Variable speed drives (VSDs) are generally considered as vital contributors to energy efficiency, but they also have features that can reduce the operational disruptions caused by loadshedding.
“Any industrial operation that relies on electric motors will face severe challenges to its continuous workflow when loadshedding strikes,” says Pieter de Villiers, Gqeberha branch manager for Zest WEG. “Much of the disruption is related to the process of starting machinery up again after a power loss, which often must be conducted as a series of sequential actions that an operator must oversee and implement.”
He adds that many motor users are not aware of the usefulness of WEG VSDs in automating and controlling this start-up. WEG VSDs can be programmed to initiate a sequence of actions, so that this does not have to be done manually by the operator. A simple example to illustrate his point is where water is being pumped through pipelines which drain out during loadshedding. In most cases, the pumps cannot simply be started up again at full speed in a dry condition, without the risk of cavitation and other damage.
“In cases like this, the WEG VSD can be programmed to start the pump at a lower speed until the pipeline is full of water, after which it could resume full pumping duties,” he says. “Similarly, it is important for a siren to be sounded on a mining operation before a conveyor system is re-activated after the start of loadshedding, for safety reasons. The WEG VSD can also be programmed to automate the re-start process, and it initiates the siren to warn staff that the conveyor will be running again.”
He highlights that the full range of WEG VSDs have built-in PLC capability, allowing them to be programmed in this way – without the need for PLCs to be added to the system. Another function of VSDs that makes them valuable assets in times of loadshedding is to prevent equipment from tripping out. This can happen when there is too much ‘dead time’ between grid power turning off and a back-up generator kicking in.
“If dead time lasts more than a few seconds, many motor-driven applications can trip out and require a re-start, which can be time consuming and labour intensive. A common way that the VSD stays live during this dead time is through the stored energy in its capacitors, allowing it to then re-accelerate the motor when the generator kicks in,” he explains. “It is also possible to set up the drive to utilise the inertia from the load and therefore power from the motor itself − essentially using the motor briefly as a generator to keep the VSD alive.”
WEG VSDs also play a useful role when energy users want to harness renewable energy sources like solar power. In a hybrid power system where a motor is connected to both the grid and to solar panels, a VSD can utilise the best source to feed the motor. If there is sufficient sunlight, the system will detect the power flowing in from the panels and optimise that power source.
“On the other hand, the VSD will switch to grid power at night or when it is cloudy,” says de Villiers. “This allows motors to be kept running while reducing the cost of energy, and also reducing the user’s carbon footprint.”
Read more...A cure for measurement headaches in contract manufacturing VEGA Controls SA
Editor's Choice
A contract manufacturing organisation provides support to pharmaceutical and biotechnology companies in the manufacturing of medications, formulations and substances. VEGA’s measurement solutions offer accuracy and reliability for monitoring levels and pressures during the manufacturing process.
Read more...PC-based control for a food capsule and pod packaging machine Beckhoff Automation
Editor's Choice
For TME, a machine builder specialising in the packaging of powdered foods, Beckhoff’s PC-based control technology offers unlimited opportunities when it comes to performance and innovative capacity in terms of flexibility, scalability and openness.
Read more...Generators: The muscle in the new energy mix WEG Africa
Electrical Power & Protection
Contrary to their reputation as noisy and dirty, generators are a key part of modern energy supplies. Generators are reliable electricity workhorses in times of need. But they are also becoming welcome additions to modern energy mixes through efficiency improvements, noise reduction and flexible design choices.
Read more...Simple and efficient level measurement in the mining, minerals and metals industries Endress+Hauser South Africa
Editor's Choice Level Measurement & Control
Measuring devices in the mining, minerals and metals industries face the challenge of varying material states and long distances in measurement height. Endress+Hauser’s answer to these challenges is the new Micropilot family.
Read more...PC-based control for fertiliser Beckhoff Automation
Editor's Choice Fieldbus & Industrial Networking
On a farm in the USA, valuable ammonia is extracted from slurry and processed into ammonium sulphate. NSI Byosis has transformed this complex process into a flexible modular system. This modular approach requires an automation solution with flexible scalability in both hardware and software, which this Dutch company has found in PC-based control from Beckhoff.
Read more...Loop signature 28: Things to consider when tuning. Michael Brown Control Engineering
Editor's Choice Fieldbus & Industrial Networking
I was giving a course at a remote mine in the middle of the Namibian desert. We were discussing tuning responses, and as I always do on my courses, I mentioned that in my opinion ¼ amplitude damped tuning is not desirable, and is in fact not good.
Read more...Control without complexity
Editor's Choice Motion Control & Drives
In an era where precision, performance and smart control define industrial success, the right driver can make all the difference. At Axiom Hydraulics, we’ve seen firsthand how the Sun Hydraulics XMD series transforms hydraulic systems, from mining and construction to agriculture and automation.
Read more...The thermal combustion balancing act
Editor's Choice
From carbon taxes to export tariffs, and cost containment to security of supply and sustainability, companies are under increasing pressure to switch to greener fuel sources. Associated Energy Services warns that this pivotal change has some potentially serious knock-on effects.
Read more...What’s driving the IE3 motor revolution? WEG Africa
Editor's Choice
The International Efficiency 3 (IE3) motor standard will soon become South Africa’s legal minimum standard, mandating that local suppliers offer more efficient electric motors. What is driving this change, and how does it affect the many industries that rely on these modern electric workhorses?
printer friendly version