Document wJxzBn7Eq0Kk94p4Vy8N2ZYJ

PLANT PROBLEMS p other guy we his headaches .mil MICKS, AiioeW* Milof 2*r' _ _____ -- n n <-- 3 When tnstoRfop the brush**, meVo sure they can movo free ly In the holders. But watch out (o< excessive side ploy Here Is (he Question THE PACTS FUOM JUNE HOWElli Commutator on 25-hp 6-pole 70-rpm dc shunt-wound elevator motor lies six equally distributed bum spots, (urretponiHaf to (be brush spacing. &Bh burn covers an area of four commutator bars, and begim to appear a few days after the commutator la resurfoeed. We'*e hud this trouble since we replaced a lew colls several years go. Believing the toll* caused It, l chreWid them repcsicdly with* out results. When elevator ascends, no sparks occur, but slight sparking ap pears when it doscends, There is somewhat more sparking during starting and stopping. We have several other machines, and though they tpnrk there are no burns. Ilow can we cure this iroableT--f/V TOPNOTCH commutation, brushes^ must be correctly installed. Photos, J above, show procedure that works < most of my jobs. Before inserting your"? new brushes, be sure inside of holder* a/e smooth. It rough, sand with e f piece of fine sandpaper glued to a A*1 A piece of wood. A Make sure shunts arc properly so { cured to the brushes and holders. H ' connectlona of the shunt* ate detectire, ; current will flow from tides of bruehes ' PUNT OKUUON AND MAIHItNANCt SECVOH gtfthe holders and eaute side-burning, g&j>avoverheollng and poor brush oper* ^Oon'i have brushes so loose in holders Jhst'there is appreciable tide ploy. Al^jyjeoough clearance lor brushes to impend without sticking at their operatN.temperaiuie. inPii'hruthts to commutator, one at a * strip of sandpaper, first coarse grade, and then o fine jW,; with ihe sotid aide turned to the Jwyib iac* Thoroughly clean brushes J^d holders belore running motor. Adj|j|pensii>n springs to about 2 p*i to hold brushes on motor commutator. Second set of photoj, above, shows how you stone a commutator that is burned, grooved or roughened from parking or abrasive action. Stoning often saves removing the armature and turning commutator in a lathe. When stoning, lilt *U brushes away from commutator. Use an external power source to tom motor. Be sure to remove all traces of oil or grease from commutator betoie stoning. Work the hand stone hack and forth several rimes to insure a smooth, true surface. Move tteady.rcit stone across surface severaf times to avoid tapering commutator from stone wear. After stoning, smooth commutator with 2/0 or 9/D sandpaper, then polish with hack of paper. Be sure commutator and armature are clean before starting the motor. Remove ell traces of copper, carbon and abrasive dust with a vac uum cleaner. Jim Spmmh Spokane, Path. TBUI COMMUTATOR, without high or low bars and correct mica clearance, will spark if coil feeds run to wrong (Continued on page 132) in im, n*Hl OfMMlOH AND MAINTENANCE SECTION