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Variable speed drives are one of the most popular items we see at Northern Industrial, for repairs, spare parts and upgrades. They are an integral part of any manufacturing plant and are often responsible for controlling critical processes, so any downtime due to a failing drive can be a big problem. However when they are in proper operation, they mean efficient and reliable plant performance, reduced downtime and decreased energy costs. As such important pieces of equipment for manufacturers, it’s essential to take quick action when any problems arise.

You have a problem with a drive, what initial points should you investigate?

Firstly, did the drive work for a reasonable period of time after commissioning? We would class a reasonable period as functioning acceptably for a month or longer. Do you have the details of the commissioning process to reference back to?

The next step would be to check if the process has changed. For example has any other equipment been added in the same area or share the same source? It may be necessary to adapt the drive to work in harmony with the changes.

Lastly, what is the performance complaint? Sometimes the problem may not be drive related and other equipment may be involved. It’s important to troubleshoot the application, not just the drive and keep an open mind that something else could be causing the problem that the drive is displaying.

Troubleshooting with fault codes

No matter which manufacturer your drive is made by, it will have a specific set of fault codes to assist with troubleshooting when a problem occurs. These codes are usually consistent within a manufacturers’ series of drives, from drive series’ for simple tasks through to those for sophisticated applications. Take the Danfoss VLT family, all the series from the Micro Drive to the AutomationDrive and the application specific drives such as HVAC and AQUA, share the same fault code structure.

However, whoever the manufacturer is, fault codes typically fall within the following general categories


Extracting fault logs

Many manufacturers provide software that enables drive users to extract the parameters and fault logs from the drive. With these tools users are able to compare the current parameter set with what occured on commissioning day. User can also analyse the data on a computer screen for more details and also enable you to find prompt and effective remote support from a company like Northern Industrial should you need it. ​​​​​​​

Gather the facts like a true drive detective

When troubleshooting a faulty variable speed drive, it’s important to ask certain questions. But before you do, make sure to have the technical information from the drive’s label to hand. If you can’t access the label, or the information is incomplete, a quick google search usually returns useful information.

What questions should you ask?

- Is proper power being applied to the drive?
- What information is being displayed on the drive’s keypad or operating panel?
- How do you control the process? Are there any industrial networks involved, such as Ethernet or Profibus?
- Is there a problem with the transmission or collection of data?
- Are there any fault codes on the drive display that can help with the analysis of the problem

If you have an intermittent fault, where the drive still operates some of the time, consider if any operational data is available for you to troubleshoot the problem, such as

- Output speed/frequency
- Drive load
- Output voltage
- Output current
- Drive temperature
- Run time
- DC Bus voltage
- Analog input/output status
- Digital input/output status

Sometimes it will be necessary to take the drive offline and send it to an industrial automation specialist like Northern Industrial for repair, or purchase a spare if repair isn’t an option. We would always recommend keeping spare units in stock for critical drives so that you can switch the drives for as little downtime as possible.

If you would like to talk about any drive problems you are experiencing, or need any advice about any variable speed drives from all manufacturers, get in touch with our team today.