Ultra Low Profile

Power Resistors

WDBR Series

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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

02.13

WDBR resistors may be customised in various ways including:

For a full Applications Note for dynamic braking see http://www.welwyn-tt.com/pdf/application_notes/WDBR.pdf

Maximum Single Overload Power

0.1

1

10

100

0.01

0.1

1

10

100

Duration of Overload (s)

DBR1/2

DBR1

DB 2

DB 3

W

DB 5

DB 7

Single Overload Energy Capacity

0.01

0.1

1

10

100

0.01

0.1

1

10

100

Duration of Overload (s)

WDBR1/2

WDBR1

WDBR2

WDBR3

WDBR5

WDBR7

Overload Conditions

Maximum peak current (A)

W

W

W

W

W

W

R

R

R

R

Value

(ohms)

12

15

20

22

25

47

50

100

150

WDBR1/2

15.2

15.2

7.6

7.6

7.6

7.6

7.6

7.6

WDBR1

21.6

21.6

21.6

8.3

8.3

8.3

8.3

8.3

8.3

WDBR2

20.3

20.3

7.6

7.6

7.6

7.6

7.6

7.6

7.6

WDBR3

25.4

25.4

25.4

25.4

11.4

11.4

11.4

11.4

11.4

WDBR5

25.4

25.4

25.4

25.4

25.4

10.2

10.2

10.2

10.2

WDBR7

44.5

44.5

44.5

44.5

44.5

20.3

20.3

20.3

20.3

Bolt Size

Typical Tightening Torque (Nm)

WDBR1/2

M2

0.6

WDBR1

M3

2

WDBR2

M5

2.5

WDBR3

M5

2.5

WDBR5

M5

3.5

WDBR7

M5

4

Application Notes

A heatsink with thermal resistance

≤0.53°C/W will enable the component to operate at its continuous power rating. Thermal grease (e.g. Dow

Corning DC340) should be used and the heatsink should have a surface finish of <6.3μm with flatness of <0.05mm. The resistor should be mounted

using an appropriate bolt as listed in the table below. This should be tightened so as to bring the whole area of the steel substrate into intimate

contact with the heatsink. The unmounted part is slightly bowed so that the centre is above the edges. Inadequate tightening will leave the centre

out of contact with the heatsink, whilst over tightening can cause the edges to rise. The tightening torque required will depend on the fixings and

heatsink used, but typical figures are given for guidance. WDBR resistors will fail safe (open circuit) under overload fault conditions and still maintain

a 1kV dielectric withstand.