Monday 31 March 2014

THREE PHASE A.C.CIRCUITS
Expression for power in a 3 phase delta connected load
 
 Power  = Power in R phase + Power in Y phase + Power in B Phase
            =VRY .IR'Y' cos Φ + VYB IY'B' cos Φ + VBR IB'R' cos Φ
But
             VRY = VYB = VBR = Vph as line voltage = phase voltage in case of delta
             IR'Y' = IY'B' = IB'R' = Iph
             P = Vph.Iph cos Φ  + Vph. Iph. cos Φ + Vph. Iph.cos Φ
P = 3ph.Iph. cos Φ  watts ( in terms of phase quantities )
 Also Vph = VL          Iph = IL/√3 and cos Φ = R/Z
                   IL
P = 3 VL --------- cos Φ
                  √3
P = VL VL cos Φ watts (Power in terms of line quantities)
3 phase reactive power Q
Q = √3 VL IL sin Φ VAR
Three phase apparent power
S =  √3 VL IL     volt amp
Worked Examples:
  1. Three equal impedances each having a resistance of 25Ω and reactance of 40Ω are connected in star to a 400 V, 3-phase, 50 Hz system. Calculate:
    1. The line current
    2. Power factor, and
    3. Power consumed
  2. Solution:
    Resistance per phase,                 Rph  = 25Ω
    Reactance per phase,                  Xph  = 40Ω
    Line voltage,                                 EL   = 400Ω
    To find: 
    Line current
    , IL:
    Power factor, cos θ:
    Power consumed, P
    Impedance per phase,          Zph  = √Rph2  +Xph2
    Therefore                              Zph=
    Phase voltage,                      EL  =   400     volts
                                                -----     -------     =   231 V
                                                 √3       √3
    Phase current,                                 Eph        231
                                                 Iph = ------- = ---------  =   4.9 A (app.)
                                                            Zph      47.17
    Line current,                        IL = Iph  as it is star connected
                                                IL = 4.9 A  (Ans)
    Power factor,                                     Rph          95
                                                cos Φ= ------  =  -------- = 0.53(lag).
                                                              Zph        47.17
    Power consumed,            P= √ 3  ELIL  cos Φ  =  √3 *  400 *  4.9 * 0.53
                                              = 1800 W (app.)
                                      (or P = 3Iph2 Rph =3 * 4.92 * 25 =1800 W)
  3. Three identical coils are connected in a star to a 400V (line voltage) 3-phase A.C supply and each coil takes 300W. If the power factor is 0.8(lagging). Calculate:
    1. The line current
    2. Impedance and
    3. Resistance and inductance of each coil
    Solution. Line voltage,     EL= 400 V
    Power taken by each coil, Pph = 300W
    Power factor,                 cos Φ= 0.8 (lagging)
     IL  ; Z ; Rph ; Lph :
    Phase voltage,                      EL       400
                                      Eph = ------ = ------  V
                                                 √3       √3
    Also                            Pph  = E ph Iph   cos Φ
                                                 400
                                      300 = ------ *  Iph * 0.8
                                                  √3
                                                  300* √3
                                      Iph = --------------- = 1.62 A
                                                  400*0.8
    Line current,               IL = phase current, Iph  as it is star connected
                                       IL = 1.62 A
                                      Eph=     400  = 230.94 V
                                                 -------
                                                   √3    
    Coil impedance,            Eph      230.94
                              Zph= ------- = ----------   =   142.5 Ω
                                         Iph        1.62
                                       ZC= 142.5 Ω. (Ans)
                                       Rph= Zphcos Φ = 142.5 * 0.8 = 114 Ω
    Coil reactance,           Xph= Zphsin Φ = 142.5 * 0.6 = 85.5 Ω
    But,                            Xph= 2 π f Lph
                                                Xph          85.5
                                      Lph = -----  =  ------------   = 0.272H
                                                2πf         2π * 50
    hence,                        Rph  =  114 Ω.  (Ans)
                                      Lph   = 0.272 H.   (Ans)
  4. A star- connected, 6000V, 3-phase alternator is supplying 4000kW at a power factor of 0.8. Calculate the active and reactive components of current in each phase.
  5. Solution.  Line voltage,                  EL  = 6000 V
                    Power supplied,                p = 4000kW
                    Power factor,              cos Φ= 0.8
    Active and reactive components of current:
    We know that ,                     P =  √3  EL IL   cos Φ
                                 4000*1000 = √3  * 6000 * IL   * 0.8
                                                          4000 * 1000
                                                 IL= --------------------- = 481A
                                                         √3 * 6000 *0.8
                                                     Iph= IL= 481
    Active component                  = Iphcos Φ = 481 * 0.8 = 384.8 A
    Reactive component              = Iphsin Φ  = 481*0.6 = 288.6 A
  6. A balanced 3- phase star connected load of 100 kW takes an leading current of 80 A, when connected across a 3-phase, 1100 V, 50 Hz supply .Find the circuit constant of the load per phase.Solution. Given: P = 100 kW; Iph(=IL) = 80; EL = 1100 V; f = 50 Hz
    Circuit constants of the load per phase, R, C:
    As the – 3 θ load is balanced and star connected, line or phase current
                                                        P                                100 * 103
                        IL= ( Iph) = --------------------- =   --------------------------------
                                               103 EL cos Φ                  √3* 1100 * cos θ
                                               100 * 103
    or,                 cos Φ  =   --------------------- =   0.656
                                          √3 * 1100* 80
                                        Eph        (1100/√3)
                                 Z = -------- = ---------------- = 7.94 Ω
                                        Iph               80
                                 R = Z cos Φ  7.94 * 0.656 = 5.2 Ω (Ans)
                                            1
    Now                    XC = --------- as the current given is leading current
                                        2 π f C
                                            1
                                 C = -----------
                                        2 π f XC 
    But                      XC = Z sin Φ = 7.94 * 0.755 * 5.99 Ω
                                                    1
                                 C = ---------------------- F
                                         2π * 50 * 5.99
                                                 106
                                    = --------------------- μF = 531.4 μF. (Ans)
                                         2π * 50 * 5.99

