TL;DR
Intermittent stops or restarts almost always come from loose electrical connections or a worn contactor. Check the contactor first, then torque-test the conduit box terminals.
What you might see
- motor randomly stops and restarts
- intermittent overload trips
- starter chatter
- warm or discolored connector lugs
Likely causes
Loose connection in the conduit box, contactor, or upstream junction box
Worn contactor main contacts arcing under load
Failing overload relay
Sticky control circuit, relay coil, push-button, or interlock
Required tools
- Torque screwdriver or wrench
- LOTO kit
- Multimeter (continuity setting)
- Insulated screwdrivers
- Cleaning brush
- Replacement contactor (if needed)
Safety first
- Never tighten energized connections. Always lock out before touching electrical terminals.
- Worn contactors arc visibly when reclosing. If you hear chatter or see flashes, do not run the motor.
Procedure
- 1
Lock out and tag out the disconnect. Verify zero voltage.
- 2
Open the conduit box and inspect each lead connection for discoloration, looseness, or arcing damage. Discoloration is the strongest visual indicator of a chronic loose connection.
- 3
Torque each terminal lug to the value on the Baldor wiring diagram. Typical values are 35-45 in-lb for #4 AWG copper.[1]
- 4
Open the contactor enclosure and inspect the main contacts. Pitted, welded, or visibly worn contacts need replacement, do not file them.
- 5
Press the test button on the overload relay. It should trip and reset cleanly. Replace the overload if it sticks.
- 6
Trace the control circuit from start button through any interlocks, relay coils, and pilot devices. Check each pilot device for clean contact closure.
- 7
After repairs, run a heat-rise test under load. Re-check all connections after 30 minutes, chronic loose connections will warm visibly.
Sources
Baldor Reliance Industrial Motor Maintenance Manual, Baldor Electric Company (ABB)
Baldor Industrial Motor Maintenance Manual, terminal torque specifications (general)
View source
More guides for Baldor Super-E (EM/EJMM)
How to diagnose bearing noise and vibration on a Baldor Super-E motor
Vibration is most often a worn bearing. Listen for grinding, log a vibration reading, and plan a bearing replacement during the next planned outage.
How to fix a Baldor Super-E motor making noise from coupling misalignment
Misalignment between the motor and the driven equipment creates a knocking or rumbling noise. Check soft foot first, then measure parallel and angular alignment with a dial indicator or laser tool.
How to fix overheating and excessive current draw on a Baldor Super-E motor
Overheating with high current is usually mechanical overload or supply phase imbalance. Measure phase currents, check the load, and verify supply voltage balance is within 1%.
How to fix reduced speed on a Baldor Super-E motor running on a VFD
If the motor runs below the commanded speed, check the VFD's frequency reference, slip compensation, and supply voltage. Mechanical load increase can also drag speed down.
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