Siemens DTU3005-B Spezifikationen PDF herunterladen (Seite 33)

The following table shows the amount of apparent power (VA =

W ÷ PF) required for a manufacturing facility using 1 MW

(megawatt) of power per hour for a few sample power factors. If,

for example, a manufacturing facility had a power factor of 0.70

the utility company would have to supply 1.43 MVA (mega volt-

amps) of power. If the power factor were corrected to 0.90 the

power company would only have to supply 1.11 MVA of power.

Leading and Lagging Since current leads voltage in a capacitive circuit, power factor

Power Factor is considered leading if there is more capacitive reactance than

inductive reactance. Power factor is considered lagging if there

is more inductive reactance than capacitive reactance since

current lags voltage in a inductive circuit. Power factor is unity

when there is no reactive power or when inductive reactance

and capacitive reactance are equal, effectively cancelling each

other.

It is usually more economical to correct poor power factor than

to pay large utility bills. In most industrial applications motors

account for approximately 60% or more of electric power

consumption, resulting in a lagging power factor (more

inductive than capacitive). Power factor correction capacitors

can be added to improve the power factor.

True

Power

(MW)

Power

Factor

Apparent

Power

(MVA)

True

Power

÷ Power

Factor

= Apparent

Power

1 1

0.95 1.053

0.90 1.11

0.85 1.18

0.80 1.25

0.75 1.33

0.70 1.43

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 87 88

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Siemens DTU3005-B Spezifikationen Seite 33