Ultra Low Profile Power Resistors

WDBR Series

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

BI Technologies IRC Welwyn

www.ttelectronics.com/resistors

07.24

Application Notes

Pulse and Overload Performance

A heatsink with thermal resistance ≤0.53°C/W will enable the component to operate at its continuous power rating. Sufficient thermal

grease (e.g. Dow Corning DC340) to give void-free coverage, or a 0.5mm thick compliant thermal pad (e.g. T Global TG-X) 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.

Note:

Mounted on a 0.53°C/W heatsink with 5m/s forced air cooling, air temperature 25°C. Single pulse or low repetition rate, such that mean power ≤ 10% of rated power. ΔR ≤ 5%

Maximum Peak Current

WDBR resistors will fail safe (open circuit) under overload fault conditions and still maintain a 1kV dielectric withstand.

Soldering of solder pad (termination I) variants requires the use of a hot plate. Hand solder process recommendations are available.

WDBR resistors may be customised in various ways including:

•

Alternative shapes and dimensions up to 406mm x 406mm

•

Integration of temperature measurement elements and thermal cutouts

•

Alternative ohmic values and tolerances

•

Increased dielectric withstand voltage

•

Custom braking resistors

•

Integration of multiple power resistors

For a similar product with UL508 recognition see WDBR-UL:

https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/WDBR-UL.pdf

Maximum Surge / Overload Power

Maximum Surge / Overload Energy