Title Electrical Formulas Explanations 182.5 KB 16
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UNITS DERIVED FROM THE BASE ELECTRICAL UNIT (AMPERE)
RULES OF THUMB FOR ELECTRICAL MOTORS
ELECTRICAL FORMULAS
Inductive reactance XL
Capacitive reactance XC
TRIGONOMETRY
POWER FACTOR CORRECTION TABLE:
TRANSFORMER CALCULATIONS
VOLTAGE AND CURRENT RELATIONSHIPS
VOLTAGE AND COIL TURN RELATIONSHIPS
AMPERES AND COIL TURN RELATIONSHIPS
RESISTOR COLOR CODE
FULL-LOAD CURRENT IN AMPERES FOR DIRECT-CURRENT MOTORS
COMPARISON OF AC AND DC CURRENTS
PREFIXES USED FOR SUBDIVISIONS AND MULTIPLES OF UNITS
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##### Document Text Contents
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Electrical Formulas, Explanations

Impedance (Z)

Impedance is the total opposition to an alternating current presented by a circuit (OHMS). Total AC
resistance.

Amperes

Volts

I

E
Z == , ( ) 22)(Im CL XXRZpedance −+=

Power factor (PF)

Power factor (Pf) equals the cosine, where θ is the angle is either lead or lag.

Z

R

EI

P

werApparentPo

TruePower
PF ===

TRIGONOMETRY

Trigonometry is the mathematics dealing with the relations of sides and angles of triangles. A triangle is a
figure enclosed by three straight sides. The sum of the three angles is 180 degrees. All triangles have six
parts: three angles and three sides opposite the angles. Right triangles are triangles that have one angle of
ninety degrees and two angles of less than ninety degrees.

Hypotenuse

deOppositeSi
Sine =θ

Hypotenuse

CoSine =θ

deOppositeSi
Tangent =θ

deOppositeSi

CoTangent =θ

Hypotenuse
Secant =θ

deOppositeSi

Hypotenuse
CoSecant =θ

Note: θ = Theta = any angle

Remember: SOHCAHTOA, Sine, opposite, hypotenuse, cosine, adjacent, hypotenuse, tangent,

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HYPOTENUSE

O
P

P
O

S
IT

E
S

ID
E

60º

90º30º

“Y”

“X”

ALWAYS PLACE THE ANGLE TO BE SOLVED AT
THE VERTEX (WHERE “X” AND “Y” CROSS).