Polyphase AC Induction Motor …

1 Properly installed and maintained Lincoln Electricpolyphase AC Induction motors operated within thenameplate ratings will run trouble-free for many and premature failures often indicate inputpower system troubles, poor or deteriorating mechanicalinstallations, or malfunctions in the driven , Motor troubleshooting involves the entiresystem, not just the AC Induction MotorTROUBLESHOOTING GUIDED5T Application DataTroubleshooting GuideWARNINGA llow only qualified personnel to perform troubleshootingand maintenance of motors. Be sure such techniciansobserve standard safety precautions including those in thisTroubleshooting Guide. 2 Steps for EffectiveTroubleshooting Determine answers for the following questions:a. What are the troubles and when did theyfirst occur?b. If new, did the installation ever run properly?How long?c. If an established installation, is the trouble new or has it been occurring for years?What changes, even if minor, occurred inin the operation or maintenance of theequipment before the trouble started?

2 D. Do you have accurate meter readings ofcurrent and voltage for all three phases ofthe input circuit? Such readings are neededto correctly determine the cause of mostelectrical to Troubles and CuresSection 1: Motor VISIBLY BURNED OUTT rouble 1: Motor burned out Page 5 Section 2: STARTING TROUBLEST rouble 2: Motor won t start (No hum or heating) Page 6 Trouble 3: Motor won t start (Just hums and heats up) Page 6 Trouble 4: Overload relays trip during starting Page 6 Trouble 5: Motor starts but comes up to speed slowly Page 7 Section 3: TROUBLES WHILE RUNNINGT rouble 6: Motor frame hot to the touch Page 7 Trouble 7: Motor overheats or overload relays trip Page 8 Trouble 8: Thru bolts feel hot Page 8 Trouble 9: Motor runs but appreciably below nameplate speed Page 9 Trouble 10.

3 Excessive electrical noise or clatter under load Page 9 Section 4: EXCESSIVE NOISE OR VIBRATION,PHYSICAL DAMAGE, OR BAD BEARINGST rouble 11: Excessive vibration and/or mechanical noise Page 9 Trouble 12: Noisy bearings Page 10 Section 5: INPUT POWER AND INPUT CIRCUITTROUBLEST rouble 13: High input current in all three phases Page 12 Trouble 14: Unbalanced input current Page 12 Trouble 15: Excessive voltage drop Page 13 Troubles VS1-VS5: Page 14 Trouble BM1: Brake overheats Page 15 Trouble BM2: Coil has failed Page 16 Trouble BM3: Brake is noisy during stopping Page 16 Section 1: Motor VISIBLY BURNED OUTS ection 2: TROUBLES WHILE STARTINGS ection 3: TROUBLES WHILE RUNNINGS ection 4: EXCESSIVE NOISE OR VIBRATION, PHYSICAL DAMAGE, OR BAD BEARINGSS ection 5: INPUT POWER AND INPUT CIRCUIT TROUBLESA pplication DataTroubleshooting GuideD5T Section 6: AC MOTORS USED WITH VARIABLE SPEED DRIVESWARNINGHIGH VOLTAGE can kill.

4 Internal parts of the Motor may be atline potential even when it is not rotating. When troubleshooting requires thatmeasurements be taken with the inputpower on, the input power should be turnedon only when necessary and extreme cautionshould be taken to avoid electric shock. Isolate your body from ground and donot touch electrically hot dry insulating gloves. Disconnect all input power to the drive andmotor before performing any 7: BRAKE MOTORS WARNINGMOVING PARTS can injure. Do not operate the Motor at speedsabove the Motor maximum safe speed. Operating the Motor above maximumsafe speed may cause parts to be ejectedresulting in bodily injury. All Motor driven components must bedesigned by the machine builder tooperate safely at the Motor maximumsafe speed listed on the a Motor fails to run properly when first installed, ALWAYS check the connection arrangement of the Motor leads and theinput power lines.

5 The connections must be made in conformance with either the across-the-line start diagrams on the motornameplate or the reduced voltage start diagrams available from the Motor manufacturer. If the connection arrangement iscorrect, proceed to identify the trouble using this Troubleshooting motors are suitable for full voltage or across-the-line start. See the Motor nameplate for proper connection standardLincoln Electric motors are also capable of PWS, YDS or both as indicated in the following RatingsVoltageConnectionLeadsPWSYDS56 - 256T1/2 - 25 230/460Y9 NoNo3600284T - 405T30 - 150 230/460 12 NoYes444T - 445T125 - 250 460 6 NoYes56 - 256T1/3 - 20 230/460Y9 NoNo1800284T - 405T25 - 125 230/460 12 NoYes444T - 445T125 - 250 460 12 YesYes447T - 449T250 - 300 460 6 NoYes56 - 256T1/2 - 10 230/460Y9 NoNo284T - 286T15 - 20 230/460 12 NoYes1200324T - 365T25 - 50 230/460 12 YesYes(lower voltage only)404T - 405T60 - 75 230/460 12 NoYes444T - 445T100 - 150 460 12 YesYes900143T - 256T1/2 - 7-1/2 230/460Y9 NoNoNEW INSTALLATIONSD5T Application DataTroubleshooting Guide 4 REDUCED VOLTAGE START CONNECTION DIAGRAMSA pplication DataTroubleshooting GuideD5T HP _____ RPM _____ FRAME _____VOLTS _____ PHASE ____ HERTZ _____AMPS _____ TIME RATING _____CAN BE USED ON208V SYSTEM UP TO _____ AMPSMAY NOT MEET ALL NEMA PERFORMANCELIMITS ON 208V SYSTEMSERVICEMAXINS _____ FACTOR_____AMB _____OCNEMA CODE ____ NEMA DESIGN ____ TEMP RISE ____SERIAL_____TF_____THE LINCOLN ELECTRIC CO.

