SECTION A THE WINDINGS AND THE MAIN RECTIFIER ASSEMBLY

Motor Starting - TM-55-1930-209-14P-9-4_789

Replacement of Faulty Diodes (See Fig. 11).

TM-55-1930-209-14P-9-4 Water Purification Barges (NSN 1930-01-234-2165) Electric Power System Manual
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SECTION FOUR SERVICE AND MAINTENANCE MAINTENANCE Routine servicing of the a.c. generator is confined to an insulation resistance check on the windings if the machine has not been run for a considerable length of time. Insulation Test Prior to testing the insulation to earth of the various windings, it is advisable that the A.V.R. is isolated from the windings by disconnecting the push-on terminals. The machine can then be "Meggered" without risk of damaging the control circuits. FAULT FINDING PROCEDURE Fault finding can be simplified considerably, by dividing the machine into two test sections: A. THE WINDINGS AND THE MAIN RECTIFIER ASSEMBLY B. THE ELECTRONIC CONTROL SYSTEM AND ITS WIRING SECTION A THE WINDINGS AND THE MAIN RECTIFIER ASSEMBLY Separately Exciting the Machine The a.c. generator is separately excited to give an indication of the condition of the windings and main rectifier assembly. For the frame sizes covered in this manual a 12 volt d.c. battery supply is sufficient to obtain the full output voltage within + or - 10%, at no load, with the speed correct at nominal. Fig. 2. Method of Separately Exciting the Machine The d.c. supply is connected to the exciter stator leads marked X and XX , which should be removed from the A.V.R. terminals X and XX respectively. It is also advisable to remove the rest of the push-on terminals from the A,V. R. prior to this test. With the battery connected to the stator leads, the machine is now run up to full speed (it Is essential that the speed is correct for this test), and with a multimeter or voltmeter the following tests are made on the output from" the main stator terminals. Voltage is Balanced and within 10% of the Nominal This indicates that the exciter windings, main windings and main rectifier diodes are In good working order. an: it is therefore not necessary to carry out the following tests up to and including "Main Excitation Windings". Fault; finding should continue with test "A.V.R. Sensing Supply from the Main Stator". 9

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