High Voltage
Thick Film Resistors
VRW Series
•VRW37 meets the requirements of BS / EN /
IEC 60065
•High working voltage to 10kV in compact
size
•High ohmic range to 68M
•High pulse load capability
•Robust flameproof coating material
•RoHS compliant
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.
© 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
Electrical Data
Issue C · 07.06
A subsidiary of
TT electronics plc
Welwyn Components
70
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0053
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007
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002
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Standard Values E24 or E96
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Physical Data (Dimensions (mm) & Weight (g)
Type L D f dPCB Min Wt.
Max Max min Nommount bend nom
centres radius
VRW25
VRW37
VRW68
L
D
f
d
Construction
Resistive thick film material is applied to high-grade ceramic
rods. Tin-plated steel caps are force fitted and the
termination wires are welded to the caps. The value is
obtained by a helical cut in the film and finally the resistor
body is protected by a cement coating.
Marking
1% tolerance resistors are colour coded with 5 bands. 2%
and 5% tolerance have 4 bands. IEC62 colours are used.
Terminations
Material: Hot tin dipped copper wire
Strength: The terminations meet the requirements
of IEC 68.2.21
Solderability: The terminations meet the requirements
of IEC 115-1 Clause 4.17.3.2
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 under any condition of
applied temperature or power overload.
05.08
VRW68
1.0
100K to 68M
10000
70
6.2 2.5 21 0.6±0.05 10.2 0.6 0.3
9.0 3.7 19.6 0.8±0.05 12.7 1.2 0.5
15.5 5.0 27 0.8±0.05 20.3 1.2 1.15
d
High Voltage
Thick Film Resistors
SQP Series
© 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 05.08
Welwyn Components
lacipyTmumixaM
Load at rated voltage (1000hrs at 70˚C) 4.05*.1%R
C˚551 ta orezC˚07 ta rewop detar morf gnitareD
Overload (10 x 5s at 6.25 x Pr not exceeding 2 x LEV) 51.01%R
Damp heat steady state (56 days, 40˚C, 90% RH) 1.05.1%R
Climatic sequence 2.05.1%R
Climatic category 55/155/56
Temperature rapid change 50.05.0%R
Resistance to solder heat 50.05.0%R
Vibration 50.05.0%R
nim 007stlovfoorP egatloV
71
Maximum peak voltage in accordance with “IEC 60065 chapter 14.1”
50 discharges from a 1nF capacitor charged to V max. 12 discharges/minute.
Application Notes
1. Due to operating temperature limits imposed by some PCB materials, derating may be necessary. An
estimate of the temperature rise to be expected at the center of the body can be calculated using the
thermal impedance figures given under Electrical Data.
2. VRW resistors can be supplied with radial, goalpost or lancet pre-formed leads. The VRW37 is also
available in an SMD format with Z formed leads and packed in blister tape. Consult Factory for details.
Packaging
Our standard packaging for VRW is taped and
boxed. The critical dimensions are shown in
Figure 1. The component wires will not
protrude beyond the outside edge of the
tapes. Alternative packaging is available by
request. Pre-formed resistors are supplied
loose packed in plastic bags or boxes.
Performance Data
Pulse Performace
VRW Series
Pulse Performance
Overload (10 x 5s on, 45s off at 6.25 x Pr not exceeding 2 x LEV) 2
1
10
100
0.1 1 10 100
Value (megohms)
Vmax (kV)
VRW25
VRW37
VRW68
Type b c
VRW25/37 52 ±2mm 5 ±0.5mm
VRW68 73 ±2mm 10 ±0.5mm
6
mm
2f1f
6
mm
c
Body location f1-f2 1.4mm
b
* 2% for ohmic values above 24M
Ordering Procedure
High Voltage
Thick Film Resistors
SQP Series
© 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 Issue C · 07.06
Welwyn Components
71
VRW Series
05.08
Example: VRW25 at 1.2 megohms and 5% tolerance in an ammo pack box of 5000 pieces -
V R W 2 5 – 1 M 2 J I
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
F
1%
G
2%
J
5%
Packing
I
VRW25
5000/box
Standard
VRW37
2500/box
VRW68
1000/box