How to Inspect Variable Frequency Drives (VFD) – Complete Daily & Periodic Maintenance Guide.
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How to Inspect Variable Frequency Drives–Daily and Periodic Maintenance Guide
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Introduction:
- Variable Frequency Drives (VFDs) play a vital role in modern industrial and building automation system by controlling motor speed and improving energy efficiency.
- To ensure long-term reliability, safety, and maximum performance, regular inspection of VFDs is essential.
- In this guide, you will learn professional daily and periodic inspection procedures, key maintenance checklists, and expert tips to prevent common failures.
- Whether you are an engineer, technician, or automation student, this article will help you maintain VFDs according to global industrial standards.
🔍 Overview of VFD Inspection
The inverter is a static unit mainly consisting of semiconductor devices. Daily inspection must be performed to prevent any fault from occurring due to the adverse effects of the operating environment, such as temperature, humidity, dust, dirt and vibration, changes in the parts with time, service life, and other factors.
Safety Reminder
When accessing the inverter for inspection, wait for at least 10 minutes after the power supply has been switched OFF, and then make sure that the voltage across the main circuit terminals P/+ and N/- of the inverter is not more than 30 VDC using a tester, etc.
Area Of Inspection: General 🧭
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| Area Of Inspection: General |
| 1 |
|
| Inspection Item |
Surrounding environment |
| Description |
Check the surrounding air temperature, humidity, dirt, corrosive gas, oil mist, etc. |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Improve the environment |
| 2 |
|
| Inspection Item |
Overall unit |
| Description | Check for unusual vibration and noise |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Check fault location and retighten |
| 3 |
|
| Inspection Item |
Overall unit |
| Description | Check for dirt, oil, and other foreign material. |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Clean |
| 4 |
|
| Inspection Item |
Power supply voltage |
| Description | Check that the main circuit voltages and control voltages are normal. |
| Inspection Interval |
Daily |
Corrective Action at Fault Occurrence
| Inspect the power supply. |
Area Of Inspection: Main circuit 🔌
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Area Of Inspection: Main circuit
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| 1 |
|
| Inspection Item |
General |
| Description | Check with megger (across main circuit terminals and earth (ground) terminal). |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer. |
| 2 |
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| Inspection Item | General |
| Description | Check for loose screws and bolts |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Retighten |
| 3 |
|
| Inspection Item |
General |
| Description | Check for overheat traces on the parts |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 4 |
|
| Inspection Item |
Conductors, cables |
| Description | Check conductors for distortion |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 5 |
|
| Inspection Item |
Conductors, cables |
| Description | Check cable sheaths for breakage and deterioration (crack, discoloration, etc.) |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
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| Area Of Inspection: Main circuit (2) |
| 6 |
|
| Inspection Item |
Transformer/reactor |
| Description | Check for unusual odor and abnormal increase of whining sound |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Stop the equipment and contact the manufacturer |
| 7 |
|
| Inspection Item |
Terminal block |
| Description | Check for a damage |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Stop the equipment and contact the manufacturer |
| 8 |
|
| Inspection Item |
Smoothing aluminum electrolytic capacitor |
| Description | Check for liquid leakage |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 9 |
|
| Inspection Item |
Smoothing aluminum electrolytic capacitor |
| Description | Check for safety valve projection and bulge |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 10 |
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| Inspection Item |
Smoothing aluminum electrolytic capacitor |
| Description | Visual check and judge by the life check of the main circuit capacitor |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 11 |
|
| Inspection Item |
Relay/contactor |
| Description | Check that the operation is normal and no chattering sound is heard |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
Area Of Inspection: Control circuit, protective circuit 🛡️
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| Area Of Inspection: Control circuit, protective circuit |
| 1 |
|
| Inspection Item |
Operation check |
| Description | Check that the output voltages across phases are balanced while operating the inverter alone |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 2 |
|
| Inspection Item |
Operation check |
| Description | Check that no fault is found in protective and display circuits in a sequence protective operation test |
| Inspection Interval | Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 3 |
|
| Inspection Item |
Overall (Components check) |
| Description | Check for unusual odor and discoloration |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Stop the equipment and contact the manufacturer |
| 4 |
|
| Inspection Item |
Overall (Components check) |
| Description | Check for serious rust development |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 5 |
|
| Inspection Item |
Aluminum electrolytic capacitor (Components check) |
| Description | Check for liquid leakage in a capacitor and deformation trace |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 6 |
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| Inspection Item | Aluminum electrolytic capacitor (Components check) |
| Description | Visual check and judge by the life check of the control circuit capacitor |
| Inspection Interval | Periodic |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
Area Of Inspection: Cooling system ❄️
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Area Of Inspection: Cooling system
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| 1 |
|
| Inspection Item |
Cooling fan |
| Description | Check for unusual vibration and noise |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Replace the fan |
| 2 |
|
| Inspection Item |
Cooling fan |
| Description | Check for loose screws and bolts |
| Inspection Interval | Periodic |
| Corrective Action at Fault Occurrence |
Fix with the fan cover fixing screws |
| 3 |
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| Inspection Item |
Cooling fan |
| Description | Check for stain |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Clean |
| 4 |
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| Inspection Item |
Heatsink |
| Description | Check for clogging |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Clean |
| 5 |
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| Inspection Item |
Heatsink |
| Description | Check for stain |
| Inspection Interval |
Periodic |
| Corrective Action at Fault Occurrence |
Clean |
Area Of Inspection: Display 🖥️
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Area Of Inspection: Display
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| 1 |
|
| Inspection Item |
Indication |
| Description | Check that display is normal |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Contact the manufacturer |
| 2 |
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| Inspection Item |
Indication |
| Description | Check for stain |
| Inspection Interval | Periodic |
| Corrective Action at Fault Occurrence |
Clean |
| 3 |
|
| Inspection Item |
Meter |
| Description | Check that reading is normal |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Stop the equipment and contact the manufacturer |
Area Of Inspection: Load motor ⚙️
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| Area Of Inspection: Load motor |
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| Inspection Item |
Operation check |
| Description | Check for vibration and abnormal increase in operation noise |
| Inspection Interval |
Daily |
| Corrective Action at Fault Occurrence |
Stop the equipment and contact the manufacturer |
Note:
- Oil component of the heat dissipation grease used inside the inverter may leak out.
- The oil component, however, is not flammable, corrosive, nor conductive and is not harmful to humans.
- Wipe off such oil component.
- It is recommended to install a voltage monitoring device for checking the voltage of the power supplied to the inverter.
- One to two years of periodic inspection.
Conclusion
I hope you learnt something from this article.
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