Tag Archives: Trafo Power Solutions

COPPER OR ALUMINIUM FOR DRY-TYPE TRANSFORMERS?

While many experts argue the respective pros and cons of using copper or aluminium in dry-type transformers, it is important to understand that innovations in transformer design have ensured that either of these two materials can today be applied with equal effect in most applications, according to David Claassen, managing director of Trafo Power Solutions.

Dry-type transformer specialists Hammond Power Solutions (HPS) – whose products are distributed in Africa by Trafo Power Solutions – has been using both copper and aluminium in the manufacture of conductors and bus bars in its low voltage and medium voltage transformers.

HPS has been a global leader in dry-type transformers for more than a century, and both materials have been used by HPS Europe in its production process for more than forty years.
The company has found no significant difference in the transformer lifespan delivered when using either copper or aluminium; from a technical point of view, the two materials are equivalent.

There is clearly a cost advantage to selecting aluminium as a conductor, as the commodity’s price tends to be significantly less expensive than copper, and more stable over time.
It is therefore not surprising that more than 80% of HPS Europe’s transformer production over the past 40 years – across all markets and applications – incorporates aluminium windings.

However, the argument is sometimes made that aluminium is inferior in terms of conductivity – as it has only 61% of the conductivity of copper – leading to higher energy losses.
Winding temperature is, of course, always a concern, but designers at HPS have been able to maintain temperatures below the insulation rating by designing aluminium winding transformers with conductors with larger cross-sectional areas than those made of copper.

Such design innovations in aluminium conductors have succeeded in reducing their energy losses to the same level as copper. This allows transformers of similar design and with the same temperature rise to exhibit roughly equivalent losses, regardless of the conductor material.

It is also argued that the thermal conductivity of copper is superior to that of aluminium in reducing hot-spot temperature rise in transformer windings. But this is true only when copper and aluminium windings of identical size, geometry and design are compared.

Claassen notes that, in fact, the thermal conductivity characteristics of aluminium can be very close to those of copper, for any given transformer kVA size.
The aluminium coil must just be designed and built 66% larger in its cross-sectional area, for the aluminium coils to achieve the same current-carrying capacity as copper.

HPS designs the cooling surface area, the coil geometry, the air ducting and the conductor shape to produce acceptable hot-spot gradients, regardless of the winding material used.

In terms of aluminium’s lower tensile and yield strength, there have been concerns expressed about its use in cyclic load applications – with aluminium demonstrating only 20% of the rupture stress capacity of copper.
In applications where loads draw high peaks of current, electromagnetic forces can cause movement of conductors and coil leads.

Again, the use of larger sized aluminium conductors addresses this issue, giving the aluminium windings almost the equivalent strength to copper windings.
HPS has found that the ability of its transformers to withstand the long-term mechanical effects of high impact loads or short circuits really depends more on adequate coil balance and lead support than on the choice of conductor material.

Expansion of aluminium due to changing temperatures has caused some problems when bolted connections are improperly installed, as aluminium expands nearly a third more than copper.
With the right type of spring-pressure connection, however, any loosening of joints can be avoided.
This can be done using either cupped or split washers, to provide the necessary elasticity at the joint without compressing the aluminium.
The result is that aluminium joints can perform equally as well as copper joints.

When it comes to connectivity, both copper and aluminium are prone to oxidation and other chemical changes when exposed to the atmosphere.

Cleaning and brushing with a quality joint compound to prevent oxidation is recommended for both materials but is more essential for aluminium.
HPS have a solution for aluminium and copper connectors that involves applying silver or tin-plating to either or both of the conductors in the bolted connection, or by putting a cupal transition plate between the materials.

Claassen emphasises that HPS has developed dry-type transformers for a range of industry applications – from distribution and marine vessels to railway, mining and off-shore rigs.

“Both aluminium and copper have been used in various applications for many years without any problem.
With our innovative design and production procedures, it is possible to avoid the technical limitations of aluminium conductors while retaining the advantages like cost and weight,” he concludes.

TRAFO FAST TRACKS DRY-TYPE TRANSFORMERS FOR BISIE IN DRC

Alphamin Resources’ remote Bisie tin mine is being supplied with fit-for-purpose dry-type transformers by Johannesburg-based Trafo Power Solutions, in a fast track project that will see the complete solution manufactured in just 12 weeks.

