Wirewound High
Surge Resistors
WHS Series
·
·
·
·
·
Enhanced surge & pulse energy capacity
UL94-V0 flameproof protection
Radial taped form available
Surface mount Z-form available
RoHS compliant with Pb-free terminations
Electrical Data
WHS2
Power rating at 25ºC
5s overload rating at 25ºC
Short pulse performance
Resistance range
TCR
Isolation Voltage
Resistance Tolerance
Standard Values
Thermal Impedance
Ambient temperature range
ºC/watt
ºC
110
82
-55 to +155
ohms
ppm/ºC
volts
%
250
350
<20R: 5
E12 preferred
54
35
watts
watts
2
10
WHS3
3
15
1R0-330R
200
500
≥20R:
1, 2, 5
700
WHS5
5
25
WHS7
7
35
See Pulse Performance graphs
No Limiting Element Voltage applies to this series; the Rated Voltage is
√(P.R).
Physical Data
Dimensions (mm) & Weight (g)
Type
WHS2
WHS3
WHS5
WHS7
L max
9.0
14.5
16.5
25.0
D max
3.6
5.2
7.0
8.8
f min
19.80
24.55
23.55
28.30
0.8
d nom
PCB
mount
centres
12.70
20.30
22.86
31.40
1.2
Min
bend
radius
Wt. nom
0.50
1.10
1.75
4.40
d
D
L
f
Construction
A high purity ceramic substrate is assembled with interference fit end caps to which are welded the terminations. The resistive
element is wound on the substrate and welded to the caps. Flameproof silicone cement coating is applied priorto marking with
indelible ink. The components are then leadformed if required and packed.
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.
www.bitechnologies.com www.irctt.com www.welwyn-tt.com
© TT electronics plc
10. 12
Wirewound High Surge Resistors
WHS Series
Terminations
Material:
Strength:
Solderability:
Hot tin dipped copper wire
The terminations meet the requirements of IEC 68.2.21
The terminations meet the requirements of IEC 115-1 Clause 4.17.3.2
Marking
WHS2, and WHS3 resistors are marked with four colour bands in conformance with IEC62.
WHS5 and WHS7 resistors are legend marked with type reference, resistance value and tolerance.
Solvent Resistance
The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed circuits.
Flammability
The resistor coating will not burn or emit incandescent particles under any condition of applied temperature or power overload.
Performance Data
Maximum
Load at rated power: 1000hrs @ 25°C
Dry heat: 1000hrs @ 200°C
Short term overload
Derating from rated power @25°C
Climatic
Climatic category
TRC & Vibration
Robustness & solder heat
Long term damp heat (56 days)
ΔR%
ΔR%
ΔR%
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
ΔR%
ΔR%
ΔR%
ΔR%
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
55/200/56
1
1
1
Typical
3
3
1
2
Zero at 280°C (See Thermal Performance graph).
Pulse Performance
Surge / Pulse Energy Capacity
(single or low repetition rate,
R < 5%)
100
Energy (joules)
WHS7
10
WHS5
WHS3
1
WHS2
1
10
Value (ohms)
100
1000
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.
www.bitechnologies.com www.irctt.com www.welwyn-tt.com
© TT electronics plc
10. 12
Wirewound High Surge Resistors
WHS Series
(10 pulses at 30s intervals, R < 5%)
Note the voltage shown is the nett voltage across the resistor. At low
values, the generator open circuit voltage will be higher due to the
generator's 2 ohm internal impedance.
WHS7
WHS5
WHS3
WHS2
s Peak Voltage Limit
Peak Voltage (kV)
10
1
0.1
1
10
Value (ohms)
100
1000
Thermal Performance
Body Temperature Rise
300
100
WHS3
WHS2
WHS5
WHS7
Proportion of Rated Power (%)
250
Temperature Rise (°C)
Temperature Rise (°C)
80
60
40
20
0
0
50
100
150
200
250
300
350
200
150
100
50
0
0
1
2
3
4
5
6
7
8
9
10
Ambient Temperature °C
(°C)
Am bient Tem perature
Power (W)
Application Notes
1. If the resistors are to dissipate full rated power, it is recommended that the terminations should not be soldered closer than
4mm from the body.
2. Due to operating temperature limits imposed by some PCB materials, derating may be necessary. The surface temperature rise
at the centre of the body is shown under Thermal Performance.
3. WHS2, WHS3, WHS5 resistors can also be supplied with goalpost or lancet pre-formed leads. Radial form is available on
WHS2 and WHS3 only.
WHS2, WHS3, and WHS5 are also available in an SMD format with Z formed leads and packed in blister tape. See the Z-form
datasheet for details http://www.welwyn-tt.com/pdf/datasheet/Z-form.pdf
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.
www.bitechnologies.com www.irctt.com www.welwyn-tt.com
© TT electronics plc
10. 12
Wirewound High Surge Resistors
WHS Series
Radial
Goalpost
Lancet
Z-form
Packaging
The standard packaging for WHS is taped. The critical dimensions are shown in Figure 1. The component wires will not protrude
beyond the outside edge of the tapes. Taped product is then packed into boxes or onto reels. See Ordering Procedure for details.
Alternative packaging is available by request. Pre-formed resistors are supplied loose packed in plastic bags or boxes.
Dimensions mm
WHS2
WHS3
WHS5
*WHS7
b
52
67
63
85
c
5
10
10
10
Figure 1
c
f1
b
f2
-f2 < 1.4mm
*An offset lead length is available for WHS7
series. Consult factory for details
6
6
Ordering Procedure
Example: WHS2 at 100 ohms and 5% tolerance in ammo pack box of 2500 pieces -
WHS2 – 100R
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
F
G
J
Packing
A25
A1
T075
T07
Tape
Ammo
WHS2
WHS3
WHS5
WHS7
2500/box
1000/box
750/reel
700/reel
Standard
1%
2%
5%
J
A25
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.
www.bitechnologies.com www.irctt.com www.welwyn-tt.com
© TT electronics plc
10. 12
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