6 CLEVELAND, OHIO, 5 LE CODE:(Lincoln Electric Code)Completely describes the Motor forLincoln Electric. Have this numberready when talking with a 1: Motor VISIBLY BURNED OUTT rouble 1: Motor burned out(Indicated by burning odor or smoke before the Motor stopped, and/or bubbled or burned paint.)Cause 1a:Input power troubles, startingtroubles, troubles while running, or excessivenoise or vibration, physical damage to themotor, or bad 1a:Install a new Motor . ALWAYS determine the cause of the Motor s failure, starting with Section 5, pages 12 and 13,or the replacement Motor may also fail before it delivers a fulllife Application DataTroubleshooting GuideLOW VOLTAGE LINEHIGH VOLTAGE LINETEFC ENERGY EFFICIENTTOTALLY QUALIFIED AS ODP REPLACEMENTC onnection Diagrams:shown for across-the-line(full voltage) :Nominal winding voltagerating. Power system voltage mustbe within 10%.Amps:Current draw perphase at the Motor s Factor:Continuousoverload capacity of Motor ;ie: 50 HP x = draw at service factorload would approximate theamps listed times Number:Uniquenumber identifies when themotor was Code:Indicates the Motor s startingKVA code letter which can be used to approximatestarting or locked rotor current draw which istypically 5 to 6 times the rated horsepower DATA IMPORTANT TO TROUBLESHOOTING 6 Trouble 2: Motor will not start(No hum or heating.)

7 NOTE:Reset the overload relays, if tripped. Read Causes 2a through 2e. Then try to restart the Motor , and look for theconditions 3: Motor will not start(Just hums and heats up.)NOTE: Immediately shut off the power to prevent a Motor burnout. The overload relays may 4: Overload relays trip during startingCause 3a:Input circuit single phased (Novoltage in one or two phases; could havebeen a temporary condition).Cause 3b: Motor was single phased asindicated by heat damage to one or twophases of the Motor windings. Cause 3c: Motor rotor, bearings, or driven load is 3a:Have a qualified technician check for the proper voltage inall three phases. If a single phase condition exists, correct the 3b:Replace the Motor . ALWAYS have an expert check themotor windings to determine whether the single phasing occurred inthe input circuit or in the Motor windings. If in the input circuit, correctthe single phase 3c:Disconnect the Motor from the driven load.

8 If the motorshaft turns freely, the trouble is in the load. Replace the Motor oradjust the driven load as 4a:Overload relays 4b: Motor takes too long to 4a:Use the relay size specified by the National Electric Code(NEC) for the Motor nameplate current and service 4b:See Trouble 5, page 2a:Replace the defective 2b:See Trouble 3, page 2c:See Trouble 5, page 2d:Check the voltage in all three phases at the motorconnections. If there is no input voltage, locate and correct theproblem in the input circuit. If the voltage is okay, replace the determine why the Motor failed, starting with Section 5,pages 12 and 13, or the replacement Motor may also fail before itdelivers a full life 2e:ALWAYS determine why the overload relays tripped, starting with Section 5, pages 12 and 13, or the problem may sure to use the overload relay size specified by the NationalElectrical Code (NEC) for the Motor nameplate current and 2: TROUBLES WHILE STARTINGA pplication DataTroubleshooting GuideD5T Cause 2a:The Motor controller will 2b:The Motor hums and heatsbut does not start.

9 Immediately turn offthe 2c:The Motor starts but comesup to speed too slowly. Immediately turnoff the 2d:The Motor does not startand does not hum or heat up. Cause 2e:The Motor operates properly. 7 Trouble 5: Motor starts but comes up to speed slowly(10 or more seconds for small motors, 56-286T; 12 or more seconds for medium size motors, 324T-326T; 15 or more seconds for large motors, 364T-449T may cause the overload relays to trip.)Cause 6a:The heat may be normal or asign of overheating, depending on the Motor sventilation system design. For example:a. The frame of Lincoln extruded aluminumframe motors transfers heat from thewindings and laminations to the externalair. The frame normally gets too hot totouch. b. The frame of Lincoln steel frame TEFC motors allow internal cooling air topassbetween the frame and the frame remains relatively 6a:If overheating is suspected, go to Trouble 7, page TEFC Surface Temperatures (1)Temperatures were calculated for motors operating at full load and40 C ambient.

10 (2)Surface temperature between 5a:Excessive voltage drop(running voltage more than 2-3% belowline voltage).Cause 5b:Excessive starting load(running voltage no more than 2-3% belowline voltage).Cause 5c:Inadequate Motor startingtorque when using a reduced voltage starting(RVS) system. RVS systems lower motorstarting torque as follows:YDS about 33% of full voltage starting torquePWS about 50% of full voltage starting torqueAuto Transformer starting 25 to 64%of full voltage starting torque dependingon the selected transformer tap Cause 5d:Improper connections of motorleads to supply 5a:See Trouble 15, page 5b:Reduce the starting load or install a larger 5c:Three possible cures include: 1. Reduce the starting load or use a larger Use a starting system which develops higher starting Reduce the time delay between the 1st and 2nd stepson the 5d:Correct Temperature(1)Frame MaterialHPRPM C FExtruded5180065(2)150(2)Aluminum1018007 0(2)158(2)25180040 - 45105 - 115 Steel50180040 - 45105 - 115100180040 - 45105 - 115 Section 3: TROUBLES WHILE RUNNINGT rouble 6: Motor frame hot to the touchSection 2: TROUBLES WHILE STARTINGD5T Application DataTroubleshooting Guide 8 Trouble 7: Motor overheats or overload relays tripBefore considering Causes 7a through 7f, proceed as follows:Step 1: Look at the Motor .