The Ferranti Tapchanger ST series

For more information, to contact us.

(click here to contact us on the ST range)

The ST Ferranti Tapchanger series is a family of high speed resistor transition type gears, designed for continuous operation with maximum efficiency. The materials used are of high quality to give a long life and each component is more than adequately rated both mechanically and electrically to perform its duty with the minimum of maintenance. The tapchanger (tap changer) consists of a switching compartment with houses the combined selector and diverter switch mechanism and a separate compartment for the driving and timing mechanism and the control equipment required.
A throat is mounted on the tapchanger, housing the barrier board , and on the majority of transformers this eliminates the necessity of a mounting throat on the transformer tank .

Switch Compartment

In the compartment are the three phase diverter and selector switch bases which are mounted positively to withstand the mechanical forces exerted on them during the operation of the tapchanger. The mechanical end stop is of the differential gear type and the drive can be stalled from full speed without damage. The special alloy moving contact arcing contacts, which engage solidly with fixed, tipped, contacts and the main current carrying contact are of high quality material ensuring the maximum contact life. Connections from the switching compartment to the tapping windings are via sealed bushings in the barrier board.

Driving Mechanism and Timing Gear Compartment

This compartment contains the driving motor, contained in an oil filled housing, the drive assembly, timing equipment and control when required. All the components are mounted in a weather proof cabinet mounted on the side of the switching compartment. The single phase motor, proven in all Ferranti Tapchanger (tap changer) single compartment tapchangers and mounted under oil has benefits of reduced maintenance , increased reliability and the ability to be stalled for long periods without damage.
A heater is fitted in the oil filled housing and a thermostat to prevent the oil from overheating. The door of the main compartment is interlocked with the supply isolator for safety purposes.


All the control equipment is housed in the driving mechanism compartment and is
supplied in accordance with customers specification. Sufficient step switches can be
fitted to provide remote and supervisory tap position indication and facilities to parallel
the Tapchanger (tap changer) using any particular scheme required.

Pre set control equipment is mounted inside the cabinet but local switches would be in
a weather proof unit on the outside in order to maintain the door/isolator interlock.
The fitting of control enables us to offer the ST series tapchangers as complete self
contained equipments.

(click here) to contact us

Back to the main navigation page

 The Ferranti Tapchanger ST Series
On-load Tap Changer

Copyright 2001-2008 Ferranti Tapchangers Limited (UK) All rights reserved.