A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps. The kW meter currently indicates 163.6 kW, with a power factor of 0.7. If the power factor increases to 0.8, what would the new kW meter reading?
• Relationship between kW, volts, amps, and power factor in a three-phase system • How changing power factor affects real power (kW) when voltage and current stay the same • Proportional change in kW when only power factor changes
• First, recall or write down the formula for real power (kW) in a three‑phase AC system using voltage, current, and power factor. • Check whether you really need to recalculate from volts and amps, or if you can relate the old and new kW values by comparing the change in power factor. • Think about whether kW will increase or decrease when the power factor improves from 0.7 to 0.8, assuming voltage and current remain constant.
• Confirm the correct three‑phase power formula involving line voltage, line current, and power factor. • Verify that voltage (450 V) and current (300 A) are unchanged between the two cases. • Check that you scale the original kW reading by the correct ratio of power factors before comparing with the answer choices.
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