Tag Archives: a Zest WEG Group company


Testing transformer oil is a key function end-users should build into their maintenance programmes, as it speaks volumes about the condition of the transformer itself, according to Ronaldo Bertoldi, engineering manager at WEG Transformers Africa.

As one of the largest manufacturers of transformers in South Africa, WEG Transformers Africa has a state-of-the-art oil laboratory at its production facility in Heidelberg, Gauteng, and offers an extensive range of services to transformer owners.

“The dissolved gas analysis (DGA) test is one of the most important for a customer to conduct,” says Bertoldi, “as it provides the first available indication of malfunction within a transformer unit.”

Bertoldi highlights that the DGA indicates the internal condition of the unit, and identifies degradation taking place. It is therefore essential for effective monitoring and trend analysis.

The laboratory is able to perform a range of important routine tests, starting from the ‘kV’ test which passes current through the oil to test its insulative properties. The water test would then measure the parts per million of water in the oil; as a conductor of electricity, high levels of water become both damaging and dangerous to the transformer’s continued operation.

“It is also important to measure the amount of cellulose in the oil, as this is an indication of the extent to which the paper around the winding is degrading and turning to sludge,” Bertoldi says. “Judging by how much cellulose is in the oil, a prediction on the life expectancy of the transformer can be provided.”

Even the simple oil colour test has a useful function in showing oil quality, indicating that further investigation may be necessary to keep the transformer well maintained.

“All test results are kept in our extensive database, which allows a history of the trend analysis to be available to each of our customers,” Bertoldi says. “We use these figures daily in developing trends for a particular customer or even a particular transformer unit.”

Access to regular oil test results makes it easier for customers to identify potential problems arising in their transformers, and to take corrective action to avoid expensive damage or unplanned downtime.

Oil analysed for paper in oil content


A range of factors need to be considered when correctly sizing a transformer for optimal performance in any application, according to Ronaldo Bertoldi, engineering manager at WEG Transformers Africa (WTA).

Ranked among the largest manufacturers of transformers in South Africa – and serving a range of sectors including mining, industry and agriculture – WTA is a leader in distribution transformers, power transformers and mini substations.

“Sizing a transformer for a particular application can be done using a simple equation, but the selection process requires many other factors to be taken into account,” says Bertoldi. “Determining the right transformer for the job requires an in-depth assessment of the conditions under which the transformer will operate.”

He emphasises the difference between the full load current required by an application, and the start-up current if there is a direct online starting process. If the motor is initiated by a direct online start, this part of the operation could require a much higher current than when it is running.

Bertoldi also points out the significance of the distance between the source of the power and the equipment consuming the electricity, as will be a voltage drop that will affect the sizing of the transformer.

“Transmitting low voltage over long distances can also be more expensive due to the thicker cables required by the higher current,” he says. “Users can achieve a more cost effective solution in many cases by considering a step-up, step-down configuration, where the voltage is increased to facilitate longer distances, then reduced to the requirement of the equipment at its point of location.”

WTA’s years of expertise in manufacturing and repair equips it well to advise customers in the sizing and selection of the right transformer for their specific needs. Its Heidelberg facility is capable of locally manufacturing power transformers up to 40 MVA in voltages up to 132 kV as well as mini substations and ring main units. All distribution and power transformers are manufactured to SANS 780, BS 171 and IEC 60076 specifications under ISO:9001 quality standards.

The WTA mini substation production line.


Any type of power outage, no matter how short, can place crops and farm animals at risk – which is why a reliable source of backup power has become vital for agricultural operations to operate efficiently and safely.

Power disruptions on farms are even more damaging due to the economic pressures and the difficulty of surviving in this ever-changing market sector. Today, there are many factors outside of the farmer’s control that can affect profitability. Modern farming methods are also increasingly assisted by a range of automated equipment that relies upon a steady supply of electricity to do its work.

The rural and often isolated setting in which many farms operate make them even more vulnerable to power cuts and damaged power lines, as electricity supply generally takes longer to restore – thereby aggravating the impact on normal farm activities.

The result is that agriculture – like many industries – can experience catastrophic consequences as a result of power outages, and this has made it a business imperative for every farm to have a sustainable and secure supply of energy.

The good news is that solutions are available, to empower farmers to get the most out of their farming equipment without having to risk a power outage turning into a disaster. A good, dependable backup diesel power generator set – or genset – can effectively keep everything running smoothly until mains power is restored. While a quality genset does require an initial capital outlay, the benefits and cost saving in the long run turns it into a positive expense.

Industry experts like the Zest WEG Group offer the experience and capacity to design and provide high quality agricultural generator solutions with top engine brands, for reliable backup or continuous power in various farming applications.

The right solution begins with making the appropriate generator selection, by considering the load size, voltages, running cycles, access to site and delivery constraints. The Zest WEG Group – which locally manufactures generator sets at its Cape Town facility – offers fit-for-purpose solutions that are either standard off-the-shelf units or custom-built for specific applications.

