Transformer Cooling Fans; Tapchanger - Westinghouse PS-1002 Instruction Book

2.
Make the Field Tests of the Sudden Pressure Relay and
its Panel to determine whether the Relay is in proper op­
erating condition. Refer to Instruction Leaflet
3. Make insulation power factor and insulation resistance
tests and check the Transformer Turns Ratio.
4.
Remove the manhole cover for observation. Sometimes
the odor of burning is obvious.
5. Make any other tests which may be suggested by the
results of the above checks.
After the condition of the transformer and Relay have
been checked, and if no damage has been found, it is nec­
essary to decide whether the breaker should be reclosed to
put the transformer back into service. The risk of possible
further internal damage must be balanced against the pos­
sibility that there is no serious internal damage.
5 .11 Transformer Coo lin g Fans
In order to provide for greater transformer loads without
overheating the windings, a set of fans will be clamped to
the top or to the sides of the transformer cooler assembly.
Fan control will be automatic from either the liquid
temperature gauge, the winding temperature gauge, or a
t h e r m a l relay (when furnished), in parallel with a
"MANUAL-AUTO" control switch in the control cabi­
net. A starter contactor is used when fan capacity exceeds
the alarm switch duty rating. When a starter contactor is
required, a forced air control panel is supplied. TI1e forced
air control panel is located in a weatherproof cabinet nor­
mally attached to the tank wall. Automatic control con­
sists of a De-ion® type AB
"manual-auto" switch and additional terminals for alarm
or lamp indication. For manual control only the
breaker is supplied.
The thermal trip AB breaker provides short circuit pro­
tection and a means of de-energizing the panel for inspec­
tion and for maintenance.
A thermally-actuated switch included in the liquid tem­
perature gauge or the winding temperature gauge controls
the solenoid of a magnetic contactor which in turn starts
and stops the fan motors in response to a change in liquid
or winding temperature.
The circuit is energized from the load side of the panel
power circuit. The "manual-auto" switch provides a
48-065-1.
line breaker, a contactor, a
AB
means of starting the fans independently of the position
of the thermal switch. With the thermal switch in the
closed position, the fans may be stopped by opening the
AB breaker. An ''Auto-Off-Manual" switch is supplied in­
stead of the "Manual-Auto'' switch when requested by the
customer.
Fan motors come equipped with drain plugs on the
housing to prevent collection of condensate inside the
motor. WHEN INSTALLING THE FANS IN THE FIELD,
IT IS IMPORTANT TO PERMANENTLY REMOVE THE
BOTTOM DRAIN PLUG.
Fan motors are single-phase,
pacitor start and capacitor run. Rotation of the fan blade
is counter-clockwise when looking at the motor from the
lead end. The motors will operate between
v.a.c. The fan motors have permanently sealed ball bear­
ings that require no maintenance. When replacing motors
it is recommended that the capacitor also be replaced.
bad capacitor will cause the motor to draw excessive cur­
rent and fail due to overheating.
FAN BLADES ARE SHARP AND CAN CAUSE PER­
SONAL INJURY. ALWAYS
TRANSFORMER AND THE
DOING MAINTENANCE ON OR INSTALLING COOL­
ING FANS. NEVER REACH INSIDE THE FAN G UARD
OR FAN CAGE.
5.12 Tap Changer
The tap changer provides a means of changing the voltage
ratio of a de-energized transformer without breaking the
transformer seal. It is operated by means of a rotatable
handle located on the side wall or cover of transformer.
This handle is attached to the tap changer by means of a
shaft which extends through the liquid and gas tight pack­
ing gland in the tank. The tap changer is normally pro·
vided with five positions, as indicated on the tap changer
dial plate and transformer instruction nameplate.
One tap position change requires one complete revolu­
tion of the external operating handle. The transformer
must not be energized unless the tap changer is locked in
an operating position.
A locking pin holds the tap changer handle in any of
the tap positions. By pulling this pin outward, the handle
is allowed to move freely to the position desired. The
locking pin can only be reset in the indexed boss. This as-
11
50-60 1/6
Hertz, hp, ca­
208 and 240
A
DE-ENERGIZE THE
FAN CIRCUIT WHEN