Medium Voltage Load Banks & Step-down Transformers

Simplex Medium Voltage Load Bank
Simplex Medium Voltage Load Bank with Sound Attenuated Enclosure

Simplex’s load bank product line includes equipment designed for use in medium voltage power generation applications. Simplex’ medium voltage load banks use step-down transformers to provide safe and reliable operation for the owner. While other manufacturers offer load banks that accept direct application of medium voltage, that is, without the use of a step-down transformer, Simplex prefers the use of a transformer for the following reasons:

  1. Systems that utilize medium voltage load elements can develop serious issues resulting from the corona effect, creepage and flashover. The use of a step-down transformer between the energy source and the load elements will substantially limit these dangerous conditions.
  2. A properly designed array of medium voltage resistors must have proper spacing to ground, across the entire length and at the terminals. The elements must be properly fused to reflect the fault energy available.
  3. The fact that the resistance value must be very high requires long, series-connected resistors, which would lead to any one failure resulting in the opening of a large circuit.
  4. It is not cost-effective to achieve fine load step control using medium voltage devices.

Load bank designs which claim to be medium voltage rated, without a transformer, are in fact merely 600v load banks, separated by phases with the cabinets elevated above ground on insulators. These products consist of a long strings of series-connected resistors. With line-to-ground spacing being suitable for only 600v operation, one can see how a fault would be catastrophic. These designs are not safe and represent a threat to both personnel and the owner’s facility.

From a cost standpoint, the use of medium voltage contactors, fuses, wire, insulators, etc., is a much more expensive proposition than using a large dry-type power transformer. Over the life-cycle of the equipment, as components age and ultimately need replacing, medium voltage components are more expensive and difficult to source. The need for technicians to be trained or certified in replacing medium voltage components also raises the operating costs. All of these issues inevitably lead to a higher total cost of ownership.

Large dry type power transformers are very cost effective and represent a safe and conservative design approach. With the use of an isolation transformer, the medium voltage source is isolated from the low voltage load bank, which utilizes 600v devices, wire and insulators.

Simplex Medium Voltage Load Bank
Simplex Medium Voltage Load Bank (step-down transformer shown)

A Simplex medium voltage load bank will include the load bank and the step-down transformer in a single, purpose-built, enclosure. This integrated design provides safety and reliability. For service departments that need to test generators in various voltages (4.16kV, 13.2kV, etc), Simplex offers trailer-mounted load banks configured to accept various transformers as dictated by the application.

For more information on Simplex medium voltage load banks, please see this Sample Brochure,  Sample Technical Specifications, or contact our office to review your specific requirements.

Leave a Comment