Motor Troubleshooting Decision Tree

This workflow is intentionally simple. It helps route the review, not replace the drive manual or fault-history tools. Always confirm the machine is safe to inspect and test before starting.

Practical sequence — always start here

Use this order before diving into fault codes:

Confirm the machine is safe to inspect and test
Check mechanical freedom and obvious damage first
Check supply, protection, and wiring next
Review configuration and parameter data after hardware basics are known good
Use OEM fault history and scoped measurements only after the basic chain is verified

Motor will not start

Work through this chain in order:

Check	What to look for
Input power present?	Measure voltage at drive or starter input
Device healthy and powered?	No fault indication, ready state
Start command actually present?	Verify at the control input, not just at the HMI
Permissive or safety function blocking?	E-stop, door interlock, safety relay — confirm all are satisfied
Motor or cable open/shorted/disconnected?	Check motor resistance and cable continuity
Mechanical load jammed?	Try rotating the shaft by hand under zero-power conditions

Do not assume software or parameter problems until the mechanical and electrical basics are confirmed clear.

Overcurrent or immediate trip

Review in this order:

Symptom / Cause	Check
Mechanical jam or high load	Shaft free to rotate? Load removed for test?
Acceleration time too aggressive	Increase ramp time in drive parameters
Incorrect motor data in drive	FLA, voltage, frequency entered correctly?
Motor cable fault	Phase-to-phase or phase-to-ground resistance
Wrong supply or connection	Delta vs. wye, supply voltage matches nameplate
Drive hardware fault	Exclude load causes first; then suspect hardware

Overheating or nuisance overload

Determine whether the problem is primarily electrical or thermal:

Electrical causes	Thermal causes
Overload setting based on wrong FLA	Cooling reduced at low speed (VFD application)
Wrong voltage or connection arrangement	Ambient temperature or enclosure heat too high
Repetitive starts without sufficient cooling time	Motor running significantly above rated load
Long acceleration time heating the windings	High service factor consumed by process demand

Wrong speed, poor torque, or unstable running

Symptom	Review
Wrong speed	Commanded frequency or speed reference value
Poor torque	Control mode selection (V/Hz vs. vector vs. closed-loop)
Drive not matching load	Nameplate data entered correctly?
Slip higher than expected	Is actual load near or above rated torque?
Low-speed torque insufficient	V/Hz drive may not deliver rated torque at low speed

Servo instability — axis oscillates or hunts

Work through in order:

Motor and encoder model match — confirm correct motor file or parameters
Encoder polarity or direction — wrong direction produces immediate instability
Mechanical resonance — check coupling, mount, and load rigidity
Backlash or loose coupling — mechanical compliance can appear as tuning instability
Tuning values too aggressive — reduce gains before increasing them
Noise or intermittent feedback loss — check cable routing and shielding

Module	Topic
Induction Motor Basics	Motor operating principles
Motor Nameplates, Slip, and Torque	Slip, torque curves, and overload behavior
VFD Fundamentals	Drive fault behavior and protection
Servo Drive Fundamentals	Servo feedback and tuning concepts
Motor Control Methods	Control mode comparison (V/Hz, vector, closed-loop)

Workflow	When to use
Motor Selection Workflow	Review original design basis during fault investigation
VFD Commissioning Workflow	Re-run commissioning steps if parameter changes are needed
Servo Commissioning Workflow	Re-run servo axis steps for instability faults

Trust Boundary — Engineering Judgment Required

This site is a personal-use paraphrase and navigation reference for industrial automation standards. It is not a substitute for authoritative standards documents, professional engineering judgment, or legal review. All content is sourced from a local RAG corpus and has not been independently verified against current published editions.

Items marked TO VERIFY have limited or unconfirmed local coverage. Items marked NOT IN CORPUS are not covered in the local repository. Do not rely on this site for compliance determinations, safety-critical design decisions, or legal interpretation.

Motor Rotation and Overload Verification

Trust Boundary — Engineering Judgment Required