Upload
sdouglass11
View
124
Download
3
Tags:
Embed Size (px)
Citation preview
Sharing our Guidance
X
Voltage Drop
Voltage drop is the reduction in voltage in an electrical
circuit between the source and load. It is caused by the
current flow through conductors resistance (Ohms law).
What is Voltage Drop
04/12/23 2
X
Voltage Drop
• Operating voltage at electrical equipment will be less than the output
voltage of the power supply.
• Inductive loads (i.e. motors, ballasts, etc.) that operate at voltage below
its rating can overheat resulting in shorter equipment operating life and
increased cost.
• Under-voltage for sensitive electronic equipment such as computers,
laser printers, copy machines, etc., can cause the equipment to lock up
or suddenly power down
Why is Voltage Drop is undesired?
04/12/23 3
X
Voltage Drop
• VD=((2*K*L*I)/CM)*.866 (only for 3-phase)• VD= Voltage drop
• K=Resistivity 12Ω for copper
• L= Length one way
• I= Current in amps
• CM= Circular mill area of wire (Chapter 9 Table #8 of NEC)
How to Calculate voltage Drop?
04/12/23 4
• We have a Voltage Drop Calculator saved in:
• T:\Engineering\Details and Schedules - Autocad\Electrical Schedules
X
Voltage Drop
• ALL 120V BRANCH CIRCUITS IN EXCESS OF 75’ & 277V BRANCH
CIRCUITS IN EXCESS OF 120’ SHALL HAVE CONDUCTOR SIZE INCREASED
A MINIMUM OF 1 CONDUCTOR SIZE.
Example
04/12/23 5
X
Voltage Drop
• National Electrical Code (NEC)
• Section 210.19.A.1 & 215.2.A.3 requires that voltage drop shall not
exceed TOTAL 5% at the farthest outlet of connected load.
• 2% feeder conductors.
• 3% branch circuit wiring.
Voltage Drop is code required
04/12/23 6
X
Voltage Drop
• It is required by energy calculation:
• Comcheck
• T24
• Florida
Voltage Drop is code required (cont.)
04/12/23 7
Voltage DropCONCLUSION . . .
THANK YOU.