Bisie’s location – some 160 km north-east of Goma in the Democratic Republic of Congo’s North Kivu province – places constraints on the transformers’ installation that have been taken into account in their careful selection and design.

“With a very difficult access road to the mining operation, the substation and transformers have been custom designed to withstand the many stresses expected during transport,” says Trafo Power Solutions managing director David Claassen. “To deal with the extreme heat and humidity of over 90%, we have also designed the ventilation and airflow in-house.”

The delivery will involve the movement of two 3000 kVA, 400 V / 11 kV cast resin transformers housed in six metre high cube containers. The consignment will also include the ventilation systems, lighting and small power equipment. These transformers will be used for stepping up the supply from a diesel powered generator plant – from 400 V to 11 kV – to feed the mine.

Project scope also includes two 100 kVA, 400 V / 400 V Dyn11 dry-type lighting transformers for application outdoors.

“The design of these dry-type transformers makes them suitable for the climatic conditions at the mine,” says Claassen. “They require only a minimal movement of air across the windings to cool them down, although forced air options can also be employed where necessary if ambient temperatures rise high enough.”

The higher efficiency of the cast resin design means that heat losses are lower, along with cooling requirements. This efficiency also reduces the energy consumed by these transformers, and hence will reduce diesel consumption in this application.

“An important advantage in this remote location is that dry-type transformers are almost maintenance-free and could last for 25 years without significant attention,” he says. “Oil-filled transformers require regular maintenance including oil sample analysis to ensure operational consistency and safety.”

With no oil required as a coolant, the dry-type transformer is simple, safe and installable indoors without the need for its own civils infrastructure such as bund walls and structures to ensure safety and environmental protection.

“Trafo Power Solutions works with customers to engineer technically appropriate and proven solutions for their applications,” says Claassen. “The fact that we can design and manufacture within this project’s tight deadline is further evidence of our flexibility and ability to meet demanding schedules.”

DRY-TYPE MINI SUBSTATION NOW AVAILABLE FROM TRAFO

Trafo Power Solutions is extending the benefits of dry-type transformers by offering customised dry-type mini substations as a complete and customisable electrical distribution solution for users in mining, industrial, marine, commercial and residential applications.

“Using the well-proven dry-type transformer technology from global leader Hammond Power Solutions (HPS), we are now able to design and deliver mini substations that are specific to customer requirements,” says David Claassen, managing director of Trafo Power Solutions.

Mini substations are traditionally built with oil-cooled transformers, says Claassen, but the incorporation of dry-type technology makes the new offering safer due to less fire risk. In addition, dry-type units require less maintenance and present no possibility of environmental contamination through oil-spills. The units include a medium voltage switchgear for the incoming power source, a primary step-down transformer and a low voltage distribution board all contained within an enclosure.

“Customers have flexibility when it comes to the design and manufacture of the enclosure, as we can use various thicknesses of mild steel to suit the harshness of the conditions, and provide options for mobility such as a wheeled base or a skid-mounted base,” he says. “We also give the customer the freedom to choose their preferred brands on the medium voltage and low voltage switchgear.”

The capacity range offered is from 315 kVA up to 1 000 kVA, with a variety of voltages from 3,3 kV up to 11 kV on the medium voltage side and from 400 V to 1 000 V on the low voltage side.

“The transformer itself is specifically designed for Trafo Power Solutions by HPS in Italy according to our specifications, conforming to the IEC 60076-11 standard for dry-type units,” says Claassens. “Headquartered in Canada, HPS has over a century of experience in transformer design and manufacture, so have fine-tuned the application of transformers in mini substations for a range of environmental conditions. Trafo Power Solutions conducts the in-house design of the fit-for-purpose enclosure.”

He notes that an issue previously restricting the use of dry-type transformers in mini substations has been the provision for adequate cooling in an enclosure that is usually located outdoors.

“The enclosure must be well sealed to prevent the ingress of dust and moisture, but must still allow sufficient air flow to cool the transformer,” he says. “This challenge has been solved by the application of a specialised dual fan system, which pulls in fresh, cool air while simultaneously extracting the hot air.”

