Power Formula
Single phase power formula
True Power or Real Power
True power, symbol to identify the power is 'P' .
The unit for measuring true power is Watts or 'W '.
Formula : P = 240v x I x p.f
where;P - power in wattsI - current p.f - power factor commonly shall be >0.85
Apparent Power or Design Power
Apparent power, symbol to identify is 'S' .
The unit for measuring apparent power is volt-ampere or ' VA '.
Apparent power, S Formula : S = 240v x I
where;P - power in wattsI - current
Three Phase Formula
True Power or Real Power
True power, symbol to identify the power is 'P' .
The unit for measuring true power is Watts or 'W '.
Formula : P = 415v x √3 x I x p.f
where;P - power in wattsI - current p.f - power factor commonly shall be >0.85
Apparent Power or Design Power
Apparent power, symbol to identify is 'S' .
The unit for measuring apparent power is volt-ampere or ' VA '.
Apparent power, S Formula : S = 415v x √3 x I
where;P - power in wattsI - current √3 - three phase or 1.732
Reactive Power or Energy
Reactive power, symbol to identify is ' Q ' .
The unit for measuring apparent power is volt-ampere reactive or ' VAR '.
Reactive power, Q Formula : Q = √ S² - P ²
where;P - true power in wattsS - apparent power in volt-ampere
Power Factor
Power Factor
Power factor is not unit but a form factor, symbol to identify is ' pf ' .
The value for power factor are between 0.5 ~ 0.99 .
Ideal power factor in three phase supply is said to be more than 0.85 .
Power factor, pf Formula : pf = P ÷ S
where;P - true power in wattsS - apparent power in volt-ampere
Note:
If value of power factor is below 0.85, consumer may required to pay more electricity cost.