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Dealing with inverter failure: replacement or upgrade?

Dec 31, 2020

Dealing with inverter failure: replacement or upgrade?

For inverters that have failed or have been used for too long, they need to be replaced or upgraded in time. In order to minimize costs and improve efficiency, users need to know when to replace and upgrade the inverter is most appropriate.


In our era, frequency converter (VFD) is the standard configuration of motor control. Because they are mainly installed in commercial and industrial buildings, both new and old applications can benefit from the benefits of these smart devices. However, like all electronic equipment, frequency converters cannot be used forever.

For example, due to a power surge failure, or a 20-year-old inverter, which is not compatible with the building management system, it may need to be replaced or upgraded. Remote monitoring is essential for this application. In either case, replacing the inverter is not as easy as just replacing a unit, powering up and then leaving.

On the other hand, when you know what to look for and how to perform the task correctly, the task itself can actually be very simple. Most people encounter two main situations when replacing the inverter.

Scenario 1: Replace the inverter with the same model

It sounds simple, but when replacing an inverter with the same model, there are several things that need to be confirmed. The first priority is to match the models, voltage levels, and current/HP ratings of the two devices. This can also verify whether the new inverter fits the existing physical space. Next, all wiring must be connected to the same terminal name. This ensures that the I/O function of the new inverter is the same as the I/O function of the old inverter. Finally, the parameter settings should match the key settings of the application.

There are many forms of backup, especially when the old inverter can still be powered on. If it is accessible, you can write down the parameter settings, store them in a software program, or even save them to the memory of the keypad, and then transfer them to the new inverter. Ideally, this should be done before the replacement process takes place. If the frequency converter is installed in a larger device, the original equipment manufacturer may have its own parameter table. In the worst case, the user must manually set the inverter and optimize it for the application.

It may be beneficial to keep some parts from the old frequency converter. According to the severity of the inverter failure, if some components (such as keyboard, cooling fan and control/terminal board) are not damaged, they can be reused. Do not keep the main circuit components (including capacitors) of the inverter, as this may cause internal damage or greater wear.

Scenario 2: Use different models to upgrade the inverter

Upgrading inverters with different models will be slightly more complicated. This also involves other factors. For first-time users, the size should be determined and the appropriate model should be obtained, just as the inverter is used in a new application. It is necessary to consider variables such as current, voltage, enclosure, derating and application type, as well as whether the original inverter is the correct size.

Before installation, there are some other considerations to consider. Obviously, physical size adjustment is the most important. Generally, newer inverters are smaller and more compact than the previous generation, but this is not always the case. This is also true when replacing products from other manufacturers. It is recommended to always check product dimensional drawings to verify space requirements.

Existing chassis or component settings also need to be carefully studied. Most independent inverter designs are only suitable for indoor environments, and there are almost no protective measures against air dust. They are usually placed in a housing that has better resistance to harmful elements such as dust and water. Replacing the entire equipment (inverter and chassis) can be expensive, and sometimes just the inverter has failed. It seems logical to only replace the frequency converter, but the compatibility of components such as circuit breakers, filters, bypass configurations and other electrical equipment needs to be checked.

After completing the above checks, you can connect. Assuming that the terminal name of the old inverter does not match that of the other inverter, a simple classification of I/O types can help figure out where to place the wires. Once the main circuit wiring is completed, the control lines and terminal names on the new inverter can be divided into 5 categories. They are digital input, digital output, analog input, analog output and other I/O. It is best to refer to the wiring diagram to get the exact function of the terminal.

As one of the final steps, programming makes the application a reality. If a list of parameters with non-default values can be obtained from the old inverter, setting up a new model may not be so troublesome. If this is not possible, you may need to configure the inverter from scratch. In this case, decomposing the basic knowledge (such as frequency and running commands) required by the inverter will make the setting easier. Advanced functions can be completed by programming at the end. Generally, the inverter user manual will provide detailed information about specific functions and a complete list of parameters. The keyboard can even contain detailed process setup wizards.

Repair and maintenance of frequency converter

Repairing the inverter is another option. Well-maintained and repaired equipment may be usable for another ten years. The ability to do this depends on many factors, such as the availability of parts, the type or size of the drive, and the degree of damage. Spare parts are usually also available for older models, so they may be a lower cost option.

Determining the root cause of inverter failure is often overlooked. Most inverter replacements do not have this consideration, but there are only a few cases where the problem is the inverter alone. Environmental issues such as humidity, dust, temperature and corrosion should be considered first. There are many other fault causes that come from outside the inverter itself. This includes but is not limited to motor problems and input voltage fluctuations, which can stress internal components such as capacitors. The protection and preventive maintenance of the frequency converter is very important and must not be underestimated.

Key concepts:

■ Know when to replace and upgrade the inverter can bring the most benefits

■ Check the compatibility of related components before upgrading.

think for a while:

What are the benefits of upgrading the inverter for your factory?

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