Acme - Section 1 - Dry-Type Distribution Transformers (AE_CAT_1_001)

Dry-Type Distr ibut ion Transformers

S e c t i o n 1 | E n c l o s u r e D e f i n i t i o n s / T r a n s f o r m e r S e l e c t i o n s S t e p s

Enclosure Definitions

Intended for indoor use, primarily to provide a degree of protection against contact with the enclosed equipment. Intended for indoor use, primarily to provide a degree of protection against limited amounts of falling water and dirt. Intended for outdoor use, primarily to provide a degree of protection against falling rain, sleet and external ice formation. Definitions Pertaining to Enclosures Constructed to provide for circulation of external air through the enclosure to remove excess heat, fumes or vapors. Constructed to provide no intentional circulation of external air through the enclosure.

Type 1 Enclosures

Type 2 Enclosures

Type 3R Enclosures

Ventilated

Non-Ventilated Indoor Locations Outdoor Locations Hazardous (Classified) Locations

Those areas protected from exposure to the weather.

Those areas exposed to the weather.

Those areas, which may contain hazardous (classified) materials in sufficient quantity to create an explosion. See Article 500 of The National Electrical Code.

Single Phase Loads 1. Determine electrical load A. Voltage required by load. B. Amperes or kVA capacity required by load. C. F requency in Hz (cycles per second). D. V erify load is designed to operate on a single phase supply. All of the above information is standard data normally obtained from equipment nameplates or instruction manuals.

2. Determine supply voltage A. Voltage of supply (source). B. F requency in Hz (cycles per second).

The frequency of the line supply and electrical load must be the same. Select single phase transformer designed to operate at this frequency, having a primary (input) equal to the supply voltage and a secondary (output) equal to the voltage required by the load. 3. I f the load nameplate expresses a rating in kVA, a transformer can be directly selected from the charts. Choose from a group of transformers with primary and secondary voltages matching those you have just determined. A. Select a transformer with a standard kVA capacity equal to or greater than that needed to operate the load. B. Primary taps are available on most models to compensate for line voltage variations. (Refer to question #2 in the Transformer Questions and Answers Section on page 3.) C. W hen load ratings are given only in amperes, tables 1 and 2 or the following formulas may be used to determine proper kVA size for the required transformer. (1) To determine kVA when volts and amperes are known:

Volts x Amps 1000

kVA =

(2) To determine Amperes when volts and amperes are known:

kVA x 1000 Volts

Amps =

Single Phase Example Question: Select a transformer to meet the following conditions. Load is single phase lighting using incandescent lamps. Each fix ture requires 1.3 amps @ 120 volts, 1 phase, 60 Hz, power factor of unity. The installation requires 52-100 watt fixtures. The desired circuit distributing power to the light fixtures is 120/240 volt, three wire, single phase. The supply voltage is 460 volt, 3 phase.

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