The Zest gensets can be supplied in stationary or mobile configurations from 10 kVA up to 3 350 kVA – and their capacity can be increased upwards with multiple synchronised sets. All generator sets are supported by customised service and maintenance agreements.

Integrated packages that include mechanical and electrical manufacture and assembly as well as electronic design incorporating in-house control panel manufacture are available. The company also provides supply and installation of transformers, cabling, bulk fuel systems and sound attenuation with standby generators on a turnkey basis, together with project management, installation, commissioning and maintenance.

Zest WEG Group’s power generator offering comes in three ranges: the value range; the premier range; and the custom range. The value range is a cost effective 10 kVA to 2 250 kVA 50 Hz/60 Hz solution with the option of FAW, Doosan or Mitsubishi engines. The premier range is also made up of 10 kVA to 3 350 kVA 50 Hz/60 Hz units, but with engine offerings from Perkins, Volvo, Scania, Cummins, MTU and Deutz. The custom range is tailor-made for customers, built and installed for their specific applications.

The company is able to assist customers with correct generator sizing by calculating their required kVA generator load based on their unique on-site load requirements.

To keep costs down for farmers, Zest WEG Group also offers WEG softstarters and WEG variable speed drives (VSDs), which reduce the required genset power capacity.

VSD technology reduces the electric motor’s start-up current, which assists with peak load demands, and also eliminates the need to oversize the generator which would have been a requirement without a VSD.

Another important benefit of using VSDs is the power saved by controlling the output speed of the electric motor, ensuring that the customer uses less energy. Using a VSD allows for the right sizing of the generator which means that the diesel engine will run at its rated loads and maintenance and operating costs are significantly minimised. In many cases, engine capacity can be reduced, with reductions in oil and fuel consumption being realised as a result. Using a smaller engine will also have a positive effect on the cost of parts.


A wide-ranging upgrade of the electrical distribution network at a catalyst manufacturer’s plant near Johannesburg has been successfully – and speedily – completed by Zest WEG Group companies led by Shaw Controls.

According to Shaw Controls chief operating officer Bevan Richards, the work was efficiently coordinated between companies in the Zest WEG Group so that the contract could be fast tracked during a special weekend shutdown to minimise the production disruption at the facility.

“This major upgrade of the plant – which included the moving and replacement of 17 transformers and 22 medium voltage outdoor panels – had to be completed in just five days,” says Richards. “With careful planning and preparation, along with the close collaboration of the customer, we were even able to complete the job with a day to spare, allowing production to resume earlier than expected.”

To meet these demanding timeframes, Shaw Controls proposed and implemented a solution that involved an E-house – a prefabricated walk-in modular enclosure to house switchgear and auxiliary equipment – as well as two containerised substations, built in-house at the company’s ISO 9001 Bureau Veritas-certified manufacturing facility in Heidelberg.

The E-house was equipped with free-issue medium voltage switchgear from the customer, and the substations were each equipped with a 400 V main distribution board. These modular solutions allow for assembly and testing in the factory, where customers can view the build progress as well as witness the performance of the finished product before delivery is finalised.

“The medium voltage panel was installed, pre-tested, commissioned and the relays programmed before delivery,” he says. Once at the customer site, it was simply a matter of connecting the cables before getting the system ready to be re-energised.

“Part of our project management role was to develop the design and construction drawings, working in conjunction with the customer’s consulting engineer,” he says. “We brought in group companies WEG Transformers Africa (WTA) to provide two 3 MVA oil transformers that stepped down from 11 000 V to 400 V and EnI Electrical to conduct the on-site construction work, which included medium and low voltage supply, installation and termination of cabling.”

EnI Electrical received all equipment on site, undertaking substantial site preparation and pre-works prior to the plant shutdown. It then instituted a two-shift system of 12 hours each over the project period, while Shaw Controls was on-site providing overall project management. On the first day of the shutdown, with the assistance of a mobile 250 tonne crane, EnI Electrical was able to remove all the old equipment and place the new items in position ready for cabling to begin. Access to the work area was also constrained, requiring the crane to reach over an existing building.

By the end of the project, 380 metres of 11 kV cable had been laid, with two cable joints and seven terminations, as well as 1 560 metres of 400 V cable with 21 joints and 132 terminations.

“A turnaround as fast as this is really only possible due to the utilisation of the E-house and containerised substation option,” he says. “Delivering all the equipment in loose pieces and building everything on site, as well as the necessary re-testing, would take much longer and would involve considerably more production downtime for the factory.”

The new system was designed by Shaw Controls and the consulting engineer to give the customer a highly stable system with more flexibility in terms of how the loads are distributed to the plant.

Added benefits of the E-house solution for the customer are that they do not have to manage multiple service providers and suppliers in the various aspects of constructing a substation, says Richards. The process could be potentially complex, time consuming and expensive, especially when conducted in remote sites where access is difficult and infrastructure is weak.


