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.
Bolt Size
WDBR1/2
WDBR1
WDBR2
WDBR3
WDBR5
WDBR7
M2
M3
M5
M5
M5
M5
Typical Tightening Torque (Nm)
0.6
2
2.5
2.5
3.5
4
WDBR resistors may be customised in various ways including:
Alternative shapes and dimensions up to 406mm x 406mm
Integration of temperature measurement elements
Alternative ohmic values, tolerance & TCR
Increased dielectric withstand voltage
Custom braking resistors with UL approval
For a full Applications Note for dynamic braking see http://www.welwyn-tt.com/pdf/application_notes/WDBR.pdf
·
·
·
·
·
Overload Conditions
Maximum Single Overload Power
100
Power (kW)
Single Overload Energy Capacity
100
Energy (kJ)
10
1
0.1
0.01
0.01
WDBR7
WDBR5
WDBR3
WDBR2
WDBR1
WDBR1/2
10
1
0.1
0.01
W
DB
R
7
W
DB
R
5
W
DB
R
3
W
DB
R
2
W
DBR1
W
DBR1/2
W
0.1
1
10
100
0.1
1
10
100
Duration of Overload (s)
Duration of Overload (s)
Maximum peak current (A)
Value
(ohms)
WDBR1/2
WDBR1
WDBR2
WDBR3
WDBR5
WDBR7
12
15.2
21.6
20.3
25.4
25.4
44.5
15
15.2
21.6
20.3
25.4
25.4
44.5
20
7.6
21.6
7.6
25.4
25.4
44.5
22
7.6
8.3
7.6
25.4
25.4
44.5
25
7.6
8.3
7.6
11.4
25.4
44.5
47
7.6
8.3
7.6
11.4
10.2
20.3
50
7.6
8.3
7.6
11.4
10.2
20.3
100
7.6
8.3
7.6
11.4
10.2
20.3
8.3
7.6
11.4
10.2
20.3
150
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.
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