Page 229 - Electrical Equipment Handbook _ Troubleshooting and Maintenance
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SYNCHRONOUS MACHINES
11.4 CHAPTER ELEVEN
FIGURE 11.4 Slot geometries: (a) semiclosed slot with one-layer winding; (b) semiclosed
slot with two-layer winding; (c) open slot.
SYNCHRONOUS MACHINE WINDINGS
The three types of windings used in synchronous machines are distributed, solenoid, and
damper windings.
Distributed Windings. This type of winding is made of bundles of wire or insulated wire. It
is inserted in slots around the rotor or stator air gap surface. In large machines, this winding
is made of rectangular copper or aluminum bars. These bars are made from many elemental
units (known as coils) insulated from each other with a cloth of nylon or Mylar. They are
also coated with an insulated varnish and baked or thermally cured to form a rigid unit. The
bars are inserted into slots similar to the ones shown in Fig. 11.4c. These bars are known as
preformed coils.
In smaller-rated machines, these conductors are made of insulated wire known as magnet
wire. The bundles of wire are inserted into slots in the core. They are coated with insulating
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