![]() Leading Power Factor Power Factor-Balanced Load Reactive Voltamperes with One Wattmeter One Wattmeter Method Double Subscript Notation Unbalanced Loads Four-wire Star-connected Unbalanced Load Unbalanced Y-connected Load Without Neutral Millman’s Thereom Application of Kirchhoff's Laws Delta/Star and Star/Delta Conversions Unbalanced Star-connected Non-inductive Load Phase Sequence Indicators Phase Sequence Interconnection of Three Phases Star or Wye (Y) Connection Voltages and Currents in Y-Connection Delta (D) or Mesh Connection Balanced Y/D and D/Y Conversions Star and Delta Connected Lighting Loads Power Factor Improvement Parallel Loads Power Measurement in 3-phase Circuits Three Wattmeter Method Two Wattmeter Method Balanced or Unbalanced load Contd….Ĥ Polyphase Circuits C-19 Variations in Wattmeter Readings At radio frequencies a common method is a rectifier circuit arranged to respond to current in a the system is calibrated for the known circuit impedance.3 Polyphase Circuits C-19 Generation of Polyphase Voltages Radio frequency Instruments with moving coils can be calibrated for direct current or currents up to a few hundred hertz. ![]() This moves the measurement out of the problematic low-power zone. In practice accuracy can be improved by connecting a fixed load such as an incandescent light bulb, adding the device in standby, and using the difference in power consumption. If a laptop computer in sleep mode consumes 5 W, the meter may read anything from 0 to 15.25 W, without taking into account errors due to non-sinusoidal waveform. For a typical plug-in meter the error in wattage is stated as ±5% of measured value ☑0 W (e.g., a measured value of 100W may be wrong by 5% of 100 W plus 10 W, i.e., ☑5 W, or 85–115 W) and the error in kWh is stated as ±5% of measured value ☐.1 kWh. The specification for the meter should specify the reading error for different situations. ![]()
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