Cause : Current limit comes when the current being drawn by the load or motor connected to the inverter has exceeded the preset current limit. 

A501 alarm in Siemens Sinamics V20 drive indicates a current limit situation. This means the motor connected to the drive is drawing more current than the drive is set to allow.

Possible Reasons for A501 Alarm:

• Motor Overload: The motor might be experiencing an overload condition, causing it to draw excessive current. This could be due to:

• Mechanical issues like seized bearings, excessive friction, or binding in the connected machinery.
• Mismatch between the motor and application requirements. The motor might be undersized for the load it's trying to handle.

• Incorrect Drive Settings: If the current limit parameter in the Sinamics V20 drive is set too low for the motor's needs, it can trigger the A501 alarm even under normal operating conditions.
• Rapid Acceleration: In rare cases, very aggressive acceleration settings on the drive might cause a surge in current exceeding the limit during startup.
• Cable Issues: Faulty motor cables or loose connections can increase resistance and lead to higher current draw.

Troubleshooting Steps:

1. Check for Mechanical Overload:

• Turn off the power supply to the Sinamics V20 drive completely.
• Physically inspect the motor and connected machinery for any mechanical obstructions or binding issues.
• Ensure the load on the motor is appropriate for its capacity.

2. Verify Drive Settings:

• Refer to the Sinamics V20 drive manual for your specific model. It should have instructions on how to access and adjust the motor current limit parameter.
• Ensure the current limit is set to a value that aligns with the motor's rated current and application requirements. Don't set it unrealistically high for safety reasons.

3. Review Acceleration Settings:

• If applicable, consult the manual and adjust the acceleration ramp time settings to a less aggressive profile. This can help reduce the initial current surge during startup.

4. Inspect Motor Cables:

• Visually inspect the motor cables for any signs of damage or wear.
• Ensure all connections at the drive terminals and motor terminal box are secure and tightened properly.