Code 207907: <location>Internal armature short-circuit: Motor terminals are not at zero potential after pulse suppression
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Internal armature short-circuit: Motor terminals are not at zero potential after pulse suppression alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Message value: Drive object: SERVO, VECTOR Reaction: NONE Acknowledge: IMMEDIATELY Cause: The function "Internal voltage protection" (p1231 = 3) was activated. The following must be observed: - when the internal voltage protection is active, afte r pulse suppression, all of the motor terminals are at half of the DC link voltage (without an internal voltage protection, the motor terminals are at zero potential)! - it is only permissible to use motors th at are short-circuit proof (p0320 < p0323). - the Motor Module must be able to continually c onduct 180% short-circuit current (r0331) of the motor (r0289). - the internal voltage protection cannot be interrupt ed due to a fault response. If an overcurrent condition occurs during the active, internal voltage pr otection, then this can destroy the Motor Module and/or the motor. - if the Motor Module does not support the autonomous, internal voltage protection (r0192.10 = 0), in order to ensure safe, reliable functioning when t he line supply fails, an ex ternal 24 V power supply (UPS) must be used for the components. - if the Motor Module does support the autonomous, internal voltage protection (r0192.10 = 1), in order to ensure safe, reliable functioning when the line supply fails, the 24 V power supply for the components must be provided through a Control Supply Module. - if the internal voltage protection is active, it is no t permissible that the motor is driven by the load for a longer period of time (e.g. as a result of loads that move the motor or another coupled motor). Remedy: None necessary. This a note for the user. SINAMICS-Alarms Diagnostics Manual (DAsl), 03/2009
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 207907 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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