“ZNR” Transient/Surge Absorbors, Type E, Type CK, SC
2.2 Circuit Design 1
(Selection of Varistor Voltage Rating)
2.2.1 General Precautions
In selection of Varistor Voltage Ratings for line protection, following general precautions shall be taken in your consideration;
(1)Maximum operating voltage shall be lower than the specified “Maximum Allowable Voltage” of the Varistor applied.
(2)Some reasonable margin is required against fluctuation of the primary AC line Voltage where the Varistor is applied for preventing mechanical and/or electrical failures of the device.
2.2.2
(Line to Line surge protection)
●Select the ZNR Varistors recommended in Table 1. Notes: Because the primary line voltage temporarily rises due to load unbalance of separately wired loads, short circuit between the live line and the nutral line or LC resonance at switching for a capacitive load, ZNR Varistors with
✽are recommended for AC120 V or 240 V applications. (See Table 1)
2.2.3 Line to Ground Use
(Line to Ground Surge protection)
●Select the ZNR Varistors recommended in Table 1. Notes: When 500 V insulation resistance test of the circuits employing ZNR Varistor is conducted, the ZNR Varistor shall be removed after getting approval from the customer, or the ZNR Varistor ✽ ✽ with the Maximum Allowable Voltage exceeding to the test voltage shall be
applied. (See Table 1)
When AC1000 V or 1200 V dielectric with standing test is conducted, ZNR Varistors shall be removed after getting approval from the customer according to the relevant regulations, or ZNR Varistor ✽ ✽ ✽ with the Maximum Allowable Voltage exceeding to the test voltage shall be applied. (See Table 1)
2.3Circuit Design 2 (Fusing Varistors)
2.3.1When a line current of equipment is higher than the recommended current rating of the fuse in Table 2, the location of the fuse shall be arranged according to Fig 2.
Fuse
Protected
Equipment
ZNR
Varistor
Fig. 2 Alternative Fuse Location/placement
for Varistor Protection
2.4Environmental Conditions
(1)The ZNR Varistors shall not be exposed outdoors, because of being designed for indoors
use.
(2)The ZNR Varistors shall not be operated beyond the Specified Operating Temperature Range and shall not be exposed to direct sunlight and heating part of equipment.
(3)The ZNR Varistors shall not be operated under severe conditions of high temperatures and high humidities such as places exposed to rain, wind and vapor.
(4)The ZNR Varistors shall be free from dust, salty wind and atomospheres polluted by corrosive gas.
2.5Precautions for Assemblies and Handlings
2.5.1 Solvent Cleaning
Organic solvents such as thinner and acetone etc. shall not be applied to the ZNR Varistors for preventing deterioration of the external coating or molding resin.
2.5.2 Abnormal Mechanical Stresses
Abnormal mechanical stresses beyond the specified values such as strong falling shocks, ribrations and bending/pulling forces, shall be kept minimum to preventmechanical/electrical
failures of the devices. 2.5.3 Plastic Molding
If another plastic molding is applied to the ZNR Varistors on your option, the influences on reliability of the ZNR Varistors shall be carefully investigated in your equipment.
2.6Long Term Storage
(1)The ZNR Varistors shall not be stored under severe conditions of high temperatures and high humidities. Store them indoors under 40 °C max. and 75 %RH max. Use them within one year, if stored beyond the limit, check the solderbility before use.
(2)The ZNR Varistors shall not be stored under corrosive atomospheres such as hydrogen sulfide, sulfurous acid, chlorine and ammonia.
(3)The ZNR Varistors shall not be exposed to direct sunlight and shall not be stored under dew formation.
2.7 Regarding to “Safety Regulations of the Varistors”
In case of applications to UL and CSA standards, refer to “Application Notes for UL and CSA Recognized” ZNR “Varistors”
2.8Parallel Capacitances of the ZNR Varistors
The ZNR Varistors have relatively high capacitances specified in the individual specifications, special consideration shall be taken into account in applications to high frequency transmission lines or circuits.
00 Apr. 2008
– EC130 –
