🔍Quick Description of the Issue
During operation, many technicians encounter the following situation:
- The inverter is powered on, and the display is active
- The system appears to be in RUN mode
- Frequency and even current may be displayed
👉 But the motor does not rotate
This is a fairly common issue, especially in systems that have been using AC or DC drives for a long time.
⚠️1. No Actual RUN Command
Causes:
- The inverter is powered on, but no RUN command is given
- Incorrect wiring of digital input (DI) signals
- The PLC is not sending the start command
How to Check:
- Check the RUN status on the inverter display
- Measure the digital input (DI) signals (Start/Enable)
👉 In many cases, it may appear to be running, but in reality, the inverter has not received a true RUN command.
🔌 2. Power Circuit Fault (No Output to Motor)
Causes:
- Broken or disconnected U–V–W motor cables
- Loose terminals
- Output contactor not engaged
- Faulty intermediate relay
How to Check:
- Measure the inverter output voltage
- Check motor cable continuity
👉 This is a very common issue in real-world industrial environments.
⚙️ 3. Motor Mechanically Jammed or Overloaded
Causes:
- Mechanical parts are jammed
- Damaged or worn bearings
- Load is too heavy
Symptoms:
- Current is present, but the motor does not rotate
- The inverter may or may not trigger an overcurrent alarm
👉 Many technicians assume it’s an inverter fault, but in reality, it is often a mechanical issue.
🔄 4. Incorrect Parameter Settings
Common Causes:
- Minimum frequency set to 0 Hz
- Torque limit set too low
- Output not enabled
- Incorrect control mode selected
Practical Example:
Setting the torque limit too low → the motor does not have enough torque to rotate
👉 This issue commonly occurs when:
- The system is newly configured
- The inverter has just been replaced
⚡ 5. Inverter Power Stage Fault (IGBT / Drive Stage)
Causes:
- Damaged IGBT
- Power board failure
- Output phase loss
Symptoms:
- No output voltage to the motor
- There may be no clear fault indication
👉 This is a critical and hard-to-detect issue if proper measurements are not performed.
🔒 6. System Interlock Not Allowing Operation
Causes:
- PLC has not granted RUN permission
- Sensor faults (limit switch, pressure, safety signals)
- Emergency stop (E-stop) is active
👉 The inverter may appear to be running, but it is actually being logically inhibited by the system.
🧩 7. Encoder / Feedback Fault (Closed-Loop Systems)
Causes:
- Faulty encoder
- Loss of feedback signal
- Incorrect wiring
👉 This issue is especially common in:
- Printing machines
- Drawing machines
- Tension control systems
🛠️ Quick Troubleshooting Procedure (Practical)
👉 When encountering this issue, you should check in the following order:
- Is there a RUN command?
- Is there output voltage from the inverter?
- Are the motor cables OK?
- Is the motor mechanically jammed?
- Are the parameters set correctly?
- Is there any system interlock?
- Check the power stage
👉 Following this sequence will help you identify the problem much faster.
🎯 Conclusion
The issue “inverter running but motor not rotating” is not always caused by the inverter itself.
👉 In about 80% of cases, the causes are:
- Wiring issues
- Mechanical problems
- Incorrect parameter settings
👉 Only around 20% are due to actual equipment faults.
📞Need On-Site Inspection & Troubleshooting Support?
We specialize in:
- Fast on-site inverter troubleshooting at your factory
- Repair of AC / DC drives
- Consulting and replacement solutions for Parker drives
👉 Contact us now for fast and professional technical support:
📞 Hotline: +84 908 353 714 (Mr. Lâm)
📧 Email : info@kythuatviet.vn
