(b)  Connect  the  frequency  meter  to  one  of the   armature   coils   of   the   generator. (c)  Provide  separate  excitation  for  the exciter   field. (2)   Test. (a)   Start   and   operate   the   generator   at   rated frequency  and  at  no  load. (b)  Adjust  the  excitation  so  that  any  one  of the  coil  voltages  is  at  rated  value. (c)   Read   and   record   the   generator   frequency (speed)  and  the  voltage  of  each  armature  coil. (2)   Test. d.   Generator   with   separate   excitation (1)  Determine  from  the  data  obtained  in  16-13d. (2)   the   maximum   and   minimum   armature   coil   voltages. (2)   The   voltage   unbalance   is   the   difference   be- tween   the   maximum   and   minimum   armature   coil voltages.  To  express  this  in  percent  divide  this difference   by   rated   armature   coil   voltage   and   multiply by 100. (a)   Start   and   operate   the   generator   set   and allow   the   set   to   stabilize   at   rated   load,   rated   voltage and   rated   frequency. During   this   period   record   all instrument   readings   including   thermal   instrumenta- tion   at   minimum   intervals   of   10   minutes.   If   necess- ary,   adjustments   to   the   load,   voltage   and   frequency may  be  made  to  maintain  rated  load  at  rated  voltage and   frequency. Adjustments  to  the  voltage  and  fre- quency   shall   be   limited   to   those   adjustments   avail- able   to   the   operator,   specifically   adjustments   to   the voltage  or  frequency  adjust  devices.  On  sets  utili- zing   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  the  data  sheet  at  the  time  of adjustment. Stabilization   shall   be   considered   to   have occurred   when   four   consecutive   voltage   and   current readings   of   the   generator   (or   exciter)   field   either remain   unchanged   or   have   only   minor   variations about  an  equilibrium  condition  with  no  evident  contin- ued   increase   or   decrease   in   value   after   the   last   ad- justment   to   the   load,   voltage,   or   frequency   has   been made. Voltage  Unbalance  (Coil),  in  percent  = (3)  Compare  the  results  of  step  (2)  above  with the    requirements. 16-14.   Regulator   Range   Test. a.   General.   The   voltage   adjust   device   associated with   the   voltage   regulator   provided   with   the   generator set   must   have   adjustment   capable   of   varying   the   reg- ulated  voltage  throughout  the  limits  and  under  the various   load   conditions   and   temperature   ranges   with- out  causing  the  voltage  droop  of  the  set  to  exceed specification    limits. The   voltage   adjust   device   also must  be  capable  in  some  cases  of  providing  an  oper- ating   voltage   other   than   rated   voltage   for   special types  of  equipment  and  to  compensate  for  external line   drop. b.   Apparatus. Instrumentation   for   measuring load  conditions,  ambient  temperature,  and  the generator   field   (or   exciter   field)   voltage   and   current shall   be   as   described   and   illustrated   in   MIL-HDBK- 705. c.   Preparation   for   Test. (1)   Preparation   for   test. (a)   Connect   the   load   and   field   instrumenta- tion  in,  accordance  with  the  applicable  figure  of  MIL- HDBK-705,   Method   205.1,   Paragraph   205.1.10   for one  voltage  and  frequency. (b)  No  further  adjustments  shall  be  made  to any  set  control  for  the  remainder  of  this  test  except the   control   panel   voltage   adjust   device. (c)   Record   all   instrument   readings. (d)   Remove   load. (e)  Record  all  instrument  readings  (after transients-have    subsided). (f)   Adjust   the   terminal   voltage   to   the   maxi- mum   specified   value. (g)  Record  all  instrument  readings. NOTE At   voltages   above   rated   values,   the generator   will   be   supplying   less   than rated   current;   and   at   voltages   below rated   values,   the   generator   will   be supplying  greater  than  rated  current. Caution  should  be  taken  to  avoid damage   to   instrumentation   and   load banks. (h)  Apply  rated  load  (rated  kw  at  rated  power factor). (i)   Record   all   instrument   readings   (after transients–have   subsided). (j)  Remove  load  and  adjust  voltage  to  the maximum  attainable  value  or  to  a  value  just  prior  to actuation   of   the   overvoltage   protection   device. 16-4