The Head And Field Cooling Fan - BRUEL & KJAER System V Instruction Manual

4.2.1. The Head and Field Cooling Fan
The Head and Field Cooling Fan draws air through the Exciter Coils and past the Driver
Coil. The air is exhausted through an air duct. The fan is a centrifugal fan driven by the
Blower Motor mounted directly below on the Motor and Field Supply mounting plate.
Fig.4.2 shows the path taken by the cooling air. The cooling air flows downward
through the Exciter. The air enters the Exciter through perforations around the top of
the Exciter Head. It is drawn through the Magnet Assembly by the Head and Field Cool­
ing Fan and exhausts at the lower rear of the exciter.
4.:1
4.2
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Fig. 4. 2. Seetional view of an Exeiter Body and Head showing diree­
tian of eooling air flow
In the Magnet Assembly the air flows through two paralIei paths. The outer path is
through openings in the Upper Wheel, through the annular passages in the Upper Field
Coil, through openings in the Centre Bowl, through the annular passages in the Lower
Field Coil, and then through openings in the lower part of the Stem. The inner path is
through the openings in the Upper Wheel, radially inward to the post of the Stem,
downward along the inner and outer surfaces of the driver Coil and the inner and outer
Secondary Bands, and then to the openings in the lower part of the Stem. Rubber seals
between the Field Coils and the Centre Bowl keep the inner and outer air paths separate
and prevent "short circuiting" the Driver Coil cooling.
Air through the outer path cools the Upper and Lower Coils. Air through the inner path
cools the Driver Coli and the Secondary Bands.
The motor-cooling fan is mounted directly on the lower end of the motor drive shaft. It
takes in air from below the Exciter and exhausts through side vents.
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