Fault codeF7900
The motor is blocked or the speed controller is at its limit due to torque exceeding limits or oscillating speed below 120 rpm. The manual's first action is: “['• Check whether the servo motor can rotate freely or not.\n• Check the torque limit.\n• Check the inversion of the actual value.\n• Check the motor encoder connection.\n• Check the encoder pulse number.']”
- Model
- Siemens SINAMICS V90, SIMOTICS S-1FL6
- Display shows
- Motor blocked/speed controller at its limit (F7900)
- Type
- Fault code
- Source
- Manual p. 298
What F7900 means
Motor blocked/speed controller at its limit p. 298
Common causes
- The servo motor has been operating at the torque limit longer than 1 s and below the speed threshold of 120 rpm . This signal can also be initiated if the speed actual value is oscillating and the speed controller output repeatedly goes to its limit. p. 298
Safety warnings — read before you start
- DANGERGeneral Safety Instructions. Qualified Personnel The product/system described in this documentation may be operated only by personnel qualified for the specific task in accordance with the relevant documentation, in particular its warning notices and safety instructions. p. 2
- WARNINGRisk of Electric Shock and Fire. Risk of electric shock and fire from supply networks with an excessively low impedance Excessively high short-circuit currents can lead to the protective devices not being able to interrupt these short-circuit currents and being destroyed, and thus causing electric shock or a fire. p. 12
- WARNINGElectric Shock if No Ground Connection. Electric shock if there is no ground connection For missing or incorrectly implemented protective conductor connection for devices with protection class I, high voltages can be present at open, exposed parts, which when touched, can result in death or severe injury. p. 12
- WARNINGElectric Shock Due to Unsuitable Power Supply. Electric shock due to connection to an unsuitable power supply When equipment is connected to an unsuitable power supply, exposed components may carry a hazardous voltage that might result in serious injury or death. p. 12
What to do
- ['• Check whether the servo motor can rotate freely or not.\n• Check the torque limit.\n• Check the inversion of the actual value.\n• Check the motor encoder connection.\n• Check the encoder pulse number.'] p. 298
If F7900 is still not resolved
- Contact service / dealer for assistance p. 2 “Qualified Personnel The product/system described in this documentation may be operated only by personnel qualified for the specific task in accordance with the relevant documentation, in particular its warning notices and safety instructions.”
- Contact service / dealer for assistance p. 13 “NOTICE Property damage due to loose power connections Insufficient tightening torques or vibration can result in loose power connections. This can result in damage due to fire, device defects or malfunctions.”
This page summarises what the manufacturer’s manual says about F7900; each statement links to the page it comes from, and quoted lines are copied word for word. It is not a substitute for the manual or for a qualified installer. ManualLib is not affiliated with Siemens. Found a mistake? Report an error.