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November, 1938 Cutler-Hammer PIONEER MANUFACTURERS OF ELECTRIC CONTROL APPARATUS . M IL W A U K E E . WIS.. P R IN T E D IN U . S . A . J PUBLICATION NO. 5753 INSTRUCTION SHEET— Bulletin 9141 Auto-Transformer Type Starters DESCRIPTION These auto-transformer starters consist of two essential parts, an auto-transformer assembly and a manually operated oil-immersed switch mechanism. An auto-transformer connected in Open delta is used. See Fig. 3. Taps are provided on the auto-transformer coils to provide various starting voltages. OPERATION Befprp attempting to operate this device) make sure that all connections have been properly made. See. that the oil pan is filled to the proper level as in­dicated" by the raised lettering on the front of the pan. Use only the °il supplied for this purpose". Fig. 1- To start—pull lever forward Starting: To start the motor, pull the lever forward to the starting posi­tion. See Fig. 1., Hold it in this position until the motor comes up to speed. This should not take longer than fifteen or twenty seconds. Then throw it quickly into the running position, see Fig. 2, Where it will be held by the low-voltage latch. Make the transition from starting to running position quickly, with a firm positive thrust on the lever. If this is not done, the lever will be latched in the “ off” position and it will be necessary to make another start. Do not try to throw the lever directly into the running position as this is. pre­vented by the use of a suitable inter­lock. Auto-transformer starters are ship­ped with connections made to the 65% tap for average starting conditions. On 50 hp and smaller controllers 65% and 80% taps are provided. Above 50 hp a 50% tap is provided in addition to the 65% and 80% taps. All of the taps pro­vide the given percentage of full line voltage on starting. Since the start­ing torque is proportional to the square of the voltage the torque obtained on the various taps compared to that obtained on full voltage starting will be: 80% tap — .64; 65% tap = .42; .50% tap =||.25. These figures also indicate the relative amount of torque obtained on the various taps. For example on the 80% tap the starting torque will be .64/.25 = 2.57 times that ob­tained on the 50% tap. If the motor starts too quickly, that is in less then five seconds, change the transformer connections to the 50 per cent tap. On the other hand, if the motor does not start witmn fifteen or possibly twenty seconds, change the connections to the 80 per Cent tap. The various taps are plainly tagged and can readily be distinguished. Fig. 2—When motor is up to speed push lever quickly back as far as it will go. Stopping: To stop the motor it is only necessary to press the stop button in the cover. This releases the low voltage latch and allows the switch to return to the “ off” position. The motor can also be stopped by operating any of the pushbuttons, if these are used. An adjustable thermal overload relay giving inverse time limit overload protection is provided. See Publication 1759 for instruc­tions on this relay. Transformer Coil: Due to the simple assembly of the transformer, the replacement of coils, if ever required, is greatly facilitated. It is only necessary to remove the clamping bracket and remove the coil and the core upon which it is wound. CARE Keep Oil Pan Filled: The oil pan should be kept filled to the level indicated. At regular intervals drain off the sediment which collects in the oil and replenish with fresh oil. Intervals at which this is necessary depends a great deal on the service and location of the starter. Under severe service conditions, the oil will carbonize more rapidly and if located in damp places will in time absorb quantities of moisture. The oil furnished has all the properties necessary to insure cor­rect and prolonged operation of the starter. Special means are used to make the oil perfectly dry. When a new supply is needed, it can be purchased from Cutler-Hammer Inc., Milwaukee, Wis. (See Item 42) Keep Contacts in Good Condition: The movable copper contacts should be smoothed off occasionally with a fine file. When worn badly on one end, they should be turned around, but not over, and the other edge used to break the cur­rent. Contacts should be. renewed when worn to about one-third of the original thickness. The stationary contact fingers have a long life and seldom have to be renewed- However, they should not be neglected and when badly worn the tips should be re­newed. - Contact Finger Adjustm ent: The fingers are adjusted at the factory to have the proper wipe. When necessary to readjust the fingers because of wear, the follow­ing procedure is recommended SpS-Have the finger make contact with the segment as shown in Figure 4. Turn the adjusting screw “ A ” to the right until contact “ B ” just begins to leave the segment “ C” . Now turning adjusting screw one full revolution to the left. The clamping spring “ D ” will secure the adjusting screw into position. Low-Voltage Release: An occasional drop of oil on the moving parts of the low-voltage release will help to keep it in good operating condition. The bearings of the operating lever should be oiled to insure easy operation. SEE THE FOLLOWING PAGES FOR RENEWAL PARTS LIST Supersedes Pub. No. 577 Made in U. S. A. PAGE 1