Is it time to embrace variable speed drives?

For decades the take-home message about variable speed drives (VSDs) has been that they can save process operators a lot of energy. While energy remains high on the agenda, the rise of the Industrial Internet of Things (IIoT) and automation more generally means that the smart electronics built into VSDs now promise even more benefits.

VSDs save energy by automatically matching the speed of motors to meet variable demand when running equipment such as pumps, fans and compressors. This contrasts with more wasteful control techniques that run motors at a constant speed and instead rely on downstream devices to choke off the output when demand drops.

“Energy savings are very important to clients so will continue to be a key driver. However, we see process optimisation and management as a big factor going forward as the digital side of this technology develops,” says Stuart Melling, head of ABB’s VSD and controls business in the UK.

Smart direction

Similarly, Paul Pryor, product marketing manager for drives at Schneider Electric, says that energy is just part of the equation: “Smart drives are now facilitating more than energy management optimisation, although clearly this is a very important driver.

“As companies start to understand that other information can be gained from machine patterns of usage, uptime, downtime figures and many more, the end user can start to understand usage and stresses that limit efficiency. By evaluating data to understand the usage patterns, the user can predict when failures may occur and put in place proactive preventative measures to extend the life of his process.”

Smart drives are now facilitating more than energy management optimisation, although clearly this is a very important driver

Paul Pryor, product marketing manager for drives, Schneider Electric

So investing in smart drives up front is the key to unlocking longer-term benefits, although that can sometimes mean paying a premium, acknowledges Pryor: “Saving capital expenditure (CAPEX) by beating down the unit costs by one or 2% is often seen as a way of saving money, but actually this can be detrimental to the operating expense (OPEX) costs. Why? Smart devices that are designed to provide IIoT compatibility are not always the cheapest.

“By going for the cheaper option, companies limit what information is available to optimise their processes. The long-term gains in OPEX far outweigh the small short-term wins in CAPEX and can be in the magnitude of 10-20 times.”

Melling adds that even where there is additional CAPEX it is likely to be very modest: “There may be some special functionalities that are a cost adder but much of the digital developments are standard.

“Some of our smaller machinery drives (such as servo controllers) would simply never need some of the features discussed so they are not enabled. Our most popular ACS580 and ACS880 drives come with many digital features as standard, but there are also industry and application specific variants (for example the ACQ580 for water applications), which have features unique to those industries. As an example, our ACQ580 comes with intelligent pump control (IPC) and anti-rag functionality to improve productivity of water and wastewater pumps.”

Enabling predictive maintenance is one of the main selling points of IIoT in general, and that’s also true when exploiting the smart features of VSDs.

“The performance and use of the drive is closely related to its future health. Based on decades of knowledge of failure patterns, algorithms can now predict future health and have been refined to the level that a realistic timescale can be put on expected events,” says Melling.

Oxygen of innovation

All VSDs are part of an overall system, with the motor and the equipment that they’re driving completing the picture. So can the data from a VSD help pinpoint where trouble is brewing within such a system? The answer is yes, according to Melling: “We have a recent case study on a milk delivery system in New Zealand where the drive sees pump cavitation and corrects flow rates to mitigate it. Algorithms are used in sensing mechanical problems based on the electrical signature that the drive is seeing. In addition, ABB recently launched a digital power train system, which uses Cloud-based technology to look at the full power train from pump to VSD.”

But improved maintenance is not the whole story, say suppliers, stressing that other potentially valuable insights can be gleaned from VSD data. “Better and more intelligent control is often the key,” says Melling. “For example, UK water companies use ABB drives to intelligently reduce spikes in pipe pressure, therefore reducing leaks. As another example, tighter control and more developed software platforms are now allowing active heave control for marine winches to be a feature in the drive which allows cargo lifts in more extreme sea conditions for a wider operating envelope.

“The benefits of Cloud-based algorithms give sufficient processing power and provide the ‘oxygen’ to fuel these advances. It is also clear that the whole movement has inspired an innovation culture.”

ABB’s ACS580 and ACS880 drives provide a good example of this knock-effect of technology enabling new ways of working. ABB says that these drives are now Bluetooth-enabled, allowing parameterisation, commissioning and fault diagnostics via a mobile device. Melling notes that this is especially useful if drives are positioned in inaccessible locations. The Bluetooth connection is being further developed to allow more Cloud-based services to be implemented.

“Preventative maintenance is a key part of the IIoT message, but there is so much more that can be achieved,” agrees Pryor [pictured]. “Simply understanding the uptime/downtime ratios of the processes your plant runs could give huge insight into operating procedures, shift patterns and other processes. IIoT is all about ‘getting to know your process’. The more you understand, the better your ability to improve.”

Schneider Electric says its Altivar Process ‘services-oriented drives’ provide a good example of what’s currently on offer. A range of features are designed to help users to manage increased data volumes, improve services and boost overall efficiency.

Altivar Process drives offer real-time intelligence, they’re user-friendly and designed to integrate seamlessly into existing plant structures, says the company. They’re also Green Premium products. So in addition to promising energy savings of up to 25%, the drives are built from ethical materials and are designed to be easy to recycle.

With all this in mind, why wouldn’t process operators use VSDs? It’s a good question, but suppliers have been highlighting the major energy savings on offer for several decades now and there are still huge numbers of eligible applications where they’re not being used.

So what are the chances of all these extra benefits finally tipping the scales for organisations that are still dragging their heels? Suppliers believe the answer is likely to depend whether potential users are embracing the IIoT/Industry 4.0 more widely.

Many industries are looking for real results of IoT before making large investments and so we are seeing a lot of smaller scale ‘experimentation’ across most industries

Stuart Melling, head of ABB’s VSD and controls business in the UK

“The new Altivar Process logs and makes process information available to the end user, but what do they do with it? Many customers are starting to realise that automating reporting takes a lot of time and expertise and therefore a lot of data potential is left untapped. Schneider Electric is working to bring online Cloudbased services to help you foresee your full IIoT potential and save you the total costs of report creation and management,” says Pryor.

Meanwhile Melling adds that the drivers will depend on the priorities of different process industries: “For obvious logistical reasons, the marine industry has embraced the benefits around remote support as an ‘early adopter’. Many industries are looking for real results of IoT before making large investments and so we are seeing a lot of smaller scale ‘experimentation’ across most industries. We have seen perhaps the most interest in the water industry from existing clients, but the food industry seem very keen to understand potential benefits.”