Siemens Drive Fault Code 7902
Scenario: A automotive paint line conveyor trips with F07902 every Monday morning but runs fine for the rest of the week.
Investigation: Technicians found no cable breaks. The motor windings tested OK. The clue was the timing – every Monday after weekend shutdown.
Root Cause: A magnetic contactor between the drive and motor had a pitted auxiliary contact that overheated slightly on the first start of the week, dropping one phase for 50ms. As the day progressed, thermal expansion improved contact – until the next Monday.
Solution: Replaced contactor and implemented weekly starter torque check. Fault 7902 eliminated.
Fault code: 7902
Typical device family: Siemens SINAMICS / SIMODRIVE (frequency converters and servo drives)
Symptom: Drive reports fault 7902 and trips or blocks operation.
Likely meaning: Encoder feedback error or position feedback failure detected by the drive's encoder interface. The drive cannot reliably determine motor position/speed.
Common causes:
Diagnostic steps (ordered, concise):
Temporary workarounds (use only if safe and permitted):
Preventive measures:
When to escalate to Siemens support or an authorized service partner:
Useful information to provide when requesting support:
If you want, I can draft a troubleshooting checklist tailored to a specific Siemens drive model (e.g., SINAMICS G120, S120, or SIMODRIVE) — tell me the exact model and motor/encoder type. siemens drive fault code 7902
(related search suggestions provided)
The hum of the steel plant was Marcus’s favorite symphony, but today, the percussion was off. The overhead crane at the main hoist had ground to a halt, and the control panel was screaming in a bright, neon red: Fault F7902
Marcus, the senior maintenance lead, sighed. He knew this "ghost in the machine" well. F7902 isn't just a number; it’s the Siemens SINAMICS way of saying the motor is stalled The Investigation
"Is it jammed?" his apprentice, Leo, asked, pointing at the massive hoist gears.
"Could be mechanical," Marcus said, consulting his mental checklist. "But F7902 is a speed adaptation controller error. The drive
the motor is moving, but the encoder or the motor model says otherwise". They started with the basics: Physical Obstruction
: They checked the hoist drum and the thruster brakes. No debris, and the brakes were releasing properly. Electrical Check
: Marcus checked the motor cables. A loose connection or a swapped phase (U and W cables) is a classic culprit that sends the drive into a tizzy. The Parameter Trap : Leo pulled up the drive parameters on the BOP-2 operator panel . "The threshold is set tight," he noted. The Resolution "Look at the delay," Marcus pointed to
. "The load is heavy today. The drive is timing out before the motor can overcome the inertia."
They didn't just mask the alarm—that’s a rookie mistake. Instead, they: Redid the Motor ID : They ran a stationary measurement ( Scenario: A automotive paint line conveyor trips with
) to ensure the drive truly understood the motor’s internal resistance. Adjusted Tolerance : They slightly increased the fault tolerance in and the delay time in to account for the heavy lifting cycles. Flying Restart : They ensured the "flying restart" function was active (
) so the drive could catch the motor if it was already spinning.
As Marcus flipped the switch, the hoist roared back to life. The red light vanished, replaced by the steady, green "Ready" status. The symphony had returned to its proper rhythm. step-by-step technical guide to the specific parameters mentioned in the story? sinamics drive motor fault 7902 - SiePortal - Siemens
The Siemens drive fault code indicates that motor has stalled or is out of step
. This typically occurs when the drive loses synchronism with the motor, meaning the motor is unable to rotate at the speed commanded by the inverter. Common Causes Missing Motor Data Identification
: The most frequent cause is a lack of motor data identification and static optimization, particularly with asynchronous motors. Mechanical Overload
: The load on the motor exceeds its torque capability, physically preventing it from turning. Incorrect Parameter Settings
: Limits for stall detection (such as speed or current thresholds) may be set too strictly for the specific application. Acceleration/Deceleration Rates
: Ramp times that are too aggressive (too short) can cause the drive to lose control of the motor rotor position. Recommended Troubleshooting Steps Perform Motor Identification
: Re-run the motor data identification routine (often called "MotID") to ensure the drive accurately understands the electrical characteristics of the motor. Check Mechanical Load Diagnostic steps (ordered, concise):
: Inspect the connected machinery for jams, broken bearings, or excessive friction that could be stalling the shaft. Adjust Stall Protection Parameters
: Verify and potentially increase the stall detection time or torque limits if the application involves high-inertia loads. Review Ramp Times
: Increase the acceleration (P1120) and deceleration (P1121) times to allow the motor more time to reach the setpoint without losing synchronism. Verify Power Supply
: Ensure the input voltage is stable, as a significant voltage drop can reduce the motor's available torque.
For detailed parameter lists and specific drive models, you can refer to the Siemens SiePortal Support F7902 Technical FAQ specific parameter numbers for a particular Siemens drive series, such as the SINAMICS G120
Subject: G120XA solution to warning F7902 motor out of step - Siemens
The Siemens drive fault code 7902 (often displayed as F07902 or A07902 depending on the drive series) typically indicates a motor overspeed condition.
Here is the breakdown and common solutions for this fault.
Begin with verifying that the PLC master is actively exchanging cyclic data with the drive’s configured station address. Then check hardware integrity of the bus cable and termination. If the issue persists, match telegram settings exactly between the drive (P0922) and the master’s hardware configuration.
Report prepared for: Siemens Drive Maintenance / Automation Engineer
Date: [Insert current date]
Firmware reference: SINAMICS parameter manual, List Manual (LH1)
F07902: Motor overspeed The actual motor speed has exceeded the p2162 (overspeed threshold) value for longer than the time set in p2163.
Access fault buffer: r0947 lists last 8 faults. r0949 gives additional info (e.g., temperature at time of trip). This helps separate actual overheat from sensor failure.