Usage:
3406 (8NS) Engine-Generators
Introduction
This Special Instruction provides the necessary information required to convert the following Frame Generators from Self Excited (SE) to Permanent Magent (PM).
Reference: Service Manual Module, SENR5359, "SR4B Generator".
Reference: Service Manual Module, SENR4794, "Connection Diagrams: SR4 & SR4B Generators, Voltage Regulators, Options".
System Components
The following components already exist on the SE generator, and are re-used when converting to PM:
Exciter Stator: The exciter stator together with the exciter rotor provides DC current to the main field. The stator is located in the same position on the PM and SE generators covered by this instruction. It is bolted to the outboard edge of the bearing bracket.
Exciter Rotor: The exciter rotor together with the exciter stator and rectifier block provides DC current to the main field. The rotor is located in the same position on the rotor shaft for both the PM and SE generators covered by this instruction.
Rectifier Block: The one-piece 6-diode bridge rectifier circuit receives three-phase AC from the exciter rotor and converts (rectifies) this power into DC. The DC power is then routed to the main field. The rectifier is bolted to a powder metal washer on the end of the rotor shaft by two screws.
The following components are the major parts of the new 142-6021 Conversion Group-Generator kit to convert from SE to PM:
Pilot Exciter Stator: The pilot exciter stator together with the pilot exciter rotor provide AC power for the voltage regulator. The regulator rectifies the AC power to DC and a controlled amount is fed to the main exciter. The stator is bolted to the bearing bracket.
Pilot Exciter Rotor: The permanent magnet pilot exciter (rotor) together with the pilot exciter stator provide AC power for the voltage regulator. The regulator rectifies the AC power to DC and a controlled amount is fed to the main exciter. The PM rotor is keyed to the rotor shaft and is held in place by a spacer.
NOTE: A new 114-5510 PM Voltage Regulator is also required for this conversion.
Procedure for Removing SE Components
Typical Generator Set showing side (1) and rear access panels (2)
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Before working inside the generator, make sure that the starter motor can not be activated by any automatic or manual signal. |
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1. Remove the side and rear access panels from the generator
2. Disconnect exciter wires F1 and F2 from their termination point on the voltage regulator. Pull the wires from the harness bundles and place them near the exciter field (stator). Note the location of the F1 and F2 leads on the exciter stator for re-installation.
Diode rectifier block & attached heatsink, showing proper lead-terminal attachments.
3. Disconnect the leads from the rectifier bridge, making note of the terminals they are attached to for reference during re-installation.
4. Remove the rectifier bridge and attached heatsink by removing the two #10-32 allen screws. Set aside for later re-installation.
5. Remove exciter cover assembly (3) by removing four 5/16 bolts (4). These bolts also attach the exciter stator to the bracket. Set aside for later re-installation.
6. The exciter stator (5) is now unbolted but still held on by the four slotted arms of the bracket. Remove by pulling or gently tapping the stator iron. Set aside for later re-installation.
Exciter Rotor and Powder Metal Washer (Exciter Stator has been removed).
7. Remove the powder metal washer (6) by removing the four 5/16-18 bolts (7). Carefully pass the generator leads through the openings in the washer while removing the washer. Remove the exciter rotor, and set all parts aside for later re-installation.
8. Remove the spacer by carefully sliding it off the rotor shaft, ensuring that it clears the exciter leads. This part in not re-used in the conversion.
Procedure for Installing PM Components
The components required to making the conversion come (unassembled) in the 142-6021 Generator Conversion Group as shown in the illustration and parts list:
142-6021 Generator Conversion Group:
NOTE: When performing the following installation procedure, all re-used bolts must be wire-brushed to remove any cured Loctite residue. All tapped holes must be blown out with pressure air to remove any debris. All bolts (except those for electrical connections) must be coated with 9C-3263 Thread Lock or 4C-4030 Thread Lock (Loctite #242) before reassembly.
PM Pilot Exciter shown installed.
1. Install the new 110-4874 PM Rotor (11) by sliding it on to the main rotor shaft. The rotor has a built-in key which slides in the keyway machined into the shaft. Be sure the bolt heads on the side of the rotor are facing the bearing bracket, with the nuts facing to the rear of the generator.
2. Install the new 110-4875 PM Stator (8) by bolting it to the bearing bracket using four 1B-2713 Bolts (1/4-20) and washers (9). Tighten the new bolts (10) to a torque of 6 ft lb (8 N·m) minimum, 12 ft lb (16 N·m) maximum. Be sure the lead wires are facing to the rear of the generator, and at the 12 o'clock position.
3. Slide the new 112-9430 Spacer (12) on the main rotor shaft.
Exciter Rotor and Powder Metal Washer shown installed.
Powder Metal Washer tightening sequence #1. #3. #2. #4.
4. Slide the Exciter Rotor (13) on to the rotor shaft and tap the key back in to be flush with the iron on the core of the rotor. Retain the rotor on the shaft by re-installing the Powder Metal Washer (14) using four bolts (5/16-18) and washers (15). Use care when threading the revolving field leads through the slots in the washer. Tighten the bolts to a torque of 13 ft lb (18 N·m) minimum, 23 ft lb (31 N·m) maximum using the sequence in the illustration.
Rectifier block and heat sink shown installed
5. Reinstall the rectifier block (16) and the attached heat sink using two screws (#10-32). Tighten the screws (17) to a torque of 21 ln lb (2.4 N·m) minimum, 23 ln lb (2.6 N·m) maximum. Do not over-torque the rectifier block. Re-connect the wire leads to the proper terminals, as noted during disassembly.
6. Reinstall the exciter stator by lining up the bolt holes with the four tapped holes of the bracket-it will be a very tight fit. Match up the bolt holes in the shroud with those of the stator and fasten both to the bracket with the four bolts (5/16-18) removed during disassembly. Tighten the bolts to a torque of 13 ft lb (18 N·m) minimum, 23 ft lb (31 N·m) maximum.
7. Remove the former SE voltage regulator and install the new 114-5510 PM voltage regulator, re-connecting all wires to their corresponding numbered terminals. The green ground wire is screwed to the terminal on the back of the voltage regulator. The PM Stator wires 11, 12, and 13 are connected to the voltage regulator terminals 26, 28, and 30, respectively. Refer to the following connection diagram when installing the new voltage regulator.
Permanent Magnet Excited Generator Connection Diagram
