ELECTRICAL VOLTAGES AVAILABLE
TESTING AND ADJUSTING
Note in this Y, Wye, or Star arrangement that a single-
phase voltage is always equal to the higher voltage
divided by 1.732.
Figure 2
3-Phase Delta Common Voltages:
110/220; 120/240; 208; 440; 460; 480
The lower voltage of this delta, dual voltage system is
obtained from one Line (L1 or L2) and the center tap (C)
of one transformer coil. That center tap is usually
connected to an earth ground. Note that these lower
single-phase voltages are equal to one-half of the higher
voltage. The higher listed voltage can be single-phase
obtained from any two Lines: L1 to L2, L2 to L3 or L3 to
L1. A three-phase voltage can also be obtained from a
connection to L1, L2 and L3. Some industrial plants may
also require 208 volts single-phase in addition to
120/240 volts single-phase, and 240 volts three-phase.
The 208 volts can be obtained by connection to L3 and
C.
Commercial power sources often identify their secondary
(user) distribution by voltage and phase. (Example, 240-
1o, 460-30.)
FREQUENCY/VOLTAGE AVAILABLE FROM SR 4
GENERATORS
All SR 4 Generators can readily operate at either 50 Hz
or 60 Hz. Regulated voltage output is proportional to
generator speed. As an example, the 480 volt 60 Hz
(1800 rpm) generator will produce a 400 volt 50 Hz
supply at 1500 rpm.
SR 4 Generators are offered in three basic voltage
levels. The nominal voltage available from one of these
basic voltage levels, plus reconnectable line leads, and a
wide voltage level adjustment range, permit the SR 4 to
match the commercial frequencies, and most of the
commercial voltages.
SR 4 Generators are "Y" (Star) connected three-phase
machines and have 10 line leads, as shown in Figure 3.
These leads can be field connected, as illustrated in
Figures 4 and 5, to produce the following voltages at the
frequency shown:
Frequency (1)
Nominal
Nominal
Voltage
Adjustment
Range
Up
Down
Hz
(Volts) (2)
(Volts)
(Volts)
60
120/208Y
6/11
6/11 (3)
or
240/416Y
12/21
12/21 (4)
60
139/240Y
7/12
7/12 (3) (5)
or
277/480Y
14/24
14/24 (4) (5)
50
115/200Y
6/10
6/10 (3)
or
230/400Y
12/20
12/20 (4) (6)
60
173/300Y
9/15
9/15 (3)
or
346/600Y
17/30
17/30 (4)
50
139/240Y
14/24
7/12 (3)
or
277/480Y
28/48
14/24 (4)
NOTES:
1.
SR 4 Generators are designed for 50 or 60 Hz
operation. Nominal voltage is proportional to
speed.
2.
The slant line indicates a line-to-neutral single
phase' voltage and a line-to-line three-phase
voltage. Both voltages are available at the same
time.
3.
Generator coils are parallel connected.
4.
Generator coils are series connected.
5.
The 139/240Y or 277/480Y volt 5N43, 5N46,
5N48, 5N56, and 5N58 Generators have a broad
range voltage regulator capable of adjustment
down to 120/208 or 240/416 volts.
6.
400 volt, 50 Hz SR 4 Generators will develop up to
420 volts, no load.
Application
Larger 50 Hz industrial loads require three-phase power
in the range of 380 to 420 volts. Additionally, these
systems often require single-phase voltages in the range
of 220 to 240 volts. The 400 volt 50 Hz
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