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# ee381 - 8&me Ski/CM.~ Wednesday 22 2003 BB 381 Quiz 1...

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Unformatted text preview: 8&me Ski/CM .~ Wednesday. 22, 2003 BB 381 Quiz 1 Name: Last First 1. A 120 V. 60 Hz. source supplies two loads: Load 1: A single phase motor drawing 4662 watts at 0.8 pf lagging. Load 2: A 1200 watt microwave operating at unity power factor. Find the following: Supply current, supply power factor (indicate lagging or leading). A @445 5’, = 46c2+j 405.228"; (c4529: 4£é2+js497 v. LandZ: \$1.: [200+Jo : [ZOO-f) O , 5‘8£2 +j 3497K A 573+”; = 5842 +33497 = 692528 30-87.‘ VA . Sufi“? a...“ z z = \$3133.? .- a gag]? meM-m 2. A 3-phase balanced, Y-connected load has 4 + j3 ohms per phase. The line voltage is W 400 V. Find: a) Line current. b) Power factor. c) Total KW. (1) Total KVAR. e) Total KVA. ' II E if no 53 W #9 ‘0 Ia, - Q—é’ 3. is? i, Wed. Feb. 05, 2003 E 381 Quiz 2 Name: Last First . 1. For a certain ferromagnetic core the following data are given: Pl. = 20 watts and P.=5wattsatf=50Hz. andBm= 1.2T. FindP.l andP.atf=400Hz. and m = 0.8 T. Steinmetz exponent n = 1.6 mg; P..=K.f 3...“; Pc=KefiBm2 . 1.6 h = 400 (0'8) =4.l816 San = 4.1816 ' 20 = 83.63 watts Pm 50.0.2)“ P“.00 =[40003 50-12 2 P ] =28.44 SOM=28.44-5=142.22watts .50 2. Aringmadeofcaststeelcaniesa3000nnncoil. lfﬂieringhasaerost-sectional area of4>st¥are ems. and mean length of 1 meter ﬁnd the following for a ﬂux density ostflﬁ' . . (a)Cmreminthecoil(Seecurveatlhebackofthequiz). (b)Forthecunentin(a),whatwouldbetheﬂuxdensityB,intheringifthesteelis (replaced byair (”=4a- 10") We in (a) For a ﬂux density of B = 1.5 T the magnetic ﬁeld intensity H = 3000 ATlm from thecurve. Sommf .9: H'[=§000-l=3000AT. Hence I=%:g%=lampere (b) Volume of the core is = l - (4 :10") cubic meter. ‘ 1 ‘ ' _ Lot 4-u-10‘7 x440" 167: 3- 3000-161: . ¢ 3000-1611' 4 Fl =-—-=———.Flu densit B=———=———=121r-10 T “W St 10“ x y Area 10“.4-10* Reluctance of the ring = n = 3.77- 10" Tesla. I8 IIIIII aggmlg ,IIII 55 _;==Ig===== II ;.IEIIIEWIIIIIII Il,471llllllllllllll Illrh IIIIIIIIIIIIII ;lﬂléilllllllllllllll -nInIIIIIIIIIIIIIIIII MIIIIIIIIIIIIIIIIIII nmIIIIIIIIIIIIIIII!I nnIIIIIIII ll! ==-I ﬂﬂlIIIIIll‘nullllllI "IIIIIEE IIIIIIIIIIII IIIIIIIIIIIIIIIIIIII II‘IIHIIIIIIIIIIIIIIII lllInIIIIIIIIIIIIIIIII FLUX DENSITY 0'2quIIIIIIIIIIIIIIIII OrrIIIIIIIIIIIIIIIIIII 0100020003000400050006000700080009000 Magneuc ﬁeld strength [AT/n] Wed. Feb. 12, 2003 E 381 Quiz 3 ~- Name: " Last First 1. For the ideal transformer shown V; = 120 m“ V. End the following: II, 1;, V1, reﬂected load- impedanee on the input side. Draw the phasor diagram 0.: 2 f a mm" mm. - “#53615; 2 9+3 4 4.- M7 ﬁzz 5’4 V=0VVI 2. For the no-load equivalent circuit shown. ﬁnd the following: 1., P...,Pf VARM Is the power factot’lagging or leading? Give reasons for you: W’i‘m ' _ 24OLD_ * , _2, t6. _ my 24L: A - 1m “DE—i; I : L01; 1‘. ° :2 V C o J _- I l WhL ﬂv— [Jo-Me. ﬁwi—rv Bo {nag-'4»)? 