[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)
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contains service conditions, tests, classifications, performance characteristics, and construction data for<br />
the transformers.<br />
Class 2 <strong>Transformer</strong>s: These transformers are dry-type, step-down, insulating specialty transformers<br />
suitable for use in National <strong>Electric</strong>al Code Class 2 circuits. They are generally used in remote-control,<br />
low-energy power, and signal circuits for the operation of bells, chimes, furnace controls, valves, relays,<br />
solenoids, and the like. Their secondary voltage is limited to 30 V.<br />
kVA range: 0 to 5 kVA, single phase<br />
Voltage<br />
Control transformers through 4800 V<br />
Ignition and luminous tube transformers through 15,000 V<br />
3.14.3.1.2 ANSI/UL 506, Standard for Safety for Specialty <strong>Transformer</strong>s<br />
These requirements cover air-cooled transformers and reactors for general use, and ignition transformers<br />
for use with gas burners and oil burners. <strong>Transformer</strong>s incorporating overcurrent or over-temperature<br />
protective devices, transient-voltage surge protectors, or power-factor-correction capacitors are also<br />
covered by these requirements. These transformers are intended to be used in accordance with the<br />
National <strong>Electric</strong>al Code, NFPA 70.<br />
These requirements do not cover liquid-immersed transformers, variable-voltage autotransformers,<br />
transformers having a nominal primary rating of more than 600 V, transformers having overvoltage taps<br />
rated over 660 V, cord- and plug-connected transformers (other than gas-tube-sign transformers), garden-light<br />
transformers, voltage regulators, swimming pool and spa transformers, or other special types<br />
of transformers covered in requirements for other electrical devices or appliances.<br />
These requirements also do not cover:<br />
Autotransformers used in industrial control equipment, which are evaluated in accordance with the<br />
requirements for industrial control equipment, UL 508.<br />
Class 2 or Class 3 transformers, which are evaluated in accordance with the Standard for Class 2 and<br />
Class 3 <strong>Transformer</strong>s, UL 1585.<br />
Class 2 transformers: These transformers are dry-type, step-down, insulating specialty transformers<br />
suitable for use in National <strong>Electric</strong>al Code Class 2 circuits. They are generally used in<br />
remote-control, low-energy power, and signal circuits for the operation of bells, chimes, furnace<br />
controls, valves, relays, solenoids, and the like. Their secondary voltage is limited to 30 V.<br />
Class 3 transformers: These transformers are similar to Class 2 transformers, but their output<br />
voltage is greater than 30 V and less than 100 V.<br />
Toy transformers, which are evaluated in accordance with the Standard for Toy <strong>Transformer</strong>s, UL 697.<br />
<strong>Transformer</strong>s for use with radio- and television-type appliances, which are evaluated in accordance<br />
with the requirements for transformers and motor transformers for use in audio-, radio-, and<br />
television-type appliances, UL 1411.<br />
<strong>Transformer</strong>s for use with high-intensity discharge lamps, which are evaluated in accordance with the<br />
Standard for High-Intensity-Discharge Lamp Ballasts, UL 1029.<br />
<strong>Transformer</strong>s for use with fluorescent lamps, which are evaluated in accordance with the Standard for<br />
Fluorescent-Lamp Ballasts, UL 935.<br />
Ventilated or nonventilated transformers for general use (other than compound-filled or exposed-core<br />
types), which are evaluated in accordance with the requirements for dry-type general purpose and<br />
power transformers, UL 1561.<br />
Dry-type distribution transformers rated over 600 V, which are evaluated in accordance with the<br />
requirements for transformers, distribution, dry-type — over 600 V, UL 1562.<br />
<strong>Transformer</strong>s incorporating rectifying or waveshaping circuitry, which are evaluated in accordance<br />
with the requirements for power units other than Class 2, UL 1012.<br />
<strong>Transformer</strong>s of the direct plug-in type, which are evaluated in accordance with the requirements for<br />
Class 2 power units, UL 1310.<br />
<strong>Transformer</strong>s for use with electric discharge and neon tubing, which are evaluated in accordance with<br />
the Standard for Neon <strong>Transformer</strong>s and <strong>Power</strong> Supplies, UL 2161.<br />
A product that contains features, characteristics, components, materials, or systems new or different<br />
from those in use when the standard was developed — and that involves a risk of fire, electric shock, or<br />
injury to persons — shall be evaluated using the appropriate additional component and end-product<br />
requirements as determined necessary to maintain the level of safety for the user of the product as<br />
originally anticipated by the intent of this standard.<br />
3.14.3.1.3 ANSI/UL 1446, Standard for Safety for Systems of Insulating Materials — General<br />
These requirements cover test procedures to be used in the evaluation of Class 120(E) or higher electrical<br />
insulation systems intended for connection to branch circuits rated 600 V or less. These requirements<br />
also cover (1) the investigation of the substitution of minor components of insulation in a previously<br />
evaluated insulation system and (2) the test procedures to be used in the evaluation of magnet wire<br />
coatings, magnet wires, and varnishes.<br />
These requirements do not cover a single insulating material or a simple combination of materials,<br />
such as a laminate or a varnished cloth.<br />
These requirements do not cover insulation systems exposed to radiation or operating in oils, refrigerants,<br />
soaps, or other media that potentially degrade insulating materials.<br />
These requirements shall be modified or supplemented as determined by the applicable requirements in<br />
the end-product standard covering the device, appliance, or equipment in which the insulation system is used.<br />
Additional consideration shall be given to conducting tests for an insulating material, such as a coil<br />
encapsulant, that is used as the ultimate electrical enclosure.<br />
Additional consideration shall be given to conducting tests for an insulating material or component<br />
that is a functional support of, or in direct contact with, a live part.<br />
A product that contains features, characteristics, components, materials, or systems new or different<br />
from those in use when the standard was developed — and that involves a risk of fire, electric shock, or<br />
injury to persons — shall be evaluated using the appropriate additional component and end-product<br />
requirements as determined necessary to maintain the level of safety for the user of the product as<br />
originally anticipated by the intent of this standard.<br />
3.14.3.1.4 IEC TC 96<br />
This document covers standardization in the field of safety of transformers, power-supply units, and<br />
reactors with a rated voltage not exceeding 1000 V and a rated frequency not exceeding 1 MHz of the<br />
following kinds:<br />
<strong>Power</strong> transformers and power supply units with a rated power less than 1-kVA single phase and 5-kVA<br />
polyphase<br />
Special transformers and power supply units other than those intended to supply distribution networks,<br />
in particular transformers and power-supply units intended to allow the application of<br />
protective measures against electric shock as defined by IEC TC 64<br />
<strong>Electric</strong>al installations in buildings, with no limitation of rated power, but in certain cases including<br />
limitation of voltage<br />
Reactors with a rated power less than 2-kVAR single phase and 10-kVAR polyphase<br />
Special reactors other than those covered by IEC 289<br />
Note: Excluded are switch-mode power supplies (dealt with by SC 22E)<br />
Safety group function:<br />
Special transformers and power supply units other than those intended to supply distribution networks,<br />
in particular transformers and power supply units intended to allow the application of protective<br />
measures against electric shock as defined by TC 64, with no limitation of rated power but in certain<br />
cases including limitation of voltage.<br />
Table 3.13.2 provides a list of relevant documents.<br />
© 2004 by CRC Press LLC<br />
© 2004 by CRC Press LLC