NEW ERA UNIVERSITY
COLLEGE OF ENGINEERING AND TECHNOLOGY
ELECTRICAL ENGINEERING DEPARTMENT
EE 552D
ELECTRICAL MACHINE DESIGN
W: 10:00AM – 1:00PM
DESIGN II – B
DESIGN OF MAGNETIC CIRCUIT OF DISTRIBUTION TYPE TRANSFORMER
(FROM ITEM 24 TO ITEM 32)
NAME: Molina,Gillian S. RATING:
COURSE: BSEE DATE OF START: SEP 13,
DOS: SEP 22, 2010
ENGR. REYNALDO DELA CRUZ
INSTRUCTOR
I. OBJECTIVES
1. To have preliminary calculations of winding design of primary and secondary
item 1 up to item 23.
2. To determine the final data of the primary an secondary winding design.
II. EQUIPMENT NEEDED
1-calculator
1-design book manual
1-laptop or computer
1-other reference book
III. PROCEDURES
Item 1: It is proposed to design a core – type transformer with rectangular coils.
A subsequent design, Art. 147, will be devoted to the calculation of a cruciform-
core type of transformer.
Description . This is a distribution transformer of standard type for maximum
output rating. It is oil – immersed and self – cooling, without tape for voltage
adjustment.
Insulation tests (in tank with oil) ; voltage applied for 1 min
H.T. winding to L.T. winding and core, 10,000 volts
L.T. winding to core, 4,000 volts
The specified temperature rise of 55C means that the temperature of the
windings, as measured by the resistance method, after the transformer has been
operating continuously at full load, will not be more than 55C above the
temperature of the surrounding air.
Item 33. By the formula the efficiencies at unity factor are :
At full load , 1- = 0.9748
At half=load, 1- = 0.9766
The calculated values for other loads are:
At 25 percent overload, 0.9718
At ¾ full load, 0.9769
At ¼ full load, 0.9668
The maximum efficiency occurs when the total copper losses are equal to the
core loss, under which condition the fraction of rated load is
.
Core loss
√F . L . copper loss
36.9/92.3 =
Thus, at the point of maximum efficiency the load is 5
the maximum efficiency is
1- = 0.9772
Item 35. The magnetizing component Ic of the total exciting current is
calculated by making use of the BH curve and estimating the approximate mean
lengths of the flux paths wherein the flux density is approximately of constant
value throughout the length of path considered. Thus, for the two limbs under
the windings, we have B” = 66,700; mean length = 17 in. ; whence (TI) = 17 x
4.6 = 78.2.
For the two ends of the core (outside the windings) B” = 46,200; mean
length = about 15 ¼ in., whence (TI) = 15.25 x 2 = 30.5.
In order to estimate the ampere-turns required for the four joints in the
core, we refer to the figure.
For the two joints with core density B” = 66,700, we have (TI) = 2 x 21 = 42 and
for the two joints with core density B” = 46,200, we have (TI) 2 x 3 = 6, making
a total of 156.7 amp-turns. The magnetizing component of the primary current is,
therefore,
ID = = 0.0565 amp
The energy component is Iw = 36.9/2,300 = 0.016 amp and the total exciting
current component is √ 0.0565 ²+0.016 ² = 0.059 amp.
IV. CIRCUIT DIAGRAM
V. DATA AND RESULT
Item Summary of Calculation
No.
24. Dimension of window, in………………….. 16 1/4 x 5 1/2
25. Total flux, maxwells………………………... 1,000,000
26. Flux density in core under windings, lines per 85,000
sq in.………………………….
27. Cross section of iron in core under windings, 41
in2………………………………………
28. Width of stamping in core under windings, in. 4 1/2
……………………………………… 619.84
29. Gross thickness of core, in………………
30. Watts loss in iron (compare with guarantee), 268.22
lbs……………………………………….. 269.206
31. Total wt. of iron in core, lbs……………….
32. Total full load losses, 1036
watts……………………………………
Design Calculation
Item No. 24: Dimension of “Window”, in
11 1/2 x 6 1/4
Item No. 25: Total Flux, maxwells
1,000,000 Maxwells
Item No. 26: Flux density in core under winding.
Bg “ = 85,000 Lines/in2
Item No. 27: Cross section of iron in core under winding.
= 0.9 (S x L) = 0.9x38.32x19.16
= 660 in.
Item No. 28: Width of stamping in core under windings.
L=4.5 or 4 ½
in
Item No. 29: Gross thickness of core
S =38.32 in
Item No.30: Total wt. of iron in core
Wt of iron = 0.28(SFxSxM) x2 (H+M+S+L)
= 0.28(0.9 x 19.16 x 38.32) x2(5.145+10.16+38.32+38.32)
= 843.84 lbs.
Item No. 31: Watts’s loss in iron (compare w/ guarantee)
Watts/lbs = 268.22 watts
Item No. 32 Total Full load losses, watts
= 268.22 + .986 = 269.206 watts
VI. GRAPH AND TABLE
VII. REMARKS
VIII. CONCLUSION
Therefore I conclude that in this design of magnetic circuit it is very difficult
because of they have a less complex or variable. Thus also I conclude that the
emf voltage induced by the alternating flux in the primary and secondary coils will
be directly proportional to the number of turns in the perspective windings.
