Power factor

1. Guide by- Presented by-
Prem Prakash Mishra
1401219124(EEE)

2.  Introduction
 Difference between Brushless and Brushed Alternator
 Construction of brushless alternator
 Working principle
 Losses
 Application
 Conclusion
 Reference

3. The electrical power requirements in automobiles have been rising rapidly for many
years and are expected to continue to rise.
 Slip ring and brushless removal leads to construction simplification, to decrease of
production and operational costs, to increase of service life and reliability.
In these systems, both the exciter machine and the rectifier are mounted on the
same shaft as the main alternator.
The output voltage is regulated by controlling the exciter’s field current.
the high frequency ac supply which is generating on winding which is also located on
rotor provide excitation supply for main alternator field winding are not require to use
brush hence it is called brushless alternator.

4.  Brushed alternator: In brushed alternator DC voltage for field excitation (located on
rotor) is provided from DC source through contacts of slip ring and brushes.
 Maintenance required for slip rings, brushes, and commutator.
 Speed limitation.
 Losses at brushes.
 Heating of contact parts (cooling system required).
 Brushless alternators: In brushless alternator DC voltage for field excitation (located
on rotor) is supply through rotating bridge rectifier (located on rotor) and high also
located on rotor. To provide excitation supply for main alternator field winding we are
not require to use brush hence it is called brushless.

5.  A brushless alternator is composed of two alternators built end-to-end on
one shaft.
 Smaller brushless alternators may look like one unit but the two parts are
readily identifiable on the large versions.
 The larger of the two sections is the main alternator and the smaller one is
the exciter. The exciter has stationary field coils and a rotating armature
(power coils).
 The main alternator uses the opposite configuration with a rotating field
and stationary armature.

7. • Brushless alternator have two parts
(a) Excitation alternator part
(b) Main alternator part

9.  Here Armature is rotor and Exciter Field winding is stator.
 Exciter field produce a magnetic field by the help of AVR or Residual
magnetism. When it starts rotating a voltage is generated in Exciter
armature which gives current to the main field to produce magnetic field
in Main alternator.

10.  Here main field is rotor and armature is stator.
 Voltage Produced in the exciter armature pass through the Diode
Mounting plate(Rectifier) and goes to the Main Field which produce a
magnetic field. When this magnetic field cuts the Main Armature a
potential difference is procured.
 we can take supply out directly, no brushes required . Here the voltage
produced can be regulated by exciter field current

11.  AVR controls the Output voltage by controlling exciter field current.
 AVR , sensing the out put voltage from main armature , compares it
with the set value and then changes the exciter field current.
 AVR having diodes which converts A/c into D/c for exciter field.

12.  Brushless exciter losses - These are small loses due to electrical energy going
into the exciter and rectifier.
 I2R losses in the armature and field - These heat losses are due to resistance
in the windings and can be reduced by using more copper or by running at
cooler temperatures.
 Friction and windage losses - These are losses due to the bearings, fans or
blowers and the rotor itself. Optimising the fan design is the best way to
reduce these losses.
 Core losses - These are losses caused by hysteresis and eddy currents (induced
electrical currents)..

13.  Wind turbine
 Train
 Only use in AC case
 Early Honda four-cylinder motorcycles (CB750F, CB350F, CB500F, CB550F)
used a brushless Hitachi 200W alternator.

14.  This shows that brushless design is most advantageous and the design is
working condition. Here, the output voltage is independent on engine
mechanical power.
 Need of brushless alternator in the automotive industry has been
identified. Various results from MATLAB simulation is obtained for both
brushed and brushless alternator model.
 The power output of brushless alternator is found to be higher than
brushed alternator in all consequences. Thus brushless alternator for
automotive industry will enhance the electricity need for more comfort
in vehicles. Besides it removes the losses occurring at the brushes for car
alternators.

15.  E.C. Lovelace, “High-power starter/alternator project status review”, MIT
Consortium on Advanced Automotive Electrical/Electronic Components
&Systems, Sept., 22-23, 1997.
 D.J. Perreault and V. Caliskan, “Automotive power generation and
control”, LEES Technical Report TR-00-003, May 24, 2000.
 BY intearnet

16. THANK YOU