by  the  rated  voltage  of  the  generator  and  multiply  by 100  to  convert  to  percentage. (4)   To   determine   the   maximum   overshoot   and undershoot   at   each   load   step,   and   express   this   as   a percentage   of   its   rated   voltage,   proceed   as   follows: (a)   From   the   meter   recording   charts,   deter- mine  the  maximum  amount  that  the  voltage  trace  goes beyond  the  line  (3)  of  the  observed  voltage  band  follow- ing  the  load  change. See   figure   16-1   for   illustration of  overshoot  and  undershoot. (b)  Divide  the  result  obtained  in  (a)  by rated   voltage   (as   given   on   the   generator   nameplate), then  multiply  by  100  to  convert  to  percentage. CAUTION Do  not  use  the  constant  operating  voltage at  each  load  as  the  divisor  in  the  compu- tation.  Use  only  the  rated  voltage  of  the generator. (5)   To   determine   the   time   required   to   restore stable   voltage   conditions   after   each   load   change (recovery    time): (a)  The  prescribed  steady  state  voltage bandwidth,  extended  to  the  point  at  which  the  voltage trace  leaves  the  prescribed  steady  state  band,  shall be  considered  as  the  time  at  which  the  transient  con- ditions   begin. The  point  at  which  the  voltage  trace enters   and   remains   within   the   prescribed   band   after a  load  change  shall  be  considered  as  the  point  at  which stabilization   begins. (b)  Measure  the  distance  (in  inches)  on  the chart   from   the   point   where   the   voltage   trace   leaves the  prescribed  steady  state  band  to  the  point  where it   re-enters   and   remains   within   the   prescribed   voltage band  for  the  next  load  condition. (c)  Divide  this  distance  by  the  chart  speed (in   inches-per   second). This  will  give  the  voltage recovery  time,  in  seconds. (6)   Determine   the   voltage   regulation   for   all load  changes  (e.  g.  rated  load  to  no  load,  1/2  rated load  to  no  load  to  1/4  load,  etc.  )  as  follows: (a)   Using   the   indicating   voltmeter   readings subtract  the  load  value  of  voltage  from  the  no  load value  for  each  load  change  (e.  g.  step  (a)  to  step  (b)). (For   voltage   regulators   utilizing   single-phase   voltage sensing,  the  value  of  voltage  in  the  sensed  phase  only shall  be  used  in  the  above  calculations. For   voltage regulators   utilizing   multi-phase   voltage   sensing   the average  value  of  the  sensed  voltage  shall  be  used.  ) (b)  Convert  each  of  the  values  obtained  in  (a) above  to  a  percentage  of  rated  voltage  by  dividing  by the  rated  voltage  and  multiplying  by  100.  This  is  the voltage   regulation   expressed   in   percent. (c)   Repeat   paragraph   16-15d.   (1)   above   sub- stituting   frequency   for   voltage. (d)   Compare   the   results   tabulated   in   para- graphs  16-15d.  (1)  and  16-15d.  (6)(c)  with  the  require- ments  of  Table  16-1. 16-16.   Frequency   Adjustment   Range   Test. a.  General.  It  is  necessary  that  the  frequency  of a   generator   set   be   adjustable   to   provide   rated   fre- quency   at   various   load   conditions   as   required   in certain   applications   and   to   synchronize   two   or   more generator   sets   for   parallel   operation. b.   Apparatus.   Instrumental   ion   for   measuring load   conditions,   field   voltage   and   current,   and ambient   temperature   shall   be   as   described   and illustrated   in   MIL-HDBK-705. c.   Procedure. (1)   Preparation   for   test.   Connect   the   load   and field   instrumentation   in   accordance   with   the   applicable figure   of   MIL-HDBK-705,   Method   205.1,   paragraph 205.1.10. (2)   Test. (a)   Start   and   operate   the   generator   set and   allow   it   to   stabilize   at   rated   load,   rated voltage   and   rated   frequency. During  this  period,  readings  of  the  load  and  field instrumentation   shall   be   recorded   at   minimum   in- tervals   of   10   minutes.   If   necessary,   adjustments   to the  load,  voltage  and  frequency  may  be  made  to maintain   rated   load   at   rated   voltage   and   rated   fre- quency.   However,   adjustments   available   to   the operator,  specifically  adjustments  to  voltage  and frequency   adjust   devices.   Adjustments   to   the   load, voltage   or   frequency   shall   be   noted   on   the   stabiliza- tion   data   sheet.   Stabilization   will   be   considered   to have  occurred  when  four  consecutive  voltage  and current   readings   of   the   exciter   field   either   remain unchanged  or  have  only  minor  variations  about  an equilibrium  condition  with  no  evident  continued  in- crease   or   decrease   in   value   after   the   last   load, voltage   or   frequency   adjustment   has   been   made. (b)  No  further  adjustments  shall  be  made  to any   set   control   for   the   remainder   of   this   test   except for   the   control   panel   frequency   adjust   device. (c)  For  each  of  the  conditions  in  the  follow- ing  steps  allow  approximately  2  minutes  between  each adjustment   and   the   subsequent   instrument   readings. (d)   Adjust   the   generator   set   frequency   for the   specified   maximum   frequency   at   rated   load. Read   and   record   all   instrument   readings. (e)   Adjust   the   generator   set   frequency   for the   specified   minimum   frequency   at   rated   load. Read   and   record   all   instrument   readings. (f)  Reduce  the  load  to  zero. (g)   Adjust   the   generator   set   frequency   for the   maximum   attainable   frequency.   Read   and   record all  instrument  readings.  If  the  overfrequency  or 16-8