If an AC motor is experiencing high or abnormal vibrations, it may be due to one or more of the following reasons:

1. Unbalanced load: The motor may be operating with an unbalanced load, causing it to vibrate excessively.

2. Misalignment: The motor shaft may be misaligned, causing the motor to vibrate and wear out faster.

3. Worn bearings: The motor's bearings may be worn or damaged, causing the motor to vibrate excessively.

4. Loose components: The motor's mounting bolts, shaft couplings, or other components may be loose, causing the motor to vibrate excessively.

5. Electrical issues: The motor may have electrical issues such as damaged windings, improper supply voltage or frequency, or a faulty starter, causing it to vibrate.