Electrical Engineering › Section M · Transformers and polyphase systems › Topic M.9
Three-phase power and wattmeter methods
Three-phase power is three single-phase powers added together, and for balanced loads one tidy formula, √3 V_L I_L cos θ, covers both Y and Δ. Measuring it takes three wattmeters, or, on a three-wire system, cleverly just two.
In this topic
- Power in each phase
- Totals from line quantities
- Worked example: a balanced Y load
- The three-wattmeter method
- The two-wattmeter method
- What the two readings reveal
- Worked example: two wattmeters on the same load
- Unbalanced four-wire Y loads
- Unbalanced three-wire Y loads
- Common mistakes to avoid
- Key takeaways
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