Real-Life Math
Most of what an electrical engineer does involves some math. Jim
Clouston is a senior engineer with a power company.
His responsibilities
include overseeing the engineering for the electrical distribution system,
planning future distribution systems, forecasting the load growth
on the systems, administering the proper upkeep of all the system drawings,
developing computer programs and ensuring the quality of power reaching the
customers.
"I look after customer complaints -- including going out
to customers to test their electricity, then doing an analysis of the monitoring
period," Clouston says.
Math is involved in every step. "I use math
for power calculations, figuring out the load on circuits and determining
voltage drops along a power system," he says. Clouston also uses it to calculate
fault levels. In your house, for instance, the fault level is the point at
which a breaker blows because of a short circuit.
"A lot of the math
is done by computer programs now," says Clouston, "but we still do some manually."
Sometimes electrical engineers do quick calculations involving power, current
and voltage.
A large shopping mall is being built in your community.
The mall's owners have decided to have their own transformer supply power
to the mall. It's a 1-million volt-amp transformer. The power supplied through
your company's 3 phase lines is at 25,000 volts. Any fuses that are put on
the electrical system must be able to handle the amps flowing from the transformer
at full load.
A fuse is connected directly into an electrical circuit.
If the electric current surges to a dangerous level, the metal in the fuse
melts and the circuit is broken. This prevents the overheated wires in the
walls of the house from starting a fire. A fuse of greater capacity than that
specified for a particular circuit should never be used. If the fuse has the
ability to carry more current than originally designed, the wires will heat
up before the fuse melts, and this could start a fire.
Power (volt-amp)
= [square root of 3] x voltage (volt) x current (amps)
You have
a choice of using three fuses -- 20, 23 or 25 amp. What one should you use?