Why do drives fail?

ABB Automation Technologies (Drives and Motors)visit website


A drive could theoretically last for a lifetime, but only if properly taken care of. Modern variable-speed drives (VSDs) are exceptionally reliable these days, but they are not indestructible. That said, if you notice similar persistent or repeated trips in a VSD, then chances are that the drive is not actually the problem. If such trips are ignored (eg overtemperature), they can sometimes result in the failure of the drive. Here we outline some of the primary factors that can contribute to why variable-speed drives trip and/or fail.

Incorrect installation

This is the single most important contributory factor to drives tripping or failing, and yet the one that should in theory be the easiest to avoid. For starters, the ambient temperature around the drive should not exceed 40degC. If the location of the drive makes this impossible then there are ways around it, for instance by cooling the drive externally, but this is not an ideal situation and will of course increase energy usage. It is also important to keep the drive free of dust, as dust can impede the air-flow and lead to overheating.

The drive must be kept dry, as moisture will corrode the circuit boards over time. This can be difficult in, for instance, the food industry where equipment has to be regularly washed down, but again there are ways around it such as mounting the drive in an enclosure with the appropriate ingress protection (IP) rating. Any ABB authorised value provider will know all of this, but it’s up to the customer to ensure that the AVP is briefed properly on exactly where and how the drive will be used.

Poor maintenance

Planned maintenance is far more cost-effective than unplanned breakdown repair, so to prolong the life of your drive as well as saving time and money, it is vital to have in place a programme of preventive maintenance. ABB and its authorised value providers offer a range of maintenance services to suit your needs, from annual inspections all the way up to remote monitoring services that can tell ABB that something’s amiss in your drive long before it displays any signs of wear.

Whilst these things are generally best left to the professionals, there are some maintenance activities you can carry out yourself. Spraying compressed air (make sure it’s dry and oil-free) through the heat sink fan will help to keep it clear of dust, and checking connections can prevent arcing from heat cycles and mechanical vibrations. The capacitors in a drive will also wear out over time (usually 5–10 years) and require replacing, so this is something that needs to be checked. Capacitors work much like batteries, and so if the drive is rarely run at full output it’s a good idea to power it up every 6 months or so to ensure that the capacitors remain at peak performance capability.

Excessive loads

When an operator gets to know their machine it is natural to want to push the boundaries and see what it can do. However, your drive won’t thank you for running it over its rated level. Often drives are run over capacity due to a lack of experience and/or training, so it is important to ensure that all operators are aware that running a drive beyond its capabilities can and will damage it.

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13 October 2015

ABB Automation Technologies (Drives and Motors)visit website
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