DONE BY MY COLLEAGUES IN COLLEGE BSEE-5

1. EFFICIENCY, RATING, AND
APPLICATIONS OF DYNAMOS
Camille Alexis J. Roxas
Maria Janine B. Losabio
Jemar N. Palermo

2. APPLICATIONS OF
DYNAMOS

3. One of the disadvantages of DC systems is that
the generated voltage cannot be readily raised
or lowered efficiently.
(AC Systems using transformers make voltage
change efficiently possible).
So, THREE-WIRE GENERATOR is an attempt
to overcome this difficulty.

4. What is a THREE-WIRE GENERATOR?
• It is a generator that makes two available
voltages, one twice as much as the other.
Usually, this generator is designed for 230-V service,
but it has provision for neutral, which serves to
provide 115-V between it and either side of the line.

5. THREE WIRE GENERATOR

6. The use of the balancer set is to provide voltage balance on a
three-wire system.
The balancer coil is simply a pair of reactor coils connecting
points 180 electrical degrees apart on the armature winding and
being themselves connected. The point at the reactor-coil
connection is connected to the middle line of the three-wire
system.
Inasmuch as any pair of reactor coils connects two points on the
armature 180 electrical degrees apart, the voltage across a pair
of coils is alternating.
The coils are wound on separate iron cores mounted on the
armature, or are wound on separate cores outside the machine.
With coils mounted on the armature, only one slip-ring is
necessary; whereas, with separate cores outside the machine,
two or more slip-rings are necessary.

7. Example:
A 250-KW, 230/115-V three-wire generator delivers a 150-
KW, 230-V load, a 30-KW, 115-V load between positive and
neutral and a 50-KW, 115-V load between negative and
neutral. Calculate the current in each line wire and the
current in the neutral.
Solution:
I230 =
150,000
230
= 652 Amp
I115+ =
30,000
115
= 261 Amp
I115- =
50,000
115
= 435 Amp
I(+) = 652 + 261 = 913 Amp
I(-) = 652 + 435 = 1, 087 Amp
IN = 435 – 261 = 174 Amp

8. Third Brush Generators
• Often used on automobiles to provide necessary
electric power for the charging of the storage
battery and the operation of lights.
• It is a special shunt generator with the field
winding connected between the main brushes
and the auxiliary, or the third brush.

9. Third brush generator, showing field distribution.

10. As the speed of the automobile increased, thereby
increasing the speed of the generator, the voltage tended
to increase. This increase in the voltage increased the
current delivered by the generator. But the increase in
current so changed the magnetic flux distribution in the
machine that the voltage between the third brush and main
brush was reduced. This reduced the field current and
therefore the flux of the machine and tended to bring the
main voltage between the main and third brush back to its
former value. This action did not maintain an absolutely
constant voltage for different speeds, but the voltage was
held within certain limits so that the extensive voltage
which would overcharge the battery and shorten the life of
the lamps was not developed at high speeds.

11. Diverter Pole Generator
• A special type of dc generators that have particular
advantages for charging of batteries.
The machine is constructed with additional pole pieces ( the
diverter poles) located midway between the main poles in the
same manner as commutating poles. Each main pole is
connected by a magnetic bridge to a one diverter pole. The
winding of the main poles are connected in shunt with the
armature winding, and the windings of the diverter poles is in
series with the armature winding.

12. DIVERTER POLE GENERATOR

13. At no load, the diverter-pole current is zero, under which
condition it produces no mmf; a good part of the main-
pole flux is thus diverted through the magnetic shunts to
the diverter poles. The flux is limited by the saturation of
the bridges.
Under load, however, the mmf of the diverter poles,
prevents the main-pole flux from passing it to the diverter
poles. Thus the diverted flux decreases as the load
increases, the result being that the emf of the machine
tends to be remain constant for all values of the load.
By proper design of the bridge areas and their slots, it is
possible to have a characteristic that is flat.

14. 