Tuesday 21 January 2014

Top 100 Universities In Africa – Obafemi Awolowo University Came 10th In Africa and 1st In Nigeria [See List]
The rankings of Africa’s top higher education institutions has been provided by the 4 International Colleges & Universities (4icu). 4icu is an international higher education search engine and directory reviewing accredited Universities and Colleges in the world. 4icu.org includes 11,160 Colleges and Universities, ranked by web popularity, in 200 countries.
A quick look shows that South African universities dominate the top despite the fact that South Africa ranks very low on the quality of education in the world.
The first Nigeria University on the list came in at no 10 which is Obafemi Awolowo University, Ile-Ife
See full list below:-
1. University of South Africa – South Africa
2. University of Cape Town – South Africa
3. Universiteit Stellenbosch – South Africa
4. University of Dar es Salaam – Tanzania
5. University of KwaZulu-Natal – South Africa
6. University of Pretoria – South Africa
7. Cairo University – Egypt
8. University of the Witwatersrand – South Africa
9. University of the Western Cape – South Africa
10. Obafemi Awolowo University – Nigeria
11. Makerere University – Uganda
12. University of Botswana – Botswana
13. Mansoura University – Egypt
14. Rhodes University – South Africa
15. Alexandria University – Egypt
16. The American University in Cairo – Egypt
17. Zagazig University – Egypt
18. University of Johannesburg – South Africa
19. Assiut University – Egypt
20. University of Nairobi – Kenya
21. Université Cheikh Anta Diop – Senegal
22. University of Zambia – Zambia
23. North-West University – South Africa
24. University of Lagos – Nigeria
25. Tanta University – Egypt
26. University of Ghana – Ghana
27. Université de Ouagadougou – Burkina Faso
28. Université Mohammed V – Agdal – Morocco
29. Nelson Mandela Metropolitan University – South Africa
30. Cape Peninsula University of Technology – South Africa
31. Université d’Antananarivo – Madagascar
32. Ain Shams University – Egypt
33. University of Ibadan – Nigeria
34. Kenyatta University – Kenya
35. University of Namibia – Namibia
36. Universiteit van die Vrystaat – South Africa
37. University of Nigeria – Nigeria
38. The German University in Cairo – Egypt
39. University of Limpopo – South Africa
40. Université de la Reunion – Reunion
41. University of Khartoum – Sudan
42. Benha University – Egypt
43. Universidade Eduardo Mondlane – Mozambique
44. Helwan University – Egypt
45. École Nationale d’Architecture – Morocco
46. University of Fort Hare – South Africa
47. Université Nationale du Rwanda – Rwanda
48. Al Akhawayn University – Morocco
49. Université Catholique de l’Afrique de l’Ouest – Benin
50. Tshwane University of Technology – South Africa
51. Jomo Kenyatta University of Agriculture and Technology – Kenya
52. Minia University – Egypt
53. Addis Ababa University – Ethiopia
54. Fayoum University – Egypt
55. Moi University – Kenya
56. University of Ilorin – Nigeria
57. October 6 University – Egypt
58. South Valley University – Egypt
59. Sokoine University of Agriculture – Tanzania
60. Université Mouloud Maameri de Tizi Ouzou – Algeria
61. Université Mohammed V – Souissi – Morocco
62. Al-Azhar University – Egypt
63. Kwame Nkrumah University of Science and Technology – Ghana
64. Misurata University – Libya
65. Minoufiya University – Egypt
66. Université d’Oran – Algeria
67. Université Hassan II Mohammedia – Casablanca – Morocco
68. Polytechnic of Namibia – Namibia
69. Université d’Alger – Algeria
70. University of Zimbabwe – Zimbabwe
71. University of Cape Coast – Ghana
72. The British University in Egypt – Egypt
73. Université de Tunis El Manar – Tunisia
74. University of Zululand – South Africa
75. University of Agriculture, Abeokuta – Nigeria
76. University of Malawi – Malawi
77. Université Cadi Ayyad – Morocco
78. Université Mentouri de Constantine – Algeria
79. Suez Canal University – Egypt
80. Université de Yaoundé I – Cameroon
81. Egerton University – Kenya
82. University of Swaziland – Swaziland
83. Kafr el-Sheikh University – Egypt
84. Université Ibn Tofail – Morocco
85. Université de la Manouba – Tunisia
86. Université Hassan II – Casablanca – Morocco
87. Covenant University – Nigeria
88. University of Benin – Nigeria
89. École Nationale Supérieure en Informatique – Algeria
90. Université des Sciences et de la Technologie Houari Boumediène – Algeria
91. Durban University of Technology – South Africa
92. Strathmore University – Kenya
93. Ahmadu Bello University – Nigeria
94. Université Ibnou Zohr – Morocco
95. Universidade de Cabo Verde – Cape Verde
96. Sudan University of Science and Technology – Sudan
97. University of Mauritius – Mauritius
98. Muhimbili University of Health and Allied Sciences – Tanzania
99. Gulu University – Uganda
100. Vaal University of Technology – South Africa
Do you think this List is Credible Enough?