DRY-TYPE MINI SUBSTATION NOW AVAILABLE FROM TRAFO

Trafo Power Solutions is extending the benefits of dry-type transformers by offering customised dry-type mini substations as a complete and customisable electrical distribution solution for users in mining, industrial, marine, commercial and residential applications.

“Using the well-proven dry-type transformer technology from global leader Hammond Power Solutions (HPS), we are now able to design and deliver mini substations that are specific to customer requirements,” says David Claassen, managing director of Trafo Power Solutions.

Mini substations are traditionally built with oil-cooled transformers, says Claassen, but the incorporation of dry-type technology makes the new offering safer due to less fire risk. In addition, dry-type units require less maintenance and present no possibility of environmental contamination through oil-spills. The units include a medium voltage switchgear for the incoming power source, a primary step-down transformer and a low voltage distribution board all contained within an enclosure.

“Customers have flexibility when it comes to the design and manufacture of the enclosure, as we can use various thicknesses of mild steel to suit the harshness of the conditions, and provide options for mobility such as a wheeled base or a skid-mounted base,” he says. “We also give the customer the freedom to choose their preferred brands on the medium voltage and low voltage switchgear.”

The capacity range offered is from 315 kVA up to 1 000 kVA, with a variety of voltages from 3,3 kV up to 11 kV on the medium voltage side and from 400 V to 1 000 V on the low voltage side.

“The transformer itself is specifically designed for Trafo Power Solutions by HPS in Italy according to our specifications, conforming to the IEC 60076-11 standard for dry-type units,” says Claassens. “Headquartered in Canada, HPS has over a century of experience in transformer design and manufacture, so have fine-tuned the application of transformers in mini substations for a range of environmental conditions. Trafo Power Solutions conducts the in-house design of the fit-for-purpose enclosure.”

He notes that an issue previously restricting the use of dry-type transformers in mini substations has been the provision for adequate cooling in an enclosure that is usually located outdoors.

“The enclosure must be well sealed to prevent the ingress of dust and moisture, but must still allow sufficient air flow to cool the transformer,” he says. “This challenge has been solved by the application of a specialised dual fan system, which pulls in fresh, cool air while simultaneously extracting the hot air.”

TRAFO SUPPLIES DRY-TYPE TRANSFORMERS FOR ZUIKERBOSCH WATER TREATMENT WORKS

The advantages that a dry-type or cast resin transformer offers played a role in Trafo Power Solutions securing an order for thirteen custom designed units. These dry-type transformers are destined for installation at the large scale Rand Water Zuikerbosch Water Treatment Works.

David Claassen, managing director of Trafo Power Solutions, says that is it most gratifying for the company to have received this order only months after the business was established. Claassen, an electrical engineer with broad ranging and high level experience in many sectors, recently established Trafo Power Solutions to distribute and service transformer products in Africa from Canada-based Hammond Power Solutions (HPS).

The contract to supply all the cast resin transformers for this waste water treatment facility will include units that range from 100 kVA up to 1600 kVA. Included in the scope of supply is the complete earth fault protection system which will be in the transformer enclosures.

Claassen says that the rationale for a project to go the route of using cast resin or dry-type transformers is for a number of reasons. “Prime among these is the inherent safety offered by these units as well as ease of installation given the fact that they are installed inside built substations as opposed to outdoors with associated special bunding and civils.

Dry-type transformers are categorised as F1 in terms of international fire resistance ratings, making them low risk as they are self-extinguishing and flame-retardant by nature. With zero risk of fire, the high safety rating of dry-type transformers allows them to be installed indoors, avoiding the cost and inconvenience of the special structures normally required to accommodate the safety and environmental hazards related to oil-filled units.

“And this results in savings because there is no need for costly civils and site work to be done,” Claassen adds

Less maintenance is another advantage; dry-type transformers are low in maintenance and could last for 25 years without significant attention, while oil-filled transformers require regular maintenance including oil sample analysis to ensure operational consistency and safety.

Claassen says that the units have been witness tested at the manufacturing facility and are scheduled for delivery to site in the first quarter of 2018.