The benefits of variable speed drives (VSDs) are making this technology a popular choice among users of electric motors; now, with the introduction of the WEG Insulation System Evolution (WISE®) to all WEG motor lines, customers have full assurance that all WEG motors are VSD-compatible.

“Not all standard electric motors are suitable to be used with VSDs,” says Fanie Steyn, manager rotating machines at Zest WEG Group. “The motor insulation systems are susceptible to insulation damage caused by the harsh switching frequencies and voltage peaks generated by VSDs.”

Steyn explains that VSDs use power transistors – typically insulated-gate bipolar transistors or IGBTs – for the switching process. To achieve the high frequencies necessary for switching, the transistors have to turn ‘on’ and ‘off’ to conduct current repeatedly at high speeds. This results in voltage pulses with a high dV/dt, or rate of voltage change over time.

“When squirrel cage electric motors are fed by these high frequencies, the voltage pulses – combined with the cable and motor impedances – may cause repetitive conditions of over voltage or voltage overshoots at the motor connection terminals,” he says. “This may degrade the motor insulation system and reduce the motor’s useful lifespan.”

To ensure that this does not occur in WEG motors, the WISE® insulation system has been developed through the use of enhanced materials in the production of the motor insulation. These materials include VSD‑compatible wire, insulation film, impregnation material and suitable cables.

WEG has also specially developed its LackTherm varnishes for the insulation systems of its electric motors, which are applied to the 99,9% pure copper wire during the enamelling process. These LackTherm varnishes have excellent dielectric strength, flexibility, hardness and chemical resistance, as well as strong adhesion properties.

During the impregnation process, the stator coils receive layers of high‑solid resins and water‑based coatings which are environmentally‑friendly and free from harmful solvents – as required by the ISO 14000 guidelines.

“This process allows any WEG motors to be used with VSDs, as the WISE® insulation system ensures that the motor windings are protected against voltage peaks and voltage variations,” says Steyn.


At the leading edge of electric motor technology and related sectors, the Zest WEG Group is also innovating its empowerment initiatives by facilitating ownership of its shares by two black owned Non Profit Organisations (NPOs) that directly benefits communities in need.

A subsidiary of the world’s leading motor and controls manufacturer WEG, the South Africa-based Zest WEG Group has taken this step to create a broader based and more sustainable ownership foundation for its compliance with the new BBBEE codes of goods practice.

Hot off the press is the announcement that the two NPOs, together with the company’s employees Trust, now hold 51.6 % of Zest WEG Electric, the South African arm of the Zest WEG Group. One of the NPOs is in the education sector and the other in the micro-enterprise support sector. Significantly, the shareholding comprises 31.68% black female beneficiaries.

Zest WEG Group CEO Louis Meiring says that not only will most of the beneficiaries of the NPOs be black women, but the arrangement will sustain the good work of these NPOs into the future.

“Significantly, the achievement of our Level 2 BBBEE status is certainly one of the best, if not the only such one, in our market sector, and we believe this initiative breaks new ground for empowerment in South Africa. It provides a model for sustainable collaboration between business and civil society while forging a more effective implementation of the original intentions of the country’s BBBEE philosophy,” he says.

Meiring says the business has always been proactive about transformation and builds the BBBEE compliance goals into its business culture.

“We previously readily achieved our Level 4 status, based on our shareholding, skills development, supplier support and community investment, and this is simply the next step in our transformation journey,” says Meiring. “Now, this ownership-related initiative takes us significantly further on our pathway as a responsible corporate citizen.”

Zest WEG Group provides a range of skills development resources to schools, universities and the broader community including teaching, equipment, financial aid and infrastructure. These aim to develop local talent and capacity, bringing young learners into the business and industry.

Juliano Vargas, Zest WEG Group’s logistics and operations director, says the organisation’s close relationships with these communities allow the identification and nurturing of talent from an early stage.

“With our double-digit growth, even through the recent downturn, our business is creating opportunities for job seekers, and we prepare them well to replenish the positions that our expansion requires,” says Vargas.

Skills are developed in-house through apprenticeships, internships and mentoring in various disciplines and are sometimes also supported with study bursaries.

“We adopt and evolve leading edge manufacturing technologies, so we need to upgrade our skill levels among all employees on an ongoing basis,” he says. “WEG in Brazil shares both their technology and their skills with us; visiting WEG factory experts conduct training for our teams regularly.”

These processes in turn promote employment equity as potential managers and leaders can be identified and developed. The company also works hard to bring small, local suppliers into the Zest WEG Group’s value chain, by developing their capacity to deliver and to become sustainable.

“Through our involvement with small business incubators, we even select and support small enterprises before they are in a position to become our suppliers,” he says. “Those that progress well may earn contracts from group companies, following which we review their performance and keep track of them to ensure that they deliver good value in their services and products.”