FIELD OF INVENTION :
The present invention relates to design and tooling developnnent for new
overhang bracing technique for Brushless Exciter for 3000 rpm 210MW rating by
using 'Resiglass Tape' as bandaging medium. The invention particularly relates to
use of Resiglass tape in place of non magnetic bandage wire otherwise used for
bracing of armature overhang of 210MW turbo-generator (TG).
BACKGROUND AND PRIOR ART OF INVENTION
Armature of a 6 pole, 3000 rpm Brushless Exciter's l^ain Exciter is a revolving
assembly. It comprises of double layer 3 phase wave wound winding. Winding
bar consists of solid rectangular conductor. Overhang of armature winding is
normally braced using steel wire, non magnetic, having high tensile strength.
Wire has a tin layer on top for helping the soldering operation. Steel wires are
held by copper strips placed all along the circumference and bent over the
bandage.
The bandaging operation involves six layers of wire bandaging carried out under
tension with each layer being profusely soldered. Complete bandaging has to be
carried out using single length wire and any accidental breaking of wire leads to
redoing of all the layers.
2

In the prior art, there was frequent rework due to breakage of wire in between
due to accidental variation in tension or malfunctioning of bandaging machine.
Also, wire being of special non magnetic grade (18Mnl8Cr) there was difficulty in
wire procurement.
Above mentioned hurdles in use of wire bandaging technology for overhang
bracing of 210MW Exciter armature lead to need for development of new design
and technology and basically laid the foundation of this development.
The invention seeks to overcome the above mentioned shortcomings of the prior
art.
A method was developed for bandaging of overhang with Resiglass tape. Poly
glass H200 tape of M/s isola, Italy was chosen as bandaging tape, due to its
inherent qualities like good mechanical strength, excellent insulating properties,
better heat resistance and moisture resistance. The tape also has excellent
withstand ability in aggressive environmental conditions. It also has no influence
on presence of chlorides etc in environment.
3

Exciter armature winding bar rests on winding support ring. The diameter over
tlie top bar is Dia 687mm. Bandaging of Resiglass tape under tension was
planned to be carried out over tliis. Top padding thickness over the top bar was
reduced so as to accommodate higher thicl