The Making of an EDCOR Transformer.

The production process for manufacturing EDCOR transformers has developed over four decades. We often get calls inquiring about the status of a transformer order, so we thought we would walk you through the steps of production to give you a better understanding of where in the process your order is. 

The Order:

When we receive an order, we first enter it in and schedule it for production.

Scheduling Chart

Production charts and labels with QR codes are created for the tracking of the order through the manufacturing process. At this time we also check if we have any sub-assemblies in stock and if so, move them to the next step in their production. If the order calls for a custom transformer or modification to an existing transformer, the order and specifications are handed off to our engineering team for design and setup.


Our engineering team uses proprietary programs to design the transformer to the specifications and then a design sheet and production chart is created for the manufacturing process. This includes a schematic, material types, material quantities, and detailed information as to how all the steps in the manufacturing process are to be carried out.

EDCOR Production Charts

The engineering team also makes sure that we have all the material, manufacturing fixtures, and all the files need for marking, labeling, and notching of the transformer for production. If the transformer needs a custom fixture for manufacturing, it is can be 3D printed, routed, cut, or milled out with one of our CNC machines.

CNC Plasma Cutter

Once everything is compiled, the order and the new production chart is turned over to be kitted.


This begins with selecting the type and size of bobbin to be utilized. The bobbin is labeled with the model number. If the production chart calls for lead wire terminations, the bobbin is laser notched for the winding process.

The order is then inspected, marked off as kitted, and turned over to the winding department.


In this step, the bobbin is turned over to one of our trained coil winders. Depending on the quantity and type, it will be given to one of our CNC winders or wound by hand.

The winder uses the production chart to determine what type of magnet wire is used, the order of the winding layers, the number of turns for each winding, and any other specifications such as taping and wire terminations. Once wound, it is inspected, marked off as wound, and turned over to our finishing department.


The finishing department is were the terminations are put on or soldered on the coil. If the bobbin is printed circuit board (PCB) mounted or has terminals molded into the plastic, the magnet wires are soldered to the pins or terminals. The process for transformers with lead wires is more extensive.

Lead Wire Finishing

Here, the finishing tech checks the production chart and pulls the correct lead wire sizes and colors needed. They then follow the production chart to determine what techniques are used for connecting, soldering, securing, and taping the lead wires to the coil. After the terminations are finished and inspected, the coil gets wrapped with finish tape. This taping is used to cover, protect, and insolate the winding on the bobbin.

The order is then inspected again, marked as finished, and sent on to have the core stacked in it.


At this point in production, the coil gets a core and becomes a transformer. The production chart states what type of core material is to be used, the size, and specifically how the core is to be stacked. We have stacking machines for interleave stacking, but we also butt stack and hand stack the cores depending on the specifications.

Final stacking is done by hand to making sure the core is fully stacked. After the core is inspected, any pre-varnish hardware is marked and installed. This may include brackets, channel frames, screws, etc.

The transformer is again inspected and sent off to varnishing.


The transformer is hand dipped in varnish and air dried in one of our custom built varnish rooms.

Varnish Room

We do not use any ovens to rush this process as baking causes the varnish to become discolored, brittle, and cracked. Once the transformer is dry, it is moved to testing.


We test the transformer to make sure it meets the specifications that are listed on the production chart.

Transformer Testing

The transformer is then marked that it sucessfully passed testing and moved for final hardware. If the transformer is rejected, it is turned over to our engineering team to investigate where in the design or manufacturing process the error occurred and corrective actions are determined.

Final Hardware:

Any final labeling and hardware is installed on the transformer as stated on the production chart.

End Bell Transformers

The order is then ready for Quality Control.

Quality Control:

At this point, the order gets its final inspection to make sure it conforms to the production chart and that the overall look of the transformer meets EDCOR's standards.

Quality Control

It is then marked for shipping. 


Our shipping department verifies the order and carefully packs every product. Over the years, our shipping department has developed different shipping techniques to make sure that the transformer gets to you undamaged.

Shipping Inspection

They are constantly monitoring shipments to make adaptations if necessary.

Well, that is the birthing of an EDCOR transformer. From the inception, through development, to the delivery. We are proud of our American-made products and work hard for every transformer that we build. Our goal is to give you a great product at a good price in a reasonable time-frame.


Beer Time




I think your shipping department is dog-gone great!! I have been using EDCORE transformers for a number of years and they never disappoint! They even LOOK as good as they Perform! I also really like that they are AMERICAN Made! Thanks for a great product and a chance to see “how it’s made”!



It’s nice that Edcor is proud to show these transformers being made. I love that they are made in the U.S.A. It makes me want to buy some more! Thank you!



I have been a proponent of Edcor transformers for a long time. It’s great to get some insight into the process and care that goes into everything I order.

Keep up the great work!

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