CIRCULATING CURRENTS TESTING AND ADJUSTING to  correctly  distribute  magnetizing  current  and  keep  the circulating currents to a minimum.  Example: Load kW 700, Load Line Amperes 1,100, Voltage 460 Generator No.  1, Load kW 250, Line Amperes 500 Generator No.  2, Load kW 450, Line Amperes 630 It   should   be   obvious   that   the   voltage   level   setting   on Generator No.  2 is too low.  Adjustments could be made to one or both until No.  1 shows a line ampere reading of  about  390,  and  the  line  ampere  reading  of  No.    2 shows  about  700  amperes.    At  these  conditions,  both generators   will   be   operating   at   the   same   load   power factor   of   0.8.      Circulating   current   is   at   a   minimum. Refinements    as    described    above    will    assure    highly satisfactory operation of paralleled generator sets. Summary Circulating  currents  exist  in  paralleled  generators  when the   several   generators   are   attempting   to   operate   at different  voltages  although  they  are  connected  together through   the   common   bus.      These   circulating   currents reduce the effective excitation of one or more generators,    and    increase    the    effective    excitation    of others.    Generator  voltage  is  directly  related  to  exciter output.          Hence,     an     attempted     generator     voltage difference is the result of different exciter output.  Exciter output is controlled by the voltage regulator, and ultimate control of circulating current is a function of the regulator. Effect of Circulating Currents On Load Sensing Electronic Governors The Woodward 2301 load sensing governor can react to excessively   large   circulating   currents.      With   correct adjustment   of   generator   voltage   regulators,   the   load sensing  governor  responds  to  true  power  or  kW  load  on the    generator    set.        However,    when    the    value    of circulating  current  between  generators  approaches  the value of the actual load current, the governors may react to  these  excessive  circulating  currents  and  change  the kW  load  division  between  generator  sets.   Load  transfer may be slow, or it may be rapid.  There is no predictable pattern    since    the    observed    action    depends    on    the condition  of  the  generator  voltage  regulators  controlling the several generators. Incorrectly   adjusted   voltage   regulators   are   the   most common cause of the "load shift" problem.  It is generally found  that  initial  generator  regulator  adjustments  fail  to include adequate voltage droop or cross-current compensation.    This  difficulty  can  also  cause  operating errors. Some  commercially  available  generator  control  panels for use with commercially avail-able generators include a switch   that   bypasses   the   voltage   droop   circuit   in   the voltage  regulator.    These  switches  have  various  names such   as   "Single-Parallel"   or   "Droop   In   Droop   Out." Operators    incorrectly    position    these    switches    during parallel  operation,  causing  one  or  more  generators  to operate without voltage droop or cross-current compensation.  Circulating currents can greatly increase under these conditions.  Governors will generally react. Switchboard   wiring   errors,   such   as   reverse-connected current transformers (used as part of the droop or cross- current  system),  can  also  cause  load  shift  problems.    In these instances, the voltage droop system causes a rise in   generated   voltage   as   the   line   current   increases. Circulating  currents  can  increase  rapidly,  and  possibly cause  circuit  breakers  to  open.    Governor  reaction  may be noted just prior to circuit breaker opening. 125