Thursday, March 25, 2010

Effects of Excess Current on the human body

Below 1 milliamperes (<1mA)
Generally not perceptible

1 milliamperes (1mA) 
Faint tingle.

5 milliamperes (5mA) 
Slight shock felt. Not painful but disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries.

6-5 milliamperes (6-5mA)
Painful shock, loss of muscular control. The freezing current or "let-go" range. Individual cannot let go, but can be thrown away from the circuit if exterior muscles are exited by the current.

Tuesday, March 23, 2010

Dangers of Electric Shock

The severity of injury from electrical shock depends on the amount of electrical current and the length of time the current passes through the body. For example, 1/10 of an ampere (amp) of electricity going through the body for just 2 seconds is enough to cause death. The amount of internal current a person can withstand and still be able to control the muscles of the arm and hand can be less than 10 milliamperes (milliamps or mA). Currents above 10 mA can paralyze or “freeze” muscles. When this “freezing” happens, a person is no longer able to release a tool, wire, or other object. In fact, the electrified object may be held even more tightly, resulting in longer exposure to the shocking current. For this reason, hand-held tools that give a shock can be very dangerous. If you can’t let go of the tool, current continues through your body for a longer time, which can lead to respiratory paralysis (the muscles that control breathing cannot move). You stop breathing for a period of time. People have stopped breathing when shocked with currents from voltages as low as 49 volts. Usually, it takes about 30 mA of current to cause respiratory paralysis.

Friday, March 19, 2010

Power Factor #2

Power factor in Relation to Power
Power is consumed only in resistance since neither pure inductor nor the capacitor consumes any power. The power consumed (True Power) in Inductor (L) and Capacitor (C) is zero. There is a circulating power that moves from the source to the load back and forth and does not do any useful work in the circuit. Current and voltage are in phase in a Resistance while they are 90 Degrees out of phase in (L) and (C). When current is in phase with voltage it produces active or True Power while it produces Reactive Power when 90 Degrees out of phase with voltage.

Thursday, March 18, 2010

The Aswan High Dam - Egypt

Some brief statistics…
Official Name:    Aswan High Dam
Length        : 3830 m
Height        : 111 m
Width (at base):980 m base, 40 m crest
Maintained by    : Muaykensan

Reservoir information
Creates    : Lake Nasser
Capacity    : 111 km3

Power Generation Information
Turbines    : 12
Installed capacity: 2.1GW

Tuesday, March 9, 2010

Ndakaini Dam is Full

The dam that supplies 75% of Nairobi’s water is now officially full to capacity. According to the Nairobi Water Company, the dam is at 94.8% capacity only one meter from its 70million cubic meter optimum capacity. This is good news for those who live in the city but is it time to celebrate yet?

Friday, March 5, 2010

Is Engineering all about money?

Sometimes I really wonder whether this world is ever going to move forward if everybody just want money but no development. I was shocked when my fellow students were looking for an attachment at local companies based on how much they pay trainees.Why would one want to be paid and yet you are even not qualifies - you are there for the practical application of what one has learned in class. Actually, I would prefer to be attached to a company that pays little or no pay as long as I acquire that invaluable exposure.Okay, I agree that yes we all need money to survive in this competitive world but should people be paid large sums of money and yet nothing is being done in terms of development?...

Wednesday, March 3, 2010

Power Factor #1

What exactly is Power Factor?
Power Factor (i.e. Cosɸ) of a circuit can be defined as:
Cosɸ = the cosine of an angle between Voltage (V) and Current (I).
R/Z = Resistance/Impedance
VICosɸ/VI = True Power/Apparent Power

The value of power factor can never be greater than 1(Unity)
It is usual practice to attach the word ‘lagging’ or ‘leading’ with the numerical value of power factor to signify whether the current lags or leads the voltage. Thus if a circuit has p.f. of 0.6 and the current lags the voltage, we generally write p.f. as 0.6 lagging.
Power factor can also be expressed as a percentage i.e. 60% lagging.

Lake Turkana Wind Power Project - Kenya

CAPACITY:     310 MW (2012)

CONGRATULATIONS! Gathuku David Ndung’u

Last year’s (2009) K.C.S.E(Kenya Certificate of Secondary Education) top student in the country, David Ndung’u who scored an average of 87.26 marks  was yesterday overflowing with joy as his hard work finally payed off. During his interview at one of the local TV stations, he mentioned that he wanted to pursue a course in Electrical & Electronic Engineering. On behalf of the 3phase community I would like to welcome him to this wonderful world of Electrical & Electronic Engineering and wish him the best in al his endeavors.