vault backup: 2025-10-09 13:25:21

2025-10-09 13:25:22 -04:00
parent a45d3674e3
commit a8b5b79942
6 changed files with 197 additions and 106 deletions
@@ -115,6 +115,14 @@ either for spec requirements or conduit fill considerations.

 ## Voltage Drop

+> [!info] Ohm's Law
+>
+> $$
+> V = I \times R, \quad R = \frac{ V }{ I }, \quad I = \frac{ V }{ R }
+> $$
+
+### Step 1: Effective Impedance $Z$
+
 $$
 Z = R \cos(\theta) + X \sin(\theta)
 $$
@@ -125,47 +133,7 @@ where
 * $X$ = Reactance
 * $\theta$ = Power factor angle = $\arccos(PF)$

-> [!info] 1-Phase, Line to Neutral Voltage Drop
->
-> $$
-> \Delta V_{LN} = I \times Z \times 2L
-> $$
-
-> [!info] 1-Phase, Line to Line Voltage Drop
->
-> $$
-> \Delta V_{LL} = \sqrt{3} \times I \times Z \times 2L
-> $$
-
-> [!info] 3-Phase Voltage Drop
->
-> $$
-> \Delta V_{3\phi} = \sqrt{3} \times I \times Z \times L
-> $$
-
-where
-* $\Delta V$ = Voltage drop in volts ($V$)
-* $I$ = Current in amperes ($A$)
-* $L$ = Length of wire one way in feet ($\text{ft}$)
-
-It is often more useful to know the maximum length
-a certain wiring configuration is suitable for.
-
-$$
-L = \frac{ \Delta V }{ I \times M } \times \frac{1}{Z}
-$$
-
-> [!info] Ohm's Law
->
-> $$
-> V = I \times R, \quad R = \frac{ V }{ I }, \quad I = \frac{ V }{ R }
-> $$
-
-> [!important]
-> "Current" is not the OCPD rating,
-> but the actual load.
-
-## Parallel Runs
+#### Parallel Runs

 The equivalent resistance of parallel resistances is given by

@@ -183,6 +151,65 @@ $$
 \end{align*}
 $$

+### Step 2: Voltage Drop
+
+> [!important]
+> This section assumes a 3-phase
+> 208Y/120V or 480Y/277V voltage system
+
+> [!info] 3-Phase Voltage
+> $$
+> V_{LL} = \sqrt{3} \times V_{LN}, \quad V_{LN} = \frac{V_{LL}}{\sqrt{3}}
+> $$
+
+3% allowable voltage drop for a 120V line-to-neutral load:
+
+$$
+\text{Max} \Delta V = 0.03 \times 120 \text{V}_{LN} = 3.6 \text{V}_{LN}
+$$
+
+3% allowable voltage drop for a 208V line-to-line load:
+
+$$
+\text{Max} \Delta V = 0.03 \times 208 \text{V}_{LL} = 6.24 \text{V}_{LL}
+$$
+
+#### Line to Neutral Loads
+
+$$
+\Delta V_{LN} = I \times Z \times 2L
+$$
+
+#### Line to Line Loads
+
+$$
+\Delta V_{LL} = \sqrt{3} \times \left( I \times Z \times 2L \right)
+$$
+
+#### 3-Phase Loads
+
+$$
+\Delta V_{3\phi} = \sqrt{3} \times \left( I \times Z \times L \right)
+$$
+
+where
+* $\Delta V$ = Voltage drop in volts ($V$)
+* $I$ = Current in amperes ($A$)
+* $L$ = Length of wire one way in feet ($\text{ft}$)
+
+> [!important]
+> "Current" is not the OCPD rating,
+> but the actual load.
+
+***
+
+It is often more useful to know the maximum length
+a certain wiring configuration is suitable for.
+
+$$
+L = \frac{ \Delta V }{ I \times M } \times \frac{1}{Z}
+$$
+
 ## Transformers

 $$