Current Loop Configuration

The configuration to use Tap Position by Positive Knowledge (Current Loop)

Procedure is shown in Figure 1 and typically includes:

• Tapchanger position output (shaft movement)

• Selsyn Transmitter

• Tap Position Monitor

• M‑2025B Current Loop Interface Module

• M‑2001 Series Digital Tapchanger Control

Tapchanger Position Output (Shaft Movement): Most LTC tapchangers have

an output shaft whose angular rotation and position are a mechanical analog

to the tapchanger tap position. In many cases, the total range of tap positions

is represented by one or two rotations of this shaft.

Selsyn Transmitter: This transmitter is mechanically connected to the

tapchanger position output shaft.

The Selsyn transmitter is an electromagnetic device used for transmitting data

on rotational position. Selsyns, or synchros, as they are sometimes called,

resemble small electric motors. They have various configurations of internal

windings. One or more windings are on a rotor and usually three windings

(stator), are stationary surrounding the rotor. By exciting the rotor windings

with an AC signal, induced voltages in the stator windings can be compared

in amplitude and polarity to determine the angular position of the rotor, relative

to the stator windings.