GE Industrial Solutions Dry-Type General Purpose Power Transformers - Manual (Page 5)

5
NOTE
AFTER INSTALLATION OF CONNECTORS AND CABLING, A MINIMUM OF 1” CLEARENCE MUST BE MAINTAINED
FROM ENERGIZED PARTS TO ALL CASE PARTS.
CAUTION
CARE MUST BE TAKEN TO PLACE ALL LEADS FROM THE SAME LOAD THROUGH ONE KNOCKOUT AND THOSE
FROM THE SAME SUPPLY SOURCE THROUGH ONE KNOCKOUT SO THAT NO PART OF THE CASE IS BETWEEN
SUCH LEADS. IF MULTIPLE KNOCKOUT HOLES ARE REQUIRED, EACH KNOCKOUT HOLE MUST CONTAIN THE
SAME NUMBER OF CABELS ROUTED TO EACH PHASE OF THE TRANSFORMER. FAILURE TO DO SO CAN CAUSE
EXCESSIVE HEATING OF THE TRANSFORMER ENCLOSURE. TO PREVENT ENCLOSURE DAMAGE, PROVIDE
PROPER SUPPORT OF TRANSFORMER ENCLOSURE PANELS WHEN PULLING CABLES THROUGH PANEL.
6.2 Grounding
Consideration must be given to equipment grounding. Grounding methods and practices are well established and are beyond the
scope of this installation guide. The grounding conductor for a transformer should have a current carrying capacity in accordance
with the NEC. Refer to enclosure assembly picture on last page.
6.3 Lighting Tap Applications
Some transformers with a 240-volt delta connected secondary have a 120-volt single-phase lighting tap. The maximum single-phase
120-volt load should not exceed 5% of the three-phase kVA rating. The load should also be balanced at 2.5% maximum between
terminals X1 to X4 and 2.5% between terminals X3 to X4.
7.0 Before Energizing
Remove all shipping hardware and store for future use. If it is desired to change location of the transformer at some future date,
reinstall all shipping hardware. Check all other bolted connections for tightness. Securely tighten all screws that hold the panels
and covers in place to eliminate possible vibration of these parts.
8.0 Operation
To maintain safe operating conditions do not remove panels of the enclosure while the transformer is energized.
CAUTION
NEVER ATTEMPT TO CHANGE TAPS OR CONNECTIONS UNLESS THE TRANSFORMER IS DE-ENERGIZED AND
ALL WINDINGS GROUNDED.
NOTE
TRANSFORMERS RUN HOT: AT FULL LOAD, TRANSFORMERS WITH 150C WINDING TEMPERATURE RISE
COULD HAVE A MAXIMUM 50C/122F TEMPERATURE RISE ON THE SURFACE AREAS OF THE ENCLOSURE. WITH
A 40C AMBIENT, THE MEASURED TEMPERATURE COULD BE AS HIGH AS 90C/194F.
8.1 Loading
In general, dry type transformers are designed to operate continuously at their nameplate kVA rating. ANSI C57.96 provides
guidance for loading under unusual conditions including: 1. Ambient temperatures higher or lower than the basis for rating; 2. Short
term loading in excess of nameplate kVA with normal life expectancy and; 3. Loading that results in reduced life expectancy.
If the transformer is experiencing increased temperatures, the following load characteristics should be considered immediately:
•
Rigorous motor starting loads, frequent multiple motor starts or other impact loading for which a specific transformer for that
application is required.
•
Over excitation of unit due to excessive supply line voltage.
•
Ambient temperatures above standard 40C maximum – 30C average over 24 hours.
•
Harmonic distortions of the supply line voltage or currents.
•
Loads that are non-linear with harmonic distortion.