“ZNR” Transient/Surge Absorbors, Type E, Type CK, SC
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1. Precautions for Safety
The “ZNR” Transient/Surge Absorbers (hereafter referred to as “The ZNR Varistors”) may fail in a short-circuit mode
or in an open-circuit mode, when subjected to severe conditions of electrical, environmental and/or me
chanical
stresses beyond their specifi ed “Ratings” and specifi ed “Conditions”, resulting in burnout, fl aming or glowing in the
worst case.
Following “
Precautions for Safety” and “Application Notes” shall be taken in your major consideration. If you have
a question about the “Precautions for Handling”, please contact our engineering section or factory.
Handling Precautions
“ZNR” Transient/Surge Absorbers, Type E
“ZNR” Transient/Surge Absorbers, Type CK, SC
1.1 Operating Conditions
1.1.1
The ZNR Varistors shall not be operated beyond
t h e s p e c i f i e d “ R at i n g s” a n d “ E nv i ro n m e n t a l
Conditions” in the Catalog or the Specifi cations to
prevent them from deterioration, breakdown, fl aming
or glowing.
●
The ZNR Varistors shall not be operated exceeding
the specifi ed “Maximum Allowable Voltage” in the
Catalog or the Specifi cation.
●
The ZNR Varistors shall not be subjected to
energy levels above their specified “Maximum
Energy Ratings” in the Catalog or the Specifi cations.
●
In case of applicatio n to repeated surge/
overvoltages, the ZNR Varistors shall not be
subjected to surge currents and energy levels
above the specifi ed maximum ratings in “Impulse
Life Rating” in the Catalog or the Specifi cations.
●
W hen surge/over voltages are intermit tently
applied to the ZNR Varistors with short durations,
the devices shall not be operated beyond the
specified “Rated Power” in the Catalog or the
Specifi cations.
●
The ZNR Varistors shall not be operated beyond
the specifi ed “Operating Temperature Range” in
the Catalog or the Specifi cations.
●
It is recommended that the ZNR Varistors, if
not fused, shall be located away from other
combustible components.
1.1.2
The ZNR Varistor shall be operated correctly
under following conditions to prevent Varistors from
causing mechanical damages and ruptures and to
protect human from serious injuries;
●
T h e Z N R Va r i s to r s s h a ll n o t b e o p e rate d
exceeding the specified “Maximum Allowable
Voltage Ratings” in the Catalog.
●
The ZNR Varistors shall not be operated beyond
the “Maximum Peak Current Ratings” in the
Catalog.
●
S o m e s a f e t y c o u n t e r m e a s u r e s u c h a s a
p r o t e c t i v e c a s e c o v e r i n g t h e Va r i s t o r i s
recommended, if necessary.
1.1.3
When the ZNR Varistors are applied to between
a live part and a metallic chassis of equipment,
following safety countermeasures shall be taken to
protect human from electric shock.
A) The metallic chassis shall be earthed to the
ground.
B) The live part shall be equipped with a protective
cover for preventing electric shock.
2. Application Notes
2.1 Protective Devices for Varistors
2.1.1
The ZNR Varistors shall be protected from serious
accidents due to unexpected physical phenomenor
by following safety countermeasures.
●
In case of “Across-the Line Use”, the ZNR
Varistors shall be protected by connecting a
ground fault circuit interrupter of fusing in series
to the devices. (See Table 1)
●
In case of “Line to Ground Use”, the short-circuit
of the Varistor may not blow the current type fuse
due to the grounding resistance (between Line
and Ground), which may cause fl aming or burn-
out of the devices in the worst case.
Following safety countermeasures (A or B) are
recommended;
A) Connecting a “leakage current circuit breaker” in
series to the Varistor to be protected. (See Table
1)
B) Use current type fuses and a thermal type fuse
which are thermally coupled each others. (See
Table 1)
✽
Fuses shall use rated voltages appropriate for circuits.
✽
Finally, confi rm that the secondary disaster does not
occur even if the ZNR mounted on equipment breaks.
✽
Set a thermal fuse to get high thermal conductivity
with ZNR.
Series
ERZC20EK
□□□
ERZC32
□
K
□□□
ERZVS34C
□□□
ERZC40CK
□□□
Current Fuse
(Line - Line)
10 A max.
20 A max.
20 A max.
Thermal. Fuse
(Line - Ground)
100 to 120 °C 5 A 100 to 120 °C 10 A 100 to 120 °C 10 A
●
Recommendation fuse
Aug. 2012
01
