Howard Small Power - Manual (Page 13)

Small Power Substation Transformers
Document 2.4.54 Revision 0
July 2006
13
!
DANGER: ALWAYS DE-ENERGIZE THE FAN
CIRCUIT WHEN INSTALLING OR PERFORMING
MAINTENANCE ON FANS. IN ADDITION, DE-ENERGIZE
THE TRANSFORMER WHEN IT IS POSSIBLE TO COME
CLOSE TO LIVE PARTS. FAILURE TO DO SO COULD
RESULT IN SEVERE PERSONAL INJURY OR DEATH.
FAN GUARDS ARE FURNISHED AND INSTALLED AT
THE FACTORY TO PREVENT ACCIDENTAL CONTACT
WITH ROTATING FAN BLADES. DO NOT REMOVE FAN
GUARDS OR ALLOW PERSONNEL TO REACH INSIDE
A GUARD. DOING SO CAN RESULT IN SERIOUS
PERSONAL INJURY AND EQUIPMENT DAMAGE.
The auto/manual switch determines the mode of
operation for the fan motors. When the switch is in
the “manual” position, fans will operate continuously.
When the switch is in the “auto” position, fans will
be automatically controlled by contacts in the fluid
temperature gauge or winding temperature gauge.
Refer to the schematic wiring diagram provided with the
transformer.
Fan motors are provided with thermal overload
protection. The overload protection is usually contained
within the motor. However, if the motors are located in a
hazardous location, the overload protection device may
be located in the control box. Refer to the wiring diagram
provided with the transformer.
Fan motors have permanently sealed ball bearings
and do not normally require maintenance, except as
explained on page 15.
When fan assemblies are installed by the user, it
is important to permanently remove the drain plug
from the motor housing of each motor. This will allow
condensation to drain from the motor housing.
De-energized Tap Changer
The de-energized tap changer may be used to adjust the
voltage ratio of a transformer while it is de-energized. It
is intended to allow adjustment of the output (secondary)
voltage to the rated value. Do not use the tap changer to
raise or lower the output voltage to any voltage other than
that indicated on the transformer nameplate. If the tap
changer is set to provide an output voltage different from
rated voltage, a high noise level, high core loss, and core
saturation may result.
!
DANGER: DO NOT OPERATE A DE-
ENERGIZED TAP CHANGER UNLESS THE
TRANSFORMER IS TOTALLY DE-ENERGIZED.
FAILURE TO DO SO WILL RESULT IN DAMAGE TO
THE TRANSFORMER AND COULD RESULT IN SEVERE
PERSONAL INJURY OR DEATH. DO NOT RE-ENERGIZE
THE TRANSFORMER UNLESS THE TAP CHANGER IS
FIRMLY LOCKED INTO POSITION.
The tap changer is operated by use of a rotating handle
located on the outside of the transformer tank. Never
operate a de-energized tap changer while the transformer
is energized. Tap changers normally have five or seven
tap positions as indicated on the tap changer dial plate
and the transformer nameplate. A locking mechanism is
provided to lock the tap changer in position and prevent
accidental operation. Do not re-energize the transformer
until the tap changer is firmly locked into a tap position.
The transformer is shipped from the factory with the tap
changer in the rated voltage position, unless otherwise
specified by the customer.
Dual-Voltage or Delta/Wye Switch
Transformers designed with dual-voltage windings or
reconnectable delta/wye windings as indicated on the
nameplate are provided with a de-energized two-position
dual-voltage or delta/wye switch. The transformer must
be completely de-energized before operating the switch.
If the transformer is not de-energized before operating
the switch, permanent damage will result.
!
DANGER: DO NOT OPERATE DUAL-
VOLTAGE OR DELTA/WYE SWITCH UNLESS
THE TRANSFORMER IS TOTALLY DE-ENERGIZED.
FAILURE TO DO SO WILL RESULT IN DAMAGE TO
THE TRANSFORMER AND COULD RESULT IN SEVERE
PERSONAL INJURY OR DEATH. DO NOT RE-ENERGIZE
THE TRANSFORMER UNLESS THE DUAL-VOLTAGE
OR DELTA/WYE SWITCH IS FIRMLY LOCKED INTO
POSITION AND AT THE PROPER VOLTAGE.