 3-phase circuit?

A 3-phase circuit is an electrical system that uses three separate phases of alternating current (AC) to power devices. It is commonly used in power distribution systems for large industrial and commercial buildings.

2. How do you calculate line current in a 3-phase circuit?

The formula for calculating line current in a 3-phase circuit is: Line Current = Total Power (kW) / (3 x Voltage (V) x Power Factor). This formula takes into account the power being delivered by all three phases and the power factor, which is a measure of the efficiency of the circuit.

3. Why is it important to calculate line current in a 3-phase circuit?

Calculating line current is important because it helps determine the amount of electrical load that is being drawn from the circuit. This information is crucial for determining the appropriate size of wires, breakers, and other components in the circuit to ensure safe and efficient operation.

4. Are there any other factors that affect line current in a 3-phase circuit?

Yes, in addition to the total power and voltage, other factors such as the impedance and resistance of the circuit, as well as the power factor, can affect the line current. It is important to take all of these factors into account when calculating line current.

5. How does line current differ from phase current in a 3-phase circuit?

Line current refers to the total current being drawn from all three phases in a 3-phase circuit, while phase current refers to the current being drawn from a single phase. In a balanced 3-phase circuit, the line current will be equal to the phase current multiplied by the square root of 3.

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