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Insight Posted 29th October 2025

Tapchanger Control Unit (TCU)

Many tapchanger drives and AVC schemes on UK networks are stuck on fixed tap due to ageing or faulty parts. Our Tapchanger Control Unit brings them back into service.
Control unit with electronic components, wires, and a dial mechanism inside a cabinet.

Fundamentals TCU (Vertical Application)

Is your tapchanger limiting performance?

Many tapchanger drive mechanisms and associated Automatic Voltage Control (AVC) schemes on the UK network are non-operational and stuck on ‘fixed tap’ due to ageing or faulty components.

This can lead to voltage constraints and reduced system efficiency.

Introducing the TCU solution

Fundamentals has developed the Tapchanger Control Unit (TCU) to address issues caused by outdated or failed control equipment within tapchanger drive mechanisms.

TCU key features:

  • Compatible with 230V and 415V motor voltages

  • 110Vac control circuit (compliant with UK DNO specifications)

  • Flexible mounting options: vertical or horizontal

  • Pre-wired looms and socket connections

  • User-friendly local control and isolation switches

  • Blocking contactor and MCB shunt trip for AVC runaway prevention and lockout

  • Tap duration and supply fail timers with configurable volt-free alarm contacts

  • Electronic or mechanical tap counter options

  • Tapchanger motor current monitoring functionality

  • Complete design documentation: schematic, wiring diagram, and general arrangement pack

  • Trialled and tested with UK DNOs

TCU benefits:

  • Unlock ‘fixed tap’ schemes

  • Extend lifetime of existing transformers

  • Interface compatible with all types of tapchanger

  • Fast installation kits designed to minimise transformer outage times

  • Increased reliability and performance

Our services include:

  • Supply of complete TCU kits (including DSS assembly)

  • Supply of separate DSS assemblies for ATL AT type, Fuller F, FBA, and HS type drive mechanisms

  • Installation and commissioning of TCU / DSS assemblies, including integration with existing AVC schemes

Interested? Lets Talk

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