Cause: AFE Modulation Rate Error comes when the drive struggles to maintain the necessary DC link voltage when the input power is insufficient. This can be caused by low input supply.

"ACF1" "AFE Modulation Rate" fault in Schneider ATV950 drive indicates that the voltage supplied to the drive is below the acceptable range for proper operation.

Here are some steps you can take to troubleshoot and resolve the issue:

1. Check the Power Supply:

• Measure Voltage: Use a multimeter to measure the voltage at the input terminals of the drive. Compare this with the rated input voltage range specified in the drive's manual.
• Supply Quality: Ensure the power supply is stable and free from significant dips or fluctuations. Poor quality or unstable power supply can cause low voltage faults.

2. Inspect Wiring and Connections:

• Tight Connections: Verify that all electrical connections are tight and secure. Loose connections can lead to voltage drops.
• Cable Condition: Check the condition of the input cables for any damage or wear that could affect voltage delivery.

3. Check Circuit Breakers and Fuses:

• Correct Ratings: Ensure that circuit breakers and fuses used in the power supply line are of the correct ratings and are functioning properly.
• Tripping: Verify that no circuit breakers are tripped or fuses blown, as this can interrupt the power supply.

4. Examine External Factors:

• Load Conditions: High inrush currents or sudden changes in load can cause temporary voltage drops. Ensure the drive is not overloaded.
• Power Factor Correction: In some cases, power factor correction devices or harmonics filters might be needed to stabilize the supply voltage.

5. Drive Settings:

• Voltage Thresholds: Check the drive parameters related to input voltage thresholds and adjust them if necessary, within the safe operating limits.
• Firmware Updates: Ensure the drive firmware is up-to-date, as firmware updates can resolve certain issues.