IEC 61643-331-2003 pdf – Components for low-voltage surge protective devices – Part 331: Specification for metal oxide varistors (MOV)

IEC 61643-331-2003 pdf – Components for low-voltage surge protective devices – Part 331: Specification for metal oxide varistors (MOV).
1 Scope This part of IEC 61 643 is a test specification for metal oxide varistors (MOV), which are used for applications up to 1 000 V a.c. or 1 500 V d.c. in power line, or telecommunication, or signalling circuits. They are designed to protect apparatus or personnel, or both, from high transient voltages. This specification applies to MOVs having two electrodes and does not deal with hybrid devices. This specification also does not apply to mountings and their effect on the MOV’s characteristics. Characteristics given apply solely to the MOV mounted only in the ways described for the tests. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60068-1 :1 988, Environmental testing – Part 1: General and guidance IEC 60068-2-6:1 995, Environmental testing – Part 2: Tests – Test Fc: Vibration (sinusoidal) IEC 60068-2-1 4:1 984, Environmental testing – Part 2: Tests – Test N: Change of temperature IEC 60068-2-20:1 979, Environmental testing – Part 2: Tests – Test T: Soldering IEC 60068-2-29:1 987, Environmental testing – Part 2: Tests – Test Eb and guidance: Bump IEC 60068-2-52:1 996, Environmental testing – Part 2: Tests – Test Kb: Salt mist, cyclic (sodium, chloride solution) IEC 60068-2-78:2001 , Environmental testing – Part 2-78: Tests – Test Cab: Damp heat/ steady state IEC 61 643-1 :1 998, Surge protected devices connected to low-voltage power distribution systems – Part 1: Performance requirements and testing methods
3 Parametric terms, letter symbols and definitions 3.1 ratings either a limiting capability or a limiting condition beyond which damage to the MOV may occur NOTE A limiting condition may be either a maximum or a minimum. 3.1 .1 single-pulse peak current I TM rated maximum value which may be applied for a single impulse of specified waveform, without causing MOV failure NOTE Unless otherwise specified, an 8/20 µs waveshape is used. In some cases, the rated line voltage may also be applied. 3.1 .2 multiple-pulse peak current I TSM rated maximum value which may be applied for repetitive applications of an impulse of specified waveform, without causing MOV failure NOTE Unless otherwise specified, an 8/20 µs waveform is used. 3.1 .3 multiple-pulse peak-current derating against pulse width graphical representation of rated multiple-pulse peak current against rectangular pulse width for different numbers of impulses NOTE Typically, curves are provided for indefinite, 1 0 6 , 1 0 5 , 1 0 4 , 1 0 3 , 1 0 2 and 1 0 pulses together with a single- pulse curve. 3.1 .4 temperature derating curve graphical representation of parameter derating against temperature NOTE Typical parameters are rated voltage, impulse current, energy and average power dissipation. 3.1 .5 single-pulse maximum energy W TM rated maximum value which may be absorbed for a single pulse of a specified waveform NOTE Unless otherwise specified, 2 ms rectangular pulse is used (IEC 60060). 3.1 .6 maximum continuous voltage V M (see Figure 1 ) voltage that may be applied continuously at a specified temperature 3.1 .6.1 maximum continuous a.c. voltage V M(AC) r.m.s. a.c. sinusoidal voltage (less than 5 % total harmonic distortion) that may be applied continuously at a specified temperature 3.1 .6.2 maximum continuous d.c. voltage V M(DC) d.c. voltage that may be applied continuously at a specified temperature
3.1 .7 dissipation de puissance maximale en fonctionnement continu, P M puissance moyenne qui peut être continuellement dissipée pendant une espérance de vie donnée 3.2 caractéristiques propriétés mesurables et inhérentes d’une MOV 3.2.1 courant de maintien, I D courant de choc d’amplitude et de forme définies NOTE 1 Il est aussi appelé «courant de fuite». NOTE 2 Dans la Figure 1 , c’est le courant crête de choc spécifié lors de la mesure de la tension de blocage V C de la MOV (voir 3.2.3). 3.2.2 tension nominale de varistance, V N tension mesurée à travers la MOV à un courant de choc spécifié (I N ), de durée spécifique (voir Figure 1 ) NOTE Le constructeur de MOV spécifie le courant. Sauf indication contraire, 1 mA est normalement utilisé. Sauf indication contraire, il est recommandé que la durée du choc soit inférieure à 40 ms. En général, la valeur nominale à ±1 0 % est spécifiée par le constructeur. 3.2.3 tension de blocage, V C tension crête mesurée à travers la MOV dans les conditions d’un courant crête de choc spécifié (I P ) et d’une forme d’onde spécifiée (voir Figure 1 )