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24-12-2010, 02:59 PM
brusless excitation system.docx (Size: 2.25 MB / Downloads: 172)
A new brushless excitation system is described for electrical motor having a stationary field system and a rotating armature diode rectifier. Field excitation is provided by astandard brushless excitation system which consists of a rotating armature, diode bridge and stationary field.
The brushless excitation system eliminates periodic brush and collector ring maintenance and replacement.
The permanent magnet generator (PMG) supplies high frequency AC power to the voltage regulator. Voltage and reactive current feedback is provided to the regulator from potential and current transformers.
The exciter provides a controlled DC output using feedback signals and a reference point established by the setting of the voltage regulator. A transfer switch provides for selection of automatic or back up automatic regulator control. A back up automatic regulator is a standard feature. Voltage regulator DC output is fed to the stationary field of the rotating exciter. Three phase, high frequency AC output from the rotating armature is rectified and applied to the main generator field. Fully rated redundant diodes with indicating fuses permit full load operation even with a diode out of service. A strobe light is furnished with unit to view the indicating fuses and determine diode failure. The system is compatible with other manufacturers’ voltage regulators. Field ground indication is provided without slip rings by means of a transmitter mounted on the diode wheel assembly. A light signal is sent across the air gap to a stationary receiver and relay to indicated presence of a ground.
According to FLEMING'S RULE
magnet is excited and its armature
"When a field
current from the supply mains , they
experience a force tending to rotate the armature".
Excitation systems have a powerful impact on
generator dynamic performance and availability, it
ensures quality of generator voltage and reactive power,
i.e. quality of delivered energy to consumers. Following
types are common:
Brushless excitation systems, with rotating exciter
directly from thyristor bridges via brushes.
Main functions of excitation system are to provide
variable DC current with short time overload capability,
controlling terminal voltage with suitable accuracy,
ensure stable operation with network and/ or other
machines, contribution to transient stability subsequent
to a fault, communicate with the power plant control
system and to keep machine within permissible
operating range So for rotating the motor or generating the power from the generator we must require a excited
So for rotating the motor or generating the power
from the generator we must require a excited
The field excitation of motor or generator is always
by D.C supply.
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