As a core power component in industrial automation, the stability of servo motors directly impacts production efficiency and equipment lifespan. When faced with sudden servo motor failure, how can issues be quickly identified and resolved?

1. In-depth Analysis of Five Common Faults in Servo Motors

1.1 Overload fault: the most common problem

1.1.1Detailed symptom manifestations:

·Abnormal increase in motor housing temperature (over 70℃)

·The drive displays an "OL" or "Overload" alarm code

·Sudden shutdown and alarm during operation

·The motor emits a dull abnormal noise

1.1.2 Deep-level cause analysis:

·Mechanical issues: insufficient lubrication of guide rails, transmission mechanism binding, misalignment of couplings, excessive load

·In terms of parameters: the driver gain is set too high, the acceleration and deceleration time is too short, and the torque limit value is set unreasonably

·Electrical issues: unstable power supply voltage, aged motor insulation, and excessive cable contact resistance

1.2 Encoder failure: the killer of precise positioning

Detailed symptom manifestation:

·Position deviation alarm (following error exceeds limit)

·Motor shakes or runs away during operation

·The drive displays a series of "Encoder Error" alarms

·Zero drift or inaccurate positioning

Analysis of underlying causes:

·Connection issues: oxidized encoder connectors, bent pins, damaged cable shielding

·Environmental factors: strong electromagnetic interference, excessive vibration, and intrusion of oil or dust

Hardware damage: encoder chip aging, grating disc contamination, and bearing wear leading to shaft eccentricity

1.3 Abnormal vibration and noise: hidden equipment killers

Detailed symptom manifestation:

·The motor vibrates significantly within a specific speed range

·Emitting abnormal whistling or buzzing sound

·Creeping phenomenon occurs during low-speed operation

·Significant overshoot occurs during machine shutdown

In-depth cause analysis:

·Mechanical resonance: mismatch between motor and load inertia, insufficient rigidity

·Parameter setting: The speed loop gain is too high, and the integral time constant is unreasonable

Mechanical issues: damaged bearings, poor rotor dynamic balance, uneven installation base

1.4 Brake failure: A safety concern that cannot be ignored

Detailed symptom manifestation:

·The shaft still rotates freely after the motor is powered off

·Overload caused by brake not being released during startup

·Brake release delay causes positioning error

·Abnormal friction noise from brake pads during operation

In-depth cause analysis:

·Electrical issues: Open or short circuit in brake coil, damaged rectifier module

·Mechanical issues: excessive wear on brake pads, spring fatigue, and oil contamination on friction plates

·Control aspect: brake control circuit fault, timing setting error

1.5 Cable and connection issues: the most easily overlooked fault points

Detailed symptom manifestation:

·Intermittent alarm, temporarily restored to normal after re-powering

·Sudden shutdown during movement

·Malfunction occurs at specific locations or in specific postures

·Multiple unrelated alarms occurring simultaneously

Deep-level cause analysis:

·Cable damage: fatigue fracture of towline cable, poor soldering of connectors, insulation damage

·Connection issues: oxidized connectors, loose plug connectors, loose terminals

Environmental factors: oil corrosion, mechanical stretching, and aging caused by excessively high temperature

2. Four-level investigation method: precise positioning from simple to complex

Level 1: Visual inspection (5-minute quick troubleshooting)

1. Visual inspection: Check the status of the indicator lights on the motor and driver

2. Auditory examination: Identify abnormal sound characteristics and sources

3. Tactile inspection: touch to check if the motor temperature is abnormal

4. Olfactory examination: Smell for any burnt insulation odor

Level 2: Diagnostic alarm code (targeted troubleshooting)

·Check the manual: Determine the scope of the fault based on the drive display code

·History: View the history of drive failures

·Parameter comparison: Compare with the parameter settings of normal equipment

Level 3: In-depth investigation by levels

Power supply inspection steps:

1. Measure three-phase input voltage (with an allowable fluctuation range of ±10%)

2. Check the DC bus voltage (±5% of rated value)

3. Test the grounding resistance (less than 4Ω)

4. Detect power supply harmonic content (THD<5%)

Signal testing method:

1. Use an oscilloscope to inspect the pulse command waveform

2. Verify the voltage level of the control signal (typically 0-24V)

3. Check the signal cable shielding and grounding

Feedback detection technology:

1. Encoder waveform test (A/B/Z-phase signals)

2. Check the number of feedback pulses (compared with the set value)

3. Data reading of communication-type encoder (using dedicated software)

Mechanical confirmation procedure:

1. Disconnect the load test and measure the no-load current (usually 30%-60% of the rated value)

2. Manually rotate the shaft to confirm the resistance torque (it should be smooth and free of stagnation)

3. Check the alignment of the coupling (radial <0.05mm, angular <0.5°)

Level 4: Parameter optimization and adjustment

·Basic parameters: motor model, encoder type, gear ratio setting

Gain adjustment: Follow the sequence of "position loop first, then speed loop, and finally electrical

The order of "flow ring"

·Filter setting: appropriately increase the low-pass filter to reduce vibration

·Special function: Notch filter setting to suppress mechanical resonance

III. Advanced Diagnostic Tools and Techniques

Professional tool recommendation:

1. Oscilloscope: Check the signal quality of the driver and encoder

2. Thermal imager: quickly identify overheated components

3. Vibration analyzer: accurately locate the vibration source

4. Insulation tester: detects the insulation status of the motor

Waveform analysis techniques:

·Normal encoder signal: clear square wave, steep edge, no glitch

·Abnormal signal characteristics: insufficient amplitude, waveform distortion, phase jitter

·Interference identification: high-frequency oscillation, ground wire loop current characteristics

IV. Establishment of Preventive Maintenance System

Daily maintenance checklist:

· Daily: Check for abnormal sounds and vibrations, and confirm the cooling system is working

· Weekly: inspect cable appearance, clean cooling fan, and tighten wiringterminal

·Monthly: Measure insulation resistance and check the tightness of mechanical connections

Every six months: replace the bearing lubricating grease and clean the encoder window

Early warning indicator monitoring:

·Temperature warning: A warning should be issued when the temperature of the motor housing exceeds 60℃

·Vibration warning: When the effective value of vibration speed exceeds 4.5mm/s, it is necessary to follow

·Current trend: The continuous rise in operating current indicates potential issues

Spare parts management strategy:

Key spare parts: encoder module, brake coil, power module

·Consumable spare parts: cooling fan, bearing, connector

·Emergency spare parts: complete motor set, driver module

V. Sharing of practical cases

Case 1: Frequent overload alarms

·Problem phenomenon: The servo motor of a certain packaging equipment reports an error every 2-3 hoursoverload

·Troubleshooting process: Checked the mechanical load and found it to be normal. Measured the current and found Peak current anomaly

·Ultimate cause: The acceleration and deceleration time settings were too short, resulting in peak torque Moment exceeds the limit

Solution: Adjust the acceleration and deceleration time constants and add an S-curve

Smoothing function

Routine maintenance and prevention

Many malfunctions can be avoided through routine preventive maintenance, such as cleaning the dust on the motor surface every three months, conducting regular maintenance on the cooling system, replacing bearing grease according to the manufacturer's requirements, saving the drive parameters in normal state, and making backups for fault recovery. When encountering a malfunction, it is recommended to follow the troubleshooting principle of "mechanical first, electrical second", and first check whether the mechanical components are blocked and whether the lubrication is good. This often saves time and reduces costs.