# Steady State Power Calculation - PowerPoint PPT Presentation

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Steady State Power Calculation. Section 10.1-10.4. Instantaneous Power. Instantaneous Power. Use current as point of reference. Apply Some Trig Identities. Power for Purely Resistive Circuits ( θ v = θ i ). For purely resistive circuits , θ v = θ i. θ v = θ i.

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#### Presentation Transcript

Section 10.1-10.4

### Instantaneous Power

Use current as point of reference

### Power for Purely Resistive Circuits (θv= θi)

• For purely resistive circuits , θv= θi

θv= θi

(all the electric energy is dissipated in the form of thermal energy)

### Power for Purely Inductive Circuits (θv= θi+90 deg)

• For purely inductive circuits , θv= θi+90 deg

θv= θi+90 deg

(Q is 1 VAR)

Volt-Amp Reactive

(Voltage leads current by 90 deg)

(No transformation of energy from electric energy to nonelectric form)

### Power for Purely Capacitive Circuits (θi= θv+90 deg)

• For purely inductive circuits , θi= θv+90 deg

θi= θv+90 deg

(Q is -1 VAR)

Volt-Amp Reactive

(Current leads voltage by 90 deg)

(No transformation of energy from electric energy to nonelectric form)

### Power Factor

(power factor angel)

Knowing the power factor does not tell you the value of power factor

angle.

We need to use descriptive language:

Lagging power factor: current lags voltage. (most appliances such as

lighting fixtures and washing machine…etcoperate at a lagging power

factor. We usually want to operate a power factor of 1.