Download AC/DC generato AC/DC generator

AC/DC generator
Physics 521
May 6, 2010
Kei Iizumi
Explanation of diagrams
In this page, components and colors used in the models is explained, in order to understand the model correctly.
-All diagrams in this report use Red for N, and Blue for S.
-Magnets have both North and South pole for accuracy.
-Cables are coloured in this texture
-Brush
-Gear linkage used for
AC/DC converter
-Cylinder made from plastic
-Cables
Cables are placed on cylinder’s
cylinder
surface
Cables
Plastic shaft
Split-ring commutator used in DC generator
Plastic columns
Metal ring
Commutator used in AC generator
Plastic shaft pillar
General Concepts
Fleming’s left hand rule
Both alternating current (AC) and direct current (DC) generators work by Fleming’s left hand rule. Below is the detailed explanation of this rule.
1
○
2
○
Current (I)
When an electric current is
applied to a cable in the direction
of the arrow, magnetic field is
produced in an anti-clockwise
direction.
cable
S N
S N
1 is placed
When the cable from ○
between permanent magnets,
magnetic field from the cable
interferes with the magnetic field
from the permanent magnets.
Interference reduces the strength of
upper part of magnetic field, while
increasing the strength of lower part.
3
○
S N
S N
Due to the strength difference of
magnetic field between upper and
lower part, cable experience an
upward force.
Diagram 1 is a simplified version of the above process. A
An electric cable is placed perpendicular to the magnetic field (B)
acting from left to right. When an electric current (I) is applied to the cable, force (F) acts upwards.
Force (F)
The magnitude of the force is given by the following formula:
Current (I)
F BIL
F= force
B= magnetic field (in teslas)
I= current
Magnetic Field (B)
Diagram 1
L= length of cable (in meters)
This rule allows us to convert kinetic energy into magnetic energy and vice versa, by using pair of permanent magnets.
magnets
Mechanics of DC generator
Graph 1
Graph 1 shows the voltage change of direct current over time, and purple line represents the status of DC generator at its original position (Model 1)
1).
In Model 1, split-ring
ring commutator is connected to the brush, thus current is flowing in the direction of yellow arrow. Model 2 shows how
ho force(F),
magnetic field(B) and current(I) is working in the generator.
+
voltage
time
Model 1
F
I
Model 2
B
B
I
F
Graph 2
Graph 2 shows the status of cylinder rotated 90° (Model 3). In Model 3, split-ring
ring commutator is disconnected from the brush, thus current
isn’tt flowing. Model 4 shows the cylinder rotated 100°, where commutator is re-connected to the brush. When re
re-connected, ONLY the
direction of current flowing through the cylinder is inversed.
in
As shown in Model 4, force (F) and current (I) is acting in the opposite direction
as before. Thus generator
enerator keeps producing DC electricity.
electricity
+
voltage
time
In Graph 1 and 2, normal
ormal DC would show a straight line, since voltage, direction of current, and charge (+ -)) doesn’t
doesn change over time. But
electricity from DC generator shows a “full-wave rectification,” since voltage reach 0 when split-ring
ring commutator is disconnected from the
brush, and voltage rise/drop as cylinder rotate.
Model 4
I
Model 3
F
F I
B
B
Mechanics of AC generator
Graph 3
time
voltage
Compared to DC generator, AC generator doesn’t
doesn use split-ring commutator, since voltage, direction of current, and charge (+ -) changes
periodically. Graph
raph 3 shows the change in voltage overtime, and purple line represents the status of AC
C generator at its or
original position
(Model 5) . Since this distinctive
dis
characteristic of AC already function like a split-ring
ring commutator, it is unnecessary for AC generator. In
model 5, current is flowing in the direction of yellow arrow. Model 6 shows how force(F), magnetic field(B) and current(I) is working in
the generator.
Model 6
Model 5
F I
I
B
Graph 4
time
voltage
Model 7
B
F
Graph 4 shows the status of cylinder rotated 90° (Model 7). In Model 7, ring is still connected to the brush, thus current is flowing. But at
this point, the direction of current flowing through the whole circuit is about to inverse, due to the characteristics of AC. Model 8 shows the
cylinder rotated 100°,
100 where force(F) and current(I) is acting in the opposite direction as before. Thus generator keeps producing AC
electricity.
Model 8
I
F
F I
B
B
Mechanics of AC
AC/DC converter
AC/DC converter is a combination of AC and DC generator, where AC electricity is converted to DC electricity and vice versa, through intermediate
intermed
conversion to kinetic
energy.
AC to DC
AC electricity input into AC generator rotates the cylinder clockwise, and the kinetic energy is transferred
sferred to the DC generator cylinder through gears,
rotating the cylinder anti-clock
clock wise (viewed from AC input side). When split-ring
split ring commutator disconnects from brushes, no force will act on the cable,
but inertia keeps the cylinder rotating, and commutator reconnects to the brushes. As a result, AC electricity input is converted to DC electricity output.
DC to AC
DC electricity input into DC
C generator rotates the cylinder clockwise, and the kinetic
kineti energy is transferred to the AC
C generator cylinder through gears,
rotating the cylinder anti-clock wise (viewed from DC
C input side). As a result, DC electricity input is converted to AC
C electricity output.