TM  5-6115-584-34 NAVFAC  P-8-622-34 TO-35C2-3-456-2 TM-0568C-34 period  of  time.  The  applied  voltage  must  not  be  so high as to injure the insulation unless the insulation was  initially  defective. (2) Apparatus. Use acceptable high potential test apparatus, following the operating instructions of the manufacturer. (3) Procedure. (a)  Adequately  ground  high  potential  apparatus to  a  water  pipe  or  similar  electrical  ground  in  ac- cordance  with  instructions  accompanying  the  appara- tus. b) Disconnect or remove rectifiers and semi- conductors  from  the  circuit  prior  to  conducting  the tests. (c) Isolate the rotor windings, the main stator windings,  and  the  exciter  stator  windings.  This  is accomplished by disconnecting the various windings from  any  associated  control  circuits  or  other  con- nections. (d)  Connect  the  high-voltage  lead  from  the  test apparatus to the winding or circuit under test. When testing stator rotor, all windings and circuits must be securely connected to ground. When testing rotor, all stator  windings  and  circuits  must  be  connected  to ground. (4) Test. (a) Turn on test apparatus in accordance with manufacturer’s  instructions,  after  making  sure  that the initially applied voltage will be not greater than 600   volts. (b) The test voltage then shall be raised uni- formly to the required maximum. This increase shall be accomplished in not less than 10 seconds nor more than 30 seconds. The maximum test voltage for rotor windings shall be equal to 1,000 volts plus twice the highest rated voltage of the generator. The test volt- age for stator wtndings shall be equal to 10 times for exciter ceiling voltage but in no case less than 1,500 volts  nor  more  than  3,500  volts. (c) Apply the minimum voltage for 1 minute. (d) After 1 minute of applied maximum voltage, the  voltage  then  shall  be  reduced  gradually  to  the voltage initially applied. This reduction shall not be accomplished  in  less  than  5  seconds. (e) Turn off test apparatus. Ground the high- voltage lead of the test apparatus to make sure that no charge remains on the windings which have been under test. (f)   Remove   the   high-voltage   lead   from   the winding and proceed with the tests of the remaining circuits  to  be  tested.  Make  sure  that  all  circuits  not under test are securely grounded. (5)  Results.  Any  evidence  of  insulation  break- down   is   cause   for   replacement   of   the   equipment under test. f.  Winding  Resistance  Test.  Perform  winding  re- sistance test using a Wheatstone bridge. Follow the manufacturer’s instructions given on the bridge. Re- sistance reading should be 36 ohms  ± 3.6 ohms. Check resistance  between  each  lead  and  frame.  A  low  re- sistance shows that the stator is shorted. g.  Testing  Exciter  Rotor.  Perform  winding  resis- tance test and high  potential test per MIL-STD-705A, methods  401.1  and  302.1.  Test  between  T₁-T₂, T₂- T₃, T₁T₃.  See  figure  8-2  for  location  of  test  points. Resistance for each winding should be 0.677 ohms ± 0.067  ohms.  Also  test  for  shorts  between  windings and between each winding and rotor  core. h. Testing Generator Stator. (1) High Potential Test. Test generator stator as given  in  paragraph   8-2e   of   this   manual.   Replace stator  having  faulty  insulation. (2)  Winding  Resistance  Test.  Perform  winding  re- sistance test using a Kelvin bridge. Follow the manu- facturer’s  instructions  given  on  the  bridge.  Resis- tance readings should be made on the pins of P9 and P10  (see  figure  8-3).  Resistance  between  lead  pairs T₁- T₄,   T₂- T₅,   T₃- T₆,   T₇- T₁₀,   T₈- T₁₁  and   T₉^-- T₁₂ should be 0.355  ± 0.036 ohms at 77°F (25°C). Refer to the table in figure 8-3 for location of the terminals. Also check resistance between each pin A through F of P9 and P10 and the stator frame. Low resistance indicates a shorted stator. i. Testing Generator Rotor. (1) High Potential Test. Test generator rotor as given in paragraph 8- 2e of this manual. Replace  rotor having faulty insulation. (2)  Winding  Resistance  Test.  Perform  winding resistance test using a Wheatstone bridge. Follow the manufacturer’s instructions given on the bridge. Re- sistance  reading  should  be  3.31  ohms  ±0.33  ohms. Check  resistance  between  each  lead  and  frame.  A  low resistance  indicates  that  the  rotor  is  shorted,  a  high resistance  indicates  open  winding. j.  Reassembly. (1) Install diodes (42 and 43, figure 8-1) on heat sink and secure with lockwashers (41) and nuts (40). (2) Assemble shaft collar (34), bearing retainer (33), bearing (32) to the generator shaft using screw (29), lockwasher (30) and flatwasher (31). (3) Place rotor assembly into stator (53). (4) Position fan (28) in housing (53). 8 - 4 Change 3