5
INTRODUCTION
The Model 1250-LTC Programmable Position Monitor is a highly advanced solid-
state instrument, which measures the absolute position of a synchro transmitter. It provides
both a user definable visual panel indication and optional analog and digital signal outputs
suitable for a variety of monitoring and control applications.
The INCON 1250-LTC series is unique in its capability to monitor up to 40 user-
definable position segments. It is specifically designed for monitoring power transformer
load tap changer position, where the desired readout is in whole tap numbers. Its transmitter
can be attached to any operating shaft on the LTC and the 1250 programmed to read out in tap
positions. The display and all outputs follow a “stair step” function defined in the program.
The INCON 1250 has become the industry standard for LTC position monitoring.
In addition to basic LTC tap position, the 1250-LTC can provide useful information
about the movement of the LTC. Beginning with a momentary (optional) relay closure after
each successful tap change, the 1250-LTC keeps records on seven important issues relating to
LTC movement, including: total number of tap changes; number of days since last “pass
through neutral”; number of changes “up to” and “down to” each tap; and more.
Most LTC’s rotate about 9 to 11 degrees with each tap change. The 1250-LTC can
measure in increments of 1/10
th
of a degree. A special feature of the 1250-LTC is its ability
to monitor small discrepancies in tap position. A programmable limit can be set to give an
alarm when the discrepancy in tap position reaches the limit. Inaccurate tap position can be
an early indicator of wear in the LTC mechanism or possible impending failure.
The 1250-LTC may be wired in parallel with existing synchro
transmitter/receiver
pairs or wired directly to the synchro transmitter. Additional 1250’s may be wired to the
same transmitter without compromising the accuracy or reliability of the system.
1.0 INSTALLATION
•
The Model 1250-LTC is designed for use in any 50/60 Hz, five-wire synchro system
compatible with electrical specifications given in Section 6.0, page 51. These devices
include CX, TX, CDX, and TDX function synchros, as well as Self-Synchronous
Indicator devices. (INCON’s model 1292 Synchro is a highly specified robust
transmitter with a history of proven performance.)
•
The panel-mount case is designed to snap-fit into a
standard 1/8
DIN rectangular
cut-out of 44mm (1.73 in.) by 92mm (3.62 in.)
•
Wiring is done to the rear of the case. #16 AWG (min.) type THHN, THWN, TFFN,
or equivalent wire is recommended for the five AC synchro lines. #20 AWG (min.)
shielded twisted pair wire is recommended for analog output wiring. Use appropriate
spade lugs (provided) when connecting to the case terminals.
•
Contact INCON Technical Service (1-800-872-3455) for application assistance if the
synchro transmitter and the 1250-LTC monitor are separated by a wire run of more
than 1200 feet.