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3.7: TRANSFORMER THERMAL AND SOUND CHARACTERISTICS

By Robert B. Hickey
From Electrical Engineer's Portable Handbook, Second Edition

3.7 TRANSFORMER THERMAL AND SOUND CHARACTERISTICS

In addition to transformer electrical characteristics, their thermal and sound level characteristics are very important. Thermal characteristics are determined by industry standards (UL/ANSI 1561-1987) and are generally only of concern to the electrical design professional. Sound levels, on the other hand, are of concern to everyone, especially the architect and occupants of the building. Electrical design professionals must be sensitive and aware of the sound levels of electrical equipment and their impact on the occupants of the building and exercise appropriate measures to mitigate their effects. These could include remotely locating the equipment, sound attenuation techniques, and/or structural isolation. To assist you in evaluating these considerations, Figure 3.36 shows the thermal characteristics of dry-type distribution transformers, and Tables 3.37 and 3.38, respectively, show the maximum average sound levels of drytype and liquid-filled transformers and typical ambient sound levels.


Figure 3.36: Transformer insulation system temperature ratings.
Table 3.37: Typical Building Sound Levels

Radio, Recording and TV Studios

25-30 db

Theatres and Music Rooms

30-35

Hospitals, Auditoriums and Churches

35-40

Classrooms and Lecture Rooms

35-40

Apartments and Hotels

35-45

Private Offices and Conference Rooms

40-45

Stores

45-55

Residence (Radio, TV Off) and Small Offices

53

Medium Office (3 to 10 Desks)

58

Residence (Radio, TV On)

60

Large Store (5 or More Clerks)

61

Factory Office

61

Large Office

64

Average Factory

70

Average Street

80

Table 3.38: Maximum Average Sound Levels for Transformers

kVA

Dry-Type

Liquid-Filled

Self-Cooled Rating (AA)

Forced-Air Cooling...

Copyright The McGraw-Hill Companies, Inc. 2004 under license agreement with Books24x7
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Industrial Control Transformers
Industrial control transformers are designed for industrial applications that require relays, solenoids, and other electromagnetic devices. They contain capacitors or other filtering devices to minimize variations in output, and are well-suited for applications that require constant current or constant voltage with a low volt-amp or low power rating.
Signal Transformers
Signal transformers transfer information from one circuit to another by electromagnetic induction. They are used to increase or decrease the voltage from one side of a power transformer to the other.
Board Mount Transformers
Board mount transformers are transformers designed to be embedded in or mounted on computer boards.
RF Safeguarding Devices
RF safeguarding devices are used to control machine operations by detecting changes in the RF field.
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