Code 205052: <location>Parallel circuit: Illegal current dissymmetry
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical <location>Parallel circuit: Illegal current dissymmetry 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: %1 Drive object: A_INF, B_INF, S_INF, VECTOR Reaction: NONE Acknowledge: NONE Cause: The deviation of the individual currents of the power units exceeds the alarm threshold specified in p7010. Alarm value (r2124, interpret decimal): 1: Phase U. 2: Phase V. 3: Phase W. Remedy: - inhibit the pulses of the faulted power unit (p7001). - check the connecting cables. Loose c ontacts can cause current spikes. - the motor reactors are non-symmetrical or faulty and must be replaced. - the CTs must be calibrated or replaced.
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 205052 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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