Brochure

Varistors Introduction
TECHNICAL NOTE
Technical Note
www.vishay.com
Vishay BCcomponents
Revision: 04-Sep-13
12
Document Number: 29079
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Multi choice selection chart to determine the correct size (i.e. correct energy absorption)
WHICH PARAMETER
OF LINE IS KNOWN?
ORIGIN OF THE
PULSES NOT KNOWN
ORIGIN OF THE
PULSES KNOWN
LIGHTNINIG OR
INDUSTRIAL INDUCTIVE
LOAD ON LINE
SOLENOID
(e.g. transformer,
electromagnet etc.)
SHORT CIRCUIT
CURRENT
VALUE NOT KNOWN
SHORT CIRCUIT
CURRENT
VALUE KNOWN
REPETITIVE PEAK
CURRENT EQUALS
VALUE OF PEAK
CURRENT PASSING
THROUGH SOLENOID
(do not forget to
calculate the dissipation
when the recurrent time
is short i.e. < 5 minutes)
RCL LINE
IMPEDANCE KNOWN
RCL LINE IMPEDANCE
NOT KNOWN
VALUE OF
REPETITIVE
PEAK CURRENT
EQUALS SHORT
CIRCUIT CURRENT
VALUE
MULTIPLY NOMINAL
VAOLTAGE BY 10,
DIVIDE RESULT
BY RCL LINE
IMPEDANCE VALUE
TO FIND THE
REPETITIVE
PEAK CURRENT
SURGE CONDITIONS
1.2/50 µs 6 kV,
8/20 µs 500 A
SURGE CONDITIONS
1.2/50 µs 6 kV,
8/20 µs 3 kA
LINE CONFORMS
TO CATEGORY B ACC.
ANSI/IEEE C62.41.1-2002
OR TYPE 2 LOCATION
SPD UL 1449 ED. 3
(Feeders and short
branch circuits, distribution
panel devices, lightning
systems in large buildings)
LINE CONFORMS
TO CATEGORY A ACC.
ANSI/IEEE C62.41.1-2002
OR TYPE 3 LOCATION
SPD UL 1449 ED. 3
(Long branch
circuits and outlets)
WHEN THE SHORT CIRCUIT SURGE
CONTITION IS
VDR
6 kV/0.4 kA S07/H05
6 kV/1.0 kA S10/H07
6 kV/1.5 kA S10/H10
6 kV/3.0 kA S14/H14/S20/H20
6 kV/5.0 kA S20/H20
WHEN THE REPETITIVE PEAK
CURRENT IS MAX.
VDR
50 A S05/H05
80 A S07/H05
120 A S07/H07
175 A S10/H07
250 A S10/H10
350 A S14/H10
500 A S14/H14
700 A S20/H14
1000 A H20