Watts PWR4021 - Manual (Page 12)

12
Motor Troubleshooting Chart
PRoblem Possible cause coRRective action
Motor fails to start Blown fuses Replace fuses with proper type and rating
Overload trips Check and rest overload in starter.
Improper power supply Check to see that power supplied agrees with motor nameplate and load factor.
Open circuit in winding or control switch Indicated by humming sound when switch is closed.
Mechanical failure Check to see if motor and drive turn freely. Check bearing and lubrication.
Short circuited stator Indicated by blown fuses. Motor must be rewound.
Poor stator coil connection Remove end bells, locate with test lamp.
Rotor defective Look for broken bars or end ring.
Motor may be overloaded Reduce load.
Motor Stalls One phase connection Check lines for open phase.
Wrong application Change type or size. Consult manufacturer.
Overload motor Reduce load.
Low motor voltage See that nameplate voltage is maintained. Check connection.
Open circuit Fuses blown, check overload relay, stator and push buttons.
Motor runs and then dies down Power failure Check for loose connections to line, to fuses and to control.
Motor does not come up to speed Not applied properly Consult supplier for proper type.
Voltage too low at motor terminals because of line drop. Use higher voltage on transformer terminals or reduce load. Check connections. Check
conductors for proper size.
Broken rotor bars or loose rotor. Look for cracks near the rings. A new rotor may be required as repairs are usually temporary.
Motor takes too long to accelerate Open primary circuit Locate fault with testing device and repair.
Excess loading Reduce load.
Poor circuit Check for high resistance.
Defective squirrel cage rotor Replace with new rotor.
Applied voltage too low Get power company to increase power tap.
Wrong rotation Wrong sequence of phases Reverse connections at motor or at switchboard.
Motor overheats while running
under load
Overloaded Reduce load.
Frame or bracket vents may be clogged with dirt and
prevent proper ventilation of motor.
Open vent holes and check for a continuous stream of air from the motor.
Motor may have one phase open Check to make sure that all leads are well connected.
Grounded could Locate and repair.
Unbalanced terminal voltage Check for faulty leads, connections and transformers.
Motor vibrates after correcting
have been made
Motor misaligned Realign
Weak support Strengthen base.
Coupling out of balance Balance coupling.
Driven equipment unbalanced Rebalance driven equipment.
Defective ball bearing Replace bearing.
Bearing not in line Line properly.
Balancing weights shifted Rebalance motor.
Polyphase motor running single phase Check for open circuit.
Excessive end play Adjust bearing or add washer.
Unbalanced line current on
polyphase motors during normal
operation
Unequal terminal volts Check leads and connections
Single phase operation Check for open contacts
Scraping noise Fan rubbing air shield Remove interference.
Fan striking insulation Clear fan.
Loose on bedplate Tighten holding bolts.
Noisy operation Airgap not uniform Check and correct bracket fits or bearing.
Rotor unbalance Rebalance.
Hot bearings general Bent or sprung shaft Straighten or replace shaft.
Excessive belt pull Decrease belt tension.
Pulleys too far away Move pulley closer to motor bearing.
Pulley diameter too small Use larger pulleys.
Misalignment Correct by realignment of drive.
Hot bearings ball Insufficient grease Maintain proper quantity of grease in bearing.
Deterioration of grease, or lubricant contaminated Remove old grease, wash bearings thoroughly in kerosene and replace with new grease.
Excess lubricant Reduce quantity of grease: bearing should not be more than ½ filled.
Overloaded bearing Check alignment, side and end thrust.
Broken ball or rough races Replace bearing: first clean housing thoroughly.
These instructions do not cover all details or variations in equipment nor provide for every possible condition to be
met in connection with installation, operation or maintenance. Chart courtesy of Marathon Electric.