a) The apparent power of the load can be calculated as the real power divided by the power factor:
Apparent power = Real power / Power factor = 60kW / 0.8 = 75kVA
In a three-phase system, the apparent power is equal to the line voltage multiplied by the line current:
Apparent power = √3 x Line voltage x Line current
We can rearrange this equation to solve for the line voltage:
Line voltage = Apparent power / (√3 x Line current)
Since the alternator is star-connected, the phase voltage is equal to the line voltage. Therefore, the phase voltage is:
Phase voltage = 75kVA / (√3 x Line current)
b) To calculate the phase current of the alternator, we can rearrange the equation above:
Line current = Apparent power / (√3 x Line voltage)
Given that the apparent power is 75kVA and the line voltage is the same as the phase voltage, the line current is:
Line current = 75kVA / (√3 x Phase voltage)
c) The electrical power input to the alternator can be calculated as the real power divided by the efficiency:
Electrical power input = Real power / Efficiency = 60kW / 0.85 = 70.5882kW
Since the mechanical power needed to drive the alternator is equal to the electrical power input, the mechanical power required is:
Mechanical power = 70.5882kW
A 60kW 2,2kW three-phase star-connected alternator supplies a load operating at a power factor of 0,8 lagging. If the alternator at an efficiency of 85%, calculate
a) The phase voltage of the alternator
b) the phase current of the alternator
c) the mechanical power needed to drive the alternator
1 answer
1 answer