IEEE Std C62.33 pdf free download
IEEE Std C62.33 pdf free download.Test Methods and Performance Values for Metal-Oxide Varistor Surge Protective Components.
5. Electrical characteristics
5.1 General
MOVs of various types should have the characteristics listed in Table 1 when tested as specified.
For the tests for electrical characteristics, a statistically significant number of samples should be chosen. Generally, “statistically significant” is 30 samples, but guidance such as acceptable quality level (AQL) tables or customer requests may apply.
5.2 Varistor voltage
5.2.1 Preferred voltage values
When tested according to 5.2.2, varistor voltage should be within the specified limits. Table 2 and Table 3 show the nominal varistor voltages of high voltage and low voltage disc types that arc commonly used their allowable tolerances arc ± 10%. Components with voltages higher than Table 2 are less commonly used and individual suppliers should be contacted to find the voltages available.
The nominal varistor voltages and tolerances listed in Table 4 are typical for SMD types.
5.2.2 Test method
A power supply of constant current source of I mA dc ± 10% shall be used. The voltage across the tested MOV should rise from a lower value than that of the varistor voltage measured, rather than declining from the maximum voltage of the current source. The ripple of dc voltage shall be no more than I %. The time of applied test current 1 mA shall be within 20 ms to 100 ms prior to taking the voltage reading. The accuracy of the voltmeter shall be ±0.5%. The voltage shall be measured for positive and negative polarities of the test current.
NOTE—Two successive measurements may give slightly different outcomes, usually the first is less than the second. Unless otherwise specified, the first is taken.
5.3 Leakage current dc
5.3.1 Requirements
When tested according to 5.3.2. the leakage current, de, under maximum continuous dc voltage. Va.. shall be less than the maximum value specified by the manufacturer and there shall be no upward drifting during the application of the test voltage V.
5.3.2 Test method
A test circuit such as shown in Figure 1(a) or Figure 1(b) shall be used for dc leakage current measurement. The output voltage of dc voltage supply (PS) shall be V. ±0.5% (Va. is the maximum continuous dc voltage of’the MOV). The ac ripple of V. shall be less than 1%.
To measure the leakage current. a resistor Ry shall be connected to the MOV in series [Figure 1(a)], but its resistance should be small enough that the voltage across it is less than 0.5% of J’.
Figure 1(b) is an alternative test circuit which is suitable for low voltage MOVs. In this circuit, the leakage current is converted to voltage by operational amplifier A and resistor Ry.
The voltmeters VI, V2, and resistor Ry shall have relative tolerance of±I%. The current shall be measured for positive and negative polarities of the test voltage.IEEE Std C62.33 pdf download.
