Electrical Test and Electric Motors

Electricity is found in two common forms:

• AC (alternating current)

• DC (direct current).

An electrical circuit has the following three basic components irrespective of its electrical energy form:

• • Voltage (volts)

• • Ampere (amps)

• • Resistance (ohms).

All three are bound together with Ohm’s law, which gives the following relation between the three:

V=I x R

In DC circuits, power (watts) is simply a product of voltage and current.

P = V x I

Relationship between powers:

Apparent power (VA) = V x A

True power (Watts) = VA x cos?

Reactive power (VAR) = VA x sin?

Power factor is defined as the ratio of real power to apparent power. The maximum value it can carry is either 1 or 100(%), which would be obtained in a purely resistive circuit.

Power factor = True power/Apparent power

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