Here's how electrical transformers are made in a factory

Find out how an electrical transformer is made from start to finish.
Christopher McFadden

Transformers (no, not that kind) are vital in any country's electrical grid. Designed to act as a passive component in transferring electrical energy from one circuit to another (or multiple), most also act as step-down or step-up converters for currents. 

They are fairly old technology and today come in a wide range of designs and sizes depending on their use. But have you ever wondered how these critical electrical devices are actually made? 

making a transformercomplete
Source: Interesting Engineering

Let's follow one being born from manufacture to installation. 

Step 1: Make the basic components

At least for this particular model, the first step is to design and create the basic components. In this case, some of its delicate circuitry is designed using a computer-aided design software package.

These designs are then fed into a specialist plasma-cutting CNC machine. The parts, that needed to be made in the factory, start our life as large sheets of sheet metal.

making transformers cnc
Source: Interesting Engineering

These are fed into the CNC machine, which then cuts out the design of the parts in large batches. Other automated machines can also be used to physically punch holes, and other features, through the metal sheet too. 

Once that is done, the completed sheets are then fed out of the machine and passed on to specialists workers who separate each component by hand, where needed. 

making transformers parts
Source: Interesting Engineering

Those parts that need further shaping are then placed in a set of other machines to press them into shape. This is done by human workers, who placed the parts under an automated press to bend the metal sheets into angles or shapes as required. 

Completed parts are then piled up, ready for the next stage in construction. 

making transformers shapes
Source: Interesting Engineering

Other parts, like steel rods, are also shaped and cut to size as needed using other specialist machines in the factory. Where required, these lengths of the metal rod are then fed into automated lathes to shape them into other specialist parts ready for the transformer. 

making transformers lathe
Source: Interesting Engineering

Holes and other features are also machined into the parts as needed too. Most of this process is automated, but it can require human input for delicate parts or changing drill heads, etc.

making transformers machining
Source: Interesting Engineering

Once parts are made, they are then piled and stacked in batches ready for the main assembly of the transformers later on. 

Step 2: Quality checking and refining parts

With the main parts completed, the next step is to give each one a thorough check. This is performed by specialist machinists who check each part individually and polish or refine them as needed. 

This could require the remaining metal barbs to be sanded down, or just give them a general polish.

making transformers sanding
Source: Interesting Engineering

Other parts, like the cut metal sheets from before, are further refined too, where needed, using bench drills and other tools. For example. screw holes are beveled and recessed, etc. 

Step 3: Begin the assembly

Once all the main components are finished, the next step is to begin to assemble the transformers. First large electrical cabling for the transformer is prepared.

This requires pulling off some layers of the sheathing to expose the metal wires within. In this factory, this is done by hand by trained and experienced electrical engineers. 

making transformers cables
Source: Interesting Engineering

With that done, electrical terminals are connected and crimped into place on the cable cores as required. Where needed, new insulation is added and heat shrunk into place as required.

making transformers insulation
Source: Interesting Engineering

Smaller electrical wires are also given a similar treatment but, obviously, on a much smaller scale.

With that done, other parts of the transformer are then welded and assembled together as required. In this case, this is also performed by specialist human workers. 

Next, all the main parts of the transformer are then assembled together as needed. Like other parts in this phase of the process, this is all done by hand. 

making transformers assembly
Source: Interesting Engineering

Nuts and bolts are firmly secured into place using powered screwdrivers, and other parts are hammered into place as needed. 

With the main mechanical parts assembled, the next phase is to begin to complete the circuitry of the transformer. This is done, as before, by specialist electrical engineers to ensure it is done correctly and precisely. 

making transformers wiring
Source: Interesting Engineering

Switches, levers, and other parts are also assembled and added to the main circuit breakers for the transformer too. 

making transformers breakers
Source: Interesting Engineering

Brushes, coils, and other major components of the transformer are also assembled, as required. 

Step 4: Finish the assembly

With all the main parts ready for installation, the final part of the process is to bring all the parts together in one package. More specialist workers begin to connect the main parts together and mount them to the frame and of the transformer.

Completed parts are then installed in place within the main cabinet or shell of the transformer. More and more parts are then added until the final transformer structure is finally completed. 

making transformers building
Source: Interesting Engineering

Wiring is then completed, and the entire transformer including its wiring and control panels, is given a series of quality checks to ensure it is fit for purpose before being shipped out.

When on-site, some final amendments are made to the transformers to ensure they can fit into and connect to the electrical system of the building in question. Ducting, cable runs, etc, are all made ad hoc for the site until the transformer's installation is complete.