Cause : Speed mismatch comes when an excessive deviation has occurred between the speed command and the detected speed. An ER9 speed mismatch indicates a significant deviation between the commanded speed and the actual speed of the motor controlled by the Fuji FRENIC-VG drive. 

"er9" fault in Fuji FRENIC-VG drive indicate " Speed mismatch error". This means a discrepancy between the expected and actual speeds. This fault typically occurs when the drive detects a difference between the commanded speed and the feedback speed from the motor or encoder, or when the drive’s internal speed calculations do not match the expected values.

Troubleshooting Steps:

1. Check Encoder and Feedback Signals:

   • Inspect the encoder and its wiring for any signs of damage or loose connections.
   • Verify that the encoder is functioning correctly and providing accurate speed feedback.

2. Verify Speed Settings:

   • Review the drive’s speed settings and parameters to ensure they are correctly configured for the application.
   • Check the commanded speed values and compare them to the actual speed readings from the encoder.

3. Inspect Mechanical Components:

   • Check the motor and load for any mechanical issues, such as excessive friction, binding, or misalignment, that could affect the speed.
   • Ensure that the motor is properly mounted and that the load is correctly connected.

4. Check Wiring and Connections:

   • Ensure that all wiring connections between the drive, encoder, and motor are secure and free from damage.
   • Verify that the wiring is correctly connected according to the drive’s wiring diagram.

5. Review Drive Configuration:

   • Verify that the drive’s configuration settings related to speed control and feedback are correctly set up.
   • Ensure that any calibration or scaling settings for speed feedback are accurate.