Load Tap Changer (LTC)
Kits, Overhauls & Upgrades

When design, manufacturing and testing of new components have all been completed and the product hits the market, that’s when our work begins—manufacturing replacement parts, evaluating performance of original designs and redesigning components to improve performance and enhance reliability. In addition to being the OEM for the now commercially available field-proven and dependable Waukesha® UZD® load tap changer, Prolec GE Waukesha is committed to becoming the industry’s preferred supplier of replacement parts and service for all LTCs, utilizing design and reverse-engineering skills, quality control and value-added manufacturing processes.

Transformer LTC Expertise
Transformer LTC Expertise
On Load Tap Changer
Transformer LTC Components


Prolec GE Waukesha offers an extensive selection of make/model replacement contacts, including low resistance contacts. Many of these are available in our extensive selection of maintenance parts kits available for most major and obsolete load tap changers. These kits, designed based on customer feedback, include most parts that wear out or need replacement. Standard maintenance kits include all respective movable and stationary contacts for all three phases of the equipment. We maintain a large inventory of these kits for emergency deliveries.

In addition to contacts, our Components Group offers a variety of “non-standard” parts, such as tap head castings, gasket kits and drive shafts, while leading the industry in the ability to reverse-engineer and manufacture insulating barrier boards and phase panels on short notice from a customer-supplied sample for single and three-phase load tap changers. Our large inventory of barrier board materials in a variety of thicknesses and sizes allows us to support our customers’ emergency needs.


HVS LogoOur company defined the standards for high quality and reliable load tap changer overhauls/upgrades, starting with our industry-leading conversion and overhaul of the GE LRT200 in 1994. This overhaul and the many years of experience gained since then have given Prolec GE Waukesha the knowledge and expertise to develop thorough and comprehensive LTC refurbishment programs for the following models:

  • General Electric LRT200, LRT200-2, LRT68, LRT72, LRT38/48
  • McGraw 500, 550B, 550C
  • Seimens TLF, TLG, TLH20, TLH21, TLS
  • Maloney MA/MB, MA1/MB1, MA2/MB2
  • Westinghouse UTS, UTS-A, UTT, UTT-A, UTT-B

Our STANDARD rebuild scope
includes the following steps:

  • Preparation of a written scope of repair specific to make/model of LTC being overhauled.
  • Thorough receiving inspection documents condition and assist in determining most probable failure mode.
  • Complete disassembly of the entire mechanism and evaluation of all parts for wear condition and probable failure damage.
  • Inspection and cleanup of all drive gears and LTC assembly frame (most are reused on the rebuilt LTC).
  • Replacement of all locking hardware, springs and pivot bushings.
  • Hi-pot and wear evaluation of vacuum interrupters (if present).
  • Inspection and cleanup of all control wires and terminations, limit switches and motor drive/spring charge mechanism.
  • Electrical testing and verification of operation of drive motors and limit switches.
  • During rebuild, all newly installed contact assemblies are adjusted and calibrated to ensure proper operation.
  • After rebuild and timing, all spring-loaded contact assembly pressures and contact resistance measurements are recorded and evaluated to ensure contacts are mating properly on all positions.
  • Depending on the model, a final verification of operation is performed in a tank under transformer oil for up to 25,000 mechanical operations across the entire tap range.
  • Each unit overhauled by our Components Group is warranted for 12 months from defects in materials and workmanship.
  • Final repair report details all items replaced/reused and a failure analysis showing “as received” condition and mode of failure is available upon request.

Prolec GE Waukesha also stocks completely rebuilt LRT200-2 LTCs in Dallas, Texas, for quick delivery.


Unique maintenance tool kits help provide for faster, easier servicing of load tap changers. Each kit contains custom tools specific to a given LTC make/model along with instructions to aid in installation and calibration/adjustment of replacement contacts.

We currently offer tool kits designed specifically for use on the following LTCs: Waukesha® UZD®; FPE TC-546, TC-525, TC-523, TC-25, TC-46; McGraw 550, 550B, 550C; GE LRT200 Series.


Now commercially available to the market, the Waukesha® UZD® load tap changer is a field-proven design. When the minimally required maintenance is performed, UZD has a reliability rate of 99.95% for units built since 1997.

Designed for high speed, reliable operation and reduced maintenance, the Waukesha® UZD® offers important features with benefits:

BUE Motor Drive Mechanism

Charges the spring battery operating the load tap changer; housed separately in an air-filled compartment. Located at a convenient height and not in the oil-filled switching compartment. Readily accessible at ground level for inspections and maintenance.

Spring Drive Mechanism

Tap changer can be operated manually while energized and carrying load. Stored energy in the spring mechanism results in high speed operation and minimum arcing time. Each tap change is consistent and unaffected by voltage interruptions or manual hand cranking speed.

Load Tap Changer & Series Transformer System

For applications with greater than 600 ampere current ratings, a series transformer is recommended to allow for an optimal volts/turn design of the main transformer windings, even step regulation and smaller leads while facilitating a reduction in current through the LTC contacts for less contact wear and longer life; a power-class series transformer design is recommended for high reliability.

Single Arm Design

Single arm simultaneously operates both the tap selector and arcing contacts for a simple basic design with few parts that helps reduce operation and maintenance costs.

Other Features

  • Designed to withstand full vacuum in tank without bypass piping to equalize pressure
  • Large opening to tap changer compartment helps make inspections quick and easy
  • Design utilizes just three openings into the main transformer tank protected with O-ring gaskets for maximum protection from leaks—fewer openings means less maintenance
  • Compact design requires only 100 gallons of oil to drain and replace
  • Full-featured control compartment equipped to meet customer requirements
  • Meets all requirements of IEEE standard for Load Tap Changers (IEEE C57.131-1995)

For product specific questions or concerns, please contact your sales representative or fill out our Waukesha® Components Request Form.