GE Industrial Solutions Seconday Substation Transformer - Manual (Page 7)

7
INTRODUCTION
Fans are used on transformers to increase
the rate of heat dissipation and thus provide
additional transformer load capacity. They are
normally shipped separately and must be
properly installed before attempting to operate
the transformer at the forced-air-cooled rating
shown on the nameplate. Fans are to be
used only on those transformers designed to
operate with a forced-air-cooled rating.
DESCRIPTION
Fans are available in 12-, 20-, and 24- inch
sizes. Mounting Arrangements differ
according to the particular application as
outlined under “Installation”. All fans used on
any transformer are the same size and their
motors ratings are given on the motor
nameplate. Ratings are also shown on the
transformer Outline drawing, along with the
fan catalog number. Fan motors are equipped
with a thermal protector to prevent
overheating due to overloads or failure to
start. When a motor is shut off by the thermal
protector, it will start again automatically after
cooling.
CONTROL
One or more switches are furnished to permit
manual operation of the fans for test purposes
or automatic control by a thermal relay. Two
types of thermal relays are available, those
which respond to changes in top liquid
temperature and those which respond to an
equivalent of the winding hot-spot
temperature. The temperature at which the
fans operate and detailed information
concerning the thermal relay are contained in
separate instructions covering that device. A
magnetic contactor will be included if the
connected load exceeds the rating of the
thermal switch or if three-phase motors are
used. Refer to the transformer Connection
Diagram for details.
INSTALLATION
In order to obtain the forced-air-cooled
rating given on the transformer nameplate, the
type, number, and location of the fans must
be as indicated on the transformer Outline (or
Supply Parts Assembly) drawing. Before
mounting, make an inspection for shipping
damage and check for proper blade
alignment. All three sizes can be mounted on
the side of the cooling tubes or radiators. In
addition, the 12- inch fans may also be
mounted. Install the fans in the positions
shown on the Outline, paying particular
attention to the support bracket spacing and
hardware assembly in order to obtain a
secure mounting. Vibration problems may be
encountered if the fans are not mounted
properly.
When installing the fans, make sure they
blow air toward the transformer cooling tubes.
If it should be necessary to change the
direction of rotation of a three-phase fan, this
can be done by interchanging any two motor
leads.
TUBE MOUNTING
To install a 12” or 20” fan on the side of the
cooling tubes, determine its center line and
locate the mounting brackets in relation to
those center. Assemble parts and using
washers over each mounting bolt, attach the
fan using clamps and lock nuts.
To install a 24” fan, determine its center
line and locate the mounting brackets in
relation to the center lines. Dimensions to be
used will be determined by the location of the
fan with respect to the tube header.
Assemble parts and using washers over each
mounting bolt, attach the fan using clamps
and locknuts.
Position 20- and 24- inch fans with their
weep holes at the bottom to allow draining of
any condensate within the motor housing and
to prevent the entrance of free water. (This will
place the motor capacitor at the top on
single-phase fans).
HEADER MOUNTING
Depending on the size of the transformer
and the configuration of cooling tubes, 12-
inch fans may be mounted above the top
headers blowing downward. In the case of