vault backup: 2025-10-07 16:32:57

alternating-current.md

@@ -6,24 +6,107 @@ tags:
   - topic/electrical
   - type/encyclopedia
 ---
-# 3 Phase Power
+# Alternating Current
+
+[Alternating current (AC)](https://en.wikipedia.org/wiki/AC_power)
+is electric current that reverses direction periodically.
+The voltage and current in an AC circuit oscillate in a sinusoidal manner.
+The frequency of the oscillation is the number of complete cycles per second measured in hertz (Hz).
+The frequency of the AC power grid in the United States is 60 Hz.
+
+* Ungrounded conductor - "Hot"
+* Grounded conductor - "Neutral"
+
+## 3-Phase Power
 
 The conductors between a voltage source and a load are called lines,
 and the voltage between any two lines is called line voltage.
 The voltage measured between any line and neutral is called phase voltage.
 
-%%
-
-## Scratch
-
 * Poles vs Phases vs Wires
 
-3Ø = 3PH 3W
-3ØY = 3PH 4W
+* 3Ø = 3PH 3W
+* 3ØY = 3PH 4W
 
-> Phase abbreviations
+> [!info] Phase Abbreviations
 > * PH
 > * Φ (capital phi)
 > * Ø (latin O with stroke)
 
-%%
+208Y/120V
+480Y/277V
+
+### Voltage Systems
+
+120/240V 1-Phase 3-Wire:
+- 120V 1-Phase 2-Wire # Line to Neutral
+- 240V 1-Phase 2-Wire # Line to Line
+
+120/208V 3-Phase 4-Wire:
+- 120V 1-Phase 2-Wire # Line to Neutral
+- 208V 1-Phase 2-Wire # Line to Line
+- 208V 3-Phase 3-Wire # Line to Lines
+
+277/480V 3-Phase 4-Wire:
+- 277V 1-Phase 2-Wire # Line to Neutral
+- 480V 1-Phase 2-Wire # Line to Line
+- 480V 3-Phase 3-Wire # Line to Lines
+
+wiring-configurations:
+- 1-Phase 2-Wire # Line to Neutral or Line to Line
+- 1-Phase 3-Wire # Line to Line and Line to Neutral
+- 3-Phase 3-Wire # Line to Lines
+- 3-Phase 4-Wire # Line to Lines and Line to Neutral
+
+## Active and Reactive Power
+
+As a consequence of the periodic nature of AC,
+and the electromagnetic "inertia" of inductance and capacitance,
+inherent of all matter,
+the power in an AC circuit is divided into two components:
+
+- **Active Power**
+  (abbreviated $P$, measured in watts)
+  also known as real power, is power that *does work*. 
+
+- **Reactive Power**
+  (abbreviated $Q$, measured in volt-amperes reactive (VAR))
+  transfers no net energy to the load.
+
+derived from these components are others:
+
+- **Complex Power**
+  (abbreviated $S$, measured in volt-amperes (VA))
+  is the vector sum of the active and reactive components.
+  It is "complex" because it exists on the real and imaginary axes
+  of active and reactive power respectively.
+
+- **Apparent Power**
+  (abbreviated $|S|$, measured in volt-amperes (VA))
+  is the magnitude of the complex power vector.
+
+- **Power Factor**
+  (abbreviated $\text{PF}$, unitless)
+  is the ratio of active power to apparent power.
+
+$$
+P = S \times \text{PF}, \quad S = \frac{P}{\text{PF}}, \quad PF = \frac{P}{\text{S}}
+$$
+
+### Power Factor Correction
+
+Capacitance and inductance can both be measured in VAR,
+but their effects cancel each other out rather than add.
+
+## Motors
+
+1hp = 746 watts
+
+full-load current (FLC) / full-load amperes (FLA)
+
+minimum circuit ampacity (MCA)
+
+$$
+\text{MCA} = 1.25 \times \text{FLC}
+$$
+