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Silica Resin Encapsulated Transformers

The Silica Resin Encapsulated transformer is the result of many years of continuous refinement by Olsun Electrics. It was developed and expanded as a result of a growing need for a compact and economical dry type transformer that was virtually impervious to harsh environmental conditions, such as those encountered in chemical plants, refineries, dairies, marinas, shipboard use and desert areas like those found in Saudi Arabia. Product durability, quiet operation and flexibility in designing for your custom application make Olsun the clear choice to manufacture your encapsulated transformer.

While the majority of our business still centers around custom applications, we have found that there are commonly used encapsulated transformers and to meet that need we have developed the
Standard Encapsulated Transformer Product Offering
featuring our 56 most requested transformers.

We have two encapsulated transformer product types widely recognized in the marketplace:


With its innovative bottom wiring compartment, hinged padlockable door and stainless steel construction, the HazPac product has been the preferred and quality choice of customers and specifying engineers for their hazardous location and corrosive environment transformer applications.


The SilPac product features identical HazPac high quality electrical core and coil design and encapsulated construction with various enclosure options but is less expensive because it does not have the HazPac’s hinged padlockable wiring compartment door.

SilPac v. HazPac Product Feature Comparison


NEMA 3R enclosure
NEMA 4 / 4X sealed enclosure
Hinged padlockable wiring compartment door
UL Listed (E59100) General Purpose encapsulated applications
UL Listed (E198883) for NEC/CEC reference Class l, Division 2, Groups A, B, C and D
UL Listed (E198883) for IEC/ATEX reference Class l, Zone 2, Groups llA, llB and llC
Relative Price

Hazardous Location Applications

All Olsun Electrics’ HazPac and SilPac Encapsulated Transformers are designed and built specifically for hazardous locations in compliance with Article 500 of the NEC and are UL* listed for Class 1, Division 2, Groups A, B, C & D locations, with a North American Temperature Classification of T3C. Our dedicated hazardous duty designs also offer high short-circuit strength and 115°C rise availability.

* UL Listing applicable to single-phase sizes up to 50 kVA and three-phase sizes up to 150 kVA, through 600 volts.

Hazardous Application Typical Specification

Per the approved electrical plans, furnish and install dry type, hazardous duty rated transformers as manufactured by Olsun Electrics Corporation or approved equal. Single-phase transformers up to 50 kVA and three-phase transformers up to 150 kVA (through 600 volts) shall meet the requirements of UL Standard 1604, latest revision, entitled “Electrical Equipment for use in Class I and Class II, Division 2, and Class III Hazardous (Classified) Locations”.

Transformer sizes (kVA ratings) shall be as shown on the electrical plans or transformer schedule. Primary taps shall be full capacity, with a minimum of 2, 5% below nominal primary voltage rating on kVA sizes through 15; 2, 2.5% above and below nominal primary voltage rating on kVA sizes above 15 kVA.

All transformers shall have a maximum full load temperature rise of 115 degrees C above a 30 degree C ambient. All insulating materials used shall have a minimum UL 180 degrees C system rating. Encapsulating resin shall have a minimum UL temperature system rating of 180° C. The temperature rise shall be designated on the nameplate.

The transformer cores are to be constructed of high grade, non-aging silicon steel laminations with high magnetic permeability and low hysteresis and eddy current losses. Magnetic flux densities shall be kept well below the saturation point. The core laminations shall be clamped together with heavy structural steel angles.

The enclosure shall be 14 gauge, or heavier, type 316 stainless steel in accordance with the latest NEMA, ANSI and UL requirements for outdoor enclosures. The enclosure shall be provided with suitable lifting means. Jacking and lifting provisions shall be provided on all units weighing in excess of 600 pounds. All enclosure seams shall be continually welded using compatible welding rod and all weld seams shall be ground smooth. An ANSI 61 gray, powder coat finish shall be applied to a minimum thickness of 1.5 mils.

The enclosure shall have adequate surface area to limit the maximum temperature rise of the enclosure to 65 degrees C above a 40 degree C ambient at full load and rated voltage.

NOTE: Enclosures can be CRS—designated NEMA 4

Related Literature

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