5am ﬂ; Fri. Feb. 21, 2003 E13 381 Quiz 4 Name: Last First . A 25 KVA, 2300/230 V, 60 Hz. transformer has the following data given: Renv = 4 ohms; Xenv= 5 ohms; Riv = 450 ohms; Xva = 300 ohms. The transformer delivers % it’s rated capacity at 0.85 pf lagging. Assume that the parallel branch is located at the input terminals. 1. Draw the equivalent circuit with the transformer circuit elements on the HV side. Show the ideal transformer with the load impedance connected on the LV side. Determine the load impedance value in complex form . A --- 4 pt? ‘I _ 25000 _ . -= 4L0 Comet? Load. W'VM) I; — 2‘25!) — 62 351'- £1444, 9.35- : 4.232» 0/7932 24/4/5149” 11 =e¢+j 2325 n 2. Find the input voltage V1 in polar form when the load voltage is 23019" V. --3pts. V, : 2305/3: + 54337314? (/4 ﬁg) lo 0 : 2332.3[0'28é V 3. What is the efﬁciency of the transformer at the indicated loading? --— 3 pts. [in t 323% = r204 Waﬁ'i_ ‘ 430m PC“ : 5.436%: Mame men 9mg! : 2900:),0-575' = “362g Mme—x 2 - Ioé2§ = 0.913 = 7 “€234 {20-94- ”84/5 7 8 7. 5 I A 9W Friday, Feb. 28, 2003 E 381 Quiz 5 ' Name: Last First . A 120 KVA, 24001240 V, 2-winding transformer has a core loss of 2144 watts, and a full load copper loss of 4375 watts. Determine the following: a) Copper loss at maximum efﬁciency. b) Volt-ampere output at maximum efficiency, KVA...“ ., c) The efﬁciency value at KVAmn if the power factor is 0.8 leading. a) pcofzﬁe. at Maxpmum agree“? 92/4/4’ ww- t) KVA - '20/_ M = ”my? .457: x. _, 4/ c) 7 ————-84°9 -”‘***@ 84x08 4 2%fo Z . The above 2-winding transformer is considered losslels and is connected as 8 2640/2400 V step-down autotransformer. a) Draw a schematic of the autotransformer indicating dot terminals. b) Show winding voltages and currents under full load conditions. c) What is the KVA output under full load? C“) r20 9 A 5 fl '.' ”A O W 1 ('20 ‘ a“ PM 550 A‘ "‘c‘) Quéw KVA: SWXEPL/ ll! 5' g; M: S M? Friday, Mar. 07, 2003 ' BE 38] Spring 2003 Test 1 1. A toroid with a ferromagnetic core has a cross—sectional area of 1.5 sq. ems. It contains an air gap of length 2 millimeters. The mean length of the iron path is 1.5 meters. The coil has 500 turns and carries a current of 2 amperes. Ifthe ferromagnetic core has a relative permeability of 1000,_determine the ﬂux density. Assume no fringing or leakage. yo = 4n v to 7 2. The eddy current loss in a magnetic circuit is 200 W and the hysteresis loss is 400 W when tested at 50 Hz. Find the total core loss if the frequency is increased to 400 Hz. and the ﬂux density is decreased by 50 %. Assume n = 1.6. 3. A 2-winding, 600 KVA, 11000/550 V, 60 Hz. transformer has a series impedance of law = 1.8 +j 9.6 ohms. Determine the %Regulation of the transformer when the transformer is supplying a load drawing 450 KW and 262.5 KVAR on the 550 v side. ‘ 4. Test ﬁgures for a 75 KVA, 230/115 V, 60 Hz. transformer are given as follows. Transformer Test Voltage, V Current, A Power, Watts Open Circuit Test, with 115 16.3 750 meters on the 115 V side Short Circuit Test with 9.5 326 1200 meters on the 230 V side :1) Determine R. , X. , Re and Xm in terms of the 230 V side. 1)) Determine the efﬁciency of the transformer when delivering rated KVA at 0.8 power factor lagging. c) Determine KVA,...” 