Blue Baby Whale Washed Off From The Ocean & Got Killed In Lagos [See Pics] 

World’s FATTEST Woman Claims, ‘I made love 7 Times A Day 

Pauline Potter is the world’s fattest woman and claims to made love than what most people would do in a day or even a week.

Pauline Potter had an understanding with her husband to work towards becoming the fattest woman in the planet. She has achieved her aim by setting the Guinness World Record for fattest female in the world; reaching a weight of 700 pounds.

Potter says she loves her body and claims to made love 7 times a day.

Her husband Alex, who weighs 200 pounds (which is less than one of his wife’s legs), insists that sex with his wife is not normal:

“It’s hard to position her and find her pleasure spots as she has a lot of fat in the pelvic area. But it turns me on knowing she’s satisfied. Although once, when she got on top, I couldn’t breathe”.

View Pictures at http://e-magin.com/worlds-fattest-woman-claims-i-made-love-7-times-a-day-photos/

15 Dead As Boko Haram Attacks Borno Villages 

Suspected Islamist gunmen shot dead 12 people in two separate attacks on villages near Nigeria's border with Niger while three others drowned in a river while fleeing, locals said Sunday.

The attackers, thought to be from the Boko Haram militant group, on Thursday shot dead seven people in Gashigar village, a fishing community in Borno state, close to the Nigerian border with neighbouring Niger, the locals said.

Three others drowned in the river while fleeing from the night raid, they added.

The attack came four days after a similar one on two other neighbouring villages -- Yawuma-ango and Jabulam -- in which gunmen shot dead five people, a former deputy local government council chairman in the district, Talba Gashigar, said.

He said most residents of Gashigar village had fled to Niger after the marauders arrived in a convoy of three vehicles and "countless motorcycles" and destroyed dozens of homes and shops.

"We all had to flee. Men, women and children had to cross over to neighbouring Niger for our dear lives," he added.

Police authorities in Maiduguri, the state capital, confirmed the Gashigar village attack but gave no details.

Gay-Marriage Law: US threatens to sanction Nigeria. 

Leading western countries piled pressure on the Federal government, yesterday, following President Goodluck Jonathan’s signing of the Same-Sex Prohibition Act 2014. The latest country is the United States of America, whose Ambassador to Nigeria, Mr James Entwistle threatened that the United States will scale down its support for HIV/AIDS and anti-malaria programmes in response to the Federal Government’s position on the gay rights issue.


