823031 6 Mercury SCREW

Personal injury or death can result from improper troubleshooting and repair procedures.The following troubleshooting and repair procedures should only be performed by qualified personnel familiar with this equipment.
If the generator is not placed into operation immediately, the generator must be protected against moisture, dirt, and high temperatures. The protection of the generator will avoid undesirable problems with the insulation integrity and resistance.The resistance of the insulation of the windings must be measured before the generator is put into operation.If the environment for generator storage is humid, the resistance of the insulation of the windings must be measured periodically during storage. There is difficultly in determining the appropriate values of insulation resistance of a generator. The reading will vary with environmental conditions such as temperature and humidity. Dust, oil, grease, and dirt will affect the condition of generator insulation resistance as well as the quality and condition of the insulating material used. Periodic monitoring records are useful to conclude whether the motor is able to operate.Note: The insulation resistance must be measured using a megohm meter.Preparation for Insulation Testing
Verify that the generator frame is grounded to earth via a low impedance path that is less than 25 ohms.
Install a barrier around the work area to limit access to only the qualified personnel essential to conducting the test.
Perform the following steps before making test instrument connections and measuring the resistance of the insulation for windings:
Ensure that the generator has stopped
Ensure that all sources of power are switched off and that the unit is electrically isolated
Ensure that the generator is de-energized
Ensure that the generator is disconnected from the load
Use proper methods to prohibit the windings from becoming energized while making connections and conducting tests.
Use safe work practices to discharge the generator windings. Discharging is accomplished by connecting the winding to the generator frame. Verify that the winding to be tested has been discharged.
Isolate the windings that are to be tested from the remainder of the generator set. Isolating the windings includes disconnecting necessary components such as the following:
Voltage regulator
EMCP
Neutral to ground bonding conductor (if equipped)
The load share module (if equipped)
Power transformers (if equipped)
Temperature of the winding has been measured
All temperature sensors are groundedNote: Make sure that all windings that are not being tested, are appropriately grounded to the generator frame. For example, if a winding in the main stator is to be checked, then all of the following must be grounded to the generator stator frame:
Main rotor
Exciter rotor
Exciter stator
Auxiliary winding
Other componentsTherefore, only the main stator winding that is being tested should NOT be grounded.
Test the winding insulation.
Ensure that there is no residual power in the windings. Immediately following testing, the winding must be discharged manually or automatically with the test instrument.
Repeat Step 8 for each winding.
The generator can be reassembled after all of the windings have been tested and discharged.
Restore the unit to normal operating condition and remove the barrier.Measurement of the Stator Windings
The test voltage used for the stator windings of the generator must be what is shown in Table 1. The voltages used are in accordance with Standard IEEE43.
Table 1
Winding nominal voltage (V)    Insulation resistance test voltage (V)    
Less than 1000     500    
1000 - 2500     500 -1000    
2501 - 5000     1000 - 2500    
5001 - 12000     2500 - 5000    
Greater than 12000     5000 - 10000    The measurement of the insulation resistance of the stator windings must be made in the main terminal box. The meter (megohm meter) must be connected between the frame of the alternator and the winding. The frame must be grounded and all three phases of the stator winding must remain connected to the neutral point. Refer to Illustration 1.
Illustration 1 g03774134
Measuring all three phases (1) Generator frame (2) Stator windings (3) Megohm meter (4) Neutral connectionWhenever possible, each phase must be insulated and tested separately. The separate test allows the comparison between the phases. When a phase is tested, the other two phases must be tied to the same ground point of the frame. Refer to Illustration 2.
Illustration 2 g03774165
Measuring individual phases (6) Generator frame (7) Stator winding being tested (8) Megohm meter (9) Grounded windings (10) Neutral connectionResistance Check for Rotor, Exciter, and Accessories
Measurement of the Main Rotor Winding
Use the following steps to measure the rotor windings.
Illustration 3 g03774475
(15) Exciter stator (16) Exciter rotor (17) Diode connections (18) Diodes
Illustration 4 g03774508
(19) Rotor cables to be disconnected
Disconnect the rotor cables (19) from the set of diodes (18) on the exciter rotor (16) .
Connect the megohm meter between the rotor winding and the shaft of the alternator.Note: