Variable frequency drive belongs to electronic products, which were composed of many components. An electronic product will not correctly work if any component goes wrong. The Common failures of frequency converters are overvoltage, overload, overcurrent and overheating. They are generally caused by improper use and the operating environment.
Meanwhile, there’s a particular service life for electronic products. The aging of the product will be more evident as the use of time increases.
According to The Tax Duty Calculation Regulation for Fixed Asset Depreciation, the lowest standard for electronic equipment service life is three years.
Many people buy a mobile phone and change to a new one after two or three years of use, even it's still working fine. Compared with the greater frequency of changing cellphones, people replace home appliances such as TV, computer, refrigerators, and air conditioner far less. Under proper use and good maintenance, the service life of these appliances can reach 15 years in theory, even though most people won’t use them for that long.
Let’s get back to VFD, an industrial electronic part, its durability and service time is much longer for sure. It is common for some factories to use VFDs for more than ten years. Some VFDs of Japanese and German brands can be used for more than 20 years.
Of course, during its service time, the busbar capacitor will be replaced. But as long as staff take good care of the workshop environment and maintenance, the overall service life of VFD will be much longer than that of household appliances.
Since the service life of VFD is so long as 10 - 20 years under normal conditions, what factors lead to some failures and shortened service life of VFD?
Here are 3 major factors that any VFD user and maintainer should know.
For all kinds of reasons, many people are unable to live in perfectly healthy and ideal environment, and it's the same with appliances.
Many VFDs may not meet the specifications of ideal conditions, but with an understanding of the adverse environment and proper maintenance, users can still maximize service life of VFDs.
Common adverse conditions are as below.
There is corrosive gas and electrostatic dust in some chemical and plastic plants, and the VFD is under no protection. The plant may not buy professional maintenance application for VFD either. It is directly installed in the workshop, without obvious separation, and often fails within a year and a half.
Dust and corrosion will directly damage the circuit board and welding joints, and static electricity or poor insulation will make electronic components break down and damage.
Some equipment vibrates greatly, such as punch press. If the VFD and its facility are installed carelessly, they will vibrate together. After a long time, the circuit connector of VFD will be loose, and so is the solder of the circuit board, causing problems such as false soldering and damage.
Therefore, install VFD as far away as possible from any vibrating equipment.
Some places are relatively humid, such as some water supply and drainage workshops, or some humidifying places, or open-air use environment. Humidity and high temperature may lead to inverter insulation break down.
Therefore, if you want to avoid the damage of the inverter and extend its service life, if possible, you should install the inverter in a separate electric cabinet workshop, matched with an air conditioner and exhaust fan, so as to reduce the damage probability.
A variable frequency drive needs to consider good grounding and appropriate lightning protection devices in some areas with frequent lightning. It’s not uncommon that the VFD is hit and damaged by lightning.
In some areas, because the grid voltage fluctuation is relatively large, or the load distance is small, we should also consider adding in line reactor, bus reactor and output filter and other accessories.
Besides choosing the proper operating environment and protection, many people also make mistakes in the choice of product model and product operation process, which will cause the product to fail to meet their expectations and failure.
A VFD is a power source that changes the frequency and voltage that drives the motors to work. So, you need to choose the right product according to the engine and the load situation.
In addition to general type of VFD, there are fan pump type and vector type of early VFD models. Now with the increasing use of VFD, many customized VFDs are developed according to the equipment, such as elevator specified VFD, ball mill specified VFD, spinning specified VFD and so on.
If a VFD is designed with a specified frequency converter, it will be more competent for the corresponding load than general models in theory, and it can cope better with the current use environment. Relatively speaking, it is not so easy to break down.
In some cases, the frequency converter needs to start frequently, so it needs to increase the capacity to avoid the damage caused by excessively high temperature, or increase the external braking unit and braking resistance to avoid the impact of long-term braking.
Some work environment doesn't require a short acceleration and deceleration time, so it should be adjusted a little longer.
For some working loads need to run at low speed, the inverter needs to be set to avoid working in the low frequency band. We can increase the speed ratio to improve the actual working frequency of the inverter, which can also extend the service life of the inverter.
If you are not sure what is a quality VFD, especially when its your first time buying electronic parts, then just go to big brands. Of course this rule applies to buying anything.
Because of years or even decades of accumulated process data, and strict quality management system, and the components used are relatively reliable, the overall probability of damage of big brand VFDs is lower than that of small brand ones.
Another key factor determining the quality of a VFD is its printed circuit board.
Over the years, VFD manufacturers have done a lot of innovations and development on printed circuit boards to make themselves have a competitive quality advantage against each other.
By now, VFD quality has reached a very high standard, heat resistance and aging resistance has been dramatically improved.
The voltage withstands value of the modules used will be higher for a quality VFD, and the current overload capacity will be more substantial. Electrolytic capacitors and other parts that can resist aging will also be of better quality.
To sum up all the above, choosing right VFD, and providing good maintenance and protections to it is the best way to maximize its service life and avoid failure.