Member countries of the European Union and Canada have expressed their objection to the law but United States Ambassador to Nigeria said he was worried about “the implications of the anti-same sex marriage law which seems to restrict the fundamental rights of a section of the Nigerian population.”

This came as a former Nigerian Ambassador to US, Dahiru Suleiman, yesterday, described homosexuality and lesbianism as “animalistic and degrading to humanity.”

Also yesterday Christians in the northern part of Nigeria under the aegis of Christian Association of Nigeria in the 19 northern states an Abuja, hailed President Goodluck Jonathan for signing into law the anti-gay bill, urging him to ignore criticisms from Western nations, saying all religions in the country are united in their condemnation of same-sex marriage.

In a reaction to the recent move of government to outlaw homosexuality from this country, the Public Relations Officer of Northern CAN, Elder Sunday Oibe told Vanguard that Christians from the North and their counterparts in other religions have unanimously expressed gratitude to the president and the National Assembly for passing the Anti-Same Sex Marriage despite opposition from Europe and the US.

Speaking to news men in Abuja, yesterday, the American envoy said his interpretation of the new law was that “it could negatively affect the nation’s fight against the HIV/AIDS pandemic”. Although the US envoy denied that his country plans to impose sanctions on Nigeria, he said: “We and other donors are looking at the issue of funding for HIV/AIDS. As you know, we put millions of dollars in the fight against HIV/AIDS.

“Although I am not a lawyer, I read the bill and it seems to me that it may put some restrictions on what we can do to help fight HIV/AIDS in this country. These are the issues we are looking at as we consider the law.”

The signing of the Same sex Prohibition Act by President Jonathan on January 7, 2014 has provoked negative reactions from member countries of EU, Canada and now the United States all of whom have alleged that the law is a violation of the fundamental human rights of Nigerians with same sex orientation.

Ambassador Entwistle said he was aware that “the issue of same-sex marriage was very controversial all over the world, including within the United States where 17 states out of 50 had endorsed it, but others still reject its legality”. According to him, “the issue that we see and I am speaking as a friend of Nigeria is that as I read the bill, it looks to me that it puts significant restrictions on the freedoms of assembly and expression; in my opinion which applies especially in advanced democracies, once government begins to say something in these areas, freedom no longer applies. It seems to me that this is a very worrisome precedent.”

Anti-gay diplomacy
A lecturer at Covenant University, Professor Kayode Soremekun said: “What is happening demonstrates the low level that the US treats its relation with Nigeria”.

He said every Nigerian should feel insulted that the US is threatening to stop assisting us on areas where we have the resources and human capacity to contend.

Said Professor Soremekun, “even when the West had their misgivings about Russia’s anti-gay law, they have not gone threatening them with sanctions and punitive action. We are not reckoned with in the international arena where we are getting assistance for HIV/AIDS, Malaria treatment drugs, polio virus crusade among other mundane issues”.

He continued: ”Nigeria is still a conservative society and the anti-gay law has united the ruling class and Nigerians outside government at this level of our national development. The US and its EU partners should be discussing serious issues; the leadership showed pro-activeness in trying to save the society from getting exposed to practices that are antithetical to our culture.

“We should be focussing on the items on the Bi-National Commission between both countries, but these threats show that we are nonentity in global arena. When the US is discussing with Iran on nuclear issues, they are threatening us on mundane issues”.

According to Soremekun, “we should be able to make the US and its EU allies realise that they cannot go to China to dictate their laws. China is still a communist country and they are falling over them selves to go to China and do business. We should make them realise what General Abacha did when he opened the door to China and Asian countries in the 1990s.”


Homosexualism, lesbianism animalistic.
However, former Ambassador Suleiman, yesterday, described homosexuality and lesbianism as animalistic acts, degrading to humanity. Suleiman served as Nigerian envoy in several countries, including Pakistan, Brazil, Angola, United States of America, Ivory Coast, Poland, Australia and Sudan, among others.

Reacting to US threat of sanctions against Nigeria over the anti-gay law, Suleiman stressed the need for Nigerian leaders not to be dependent on foreign assistance for governance.

He said: “Homosexuality and lesbianism are offences against God; if any body wants to do it, he should do so secretly. It is not only animalistic but diminishes mankind.”

“If it is the money the US gives to us, let them keep the money. Nigeria is rich enough to take care of her people unlike other countries.”