Electrical machine design; the design and specification of direct and alternating current machinery .. by Gray Alexander 1882-1921

Author:Gray, Alexander, 1882-1921
Language: eng
Format: epub, pdf
Tags: Electric machinery -- Design and construction
Publisher: New York [etc.] McGraw-Hill book company, inc
Published: 1913-03-25T05:00:00+00:00

the constant = the ratio J- - T- — rr from Fig. 185.

frame length

Tabulate three preliminary designs, one for a diameter 20 per cent, larger than that already found and the other 20 per cent. smaller.

Find the probable total number of conductors — - — = — - and

LC

assume that the winding to be used is single circuit, and Y connected if three-phase, so that I c — the full-load line current. Find the number of slots; there should be at least two slots per pole, if possible, in order to get the advantages of the distributed winding, see Art. 141, page 180, but the slot pitch should not exceed 2.75 in.; Art. 193, page 256.

-,.,,, T , , probable total conductors

Find the conductors per slot =— — r -- e i . — : take

number of slots

the nearest number that will give a suitable winding. Find the corresponding total number of conductors. Find (/) a from the formula E = 2.22 kZ$ a f 10~ 8 formula 25,

page 190. Find the actual frame length as follows: .

a

slot P ltch = total slots 5 divide this into s + t by the use of Fig. 182, page 257;

the minimum tooth area required = - " , - r—

max. tooth density

where the max. tooth density =90,000 lines per square inch

for 60 cycles

110,000 lines per square inch for 25 cycles

for open slot machines, and is 15 per cent, larger for machines

with partially closed slots;

the tooth area per pole = slots per pole X<f>XtXL n , from

which L n can be found

L c =L g + (ihe center vent ducts), where these ducts are 0.5 in.

wide and are spaced 3 in. apart. Find d, the air gap clearance, as follows:

ATX3.2

•"• •*• Q

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