Total Tapchanger Solutions

This new service innovation from Fundamentals, in partnership with Ferranti Tapchangers Ltd and Powerserve UK Ltd, provides an unrivalled one-stop-shop solution for all types of tapchangers and related control systems. 


An ageing network with increasing levels of distributed generation

Issues to overcome in order to deliver a safe, reliable and healthy network:

Age of Assets

  • Missing records (design, maintenance, usage)
  • Obsolete parts
  • OEMs ceased
  • Non-operational control schemes

Reverse Power

  • Reverse power capabilities of OLTCs unknown
  • Voltage control issues
  • Network planners under pressure to make decisions for generation connections

RIIO Deliverables

  • Improve asset health indices
  • Save money
  • Reduce customer interruptions and complaints
  • Reduce losses
  • Accommodate more generation
  • Innovation



Complete Solution 

  • Access to original designs
  • OEM spare parts
  • Full maintenance and upgrade for all types of tap changer
  • Control scheme upgrades

Reverse Power Assessment

  • Tap changer capability
  • Voltage control errors
  • Support for network planners
  • Upgrade services for full reverse power capability

More for Less

  • Extend lifetime of existing assets
  • Improve asset health and performance
  • Facilitate generation connections
  • One-stop-shop
  • Turnkey services
  • Avoid asset replacement


Examples of the tap changer types we can support:

AEI/English Electric M31, M32, M33, M51, M52, M54, M56
AEI S21, 3S21, S31, M21, 2M21
Associated Tapchangers AT, AE, ASD, AMD, AN, AG
BET/Allen West TC033, TC066, L
Brush HSR
BTH ATC range
Crompton Parkinson SDA, MDA
English Electric  Reactor (Dial 3), FDA, FDB, FDC,FDD
Ferranti DC3, DS2, DS5, DS300, DS400, DS500, ES3, ES3/19, EC4. FC4, FC6, GC6, GC12, HR6, HR12, HD12, HD14, FL6, FL12, ST, Rotary
Fuller F, FBA, H, EH, HD, HS
GEC Type J, SD, MD
Hackbridge & Hewitt Type XC033
Maschinenfabrik Reinhausen (MR) C, M, R, T, V, Vacutap
Met Vick LBT, LCT



Ferranti Tapchangers Ltd

Ferranti on-load tapchangers have been supplied worldwide for over 60 years. The quality of the Ferranti tapchanger is such that many of the earliest units are still in operation today. Ferranti Tapchangers Limited provides complete new or fully refurbished units, genuine tap changer spare parts, service and technical support to the power and utility industries as well as major international blue chip companies.


Powerserve UK Ltd

Powerserve UK Limited provides an extensive spares and accessories product range of utility equipment for tapchangers, switchgear, transformers, isolators and other HV substation equipment for the high voltage distributor, generator or user. In many cases, we are able to provide a wide range of new parts, components and assemblies for obsolete and unsupported equipment. Our technical expertise allows us to supply you with anything from a single obscure part, which requires ‘reverse engineering’ right through to new equipment in our extensive manufacturing facility. 



The tap changer is the component of the power transformer which enables voltage regulation and is therefore critical for network management. Each tap changer operation generates switching arcs on contacts which leads to carbonisation of the oil and contact wear. Mechanical components, both internally in the diverter and also externally in the motor drive and shaft arrangements, are under stress during each switching operation. Regular maintenance is therefore required.

Our maintenance technicians have been trained on all types of tap changer and related devices. With many years’ experience and with the direct support from our partners, Fundamentals can offer a premium service for tap changer maintenance.


The normal routine tasks for tap changer maintenance are as follows:

  • Dismounting and mounting of the on-load tap changer insert
  • Cleaning and inspection of the mechanical parts
  • Visual inspection of insulation distances of the on-load tap changer insert and the oil compartment
  • Parts replacement
  • Replacement of the switching oil (unused oil with a breakdown voltage of > 50 kV/2.5mm, in compliance with IEC 60156)
  • Determination of the contact wear
  • Measurement of the transition resistors
  • Inspection of the motor drive, drive shaft and protective surge relays
  • Functional test – mechanical and electrical operation of tap changer


  • Optimisation of operating condition - reduce risk of tap changer problems
  • Premium service - maintenance by qualified technicians according to manufacturer’s procedures
  • 2-year warranty on parts – genuine spares from manufacturer
  • Record keeping – maintenance history managed for customers