The Siemens drive fault code F7902 (or 7902) Motor Stalled (or "Motor out of step"). This fault occurs when the drive detects that the motor is not rotating despite a torque or current being applied, or it has lost synchronism with the drive's output frequency. Common Causes Mechanical Overload:
The load is too heavy for the motor to start or maintain rotation, causing it to stall. Incorrect Motor Data:
The drive's parameters do not match the actual motor (e.g., rated current, power factor, or resistance). Incomplete Identification:
A "Motor Data Identification" (MotID) or static optimization run was not completed correctly during commissioning. Ramp Settings: The acceleration ramp ( cap P 1120
) is too short, or the torque limits are set too low to overcome initial friction. Phase Failure:
A loose connection or broken cable between the drive and the motor. Troubleshooting & Solutions Check for Mechanical Obstructions:
Manually rotate the motor (if safe) to ensure the load isn't seized or jammed. Verify Parameter Settings:
Cross-check the motor nameplate against the drive parameters ( Perform Motor ID: Re-run the motor data identification (
or similar, depending on the model) to allow the drive to "learn" the motor's electrical characteristics. Increase Current/Torque Limits: Check if the stall detection limits ( cap P 2175 cap P 2177 ) are too sensitive for your specific application. Extend Ramp Times:
Increase the acceleration time to give the motor more time to reach speed without hitting the stall threshold. If you are using a SINAMICS G120XA
, this fault is frequently tied to asynchronous motors that haven't undergone proper static optimization. You can view the specific fault history and timestamps using the Siemens STARTER software TIA Portal specific parameter numbers for a particular Siemens drive series, like the
Subject: G120XA solution to warning F7902 motor out of step - Siemens
This report provides a comprehensive overview of the Siemens Fault Code 7902 (F07902), often occurring in SINAMICS G120XA, G120, and S120 drives. 1. What is Fault F07902?
Fault F07902 indicates that the drive believes the Motor has Stalled (Motor Locked/Blocked).
Definition: The drive has detected a speed or position discrepancy indicating the motor is not rotating as expected based on its current frequency, typically after motor identification or during operation.
Result: The drive stops operating (OFF2 or OFF3 depending on configuration) to protect the motor and mechanics. 2. Common Causes
Missing/Incorrect Motor Data: The drive was not properly tuned to the motor.
Lack of Optimization: No Motor Data Identification (Static or Rotating) was performed.
Excessive Load: The motor is struggling to turn the mechanical load.
Improper Flying Restart: Attempting to start a motor that is already spinning without the appropriate "flying restart" function active. siemens drive fault code 7902
Incorrect Cabling/Phase: Motor cables (U, V, W) are connected improperly. Brake Issues: The mechanical brake is not releasing.
Weak Power Module: The power unit cannot supply the required startup current. 3. Troubleshooting & Solutions (Step-by-Step) Follow these steps to diagnose and clear the fault: Re-commission Motor Data (Crucial): Perform a factory reset of the converter. Set p0010 = 1 (Quick commissioning). Enter exact motor nameplate parameters: Rated voltage ( ), current ( ), power ( ), Power Factor ( ), and speed ( Set p3900 = 3 (Quick commissioning for motor parameters).
Perform Static Optimization: Set p1900 = 2 to enable motor data identification at standstill.
Switch to "Hand" mode and press start to complete the measurement. Verify Mechanical and Electrical Connections:
Check for mechanical obstructions (brake locked, jammed load). Check motor cable connectivity.
If using encoder feedback, verify the encoder signal is accurate. Adjust Control Parameters:
Increase current setpoint: Increase p1610 (static torque setpoint) if stalling happens at low speeds.
Increase tolerance: Increase fault tolerance p1745 or delay time p2178 to make the drive less sensitive to minor stalls.
Activate Flying Restart: Set p1200 = 1 if the motor is still turning when the start command is given. Hardware Inspection:
Verify the braking relay control voltage. If the brake doesn't receive voltage to release, the motor will stall. 4. Relevant Parameters p0346: Motor excitation time (increase if too low) p1745: Fault tolerance p2178: Motor blocked monitoring time p1610: Static torque setpoint p1200: Flying restart 5. Summary Table Suggested Action Fault at startup Perform static/rotating motor ID (p1900=2/3). Fault under load Increase p1610 (torque) or check mechanical load. Fault after power failure Enable flying restart (p1200=1). Motor brake locked Check brake relay and release voltage. To get a more specific solution, tell me:
Which specific drive model (e.g., G120X, S120) are you using?
Does the fault happen at startup, or while the machine is running? Is your motor using an encoder?
I can then provide the precise parameter steps for your scenario. sinamics drive motor fault 7902 - SiePortal - Siemens
Siemens Drive Fault Code 7902: Understanding and Troubleshooting
Siemens drives are widely used in various industrial applications, offering reliable and efficient motor control. However, like any complex device, they can occasionally encounter faults. One such fault code that users may come across is 7902. In this text, we'll explore what the Siemens drive fault code 7902 means, its possible causes, and steps for troubleshooting and resolution.
What is Siemens Drive Fault Code 7902?
Fault code 7902 in Siemens drives typically indicates a specific issue related to the drive's operation. The exact meaning can vary slightly depending on the specific model and version of the Siemens drive. However, generally, this code points to a problem that requires attention to prevent further issues or damage to the drive and connected equipment.
Possible Causes of Fault Code 7902
Several factors can lead to the appearance of fault code 7902 on a Siemens drive: The Siemens drive fault code F7902 (or 7902)
Troubleshooting Steps
When encountering fault code 7902, follow these steps to troubleshoot and potentially resolve the issue:
Refer to the Drive Manual: The first step is to consult the user manual or documentation specific to your Siemens drive model. Siemens provides detailed descriptions of fault codes, recommended actions, and troubleshooting guides.
