MGM GENERAL PURPOSE DRY Installation Manual

5701 S M IT H W A Y ST R E E T • C O M M E R C E , C A 9 0 0 40

(323) 726-0 8 8 8 • [phone] • F A X (3 2 3 ) 7 2 6 -8224

w w w .m g m tr an sfor m e r.co m

GENERAL PURPOSE DRY - TYPE

DISTRIBUTION TRANSFORMER

INSTALLATION, OPERATION, AND

MAINTENANCE MANUAL

MGM 100-10A-04-2018

MGM 100

-

10A

WARNING

Electrical potentials hazardous to human life can exist within this equipment when it is
energized. Disconnect all input power before opening the case or touching the internal
parts

The information contained herein may not cover all variations in equipment supplied or
provide for all contingencies that might arise during the installation, operation or
maintenance for this equipment. If there is any question regarding the above items,
contact your supplier.

IT IS E
BY Q

XPECTED THAT ANY INSTALLATION OR MAINTENANCE WILL BE PERFORMED

UALIFIED PERSONNEL ACCORDING TO LOCAL

, S

TATE

, A

ND NATIONAL CODES

.

MGM 100

-

10A

Table of contents

General ...................................................................................................................... 3

Inspection upon Receipt ............................................................................................. 3

Handling ..................................................................................................................... 3

Storage ....................................................................................................................... 3

Installation Location .................................................................................................... 3

Room Requirements ................................................................................................... 3

Connections ............................................................................................................... 4

Grounding .................................................................................................................. 4

Reverse Feed or Step-up Operation ........................................................................... 4

Reducing Sound Levels .............................................................................................. 4

Prior To Energizing ..................................................................................................... 5

Maintenance ............................................................................................................... 5

Lighting Tap Applications ........................................................................................... 5

Dielectric Insulation .................................................................................................... 5

Ambient Temperature ................................................................................................. 5

Altitude ....................................................................................................................... 6

Single Phase Three Wire Operation ........................................................................... 6

References ................................................................................................................. 6

When you need Service ............................................................................................. 6

Terms and Conditions ................................................................................................ 6

Appendix A - Seismic Kit Installation Instructions (cases A, B, B+, C, C+)

Appendix B - Seismic Kit Installation Instructions (cases D & E)

Appendix C - Wall Mount Bracket Installation Instructions

Appendix D - Weatherproof Kit Installation Instructions

Appendix E - Rodent / Bird Screen Kit Installation Instructions

MGM 100-10A

3

General

Read the entire manual before attempting to perform
installation of this transformer. Dry type transformers are
suitable for indoor or outdoor use depending upon the
construction of the enclosure as well as the ability to
protect the transformer from unwarranted access to live
parts. They are cooled by the free circulation of air
through the enclosures, the average ambient
temperature over 24 hours should not exceed 30° C
(86°F), the maximum ambient temperature should not
exceed 40° C (104°F) or as otherwise specified in the
specification. Overheating may occur if the air flow is
restricted, the transformer is overloaded, it is supplied with
over or under voltage, or operated at other than rated
frequency.

Inspection upon Receipt

Units are shipped in upright position and should arrive that
way. Upon arrival, all units should be inspected for
damage during shipment. Unpack and examine for
broken or loose parts. Careful inspection should be
made of transformer coils, wiring and insulators. What
appears to be minor damage in these areas may result in
an open or short circuit. Claims for damage should be
filed with the transportation company and an MGM
Transformer Company representative must be notified
immediately. For superficial or minor case part damage,
spare parts may be available, contact an MGM
Transformer Company representative.

Handling

Lifting with hand trucks or fork lift trucks is permissible if the
blades or forks are long enough to pass completely under
the case. Since most general purpose transformers have
a high center of gravity, extreme caution should be
exercised when lifting or moving the units.

If it is necessary to move ventilated dry-type transformers
during inclement weather then they should be thoroughly
protected against the entrance of moisture.

Storage

Storage areas should be as clean and dry as possible
without extreme temperature variations. Protective
wrappings should be left intact until the transformer is
moved to its permanent location. Dry type transformers
stored under extremely wet or dusty conditions must
have cleaning and drying operations performed before the
unit can be energized. (See Maintenance Section.)

Installation Location

Factors to be kept in mind when choosing a location for
dry type transformers are: accessibility, ventilation,
environmental conditions, and noise (see ‘Reducing
Sound Levels’). Installation should be made in an area
reasonably free from dust, excessive moisture,
fertilizers, chemicals and other corrosive fumes or
vapors and separated from flammable materials in
accordance with the NEC.

General purpose dry type transformers up to case GPC+ are
supplied in dual rated enclosures suitable for indoor/outdoor
installation and eliminates the need of a weather shield kit.
Weather shield kits are for cases GPD and GPE which are
available to convert these enclosures for UL listed outdoor
NEMA 3R use. The appropriate kit can be obtained from
a MGM Transformer representative. Even with a
properly attached weathershield kit, no transformer
should be hosed off, or placed in the catchment area of a
water sprinkler. Wall-mount brackets are also available
for units up to 75 KVA.

In all locations dry type transformers must be installed in
the upright position in an area with free air
circulation. Check NEC codes for minimum required
clearances from adjacent structures. Fencing in the
transformer to prevent unauthorized access is strongly
recommended.

Room Requirements

Dry-type transformers located indoors should comply
with the application requirements of NEC.

The room in which dry-type transformers are located
should be sized to permit locating transformers with
sufficient spacing between units and sufficient
clearances to walls and other obstructions (as
specified per NEC or as indicated below nameplate) to
permit air circulation. Sufficient space should also be
provided to permit routine inspection and maintenance.

