Case Study: Mining Industry

The Customer that Mag-Tran has conducted this case study for provides materials handling equipment design, consulting services, design/supply sourcing, and general contracting to the mining and minerals processing, phosphate, waste, coal, aggregate, cement, and other bulk materials industries throughout the world.

Specifying the Transformers

Initial Request

Mag-Tran was first contacted with a basic set of specifications.

The Customer needed a Power Distribution Transformer that would supply power to motors used to operate a conveyor system at a mining facility in the United States. The transformer would be outdoors in a harsh environment and would operate at an elevation of 5,500 ft. The unit would need to be housed in a NEMA4 enclosure. The required specifications would be as follows:

Power Rating
  • 700 kVA
  • 60 Hz
No. of Phases
  • 3
  • 13,800 Vrms Delta ±2.5%, 5% taps
  • 480/230 Vrms Wye (Four Wires)
Ambient Temperature
  • Min. 10oC, Max. 50oC
  • 5,500 ft. (1,676 m.)
Design Wind Velocity
  • 46 m/s
  • NEMA4 (IP66) Painted
To Include
  • Primary Fuses
  • Lightning Arrestors
Max. voltage drop allowed during motor start
  • 12%
Designed for
  • Equipment movement
  • Conveyors operate at a ±10o slope
  • ANV cooling only

The Choice for Quality

Mag-Tran was contacted because the Customer needed the highest quality equipment and shorter lead-times. Their main concern was quality; they had received transformers from other vendors in the past that did not meet their expectations. We knew we could help the Customer improve the quality of their systems and provide lead-times that would meet their needs.

The Design


Special attention was paid to the Customer’s motor starting requirements. This included taking into account the motor inrush current and the allowed voltage drop. Furthermore, clearances were increased to meet ANSI requirements for altitudes higher than 3,300 ft. Lastly, temperature correction factors were incorporated for the higher altitude so that the transformer could operate at its full rating.

Layout and Construction

Since this unit was going into a NEMA4 enclosure, extra surface area within the enclosure was required to prevent over-heating—NEMA4 enclosures do not contain any air-ducts and are sealed for protection against sprayed water from any angle.

Extra bracing was needed to ensure the enclosure, terminations, and transformer could withstand the tilting and shifting the transformer may under-go. Computer-generated stress analysis estimates were done to ensure the enclosure could be supported by lifting eyes on top of the enclosure.


As a design philosophy, Mag-Tran never compromises performance and quality. We know that downtime for a unit is extremely costly and must be avoided. We design our transformers with copper windings and employ a Class H insulation system and a temperature rise compatible with the NEMA4 enclosure.

Design Review and Customer Approval

With the transformer design in place, our drafting department began the layout of the transformer. Careful consideration was taken to how this transformer would be supported. It was well understood that this transformer required infrastructure in place to withstand tilt and constant movement. Our mechanical engineers made 3D SolidWorks drawings as well as 2D AutoCAD drawings to present to the customer.

These drawings were incorporated and used during design reviews held with the Customer. Design review meetings were held between Mag-Tran and the Customer to ensure that no detail was forgotten and that all requirements were fully understood by both Mag-Tran and the Customer. Mag-Tran took any suggestions, requests, and changes and incorporated them into the final revision.

With those changes incorporated, final drawings were submitted for approval by the Customer. Once approval was received, materials were ordered and manufacturing began.


Mag-Tran was able to complete production of this custom 700 kVA transformer within 5 weeks.

Facilities and Equipment

Mag-Tran facilities are located in two adjacent buildings with over 16,000 square feet of floor space. Over two-thirds of this space is dedicated to coil winding, assembly, and test functions.

The winding process required specialized winding combs, air ducts for cooling, and the utmost attention to insulation integrity. Each facet of the winding of the coils was closely scrutinized and inspected throughout the manufacturing process. A coil test was performed on each individual coil to ensure that the proper number of turns was present and a HiPot test was used to confirm that the coils were adequately insulated.

The assembly of the transformer, which included putting the coil on the core, required extreme finesse and attention to detail. A high precision miter-cute, step-lap design was used to further increase efficiency. Once assembled, the following tests were performed on the transformer to ensure that all the work met Mag-Tran’s quality requirements and that the unit was functioning properly:

  • Turns Ratio Test
  • Double-Induced Test at 400 Hz
  • HiPot Test to 30 kVrms
  • Short Circuit Impedance Test
  • DC Resistance Test
  • Exciting Current Test
  • Open Circuit Voltage Test

Impregnation and Bake-Out

The units were double-dipped in epoxy resin. This process helps to solidify the core and coil and decreases audible noise.


  • HiPot Test to 30 kVrms
  • Polarity Test
  • Open Circuit Test

Manufacturing Capabilities/Processes

Close integration between several departments (e.g., Sales, Drafting, Manufacturing, Purchasing, and Shipping) was needed to ensure the completion of this project. Daily production meetings were held during the manufacturing process to further this goal.

Sales Department

The Sales Department responded to all customer requests and concerns. Any specification alterations that needed to be made were communicated between the Customer and the Engineering Department through the Sales Department.

Engineering Department

The Engineering Department was responsible for taking the Customer’s specification and turning it into a working design. Engineering worked closely with the Drafting Department to ensure the construction worked as designed as well as with the Manufacturing Department to ensure the theoretical design made by drafting worked as a real-world application in both construction and operation. Engineering helped answer production questions as they arose.

Drafting Department

The Drafting Department was responsible for taking a working design from the Engineering Department and turning into a theoretical design the Manufacturing Department would use to build the transformers. The Drafting Department was also responsible for ensuring the drawings were always up to date with the Customer’s specification alterations and in-process changes.

Manufacturing Department

The Manufacturing Department took the designed drawings and worked closely with Engineering to ensure the transformer was built to operating conditions.

Purchasing Department

The Purchasing Department works with all departments to ensure the correct materials are ordered and arrive on time.

The Shipping Department

The Shipping Department ensures the unit is packaged and crated appropriately so that all contents are secured for their destination. The Shipping Department also helps to ensure the unit is shipped on time.