0195136047.pdf

PROBLEMS 499

g 1

g 2

Figure P11.2.9

30

cm

20 cm 20 cm

g 1 g 2

Figure P11.2.10

Source N g

Figure P11.2.11

(a) Total magnetic flux.
(b) Flux linkages of the coil.
(c) Coil inductance.
(d) Total stored magnetic energy.
11.2.12Repeat Problem 11.2.11 accounting for the core’s
relative permeability of 2000.
11.2.13Reconsider Problem 11.2.3. Calculate the coil
inductanceLand the total stored magnetic energy
before and after the air gap is cut.
11.3.1A 10-kVA, 4800:240-V, 60-Hz, single-phase
transformer has an equivalent series impedance
of 120+j 300 referred to the primary high-
voltage side. The exciting current of the trans-
former may be neglected.
(a) Find the equivalent series impedance re-
ferred to the secondary low-voltage side.
(b) Calculate the voltage at the primary high-
voltage terminals if the secondary supplies
rated secondary current at 230 V and unity
power factor.
11.3.2A 25-kVA, 2300:230-V, 60-Hz, single-phase
transformer has the following parameters: re-
sistance of high-voltage winding 1.5, resis-
tance of low-voltage winding 0.015, leakage
reactance of high-voltage winding 2.4, and
leakage reactance of low-voltage winding 0.024
. Compute the following:

(a) Equivalent series impedance referred to the

high-voltage side.

(b) Equivalent series impedance referred to the

low-voltage side.

(c) Terminal voltage on the high-voltage side

when the transformer is delivering full load

at 230 V and 0.866 power factor lagging.

11.3.3A 100-kVA, 2300:230-V, 60-Hz, single-phase

transformer has the following parameters:R 1 =

0. 30 ,R 2 = 0. 003 ,RC 1 = 4 .5k,X 1 =

0. 65 ,X 2 = 0. 0065 , andXm 1 = 1 .0k,

where subscripts 1 and 2 refer to high-voltage and

low-voltage sides, respectively. Set up the equiv-

alent T-circuit of the transformer and determine

the input current, input voltage, input power, and

power factor when the transformer is delivering

75 kW at 230 V and 0.85 lagging power factor.

11.3.4A 150-kVA, 2400/240-V, 60-Hz, single-phase

transformer has the following parameters:R 1 =

0. 2 ,R 2 = 0. 002 ,X 1 = 0. 45 ,X 2 =

0. 0045 ,RC=10 k, andXm= 1 .55 k,

where the notation is that of Figure 11.3.4. Form

the equivalent T-circuit of the transformer re-

ferred to the high-voltage side, and calculate the

supply voltage on the high-voltage side when the

transformer supplies rated (full) load at 240 V

and 0.8 lagging power factor.

11.3.5For a single-phase, 60-Hz transformer rated 500