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Unformatted text preview: EE 643, Exam #1 answers, Au/05
1.a.1 W = L*i2 / 2, L = N2 / R, R = l / 0A decreases and thus W decreases. as l (length of air gap) increases, R increases, L 1.a.2 Decrease refer to last paragraph on page 134 (just before Example 3.6) 1.b Lagging power factor for Gen. (leading for motor) (Refer to Fig. 5.17, page 277 ) 1.c Br about the same for PM and ferromagnetic material; Hc much greater for PM (refer to Fig. 1.16, page 31) 2. L = N2 / Rtotal, Rtotal = Rcore + Rg + Rx, Rx = x / (0*W*D), Rg = g / (0*W*D), Rcore = lcore / (core*W*D) where lcore = (L W) + (L W) +(L W x) +(L W g) 3. 1 (W ' (i, x)) and W ' = * L * i , x 2 i 0.06 *1.15 f =- * = -0.03085 * i 2 (1 + 1.15 * x) f =
2 fld 2 2 resultant
magnetic axis of b - b' 2 a c' X b a c b'
X 4.a NR, CCW, NR 4.b same as with AC in 4.a CCW
magnetic axis of c - c' c magnetic axis of a - a' 4.c see diagram to right; note |ia| = |ib| = |ic|/2 5.a CCW and CW a' 5.b zero, since max flux penetrating plane of coil a-a'; which from Faraday's 0. law gives d(ea-a' ) dt |Emax|, by a similar argument for total flux zero Bonus: Uniform air gap (cylinder rotor) means that the air-gap remains unchanged as the rotor position changes. Note that the stator flux axis for each of the 3 phases is stationary and the inductance terms represent this flux path thru the air gap, thru the stator and thru the rotor. Thus since the rotor position does not cause a change in the flux path for the uniform air gap, the self inducatnace terms will be constant, i.e., set #2. Thus set #1 is for a salient pole machine. ...
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This note was uploaded on 12/07/2011 for the course ECE 600 taught by Professor Clymer,b during the Fall '08 term at Ohio State.
- Fall '08