Power Factor Reading When Only 10KVAR Capacitor Bank Is On, No Motors Running

The discussion addresses the power factor reading on a power factor meter when only a 10 kVAR capacitor bank is energized on a distribution board supplying two 10 kW motors, with the motors switched off. The main points clarify that with no motor load, the power factor meter will show a leading power factor due to the capacitive nature of the capacitor bank. Ideally, the real power (kW) is near zero, and the power factor, defined as kW/kVA, can be close to zero or leading, depending on the presence of minor loads such as control transformers. If the power factor meter is located after the main breaker and transformer, the reading reflects the combined effect of transformer losses and capacitor current. In the absence of load current, the meter needle may remain at the last reading or fluctuate randomly. The concept that power factor approaches unity when no current flows is challenged, as zero kW with capacitive current results in a leading power factor less than one. The role of transformer resistance and reactance ratios in influencing unloaded power factor readings is also discussed, emphasizing that small control transformers have higher resistance relative to reactance, which can increase power factor closer to unity under no-load conditions.
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