Audio-video transformer differences

Manufacturer's name, trademark, or other descriptive marking

29.1

14.3.1

Factory identification code -- required if transformer is produced or assembled at more than one manufacturing location

29.2

5.1.k

Materials used as part of a fire enclosure shall have a minimum flammability rating of V-2 in accordance with UL 94

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20.2.1

Encapsulation compound covering exterior surface of a transformer shall have a minimum flammability rating of HB in accordance with UL 94

4.4

-

Rated for the voltage and temperature reached under any condition of actual use

5.1.1

8.9.1

Rated VW-1

5.1.1

20.1.2

Rated VW-1

5.3.1

20.1.2

Flame retardant

5.3.1

20.1.2

Shall be polarized type

5.2.2

-

Conductors of a parallel flexible cord of a transformer shall not be split external to the transformer enclosure (end-bells)

5.2.3

-

Solder joints shall be mechanically secure before soldering

5.4.1

8.11

Shall be provided so that stress on each individual lead is not transmitted to the connection inside the transformer

5.5.2

-

Shall be secured in place

5.7.1

16.6

A capacitor with or without a built-in shunt resistor shall comply with UL 1414

6.3

-

A protective device (fuse, overtemperature and overcurrent protector, eutectic material) employed as part of the transformer shall comply with the requirements for the construction, performance, and use for such a device, i.e., shall be UL Recognized Components

7

-

Thermal cutouts shall comply with UL 8730-2-9

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14.5.1.1

Fuse-links shall comply with UL 248-14

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14.5.2.1

PTC's shall comply with IEC 60738 or UL 1434

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14.5.3

Resistors complying with surge test may be provided. Also, resistors complying with UL 1412 may be provided if the resistance does not differ by more than 20%

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14.1

Insulating material for the support of terminals operating at 42.4 volts peak or more or having available power of more than 15 W shall have:

1. Acceptable mechanical strength
2. Minimum flammability rating of V-2 in accordance with UL 94
3. Temperature rating suitable for end-use application
4. Suitability for the sole support of live parts as determined by investigation regarding factors such as hot-wire ignition, high-current-arc ignition, volume resistivity, and dielectric strength

See clause 9.1 for exceptions to the above requirements

9.1

-

Polymeric or fiber parts in contact with a component located in a potential ignition source (see clause 2.8.11 for definition) circuit shall have a minimum flammability rating of V-2

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20.1.4, table 13

May be rated HB or less if the transformer is encapsulated by material rated V-0 or better

10.1

-

Bobbin material must be UL Recognized V-2 at minimum bobbin thickness

-

20.1.4, table 13

Insulation shall :

1. Be resistant to moisture unless inherently moisture resistant. Acceptability of material based on insulation resistance test (see clause 26)
2. Be of equivalent mechanical strength when compared to electrical grade paper
3. Have equivalent dielectric voltage-withstand strength when compared to electrical grade paper
4. Be acceptable for the temperature involved in the end-use product

11.3

Electrical grade paper (having a total minimum thickness of 0.30 mm) or the equivalent of such insulation shall be used between:

1. Uninsulated, primary wires of opposite polarity
2. Multiple primary windings
3. Body of a primary-connected thermal protector and the adjacent windings
4. Body of a secondary-connected thermal protector located adjacent to a primary winding

11.6

Insulation between the primary winding lead connections and the shield or the transformer enclosure (end bells) shall be:

1. Electrical grade paper >=0.30 mm thick if used in conjunction with an air spacing of 1/2 that specified in 14.1
2. Electrical grade paper >=0.58 mm thick if the insulation is in contact with the end bell
3. Equivalent insulation material

11.9

Shall not be less than 0.028 inch (0.71 mm) thick.

12.1

Insulation of hazardous live parts shall not be provided by hygroscopic materials.

1. Compliance is checked inspection and/or
2. Conducting humidity conditioning of insulating materials test (see clause 8.3)

8.3

Compliance of insulation is determined by:

1. Humidity treatment test (see clause 10.2)
2. Insulation resistance test (see clause 10.3)
3. Dielectric strength test (see clause 10.3)
4. Creepage and clearances of clause 13
5. Requirements for protective screens (see clause 14.3.4.2)

8.8, 14.3.5.2

Insulation between hazardous live windings and accessible parts or parts intended to be connected to accessible conductive parts, i.e., iron core, shall be separated by double or reinforced insulation according to clause 8.8.

8.8, 14.3.5.1

Compliance of insulation is determined by:

1. Humidity treatment test (see clause 10.2)
2. Insulation resistance test (see clause 10.3)
3. Dielectric strength test (see clause 10.3)
4. Creepage and clearances of clause 13

8.8, 14.3.5.1

Spacing shall be provided between:

1. Uninsulated live primary parts of different potential
2. Uninsulated live primary part and any dead metal part (core)
3. Uninsulated live primary part and any uninsulated secondary part

14.1

0 - 50

1.6

1.6

1.6

151 - 250

3.2

3.2

6.4

Creepage and clearance distances shall be provided between:

1.    Primary and secondary windings

2. Primary windings and core
3. Parts of different polarity directly connected to the mains

13

120

Basic or supplementary

1.5

120

Reinforced

3.0

When the following tests are not conducted as part of the transformer, they are to be considered in the end-product.

1. Power input test (clause 18)
2. Temperature test (clause 19)
3. Abnormal operation tests, 7 hour or 15 day (clause 27)

17.3

Test Location:

1. Primary and core
2. Primary and secondary

23.1.1

Test specification:

1. Three samples shall be conditioning in an air-circulating oven for 7 hours
2. Following conditioning samples subjected to a 900 Vac dielectric voltage-withstand test for 1 minute

24.1

Test location:

1. Primary and core
2. Primary and secondary

24.1

Test specification:

1. Sample is exposed for 24 hours to moist air having a relative humidity of 85 ± 5 percent at a temperature of 32.0 ± 2.0 ºC.
2. Insulation resistance shall not be less than 10 megaohms

26.1

Test specifications:

1. A sample shall be placed in a humidity chamber operating at one of the following conditions:
   1. 28 to 30 ºC with a relative humidity between 90-95% for a period of two days (48 hours)
   2. 38 to 42 ºC with a relative humidity between 90-95% for a period of five days (120 hours) for an apparatus to be used under tropical conditions

10.2

Test specification:

1. Test voltages for dielectric strength and values for insulation resistance are provided
2. Test voltages are based on the type of insulation provided, i.e., basic, supplementary, reinforced, or double insulation
3. Tests shall be carried out for a period of 1 minute

10.3

Insulation between accessible parts or parts connected to them and hazardous live parts shall be subjected to the voltage surge test.

10.1

Test specifications:

1. 50 discharges, at a maximum rate of 12 per minute, from a 1 nF dump capacitor charged to 10 kV

10.1

Test is followed by:

1. Dielectric strength test
2. Insulation resistance test

10.1