Ultra Low Profile
Power Resistors
WDBR Series
Welwyn Components
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Ultra low profile thick-film on steel
500W to 7kW peak power
Single fixing heatsink mountable
Ideal for dynamic braking, inrush limit and snubber circuits
Choice of flying lead, push-on or solder terminations
Low inductance design
High isolation, even after failsafe overload fusing
RoHS compliant, non-flammable construction
Electrical Data
WDBR1/2
Resistance range
Resistance tolerance
Pulse power rating
1
Power rating on heatsink
TCR
Maximum element temperature
Ambient temperature range (heatsink)
Dielectric withstand
5
Inductance (typical)
2
WDBR1
WDBR2
10
WDBR3
WDBR5
WDBR7
47, 100, 150
ohms
%
kW
W
W
ppm/°C
°C
°C
μH
V (dc/ac peak)
22, 47, 100
0.5
160
300
1.5
180
700
12, 22, 47, 100, 150
2.0
200
780
365
-55 to +200
2500
<3
<4
<5
3.5
260
900
5.0
270
1000
7.0
280
4
Power rating on fan-cooled heatsink
3
1490
4
+500 to +600
<6
Notes:
1. For details of pulse condition see Fig. 1 in Performance Data.
2. Mounted on a 0.53°C/W heatsink with no forced air cooling, air temperature 25°C.
3. Mounted on a 0.53°C/W heatsink with 5m/s forced air cooling, air temperature 25°C.
4. Limited by the solder type; the rating can be improved for non-standard parts by using HMP solder.
5. Based on 100% production test, duration 2s minimum
Physical Data
Dimensions in mm, weight without terminations in g
L ±0.1 W ±0.1 t ±0.1 ØD nom a nom b nom c nom Wt. nom
WDBR1/2
WDBR1
WDBR2
WDBR3
WDBR5
WDBR7
31.9
49.3
61
101.6
122
152.4
28.1
35.9
40.6
70
70
101.6
1.5
0.9
5.3
2.2
3.2
7.5
3.2
4.7
13.5
14.0
15.0
3.1
11.2
13.0
22.0
23.8
51.3
4.3
6.2
5.8
10.2
7.4
9.2
6.5
12.6
17.1
50.8
60.7
181.8
L
Substrate thickness = t
W
D
c
a
b
Fixing hole is located centrally except on WDBR1/2 where the dimension from
the edge by the terminations to the mounting hole centre is 16.68mm
Construction
A high integrity dielectric layer is applied to a machined
stainless steel substrate. Thick-film conductor and resistor
patterns are printed and fired, then protected with a high
temperature overglaze. The termination pads are tinned with
Pb-free solder and optional terminals or leads are soldered on.
General Note
Welwyn Components reserves the right to make changes in product specification without notice or liability.
All information is subject to Welwyn’s own data and is considered accurate at time of going to print.
A subsidiary of
TT electronics plc
© Welwyn Components Limited
· Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0)1670 822181 · Facsimile: +44 (0)1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
01. 11
Ultra Low Profile Power Resistors
WDBR Series
Welwyn Components
Terminations
The following termination options are available
Option
Code
Nominal Dimensions
9mm
Solder pad only
SnAg (96S)
I
9mm
Flying leads
UL3134/5
40A, 600V
250mm
L
3mm
6mm
0.8mm
Push-on connectors
(WDBR1,2,3,5&7)
T
11mm
8mm
8.5mm
Thermal Performance
Maximum
Pulsed load at full pulse power rating 50,000 cycles (see Fig 1)
Mounted on a 0.53°C/W heatsink with 5m/s forced air cooling, air temperature 25°C.
Derating at heatsink temperatures >160°C
ΔR%
5
See Fig. 2
Fig. 1: Duty Cycle Waveform
% of Rated Power
1ms
P pk
120
100
80
60
40
20
0
Fig. 2: Temperature Derating
1ms
2s
8s
0
50
100
150
200
250
Heatsink Temperature (°C)
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 a screw head bolt of size M5 forWDBR2, 3, 5 & 7, M3 forWDBR1 and M2 forWDBR1/2. This should be torqued to 2.5Nm ±10%.
WDBR resistors will fail safe (open circuit) under overload fault conditions and still maintain a 1kV dielectric withstand.
© Welwyn Components Limited
· Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0)1670 822181 · Facsimile: +44 (0)1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
01. 11
Ultra Low Profile Power Resistors
WDBR Series
Welwyn Components
WDBR resistors may be customised in various ways including:
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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)
Ordering Procedure
Example: WDBR2 at 100 ohms and 10% tolerance with flying leads and packed in a box of 84 pieces:
WDBR2–100RKLW
Type
Value (use IEC62 code)
K
I
L
T
Tolerance (use IEC62 code)
10%
Termination
Solder pad only
Flying leads
Push-on connectors
WDBR1/2,1&2
WDBR3
WDBR5&7
84/box
70/box
60/box
Packing
W
Bulk
Pack
Standard
© Welwyn Components Limited
· Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0)1670 822181 · Facsimile: +44 (0)1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
01. 11
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