TLF & TLS tap changer upgrades

Author: Brian Wahl

03/01/2010 - Volume VI - Issue II

On-load tap changers (LTCs) are intricate, electro-mechanical devices often operating under severe service conditions performing tens of thousands of operations. A preventative LTC maintenance program will help customers avoid unplanned failures, lower maintenance costs and extend equipment service life. Siemens offers a comprehensive portfolio of LTC renewal part solutions and services supported by factory-trained service engineers and original manufacturer engineering departments who understand your equipment design.


Allis-Chalmers and later Siemens have manufactured the TLF single-phase and TLS three-phase LTC since the 1950s for use in feeder and bus voltage regulation and distribution power transformers. These tap changers were built to withstand severe operating conditions with a minimal amount of maintenance.


Increase reliability and extend maintenance intervals with longer life contacts


Siemens has designed an extended life contact with the following improved components:

  • Main moving contacts contain different copper alloy

  • Main stationary contacts have increased arcing life

  • Main neutral stationary has increased arcing life and is also sliver plated

  • Reversing contacts contain different copper alloy and are also silver plated.


Customer benefits include:

  • Up to 100% increase in LTC operations extending major maintenance intervals

  • Reduced operating temperature on the contacts

  • Reduced coking on the reversing switch

  • Fully tested to meet IEEE standard C57-131 as required for tap changer testing

  • 12/18 month limited warranty.

Application notes:


Although parts are interchangeable with older components on most TLS and TLF tap changers, it is strongly recommended to change all the components on the reversing switch as they are a mating set.


Other parts solutions include:

  • Gasket Kits

  • Bushings

  • Control Panel Upgrades

  • Motors

  • Gauges.

Field service


Siemens can support you with factory trained field service engineers who are familiar with OEM recommended procedures to minimize downtime and maximize equipment reliability and performance.


Regulator / LTC training


As regulator technology moves forward, do not leave your people behind. Siemens offers comprehensive training relevant to the voltage regulator industry. The College of Knowledge is a three day training program developed over a period of 40 years. Training can be tailored to meet your specific needs: from understanding the theories of voltage regulation, to learning the fine details of control technology to hands-on regulator trouble shooting.


Our training programs can be brought to your location, or your personnel can attend one of the programs conducted at Siemens' voltage regulator manufacturing facility in Jackson, Mississippi.