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Electric Formulas

 

 

 

 

 

Electric Power Formulas

 

 

(1a) W = E I

 

(1b) W = R I2

 

 

(1c) W = E2/ R

 

where

 

 

W = power (Watts)

 

E = voltage (Volts)

 

I = current (Amperes)

 

R = resistance (Ohms)

 

Electric Current Formulas

 

 

(2a) I = E / R

 

(2b) I = W / E

 

(2c) I = (W / R)1/2

 

Electric Resistance Formulas

 

(3a) R = E / I

 

(3b) R = E2/ W

 

(3c) R = W / I2

 

Electrical Potential Formulas – Ohms Law

 

 

Ohms law can be expressed as:

 

(4a) E = R I

 

(4b) E = W / I

 

(4c) E = (W R)1/2

 

Electrical Motor Formulas

 

 

Electrical Motor Efficiency

 

(5) μ = 746 Php / Winput

 

where

 

μ = efficiency

 

Php = output horsepower (hp)

 

Winput = input electrical power (Watts)

 

or alternatively

(5b) μ = 746 Php / (1.732 E I PF)

 

Electrical Motor – Power

 

 

(6) W3-phase = (E I PF 1.732) / 1,000

 

where

 

W3-phase = electrical power 3-phase motor (kw)

 

PF = power factor electrical motor

 

Electrical Motor – Amps

 

 

(7) I3-phase = (746 Php) / (1.732 E μ PF)

 

where

 

I3-phase = electrical current 3-phase motor (Amps)

 

PF = power factor electrical motor