Check the Drive’s Environment: Ensure the drive is operating in an environment that meets Siemens’ specified conditions. Check for adequate ventilation and that the ambient temperature is within recommended limits.
Inspect Electrical Connections: Verify that all electrical connections are secure and that there are no signs of damage or wear on cables and connectors.
Review Drive Parameters: Double-check the parameter settings to ensure they are correctly configured for your application.
Reset the Fault: In some cases, simply resetting the fault (if safe to do so) and monitoring the drive can resolve the issue. However, this should be done with caution, as repeated faults can indicate a more serious problem.
Contact Siemens Support: If the issue persists, it may be necessary to contact Siemens technical support or a qualified service technician. They can provide guidance specific to your situation and perform repairs if needed.
Preventing Future Occurrences
To minimize the risk of encountering fault code 7902 in the future:
By understanding what Siemens drive fault code 7902 indicates and following systematic troubleshooting steps, users can often quickly resolve issues and maintain the reliability and efficiency of their drive systems.
This draft provides a general overview and might need adjustments based on the specific requirements or details of the Siemens drive model you're working with.
Would you like to add anything specific or make any changes?
The fluorescent lights of the MagnaDrive factory floor hummed in a low, monotonous key, a sound usually drowned out by the rhythmic thwump-hiss-thwump of the heavy-duty stamping presses. But tonight, the factory was holding its breath.
Elias Thorne, a third-shift maintenance technician with twenty years of grease under his fingernails, sat in the breakroom nursing a lukewarm coffee. He was staring at the clock. It was 2:00 AM. In the world of industrial automation, 2:00 AM is the witching hour—the time when bearings decide to seize, sensors decide to sleep, and PLC logic decides to glitch.
As if on cue, the breakroom lights flickered. The deep, vibrating thrum of the plant’s ventilation system shuddered and died. A moment later, the emergency lights kicked in, bathing the hallway in an eerie, sterile red.
Elias’s radio crackled to life. It was the shift supervisor, Marcus, his voice tight with panic.
"Elias. Line 4. Main stamper. It’s down. Totally dead. The screen is screaming at me."
Elias sighed, pushing himself out of the chair. "I'm on my way. Don't touch anything, Marcus." Overheating: One of the most common reasons, overheating
Line 4 was the heart of the factory, a massive Siemens-driven servo press responsible for churning out the chassis plates for the new electric vehicle contract. If it was down, the morning shift would start with a disaster, and the plant manager would be breathing down everyone's necks before sunrise.
When Elias arrived, the massive machine stood silent, a sleeping giant. The control cabinet door was open, and Marcus was standing back, looking at the Siemens Sinamics S120 drive module like it was a bomb about to detonate.
"What’s the code, Marcus?" Elias asked, pulling his laptop bag onto a nearby workbench.
"It’s a 7902," Marcus said, reading the 7-segment display on the BOP (Basic Operator Panel). "Just '7902'. I tried resetting it, but it just clicks and throws the same code again."
Elias stopped. He pulled off his safety glasses and wiped the sweat from his forehead. He knew this code. Every drive tech knows the "standard" faults—overvoltage (F0002), overcurrent (F0001)—but the 7-series faults were different. They were communication faults. Ghosts in the machine.
"Fault 7902," Elias muttered, typing his password into the Siemens TIA Portal software on his laptop. "Communication fault. Drive-to-Drive data exchange failure."
"That doesn't make sense," Marcus snapped. "We didn't change anything. It was running fine at 1:45, and then—bang—e-stop tripped, and this code popped up."
Elias connected the Profinet cable to the drive’s CU320-2 control unit. The laptop chimed. He navigated to the diagnostics buffer. The list was populated, but one entry was highlighted in red, pulsating with urgency.
F07902: Drive-to-drive communication failure.
"It’s not the PLC," Elias murmured, scrolling through the parameters. "The PLC is talking to the drive just fine. The Profibus light is green. This fault... it means this drive isn't hearing its partner."
"Partner?" Marcus asked. "The press only has one main motor."
Elias shook his head. "It’s an S120 multi-drive system, Marcus. Look at the cabinet. One line supply module, but two motor modules. There’s a main drive for the flywheel, and a secondary servo for the feeder that pushes the metal sheets in. They talk to each other via a telegram to synchronize the speed. If the feeder drive doesn't report its position to the main drive, the main drive locks out to prevent crushing the tooling."
Marcus looked at the row of black modules in the cabinet. "Okay, so we check the second drive."
They moved to the lower section of the cabinet. The lights on the second motor module were dark. Completely dark.
"Power loss," Elias said immediately. "The module has no power. That’s why the main drive is throwing 7902. It’s shouting 'Where are you?' and getting silence."
The diagnosis seemed simple, but Elias knew better. If it was just a loose wire, the breaker would have tripped. He pulled out his multimeter.
"Breaker is on," he muttered. "Voltage at the input terminals... 480 volts, phase to phase. The power is there."
He checked the DC link voltage. The capacitors in the line module were humming, charged and ready. But the second motor
To avoid future occurrences of fault code 7902:
Use an infrared thermometer or thermal imager for accuracy.
p2040 to 150–300 ms (long enough to tolerate bus jitter, short enough to detect real loss).p2100 = 7902, p2101 = 3 → trigger different response if needed).r2060, r2074 for PROFIBUS, r2080 for PROFINET counters).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.