Principles of Operation
Functional Circuits
Refer to the block diagram in Figure 2. The voltage regulator senses the generator voltage, compares a
rectified sample of that voltage with a reference diode (Zener) voltage, and supplies the field current
required to maintain the predetermined ratio between the generator voltage and the reference voltage.
This unit consists of five basic circuits. These are a sensing circuit, an error detector, an error amplifier, a
power controller, and a stabilization network.
Figure 2. Overall Block Diagram
Application Information
Starting Large Motors or Providing Fault Current for Selective Breaker Tripping
For generators equipped with brushless exciters or for static-excited generators, the field power is taken
from the generator output voltage. A heavy load, such as a large motor, can cause generator voltage to
decrease substantially at the first few cycles after load application. A short circuit on the generator output
could reduce the voltage from the generator to zero. Either of these conditions can cause reduction of the
available field power to a level which will not sustain generator voltage. Accessory excitation support
systems are available which take advantage of the generator line currents as a source of excitation power
during either condition.
For brush-type, rotation-excited generators, the exciter armature connections can be used as an alternate
source of excitation during either of the conditions described above to provide excitation support. See the
Installation
chapter for a typical interconnection diagram. This scheme uses the other contact on the
buildup relay to connect dc voltage from the exciter armature directly to the exciter field. As an alternative,
the regulator could be used as described above.
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REQUEST A QUOTE
SHOP ONLINE
www.genpowerusa.com