(2)   Test. (a)   Start   and   operate   the   generator   set   and allow   the   set   to   stabilize   at   rated   load,   rated   voltage and   rated   frequency. During   this   period   operate   the recording   meter(s)   at   a   chart   speed   of   not   less   than 6  inches  per  hour,   and   record   all   instrument   readings including  thermal  instrumentation  at  minimum  inter- vals   of   10   minutes.   If   necessary,   adjustments   to   the load,  voltage  and  frequency  may  be  made  to  maintain rated   load   at   rated   voltage   and   frequency.   Adjust- ments  to  the  voltage  and  frequency  shall  be  limited  to those   adjustments   available   to   the   operator,   specifi- tally   adjustments   to   the   voltage   or   frequency   adjust devices.   On   sets   utilizing   a   droop-type   speed   control system   as   the   prime   speed   control,   the   speed   and droop   portions   of   the   control   may   be   adjusted.   No other   adjustments   to   the   voltage   and   frequency   control systems   shall   be   made. Adjustments   to   load,   voltage or   frequency   controls   shall   be   recorded   on   both   the data  sheet  and   the  recording   chart(s)  at  the   time  of  a adjustment. Stabilization   shall   be   considered   to   have occurred   when   four   consecutive   voltage   and   current recorded   readings   of   the   generator   (or   exciter)   field either   remain   unchanged   or   have   only   minor   varia- tions  about  an  equilibrium  condition  with  no  evident continued   increase   or   decrease   in   value   after   the   last adjustment   to   the   load,   voltage   or   frequency   has   been made. (b)   After   stabilization   has   occurred,   drop the  load  to  no  load  and  reapply  rated  load  a  number of   times   (three   should   be   sufficient)   to   assure   that   the no  load  and  rated  load  voltage  and  frequency  values are   repeatable   and   that   the   frequency   and   voltage regulation   is   within   the   limits   specified   in   the   pro- curement   document.   If   any   adjustments   are   neces- sary,   paragraph   (a)   above   must   be   repeated.   Reapply rated   load. (c)   The   recording   meter   chart   speed(s) shall   be   12   inches   per   minute   throughout   the   remain- der  of  this  test.  At  each  of  the  following  load  condi- tions  (one  step)  operate  the  set  for  a  minimum  of  40 seconds   (or   the   short-term   stability   period   plus   the allowable   recovery   time   as   specified   in   the   procure- ment   document). During  each  load  condition  read  and record   all   instrument   readings   except   thermal   instru- mentation   (for   three-phase   sets   it   is   not   necessary   to record   line-to-line   voltages).   Each   load   condition shall  be  applied  to  the  generator  set  in  one  step  at  the end  of  the  short  -term  stability  period  for  the  previous load   condition. 1. 2. 3. The   load   conditions   are: Rated  load No load Rated  load No load Rated  load No load Rated  load No load 3/4   rated   load No load 3/4   rated   load 12.   No   load 13.   3/4   rated   load 14.   No   load 15.   1/2   rated   load 16.   No   load 17.   1/2   rated   load 18.   No   load 19.   1/2   rated   load 20.   No   load 21.   1/4   rated   load 22.   No   load 23.   1/4   rated   load 24.   No   load 25.   1/4   rated   load 26.   No   load 27.   Rated   load 28.   No   load 29.   Rated   load 30.   No   load 31.   Rated   load 32.   No   load (d)  Repeat  (a)  through  (c)  for  all  voltage connections)   and   frequency(ies). d.   Results. (1)   Prepare   a   chart   giving   for   each   load   change the   momentary   overshoot   or   undershoot   and   the   re- covery  time. For   each   constant   load,   give   the   max- imum   voltage   variation, (2)   Referring   to   figure   16-1,   begin   by   deter- mining  the  observed  (B)  and  steady  -state  (D)  voltage bandwidths. (a)   Mark   numerically   the   stabilizations occurring   after   each   load   change,   starting   with   the stabilization   obtained   before   the   first   load   change. (b)   Determine   the   observed   voltage   band- width  (B)  by  marking  the  maximum  trace  excursion and   minimum   trace   excursion   in   the   stabilized portion.   Draw   two   lines   parallel   to   the   axis   of   chart movement,   one   each   passing   through   these   maximum and   minimum   trace   excursions   respectively. (c)  Draw  a  line  (C)  parallel  to  and  equi- distant  from  the  edges  of  the  observed  voltage  band- width.   Determined   in   (b)   above, (d)   Using   the   rated   voltage   of   the   generator and   given   requirements   of   table   16-1,   calculate   the steady   -state   voltage   bandwidth   (D).   Draw   this steady   -state   voltage   bandwidth   as   two   parallel   lines, parallel  to  and  equidistant  from  the  median  (C)  at the   observed   voltage   bandwidth. (3)   To   determine   the   maximum   voltage   varia- tion   at   constant   load (a)   One-half   the   observed   voltage   bandwidth (B)  is  the  plus  or  minus  value  of  voltage  deviation at   constant   load. (b)  Divide  each  of  the  values  obtained  in  (a) 16-6