Adequate ventilation is essential for the proper cooling of
transformers. Clean, dry air is desirable. Filtered air at or
above atmospheric pressure may reduce maintenance
if dust or other contaminants present a particular
problem. When transformers are located in rooms or
other restricted spaces, sufficient ventilation should be
provided to hold the air temperature within established
limits when measured near the transformer inlets. This

will usually require approximately 100 ft3/min of air per
kilowatt of transformer loss. The area of ventilating
opening required depends upon the height of the room,
the location of openings, and the maximum loads to
be carried by the transformer. Room ventilation should
not impede normal circulation of air through the
transformer.

When possible, the air inlet to the room should be near the
floor with the outlet in the opposite upper end of the room.
The exhausting air should not exceed 15°C over the inlet
air temperature. When necessary, forced air exhaust should
be used to maintain this maximum differential.

FOR ADDITIONAL INFORMATION VISIT US ONLINE AT WWW.MGMTRANSFORMER.COM

BOLT

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STEEL

Connections

Cautions: Make only those connections shown on the

nameplate or connection diagram. Before energizing,
check all tap jumpers for proper locations, and all bolted
connections for tightness. All three sets of taps on a
three phase transformer must be connected in the same
location for each phase. For instructions on how to read
nameplates and connection diagrams, please visit the
documentation section of our website at:
http://www.mgmtransformer.com .

All transformers, with bottom connections are designed for
easy accommodation of cable sizes in accordance with
NEC. Cables which will carry less than 100 amperes may
have a 60° C temperature rating or higher, and
cables which will carry 100 amperes or more must have a
75° C temperature rating or higher. All cables should be
in the lower part of the transformer enclosure in
accordance with markings on the enclosure.

Use 90° C cable sized to 75° C ampacity for the
units having terminals located above the coils. After
the first thirty days of service, re-tighten all connecting
lugs and bolts. Depending on the kVA rating, the
transformer may have flexible leads with bolted type
wire terminals, copper/aluminum (CU/AL) lug connectors,
or simply termination pads for mounting your own
crimp or lug type terminations. The table below shows
required torque for installing bolted wire connectors and
cables in lug type connectors.

SIZE

1/4-20 +/- 20% 50 4 60 5 75 6

5/16-18 +/- 20% 85 7 110 9 135 11

3/8-16 +/-20 % 145 12 195 16 240 20

1/2-13 +/-15 % 300 25 420 35 540 45

5/8-11 +/-15 % 480 40 840 70 1080 90

3/4-10 +/-15 % 720 60 1200 100 1560 130

NOTES:

1. Always use two wrenches when tightening or loosening
bolted connections to prevent damage.

2. Tighten, wait several seconds, then re-tighten all
connecting lugs and bolts.

Minimum electrical clearances in the installation of lugs
and cables must be per ANSI and NEMA Standards. All
electrical clearances that are questionable must be
insulated for the applied voltage. Particular care should
be taken with shielded cables, so that the ground termi­nation of the cables has sufficient clearance from all the
manufacturers installed live parts, including parts that
appear to be insulated.

+/- NOM

In-

Lbs

Ft-

Lbs

In-

Lbs

Ft-

Lbs

In-

Lbs

FOR ADDITIONAL INFORMATION VISIT US ONLINE AT WWW.MGMTRANSFORMER.COM

Ft-

Lbs

MGM 100-10A

Grounding

It is the responsibility of the installer to ground the
transformer enclosure assembly to the ground system in
accordance with the latest revision of the NEC Section
450-10, NEC Article 250 and ANSI/IEEE Std. 144.

Reverse Feed or Step-up Operation

Step-down transformers may be reverse fed for step-up
operation to increase voltage. This means that the incoming
power is connected to the low voltage (X’s) and the load is
connected to the high voltage (H’s). If the low voltage is wye,
the X0 terminal must NOT be connected in any way.
Likewise, if the low voltage is a delta with a 120 volt lighting
tap (high-leg), the X4 terminal must NOT be connected in
any way.

CAUTION: Much higher than normal inrush currents may
occur with reverse feed operation and may cause nuisance
fuse blowing or breaker tripping. For this reason, fuses and
breakers with time-delay characteristics must be used.

If a breaker is used for incoming over-current protection, it
must be a thermal-magnetic type breaker, not a magnetic­only type breaker.
Tap Settings are for the high voltage side and when reverse
fed the ability to adjust voltages is no longer available. This
means some performance parameters may be affected.

Reducing Sound Levels

Transformer noise originates within the steel core. It is
an inherent characteristic of all transformers and cannot
be completely eliminated. Therefore, care should be
exercised in the selection of the transformer location,
particularly in buildings where the ambient sound level is
quite low. A transformer's sound level is quite often
unintentionally amplified by improper installation, which
makes the transformer appear to be considerably louder
than it actually is. Transformer sound levels are
amplified by sound waves in the air being reflected from
surrounding objects and resonance of mounting
construction and electrical connections. This situation
should be avoided wherever possible. Trans forme rs
should be c onn ected f or and en ergiz ed at r at ed
volta ge and fr equency at n o loa d t o de termi ne the
corre ct noise l evel. Transformer sound level
problems can also be further minimized by following
these installation suggestions:

1. The case may be installed on vibration mounts for
additional reduction of sound levels.

2. Flexible conduit couplings should be used to reduce
vibration transfer from the case to the incoming and
outgoing conduit.

3. The installation should be in an area where the
sound will be least objectionable.

4. Avoid stairway and hall areas or reflecting objects
which resonate or echo. Concrete or masonry walls,
floors and ceilings are excellent sounding boards. If
these and other reflecting surfaces cannot be
avoided, acoustic absorbing materials should be
used to cover them.

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