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
Welwyn Components
Electrical Data
VRW25
Power rating at 70˚ C
Resistance range
Limiting element voltage
Isolation voltage
TCR
Resistance Tolerance
Standard Values
Thermal Impedance
Ambient temperature range
˚ C/watt
˚C
140
watts
(Ohms)
volts dc or ac peak
volts
ppm/˚ C
%
0.25
100K to 30M
1600
VRW37
0.5
100K to 30M
3500
700
200
1, 2, 5
E24 or E96
112
-55 to +155˚ C
70
VRW68
1.0
100K to 68M
10000
Physical Data
Type
L
Max
6.2
9.0
15.5
(Dimensions (mm) & Weight (g)
f
min
21
19.6
27
d
Nom
0.6±0.05
0.8±0.05
0.8±0.05
PCB
mount
centres
10.2
12.7
20.3
Min
bend
radius
0.6
1.2
1.2
Wt.
nom
0.3
0.5
1.15
d
D
Max
2.5
3.7
5.0
VRW25
VRW37
VRW68
D
L
f
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.
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
1% tolerance resistors are colour coded with 5 bands. 2%
and 5% tolerance have 4 bands. IEC62 colours are used.
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.
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
Issue C ·
05.08
07.06
© 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
70
High Voltage
Thick Film Resistors
SQP
VRW Series
Welwyn Components
Performance Data
Maximum
Load at rated voltage (1000hrs at 70˚C)
Derating from rated power at 70˚ C
Overload (10 x 5s on,6.25 off at 6.25 x Pr not 2 x LEV) 2 x LEV)
5s at 45s x Pr not exceeding exceeding
Damp heat steady state (56 days, 40˚C,
Climatic sequence
Climatic category
Temperature rapid change
Resistance to solder heat
Vibration
Voltage Proof
R%
R%
R%
volts
0.5
0.5
0.5
700 min
* 2% for ohmic values above 24M
90% RH)
R%
R%
R%
1
2
1.5
1.5
55/155/56
0.05
0.05
0.05
R%
1.5*
zero at 155˚ C
0.15
0.1
0.2
Typical
0.4
Pulse Performace
Pulse Performance
1
00
Vmax (kV)
VRW25
1
0
VRW37
VRW68
1
0.1
1
1
0
1
00
Value (megohms)
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.
Type
VRW25/37
VRW68
b
52 ±2mm
73 ±2mm
c
5 ±0.5mm
10 ±0.5mm
c
f1
6
mm
f2
b
Body location f1-f2
1.4mm
6
mm
© 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
71
High Voltage
Thick Film Resistors
SQP Series
VRW Series
Welwyn Components
Ordering Procedure
Example: VRW25 at 1.2 megohms and 5% tolerance in an ammo pack box of 5000 pieces
-
VRW25
–
1M2J
I
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
F
G
J
1%
2%
5%
Packing
I
Ammo
VRW25
VRW37
VRW68
5000/box
2500/box
1000/box
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
Issue C ·
05.08
07.06
71
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