Figure 19 - Rotor Coil Resistance Test

TM-5-3820-256-24-4 Drilling System Well Rotary Truck Mounted Air Transportable 600 Feet Capacity Model LP-12 NSN 3820-01-246-4276 Manual
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HEAVY DUTY ALTERNATORS 2. Check rotor coil resistance by connecting the ohmmeter across the two slip rings (See Figure 19). The resistance of the rotor should be within the following limits: 2312JB 4.9-5.5 Ohms 2512JB 2.3-2.7 Ohms 2612JB 2.3-2.7 Ohms 2812JB 1.9-2.3 Ohms 2912JB 1.9-2.3 Ohms Figure 19 - Rotor Coil Resistance Test. Discard rotors whose resistance values differ significantly from these figures. Before condemning a rotor for an open coil, check the solder joints at the slip ring leads, as a poor connection at either of these leads will test the same as an open coil. If the proper resistance is not obtained after resoldering these connections, discard the rotor. STATOR TEST Use a Wheatstone Bridge or an ohmmeter capable of measuring 1/1000 ohm to check stator for grounds and for phase resistance. Stator is OK when no circuit is present between lamination and each of the three leads, and resistance readings across each phase are approximately the same. It is suggested that stators be "high pot" tested by a qualified electrical shop to help identify borderline stators: Stator must be disconnected from alternator to perform these tests (See Figure 20). Defective stators or ones with damaged or charred windings must be discarded regardless of how they test. Several stators are available which can be used as service replacements on these alternators. The part numbers of these stators will be listed in the appropriate parts list. SLIP RING REPLACEMENT The slip ring assembly used in these alternators is of extremely sturdy construction and will seldom require replacement. If it should become damaged in some way, such as dropping the rotor, it may be replaced in the following manner. Figure 20 - Stator Test. 1. Unsolder the slip ring leads and lift them clear of the eyelets which serve to retain them to the rotor coil leads. Do not lose or damage the eyelets (See Figure 21). Figure 21 - Disconnecting Slip Ring Leads. 2. With a suitable puller, the slip ring assembly may now be pulled from the shaft (See Figure 22). CTS-4043A - Chapter II - Page 9

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