SECTION ONE GENERAL DESCRIPTION The  Stamford  'C'  range  a.c.    generator  is  a  brushless,  revolving  field  high  performance  machine.    The  frame  sizes covered in this book are fitted with Series 4 excitation system on SC1 - 3 frame sizes and Series 6 excitation system on PC1 frame size.  The machines are.  4 pole, A.V.R.  controlled with a broad operating voltage range and with a 12 wire reconnectable facility.  The standard windings listed below cover most world voltages. FREQ SERIES STAR PARALLEL STAR SERIES DELTA SERIES ZIG-ZAG STAR PARALLEL ZIG-ZAG WDG. No. 3 ph. 4W. 3 ph. 4W. 3 ph. 4W. 1 ph. 2W. 3 ph. 1 ph 3W REMARKS 50 *380-415 190-208 220-240 --- 220-240 211 60 *440- 480 *220 -240 254 -277 380-415 240** 12W- Reconnectable 50 440-500 220-250 --- 380-415 --- 17 60 550 - 600 --- --- 460 - 480 --- 12W Reconnectable 50 415 460 210 - 230 240 - 266 360 -400 240 - 266 19 60 --- --- --- 430480 --- 12W Reconnectable NOTES: 1. * To operate at 346 Volts 50 Hz, 416 Volts 60 Hz in Series Star or 208 Volts 60 Hz in Parallel Star de-rate machine output to 0.93. **· To operate at 240 Volts 60 Hz in Parallel Zig-Zag de-rate machine output to 0.9. 2. For  windings  211  and  17  when  connected  Series  Zig-Zag  Star  the  machine  output  must  be  de- rated to 0.87. MACHINE DESIGNATION To  facilitate  identification,  a  simple  coded  system  is  used  comprising  letters  and  numbers.    For  example  an  industrial machine with a designation SC1440 would be identified as follows:  The first letter ('S') indicates the series of machines and  the  second  letter  ('C')  the  range.    The  first  number  (1)  indicates  the  frame,  the  second  number  (4)  the  excitation system and the third number (4) the number of poles.  The letter ('D') after the numbers indicates the core length.  For marine machines, the designation is prefixed by the letter 'M' (e.g.MSC144D). CONSTRUCTION The  machines  are  ventilated,  screen  protected  and  drip  proof  to  BS4999  Part  20  and  can  be  in  either  single  or  two bearing form.  All machines are based around a cast or fabricated frame and cast iron endbrackets with a large sheet metal terminal box mounted at the non-drive end. The stator/rotor core is produced from low loss electrical grade sheet steel laminations, which are jig built and welded under  a  fixed  pressure  to  give  an  extremely  rigid  core  to  withstand  vibration  and  load  impulses  The  completed  wound components are all insulated and impregnated to Class H limits. 1