Shop Practice with Electrical Code:Voltage Drop and Short CircuitCalculation Residential SinglePhase SystemJayson Bryan E. Mutuc, REE, RMEBSEE-PUP
Voltage Drop184.108.40.206 (a) (1) FPN No. 4:Toprovide reasonable efficiencyof operation of electricalequipment, branch-circuitconductors should be sized toprevent a voltage drop not toexceed three percent. Inaddition, the maximum totalvoltage drop on both feedersand branch circuits shouldnot exceed five percent.
Voltage Drop CalculationVoltage Drop Calculation:%VD =IRVoltage Supply (V3)x100%where:I – line current, amperesR – line ac resistance, ohms
Purpose of Short Circuit CalculationThe purpose of short circuit calculation is to know the rating theinterrupting capacity of the overcurrent protective deviceIn circuit breaker there are 3 important parameters when it comes toresidential design,ampere trip, ampere frame and interrupting ratingAmpere trip– the current rating the circuit breaker set to tripAmpere frame– insulation housing for maximum long time currentavailable in physicalInterrupting Rating– the highest current at rated voltage that a deviceis intended to interrupt under standard test conditions.
Analogies to Short Circuit ConditionNormal Current OperationShort Circuit Condition with InadequateInterrupting Rating
Analogies to Short Circuit ConditionShort Circuit with AdequateInterrupting Rating