Field Power (Terminals F+ and F
–
)
The model number prefix (SR6A or SR9A) of the regulator, defines the amount of power that the unit is
capable of delivering. See the specifications in the
General Information
chapter).
The dc resistance of the field to which the regulator is connected, terminals F+ and F
–
, must be
≥
9
Ω
for
an SR6A and
≥
18
Ω
for an SR9A. If the resistance is less than the specified minimum, a resistor must
be added in series with the field. This resistor value, plus the field resistance, must exceed the minimum
preceding values.
Good generator voltage stability usually results when the regulator output is above 10 Vdc at no load
(20 Vdc for the SR9A). If the voltage is less, and a voltage stability problem exists, it may be necessary to
add resistance in series with the field. This resistance raises the regulator output voltage, thereby
increasing the stability signal.
When adding resistance in series with the field, the resistor value must not restrict field forcing during full
load conditions. The following example explains how to compute the proper resistance:
Example
An SR6A voltage regulator is required to operate into an exciter field that has a dc resistance of 4
Ω
and a
current requirement of 2.5 Adc at no load and 6 Adc at full load. Since the SR6A requires a minimum field
resistance of 9
Ω
, a resistor of at least 5
Ω
must be connected in series with the field. The regulator
output will be 9
Ω
times 2.5 A or 22.5 Vdc at no load, and 9
Ω
times 6 A or 54 Vdc at full load. This
conforms to the 10 volt minimum at no load and provides a sufficient amount of forcing at full load (up to
90 Vdc).
Interconnecting Regulator with Brush-Type Rotary Exciters (Terminal A
–
)
When making connections on brush-type rotary exciter applications, it is very important to observe the
polarities of the exciter field, exciter output, and the generator field as shown in Figure 7. If these
polarities are not known, the system should be operated on manual voltage control, and the polarities
accurately determined before connecting the voltage regulator into the system. The voltage regulator
could be damaged if interconnection is attempted before this data is known.
When manual voltage control is desired on brush type exciter applications, a Manual/Off/Auto switch and
a field rheostat are used (Figure 7). When this feature is not desired, the output of the exciter can be
connected directly to the regulator (terminal A
–
), to allow self-excitation during short-circuit or overloads.
When large motor starting or short-circuit sustaining capability is not required, it is not necessary to use
the A
–
terminal.
Input Power (Terminals 3 and 4)
The model number prefix (SR6A or SR9A) of the regulator defines the maximum input power
requirements. The current requirement of the field, to which the regulator is operating into, will determine
the actual input current. The nominal voltage applied to the regulator input power stage (terminals 3 and
4) must be 120 Vac for the SR6A and either 208 or 240 Vac for SR9A. The input power may be taken
from any generator lines that provide the correct voltage (line-to-line or line-to-neutral). The phase
relationship of this input in relation to other circuits is not important.
When the generator output voltage is different than the preceding values and exceeds the values
specified in the
General Information
chapter, a power transformer must be used to match the generator
voltage to the regulator input. If excessive voltage is applied to the regulator input (terminals 3 and 4), the
regulator may be damaged.
Caution
Without the use of this transformer, a ground at any point in the field
circuit and another ground in the generator output, could result in
failure of the regulator.
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1-888-POWER-58
REQUEST A QUOTE
SHOP ONLINE
www.genpowerusa.com