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Calculation of improved power factor

Technical Support


(kVA)2=(kW)2+(kVAR)2


Capacitor Requirement (kVAR)  



P: Effective power (kW) cosθ1 = power factor before improvement cosθ2 = power factor after improvement

Normally, the power factor cosθ is known, and the tangent value (tanθ) of the angle θ can be found in the table below.

cosθ tanθ cosθ tanθ cosθ tanθ cosθ tanθ cosθ tanθ cosθ tanθ
0.40 2.291 0.50 1.732 0.60 1.333 0.70 1.020 0.80 0.750 0.90 0.484
0.41 2.225 0.51 1.687 0.61 1.299 0.71 0.992 0.81 0.724 0.91 0.456
0.42 2.161 0.52 1.643 0.62 1.265 0.72 0.964 0.82 0.698 0.92 0.426
0.43 2.100 0.53 1.600 0.63 1.233 0.73 0.936 0.83 0.672 0.93 0.395
0.44 2.041 0.54 1.559 0.64 1.201 0.74 0.909 0.84 0.646 0.94 0.363
0.45 1.984 0.55 1.518 0.65 1.169 0.75 0.882 0.85 0.620 0.95 0.329
0.46 1.930 0.56 1.479 0.66 1.138 0.76 0.855 0.86 0.593 0.96 0.292
0.47 1.878 0.57 1.441 0.67 1.108 0.77 0.829 0.87 0.567 0.97 0.251
0.48 1.828 0.58 1.405 0.68 1.078 0.78 0.802 0.88 0.540 0.98 0.203
0.49 1.779 0.59 1.368 0.69 1.049 0.79 0.776 0.89 0.512 0.99 0.142

Type

Load Type

Power Factor(%)

Lights

Incandescent lamps (and hot wire stoves)
Series-connected incandescent lamps
Fluorescent lamps (and mercury lamps) - Without capacitor
Fluorescent lamps (and mercury lamps) - With capacitor 
Neon lamp 
Sodium-Vapor lamp - Without capacitor
Sodium-Vapor lamp - With capacitor

100
60～80
50
80～95
50～70
70
85～95

Electric motors

Three-phase induction machine

(Half Load～Full Load)

1/4～10HP( Squirrel Cage Low Pressure )

60～85

10～50HP( Squirrel Cage Low Pressure )

75～88

10～50HP( Wound low voltage )

62～85

50～270HP( Squirrel Cage High Pressure )

72～89

50～270HP( Wound high voltage )

72～89

Single phase induction machine 1/20～5HP

50～70

Synchronous motor

80～100

Table fan

65～75

ceiling fan

50～70

Electric drill

90

Electric bell

50

Greenhouse regulator - Warm air
Greenhouse regulator - Cold air

85
99.8

Welding equipment

AC arc welding machine (5～20kW)

55

AC resistance welding machine (1～400kW)

50

Iron melting furnace

Electric Arc Furnace (100～100,000kW)

85

Low frequency induction furnace (50～500kW)

60～80

Induction heater

85

Electric furnace

100

Others

X-ray generator

40～95

Silicon Rectifier

80～95


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