Varistor Glossary of Terms and Definitions
Multilayer Technology
Varistor Plus
Term
S ym bol
R ated A C V oltage
V RM S
M axim um continuous sinusoidal A C voltage (< 5% total harm onic distortion)
w hich m ay be applied to the varistor at 25°C .
R ated D C V oltage
V DC
M axim um continuous D C voltage (< 5% ripple) w hich m ay be applied to the
varistor at 25°C .
Leakage C urrent
IL
C urrent passing through the varistor at rated D C voltage at 25°C or any
other specified tem perature.
V aristor V oltage
VN
V oltage across the varistor m easured at 1m A of D C current.
C lam ping V oltage
VC
M axim um peak voltage developed across the varistor w hen passing an 8/20
µs class current pulse.
C lass C urrent
IC
A peak value of current w hich is 1/10 of the m axim um peak current for 100
pulses at tw o per m inute for an 8/20 pulse.
V oltage C lam ping R atio V C / V APP
D efinition
A figure of m erit m easure of the varistor clam ping effectiveness as defined
by the sym bols V C / V APP , w here V APP = V R M S or V D C .
W M AX
E nergy w hich m ay be dissipated for a single 10/1000 µs pulse of a m axim um
rated current, w ith rated A C /D C voltage applied, w ithout causing device
failure.
Load D um p Transient
W LD
Load D um p is a transient that occurs in an autom otive environm ent. It is an
exponentially decaying positive voltage that occurs in the event of a battery
disconnect w hile the alternator is still generating charging current, w ith other
loads rem aining on the alternator circuit at the tim e of battery disconnect.
S ingle P ulse P eak
C urrent
IP
A verage P ow er
D issipation
P M AX
M axim um average dissipated pow er at 25°C resulting from a group of pulses
occurring w ithin a specified isolated tim e period, w ithout causing device
failure.
C apacitance
C (T Y P)
C apacitance betw een tw o term inals of the varistor m easured at 1 kH z.
Inductance
L
Inductive com ponent of the varistor w hen m easured w ith a current edge rate
(di/dt) of 100m A /ns. V alues are typically m easured in nanohenries (nH ).
V JU M P
The jum p start transient results from the tem porary application of an overvoltage in excess of the rated battery voltage. The circuit pow er supply m ay
be subjected to a tem porary over-voltage condition due to the voltage
regulation failing or it m ay be deliberately generated w hen it becom es
necessary to boost start the car.
S ingle P ulse Transient
E nergy
Jum p S tart Transient
M axim um peak current that m ay be applied to the varistor for a single 8/20
µs pulse, w ith line voltage applied, w ithout causing device failure.
R esponse Tim e
The tim e lag betw een application of a surge and the varistor's "turn-on"
conduction action.
V aristor V oltage
Tem perature
C oefficient
(V N at 85°C - V N at 25°C ) / ((V N at 25°C ) x 60°C ) x 100
SEI Electronics Inc. • P.O. Box 58789 • Raleigh, NC 27658-8789 • Telephone: (919) 850-9500 • FAX: (919) 850-9504
Toll Free: (888) SEI-SEI-SEI • www.seielect.com • email: marketing@seielect.com • ISO 9002 / QS 9000 Registered
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Varistor Glossary of Terms and Definitions
Multilayer Technology
Insulation Resistance
Isolation Voltage
Operating Temperature
Storage Temperature
Current/Energy
Derating
Varistor Plus
IR
Minimum resistance between shorted terminals and varistor surface.
The maximum peak voltage that may be applied under continuous operating
conditions between the varistor terminations and any conducting mounting
surface.
The range of ambient temperature for which the varistor is designed to
operate continuously, as defined by the temperature limits of its climatic
category.
Storage temperature range without voltage applied.
Derating of maximum values when operated above the varistor's rated
continuous operating temperature.
SEI Electronics Inc. • P.O. Box 58789 • Raleigh, NC 27658-8789 • Telephone: (919) 850-9500 • FAX: (919) 850-9504
Toll Free: (888) SEI-SEI-SEI • www.seielect.com • email: marketing@seielect.com • ISO 9002 / QS 9000 Registered
2
Overview of Protective Devices (By Varistor Series)
Multilayer Technology
Varistor Plus
SEI Electronics Inc. • P.O. Box 58789 • Raleigh, NC 27658-8789 • Telephone: (919) 850-9500 • FAX: (919) 850-9504
Toll Free: (888) SEI-SEI-SEI • www.seielect.com • email: marketing@seielect.com • ISO 9002 / QS 9000 Registered
3