Throughout history academia have honored those
pioneers and discoverers that have brought mankind out of darkness and into light. The
list of famous physicists, scientists, engineers and inventors is long. Many of the units
of electrical measurement quantity and expression come from the founding fathers who first
postulated and discovered physical phenomena in electricity and magnetism. Volta, Ampere,
Faraday, Hertz, Maxwell, Newton, Watt, Weber and Tesla, are among the names that have been
synonymous with standard units of electrical and magnetic measure, since their respective
times of discovery and contribution.
Tesla was the electrical engineer who invented the AC (alternating current) induction
motor, which made the universal transmission and distribution of electricity possible.
In 1888 his discovery that a magnetic field could be made to rotate if
two coils at right angles are supplied with AC current 90° out of phase
made possible the invention of the AC induction motor. The major advantage
of this motor being its brushless operation, which
many at the time believed impossible.
One of Tesla's later experiments involved a ring with 3 coils, one
for each phase of a 3-phase system, with a steel ball in the centre. By
applying a 3-phase current to the
coils on the ring (out of phase and physically separated from each other
by 120°), a
rotating magnetic field was created. The rotating magnetic field (primary field) would in
turn induce a current in the steel ball. This current, with its own opposing magnetic
field, would act as an 'anchor' for the primary magnetic field, allowing
it to 'pull' the ball as it rotated. This was the basis for the 3-phase
induction motor, which
is used in practically every form of industry today.
Tesla's experiment with the 3-phase induction motor is the
inspiration behind the images at top of page. In place
of the steel ball rotating with-in the ring, the copper ring rotates around
the steel ball to represent the effect a magnetic
field, created by a 3-phase alternating current, would have.