IEEE 62.33-2016 pdf free download – IEEE Standard Test Specifications for Varistor Surge-Protective Devices.
3.1 .1 Environmental Conditions
1) Operating and storage temperature ranges
2) Altitude or atmospheric pressure range
3) Humidity
4) Mechanical shock and vibration
3.1 .2 Varistor Physical Properties
1) Solvent resistance
2) Solderability
3) Flammability
4) Package rupture during overload
3.1 .3 System Conditions
1) Nominal system frequencies
2) Maximum continuous system voltage
3.1 .4 Surge Rating of the Varistor under System Conditions
1) Peak single pulse transient current (I tm )
2) Lifetime rated pulse currents
3) Rated single pulse transient energy (W tm )
4) Rated transient average power dissipation (P t(AV)m)
3.2 Unusual Service Conditions
The following service conditions may require special consideration in the design or application of varistors and should be called to the attention of the manufacturer.
3.2.1 Environmental Conditions
1) Ambient temperature exceeding the standard service conditions
2) Altitudes exceeding those specified by the manufacturer
3) Exposure to:
a) Damaging fumes or vapors
b) Excessive dirt or current conducting deposits; excessive humidity, moisture, dripping water, steam, or salt spray; explosive atmospheres; abnormal vibrations or shocks
c) Radiation
4) Unusual transportation or storage conditions
5) Significance of flammability
3.2.2 Physical Conditions
Limitation on weight or space, including clearances to nearby conducting objects; particularly at altitudes exceeding those specified by the manufacturer.
3.2.3 System Conditions
1) System voltages, current or frequency operating conditions exceeding the ratings of the devices (see Section 5., Failure Modes).
2) System surge currents exceeding the rating of the device (see Section 5., Failure Modes).
4. Standard Design Test Procedure
4.1 Standard Design Test Criteria
The sk.ign test,. dnti.bcd tn 44 tlsr.*igh 4. 1.2 piowak ,tuiislaiu.,csi iiiuuiisl’, ILTI IiIua,II ‘IIIIc LPLThUI)4(IUIL UI d specified property of a s’aris.tor des ice. These properties may valy from device to device, making it necessary to provide statistical descriptions of the property in order to compare products.
4.2 Statistical Procedures
The following procedure shall be used to describe any property which has been determined to have important statistical aspects. A product sample shall be chosen in a manner consistent with the definition of design tests as provided by ANSI/IEEE SW 100-1977 131. A sufficient number of devices shall be tested and the characteristic or rating in question measured as described it the appltcthle design test until the paranieten of the underlying statistical distribution c determined within confidence limits specified by the manufacturer. Values relating to the produci sample such as. but not linsited to. mean, median. masimum. minimum, and standard deviation may then he stated.
4.3 Test Conditions
The tests of 4.4 through 4.12 should be performed on the device as required by the application. Unless otherwise specified. ambient test conditions should be as follows:
Temperature: 25±5 °C
Relative Humidity: Less than 85%
Altitude: Less than 2000 m i6562 ft)
4.4 Clamping Voltage Test (Ve)(See Fig 3)
4.4.1
The purpose of this test is to determine the voltage protection provided by a varistor when passing a surge current. The clamping vohage shall he measured with a current impulse waveform of 11120 ps. and specified crest value. A circuit functionally equivalent to Fig 3 shall he employed. The device shall he tested in both polarities unless otherwise specified
4.4.2 To establish the shape of the volt-ampere characteristic curve clamping voltage shall be measured at two current levels. These levels shall be of a medium and a high value with respect to rated surge current capability. (The measurement of nominal varistor voltage per paragraph 4.9 provides a low current observation point.) In the absence of specific requirements a peak current test in the range of 5 A to 300 A is suggested for the medium level test. For the high level test a measurement of clamping voltage is suggested during lifetime rated pulse currents test (4.6), using the current from Table 1 corresponding to the two pulse condition, one pulse in both polarities, and an 8/20 µs test waveshape. For special applications, other test waveshapes may be specified.IEEE 62.33 pdf download.