Tubular Vitreous Enamelled

Wirewound Resistors

1600/1900 Series

Tubular Vitreous Enamelled

Wirewound Resistors

1600/1900 Series

Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com

123

09.09

Welwyn Components

Maximum*

Maximum*

Maximum*

total

resistance

number

dissipation

with single

of taps

in 20°C

tap

ambient

(ohms)

(watts) with

Type

single tap

1905

14.5

9k

1

1600

15.0

12k

1

1602

15.5

9k

1

1906

19.0

13k

1

1603

22

18k

1

1604

31

29k

2

1605

41

34k

2

1908

47

38k

2

1607

66

53k

2

1606

80

78k

4

1608

101

93k

4

1609

145

140k

4

Fixed resistors can be supplied with taps to special order.

Because of the reduced winding length, the total resistance of

a tapped resistor will be less than can be offered on a fixed

resistor of the same size. The reduction is proportional to the

number of taps and Table 5 is intended as a guide.

The minimum resistance per section on all sizes is 1

Ω and the

standard selection tolerance for any section is ±10%

Ordering Procedure

Enquiries for tapped resistors must state the following details:

Resistance per section

Maximum dissipation per section

Maximum operating ambient temperature

Maximum permissible dimensions if important

Type of terminations required. (See ‘Terminations’, page 3)

Resistor style or proposed method of mounting.

Table 5

*Maximum total dissipation assumes that this will be

evenly spread over the total element length.

Low Inductance Resistors

Ayrton-Perry wound elements are supplied for low inductance

applications. This winding style has a maximum permissible

hot spot temperature of 300°C. The maximum dissipation is

defined in Table 1 under the heading Operating hot spot

temperature of 300°C, and resistance ranges are defined in

the three right-hand columns of this table.

Application Notes

When cold, vitreous enamel has excellent insulation resistance.

In common with all insulants the specific resistance of the

enamel decreases with increased temperature; therefore, if

operated at any temperature approaching the maximum, the

resistor cannot be classed as an insulated type and should not

be used in contact with any conducting materials.

The recommended dissipations for each of the resistor hot

spot temperatures applies to resistors mounted horizontally. If

the bore is completely blocked a 15% derating is

recommended. However, wherever possible, resistors should

be mounted vertically with unobstructed bore.

This makes best use of the chimney effect of the heated tube

and will encourage a cooling stream of air through the bore.

Allowances must be made, when tubular resistors are mounted

in banks, for the effects produced by radiation between tubes.

Appreciable reduction of hot spot temperature can be

achieved by arranging that resistors are subjected to some

measure of forced draught. In general, it is most efficient to

extract air from the resistor enclosure and arrange that an air

inlet is adjacent to the bottom of the tubes.

If soft soldered connections are used the resistors should be derated

where applicable to limit the hot spot temperature to 300°C.

Tubular Vitreous Enamelled

Wirewound Resistors

1600/1900 Series

Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com

123

09.09

Welwyn Components

Maximum*

Maximum*

Maximum*

total

resistance

number

dissipation

with single

of taps

in 20°C

tap

ambient

(ohms)

(watts) with

Type

single tap

1905

14.5

9k

1

1600

15.0

12k

1

1602

15.5

9k

1

1906

19.0

13k

1

1603

22

18k

1

1604

31

29k

2

1605

41

34k

2

1908

47

38k

2

1607

66

53k

2

1606

80

78k

4

1608

101

93k

4

1609

145

140k

4

Fixed resistors can be supplied with taps to special order.

Because of the reduced winding length, the total resistance of

a tapped resistor will be less than can be offered on a fixed

resistor of the same size. The reduction is proportional to the

number of taps and Table 5 is intended as a guide.

The minimum resistance per section on all sizes is 1

Ω and the

standard selection tolerance for any section is ±10%

Ordering Procedure

Enquiries for tapped resistors must state the following details:

Resistance per section

Maximum dissipation per section

Maximum operating ambient temperature

Maximum permissible dimensions if important

Type of terminations required. (See ‘Terminations’, page 3)

Resistor style or proposed method of mounting.

Table 5

*Maximum total dissipation assumes that this will be

evenly spread over the total element length.

Low Inductance Resistors

Ayrton-Perry wound elements are supplied for low inductance

applications. This winding style has a maximum permissible

hot spot temperature of 300°C. The maximum dissipation is

defined in Table 1 under the heading Operating hot spot

temperature of 300°C, and resistance ranges are defined in

the three right-hand columns of this table.

Application Notes

When cold, vitreous enamel has excellent insulation resistance.

In common with all insulants the specific resistance of the

enamel decreases with increased temperature; therefore, if

operated at any temperature approaching the maximum, the

resistor cannot be classed as an insulated type and should not

be used in contact with any conducting materials.

The recommended dissipations for each of the resistor hot

spot temperatures applies to resistors mounted horizontally. If

the bore is completely blocked a 15% derating is

recommended. However, wherever possible, resistors should

be mounted vertically with unobstructed bore.

This makes best use of the chimney effect of the heated tube

and will encourage a cooling stream of air through the bore.

Allowances must be made, when tubular resistors are mounted

in banks, for the effects produced by radiation between tubes.

Appreciable reduction of hot spot temperature can be

achieved by arranging that resistors are subjected to some

measure of forced draught. In general, it is most efficient to

extract air from the resistor enclosure and arrange that an air

inlet is adjacent to the bottom of the tubes.

If soft soldered connections are used the resistors should be derated

where applicable to limit the hot spot temperature to 300°C.

07.16

General Note

TT Electronics reserves the right to make changes in product specification without notice or liability.

All information is subject to TT Electronics’ own data and is considered accurate at time of going to print.

© TT Electronics plc

www.ttelectronicsresistors.com

BI Technologies IRC Welwyn