Troubleshoot AC Motors – Part 2

Posted 3/15/2004

Problem B – Motor runs noisy

B1: Are vibrations and noise from driven machine or power transmission system being transmitted to motor? Locate source of noise and reduce. Isolate motor with belt drive or elastomeric coupling.
B2: Is a hollow motor foundation acting as a sounding board? Redesign mounting. Coat foundation underside with sound dampening material.
B3: Check motor mounting. Is it loose? Tighten. Be sure shaft is aligned.
B4: Is motor mounting even and shaft properly aligned? Shim feet for even mounting and align shaft.
B5: Is fan hitting or rubbing on stationary part or is object caught in fan housing? Repair damaged fan, end bell or part causing contact. Remove trash from fan housing.
B6: Is air gap nonuniform or rotor rubbing on stator? Recenter rotor rubbing on worn bearings or relocate pedestal bearings.
B7: Listen to bearings. Are they noisy? Lubricate bearings. If still noisy, replace.
B8: Is voltage between phases (three-phase motors) unbalanced? Balance voltages.
B9: Is three-phase motor operating on one-phase? (Won’t start on single-phase.) Restore power on three-phases.