5. A 3-phase, 300 KVA, 124701208 V, 60 112., Y —Y connected transformer supplies power to a department store. The store load is 250 KVA at 0.8 pf lagging and connected in delta. If the transformer is assumed ideal show the following. a) The connection diagram --- showing the input and output windings and the delta connected load. b) The load impedance in complex form. c) The breaker capacities on the HV and LV side of the transformer. EVE '3 6‘ SOLUTION or 112;? i _ 6) £5? “- eﬁé 2 OIOO‘Z : (0-6): ’0 NW2}. 7, 200.5 (AA A3+ _ 431’)! 13k l-Dx r04 1/ Ym” 'r -|—. I S- = 7‘ 5 7 Q9,“ s 4" 0'" - _._____.———¥ 9 7x10 {array A13,” QrwoL/oookl-m/ B: 3’ = 5m”: =Mum .. 00.5 +7.95?) lac x/.c,, g" ’83 (18-5777) aaaaaa 3:355 §§§E§E ﬁ§§§§1 E§§§§§§ V E - " E 32/ KY5}, Load. Pf=gzi 'ﬁh? i LU: amt a 1/7 35 5mm" ., ' a yr * V = NoooLa"_+ 47341-302£x(/g+J9g)= H305 /-‘77 V 7.23: Mew“ [email protected] ”can 9933' _ 4.8 = 0029“,; BMW-.- ’2“; : 0.01/29“. 32 Xe!” “lo-019‘- 0.0!;29’ = 04023661»; 2 _ Luv- . _——; 1~7 1mg. £4.11; “c— 2 m, ma, mac Jam/49m - ’ ”f ”‘m m 6) Pearson P .Ime 75“”? : =-‘7é‘xo&+07s‘+l.z ”*WJ— 12cm - II 044/;- +J' 0-3/1: :. 2% = /, . © Ibgl W MSW-1.47 / 573-7: W Eva!» Wage]? = ”'97” LV Bveﬁw 0.15:“ {:17 t '49“ .2 67 n 75.. (mm 6 I7; 4:70.»: - m - ; _, , g» V 7, 7 #J/ gunk“ 6+0.“ , 1 ‘ ZS'D LU grub Cnfau‘ﬁa: 694x300- 33‘, 23'» SQLUTCOM‘ sot-:E'r W Friday, Mar. 28, 2003 E 381 b) d) 8) h) J) Quizti -Name: Last First How many pole pitches does the rotating ﬁeld travel during one rotation of the stator Current phasors? TM)» Fer/c, dw‘lia-nce/s' What is the synchronous speed of a 12 pole, 50 Hz. induction motor? NS = max? = may 5» - r I; Whatisthespan,inelectrical degrees. of a phase belt underapole? Q 0 ° What is meant by a full pitch coil? CM: [5,45% = mfg/wt. How many electrical degrees does an 8 pole winding have? 8 y {80 —_ I44o° tie/we. How does a distributed winding differ from aconcen ated inding? Cam/Lag? “We Muc= / 045+?! 60.46; wind”- 1;: \$142,”;6ng602 I If in a 4-pole induction motor the rotating _——-L——\$ftu¢has a synchronou speed of 18 r p. 111., what is the electrical angular velocity? ' L8G? y 4% yr 2 003? e/wg- ”way/<4 In (g) ﬁnd the mechanical angular velocity? ZN’X L292 Z‘ £07? hate/i redraw/\$10 O Ifslip rings are found on the rotor shaft of an induction motor what type of rotor does the rotor have? . ”Loam d, v0 1%», What is the stator core made of? [.QM/ha/éed, e/wér 0;], view SOLU‘noM SHEET Friday, Apr. 04, 200-5 EE 381 Quiz 7 Name: . ’ Last First 1. An 8 pole induction motor has a synchronous speed of 750 r.p.m. and ﬁill load slip of 0.05. Find: a) Supply ﬁ'equency. b) Stator angular speed. c) Rotor speed in r.p.m.. d) Rotor ﬁ'equency. e) Rotor ﬁeld speed with respect to the stator ﬁeld speed. 0} f7: PMS = 83171375 1 @ ) IZo I20 ‘ £> 1J9 : .ég?‘ 277 ‘1 (ZS—37 [Mg/“ﬂ V414. 5a; a) 2447,, SW : N” : 7.950 — 5‘03) : 7/25 ”47 Cd) Edd—5161a] fv::3[7:. O~0Sxéa “- 2-5 792 f4) 125%?» ﬁne/4. \$f>a¢ N-wzé, std—n [Sgt/ac sir/>96::@ 2. A 3-phase, 60 Hz., 4-pole induction motor has a double-layer winding connected in we The stator has 72 slots, and each coil has 3 turns with a coil pitch of 5/6. If the maximum ﬂux per pole is (Pm = 2 x 10’2 weber, what would be the induced voltage per phase in the stator? 