Siemens motor bearing rupture replacement treatment

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Siemens servo motor encoder alarm is a common fault in industrial automation systems, which may be caused by various reasons. According to the latest public information (common causes of alarms)

Wiring issues: cable wear, joint oxidation, poor shielding, or incorrect wiring, resulting in signal loss (such as A+/A -, B+/B - abnormalities)

Power supply abnormality: ± 10% fluctuation outside the rated voltage tolerance, or+5V power supply below 4.75V, causing abnormal operation of the encoder

Mechanical damage: Bearing jamming, loose shaft sleeve, coupling offset (such as 0.2mm deviation can trigger periodic alarms)

Environmental factors:

Temperature>85 ℃ causes magnetic attenuation in the magnetic encoder;

Vibration>5g causes displacement of the optical encoder disk;

Dust, oil stains, and condensation cause internal short circuits or signal attenuation

Parameter or firmware mismatch:

After replacing the absolute value encoder, the Teach in operation was not performed, triggering a "25201" position verification error;

S7-1200 and encoder pulse number settings are inconsistent;

G120 frequency converter and encoder firmware version conflict leads to "F31100" fault

Interference issue: Electromagnetic interference (EMI) causes waveform distortion of signals (such as rising edge>100ns or amplitude<4V)

Diagnostic Steps (Five Step Method)

Analyzing alarm codes: Siemens encoder fault codes are mostly in the format of "Fxxx" or "Fxxxxx", where "F" indicates a serious fault and the last few digits point to specific issues (such as F0790 associated cables, interfaces, or the encoder itself)

Detecting signal waveform: Use an oscilloscope to measure HTL/TTL signals. The normal rising edge of a square wave should be ≤ 100ns, with an amplitude of 4.75-5.25V. If there is a sawtooth wave or insufficient amplitude, check the cable impedance (recommended 120 Ω twisted pair)

Check mechanical alignment: Use a laser alignment instrument to measure radial runout (<0.05mm) and angular deviation (<0.02 °)

Check the environment and installation:

Check if the temperature, vibration, and humidity exceed the standard;

Confirm that the cable shielding layer is reliably grounded (the encoder housing and driver frame are grounded together)

Verify if original cables are used and kept away from high pollution lines

Replacement test: Disconnect the original encoder and connect it to an analog signal source; If the system returns to normal, the encoder fault will be locked

Cleaning optical encoder: Cleaning the grating disc with 99.7% isopropanol and non-woven fabric can increase signal strength by 40%

Magnetic encoder magnetization: After demagnetization, a pulse magnetic field generator (≥ 3000Oe) is needed for axial magnetization, and the residual magnetic field should be>800mT

Data recovery: The absolute value encoder with EEPROM can use the Siemens PG-740 programmer to read old data and write it to the new device, avoiding recalibration

Preventive maintenance:

Measure insulation resistance every 6 months (>100M Ω @ 500VDC);

Check the signal amplitude every 3 months;

Using SINAMICS S120 Trace function to monitor vibration in the 1kHz frequency band and provide early warning of bearing faults

Urgent handling suggestions

If the alarm appears intermittently (such as F07450 triggering only at specific angles)

6. Possible reasons include:

Mechanical installation not in place (coaxiality deviation of reducer or motor);

Although the program parameters (such as P2542, P2543) are correct, the encoder's actual response is delayed;

Suggest extending the position deviation detection time (such as increasing from 200ms to 500ms) and checking the fastening status of the coupling.