_____________________________________________________________________ Special Amplifiers
7-103. When the inductance decreases, the end result is that the power in the load (true
power) increases. The following formulas show how each is affected by a decrease in
inductance.
XL = 2π fL
(inductive reactance in the circuit)
(impedance in the circuit)
XL + R
Z=
2
2
E
I=
(current in the circuit)
Z
True power = I2R (true power or power in the load)
I increases. Finally, as I increases, true power increases. This general conclusion can be
confirmed by using some actual values of inductance in the formulas along with other
values from Figure 7-26.
7-104. If the value of inductance is 23 millihenries, the formulas yield the following
values:
XL = 2π fL
XL = (2)
(3.14) (60 Hz) (23 mH)
XL = 8.67 Ω (rounded
off)
Z=
XL2 + R 2
Z = (8.67 Ω 2 + (5 Ω) 2
Z = 100.1689 Ω
Z = 10 Ω (rounded off)
E
I=
Z
100 V
I=
10 Ω
I = 10 A
TruePower = I 2 R
True Power = (10A)2 x (5Ω5
True Power = 500 watts
23 June 2005
TC 9-62
7-37
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