A6 7 = S\0X0°"; ^ (0.0445"')`95.SX\9.]°"Ta ^ _(0.0945"')`95.SX\9.]°a
= S\0X0°"; ^ S.]0X\9.]°"; ^ 4.SGXGS9.]°"; = S\0 ^ S.\S ^ _G.S4 : S.5S ^ _\.\9 = SS].W0 ^ _5.G0 = SS].W5XG.Sb°"; [ ;@ =
A6 7B CAD-EF AD-EF
× G00""" = QQg.c!"ACQR%"A QR%"A
× G00d = :0.09Sd (The voltage regulation)
50
Solution [Continued] --- Repeated from previous page(s): 15 KVA, 2300/230-V (Transformer Rating)
+ +
: :
;< ;> ?> ?<
2300V 230V
----------------------------------------------------------------------------------------------------------------------------------
(c) --- Calculate the full-load voltage regulation at 0.8 lagging power factor, unity power factor, and
at 0.8 leading power factor --- Do a phasor diagram for each case:
A6 7 = ;/ ^ @+,H/ ^ _*+,H/ --- Using the figure above at right
· We have all components of the above equation (as shown in the above figure, right)
· We also, found the currents for the 3 cases of 0.8 lagging power factor, unity power factor,
and 0.8 leading power factor
· Using these values, we simply show the above equation using phasors --- Each of these three
phasor diagrams is shown in figures below:
51
Solution [Continued] --- Repeated from previous page(s):
+ +
: :
;< ;> ?> ?<
2300V 230V
----------------------------------------------------------------------------------------------------------------------------------
(d) --- Plot the voltage regulation as load is increased from no-load to-full load at power factors of
0.8 lagging, unity, and 0.8 leading:
The best way to plot the voltage regulation as a function of load is to repeat the calculations
presented in part (c) for many different values of the loads by writing a MATLAB program (See
your text) --- The plot produced by this program is shown in figure below:
;@ = A6 7 B CAD AD
× G00 ---
· Can you interpret these curves?
· Do this part and submit a report (See Design 1)
52
Solution [Continued] --- Repeated from previous page(s): 15 KVA, 2300/230-V (Transformer Rating)
+ +
: :
;< ;> ?> ?<
2300V 230V
H/ = 95.S"X : \9.]°"T (Full-load current for the case of power factor of 0.8 lagging)
h = eijN eFikkl !"#
× 100% = !"#
( $"& '!)*+& !"# × 100% --- The efficiency at this condition
----------------------------------------------------------------------------------------------------------------------------------
(e) --- Find the efficiency of the transformer at full load with a power factor of 0.8 lagging:
To find the transformer efficiency of the transformer, we calculate its output power and
its losses --- Using the circuit at right:
,-. = |/2| 3456 = (789:;<+
3(090>>8;?+ = 1@A;B (The copper losses)
,-CD5 = ;|EF GH |
I
J$
KI
= (3LM9NO;E+I
PQOQ;R = 8:98;B (The core losses)
,S.T = |U2||/2|;,V (The output power of the transformer at this power factor)
= (:W0;U+(789:;<+09@ = 1:X000;B
Finally, the efficiency is:
Y = Z"#
( $";&; $!)*+;&; Z"# × 100% =
P3XQQQ;[
(PN\;[;&;O39O;[+;&;P3XQQQ;[ × 100% = A@90W%
53
Design 1 [Due next week today]:
This design is related to the previous example problem --- Figures below are repeated:
+ +
] ]
Û U_ _̀ ^̀
2300V 230V
----------------------------------------------------------------------------------------------------------------------------------
(1) --- Plot the voltage regulation of the transformer as its loading is increased from no-load to full-
load at power factors of 0.8 lagging, unity, and 0.8 leading --- This is part (d) of the previous
example problem (You should plot the 3 curves in one graph for easy comparison)
(2) --- Plot the efficiency of the transformer as its load is increased from no-load to-full load at
power factors of 0.8 lagging, unity, and 0.8 leading --- This is part (e) of the previous example
problem, but extended to include the various loading as well as loads with the unity, and
leading power factors (You should plot the 3 curves in one graph for easy comparison)
(3) --- Prepare a report including: a summary of the problem, your MATLAB code, the plots and an
engineering conclusion derived from each of the plots
(4) --- The report should be submitted to me via email (Gradman@TNTech.edu) in one PDF-file and
the file should be named as follows:
Your class no -- Your last name -- Design 1 -- ECE 3610 -- Summer 2017
For example, assume my number is 99 --- Then, I will name my PDF-file as follows:
99 -- Radman -- Design 1 -- ECE 3610 -- Summer 2017