Discussion Overview
The discussion centers on calculating three-phase power using a current transformer (CT) that measures only one phase. Participants explore the implications of measuring a single phase in a balanced three-phase system and the formulas applicable for calculating kW or kVAh based on the available data.
Discussion Character
- Technical explanation, Debate/contested, Mathematical reasoning
Main Points Raised
- One participant suggests calculating power using the formula 400V * 130A * sqrt(3) for kVAh, assuming a balanced system and that 400V is the phase-to-phase voltage.
- Another participant agrees with the kVAh calculation but notes that to determine kW-hrs, the phase angle must also be known.
- A different participant challenges the initial calculation, stating that the correct approach for three-phase power is 3 * phase-to-neutral voltage * current on one phase, leading to the formula 3 * 400V * 130A.
- One participant provides two equations for calculating power in a three-phase system, emphasizing the relationship between phase-to-neutral and phase-to-phase voltages.
- Another participant expresses uncertainty about one of the equations but acknowledges the correctness of the adjusted formula using 400V/sqrt(3) for phase-to-neutral voltage.
- A suggestion is made regarding existing products that can measure current, voltage, power factor, and energy, directing participants to a specific website.
- A question is raised about which type of power is being measured: apparent power, active power, or reactive power.
Areas of Agreement / Disagreement
Participants express differing views on the correct formulas for calculating power in a three-phase system. There is no consensus on the method to be used, and the discussion remains unresolved regarding the appropriate approach and the implications of measuring only one phase.
Contextual Notes
Participants rely on assumptions about the balance of the phases and the definitions of phase-to-phase and phase-to-neutral voltages, which may affect the calculations. The discussion does not resolve the dependencies on these definitions or the phase angle for accurate kW-hr calculations.