'r’ ‘ .4 ”Uranium 0% LUL‘& -.—. '71: ”'W‘ﬂ/M' : 1:353... v ‘ T 77. l - 72. Slo‘r'l/ >6vr¢ /fV/ﬂ‘q& ; hz : ‘ -, t c i {-1 r 5‘ a ”r : éO : /b I e n , DH {yd ‘ S”) 2 — 3’5 Z - O"?§é/.L \ r7 9;, 42L if: x5»; 70- k1; : Co: B [8300’ w” 5 = 045?? ff‘» 4 44 .0 d M y A0! Y é/ -_.le,,/ : ‘ ‘ in M ‘ ,9 : 4'44Y£0X2X/0—2x YZXCJ‘IQQS‘Q‘XD.9%/4L SOLUTiON SHEET WM Friday, Apr. 11, 2000 EE 381 Quiz 8 Name: _ ' Last First A 4-pole, 440 V, 3-phase, 60 Hz. induction motor runs at 1710 rpm. and 0.8 pf lagging. It delivers a shaft power of 10,000 watts. The total stator loss is 1000 watts and Pm = 400 watts. Calculate the following: a) rotor frequency b) the rotor copper loss, PRCL c)eﬁ'1ciency (1) line current, and e) shaﬁ torque. as Ng: 120\$ ._ l2o~xézo : (BODV'P'M _ ﬁr“ g : l8n-NID_ “03., P , — 7Q : S’ﬂ: O‘O‘Cxéb =. )86’7) ) . v T 5} 8t: Qagll if“; : “500on = 104mm! F_&(_IOL.LM :/o “3‘17?”/—o-or WNW a? : O~O§YIOWJ7 : 95.4%wa I0000+ 4m) + WT? + ’07” 8/ :3 E: I : HQQ;.QW .0 Ow t M t M : m 8 (Z P’quj: [/01q7.g - 01> Z 42.1115425— HQL/léﬁ __ 5‘ 2 = mH————~ MM % C7" 2,4395.” WWW/WM / _ ‘95 Tgf M : JV “L, :- ——-——-—OOOO — 55.87 A3~I~o ”“r‘ can 17/0 viz? > 60 Scum ow S-HEET Friday, Apr. 18, 2000 E 381 Quiz 9 'Name: Last First 1. A 208 V, 60 Hz, 8-pole. 3-phase, wye-connected induction motor has negligible stator impedance and a standstill rotor impedance of 0.02 + j0.08 ohm per phase. Determine sh and Tam What is the starting torque of the motor. £2 m: m. «we» Integrate; mama. \$é= : .02 _ M Qo¥£o_ —._._ .9. ~. ;———90‘b1‘.m gé.o_og-o-s) Mg- P 8 7b i 0.58 2x M? .2365 ‘24N‘m ; Z s - 7r = . mi‘ 1‘ 349 =ﬂ5ll-S'g 03”“ 2. A 60 Hz., 8 pole. 3-phase induction motor has a full load slip of 4%. The rotor V resistance is 0.001 ohm per phase and the rotor standstill reactance is 0.005 ohms per phase. Wmfmdmespeed at T4...“ andtheratio of Tan/Tam- ! )1 ’Us _ 9.0860: €00 (PM an; new, r‘mfwwm ”agw‘k \$5 = 21 = 0.00] = 02—» 203/, X2. 0 0‘05 S {1991, 4,6. maxl‘nhn Oceania/but \$277»; 1‘; = Ng-( I ~53 = 9000 ~04) -= 77:20 «It», 73;“ _ 25pm t 2:235:12 1©3m . l r - 2 AD.‘ 7'44““. Sal-fCé ODQ + 0 Scum ow S-HEET Friday, Apr. 18, 2000 E 381 Quiz 9 'Name: Last First 1. A 208 V, 60 Hz, 8-pole. 3-phase, wye-connected induction motor has negligible stator impedance and a standstill rotor impedance of 0.02 + j0.08 ohm per phase. Determine sh and Tam What is the starting torque of the motor. £2 m: m. «we» Integrate; mama. \$é= : .02 _ M Qo¥£o_ —._._ .9. ~. ;———90‘b1‘.m gé.o_og-o-s) Mg- P 8 7b i 0.58 2x M? .2365 ‘24N‘m ; Z s - 7r = . mi‘ 1‘ 349 =ﬂ5ll-S'g 03”“ 2. A 60 Hz., 8 pole. 3-phase induction motor has a full load slip of 4%. The rotor V resistance is 0.001 ohm per phase and the rotor standstill reactance is 0.005 ohms per phase. Wmfmdmespeed at T4...“ andtheratio of Tan/Tam- ! )1 ’Us _ 9.0860: €00 (PM an; new, r‘mfwwm ”agw‘k \$5 = 21 = 0.00] = 02—» 203/, X2. 0 0‘05 S {1991, 4,6. maxl‘nhn Oceania/but \$277»; 1‘; = Ng-( I ~53 = 9000 ~04) -= 77:20 «It», 73;“ _ 25pm t 2:235:12 1©3m . l r - 2 AD.‘ 7'44““. Sal-fCé ODQ + 0 ...
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