Top 5 Reasons of VFD Failure And Prevention Methods
1. Accumulation of Dust Inside the VFD.
This is the most common
reason behind VFD failure. The accumulation is nothing but a gradual increase of
dust that is combined with plant moisture containing oil, moisture, and
metallic particles, and acidic gases which damage PCB.
When this dust starts
accumulating in your VFD, it attracts extra moisture and restricts airflow
which is essential for the proper functioning of the drive. Ultimately, more
moisture results in more heat generated by the VFD to counter the effect of
moisture, resulting in a string of undesirable events. This will result in a gradual decrease in the functioning of your VFD, followed by sudden failure of
VFD.
Prevention:
If you want to prevent
this issue from occurring follow bellow technique,
A)
Clean the entire device on a regular basis to avoid force cooling
directly on PCB. It is advisable to use a Vacuum cleaner if possible.
B)
Open the Front Cover of VFD and make sure that there is no scope for
any dust to accumulate within or outside the device.
C)
We always recommend that you must select or configure VFD on
basis of your plant environment. If your plant environment has more moisture,
it is advisable to have VFDs that are sealed instead of the ones having side vents for cooling. Go with IP (54 and more) protected VFD for harsh
environment.
2. Loose Connection of Power Components and Power connection of VFD.
If your VFD starts
operating irregular or if you observed electrical noise or smell from inside of
VFD, it may be because of loose connections in the circuit.
Loose connections are often caused by
vibrations over a period of time and human error while operating/repair,
resulting in dangerous arcing.
Prevention:
A)
If any doubt on the tightness of VFD components and connections and not possible to check then take
care while power up firstly power on and in 1-2 sec break the power and observe
smell or noise inside of VFD.
B)
Prevent this issue by monitoring the different components of the
VFD on a regular basis. Check to leak of Power capacitors, damaged fans,
corrosion, or traces on the circuit board.
3. Over-temperature of VFD and components.
This problem also very common in all VFD, over-temperature or
overheating has happened because of many reasons.
A lot of over temperature is
caused by “ACCUMULATION” as discussed above. Your VFD may also get overheated
when the current supplied exceeds the drive’s rated current.
This issue is also caused
by improper heat dissipation of SCR/DIODE and IGBT because after some days
heatsink material(paste) which helps to dissipate the heat of SCR/IGBT may get dry.
This excessive heat
results in blown Power Components such as SCR/DIODE/IGBT/CAPACITOR and other
components of your VFD.
Prevention:
A)
Selection of VFD should be done by considering Plant temperature,
external cooling, Rated current, Ambient temperature.
B)
Maintenance of VFD and replacement of thermal paste after every 1-2 a year further depend upon the condition of External cooling and ambient temperature
of the area where VFD installed.
C)
Use Air ducting for heavy rated VFD also use a proper selection of
cooling fan if VFD installed in Panel.
4. Selection of VFD and Motor.
Selection of VFD plays a very important role, if you have connected your VFD to an incompatible motor or
machine, it is going to degrade its performance. There are some machines that
work well with a soft starter instead of a VFD so select VFD wisely.
Prevention:
A)
In some application, you need to select VFD one rating higher because
of load characteristics.
B) Make sure you about the compatibility of the motor or application before you go ahead with connecting your VFD to the device.
5. Ignoring Warning and error.
The most unnoticed reason for VFD failure is ignorance. If you
ignore the early warning signs, a relatively smaller issue will turn into a much larger one, having worse consequences.
In lots of VFD, some warning or Alarm can bypass through
programming which leads to failure of the drive.
Example: Earth Fault, Heatsink Temperature, control or power
card Temperature, cooling fan alarm, maintenance warning, etc...
Prevention:
A)
Never bypass any alarm or warning until and unless there is
emergency.
B)
Check fault history of VFD daily or weekly and take necessary action.
C)
It is advisable to start with preventive measures and seek AC
VFD drive repair service as soon as you start noticing irregularities in your
device.
