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 94