Varistor Metal Oxide Varistor Products Page 16 Varistor Metal-Oxide Varistor Products

2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 09/14/17 Metal-Oxide Varistors (MOVs) Terms and Descriptions Symbol Clamping Voltage. Peak voltage across the varistor measured under conditions of a specified peak V C pulse current and specified waveform. NOTE: Peak voltage and peak currents are not necessarily coincidental in time. V C Rated Peak Single Pulse Transient Currents (Varistor) . Maximum peak current which may be applied for a single 8/20 s impulse, with rated line voltage also applied, without causing device failure. I TM Lifetime Rated Pulse Currents (Varistor) . Derated values of I TM for impulse durations exceeding that of an 8/20 s waveshape, and for multiple pulses which may be applied over device rated lifetime. - Rated RMS Voltage (Varistor) . Maximum continuous sinusoidal RMS voltage which may be applied. V M(AC) Rated DC Voltage (Varistor). Maximum continuous DC voltage which may be applied. V M(DC) DC Standby Current (Varistor). Varistor current measured at rated voltage, V M(DC) . I D For certain applications, some of the following terms may be useful. Nominal Varistor Voltage. Voltage across the varistor measured at a specified pulsed DC current, I N(DC) , of specific duration. I N(DC) of specific duration. I N(DC) is specified by the varistor manufacturer. V N(DC) Peak Nominal Varistor Voltage. Voltage across the varistor measured at a specified peak AC current, I N(AC) , of specific duration. I N(AC) is specified by the varistor manufacturer. V N(AC) Rated Recurrent Peak Voltage (Varistor) . Maximum recurrent peak voltage which may be applied for a specified duty cycle and waveform. V PM Rated Single Pulse Transient Energy (Varistor) . Energy which may be dissipated for a single impulse of maximum rated current at a specified waveshape, with rated RMS voltage or rated DC voltage also applied, without causing device failure. W TM Rated Transient Average Power Dissipation (Varistor). Maximum average power which may be dissipated due to a group of pulses occurring within a specified isolated time period, without causing device failure. Varistor Voltage . Voltage across the varistor measured at a given current, I X . V X Voltage Clamping Ratio (Varistor). A figure of merit measure of the varistor clamping effectiveness as defined by the symbols (V C ) (V M(AC) ), (V C ) (V M(DC) ). V C /V PM Nonlinear Exponent. A measure of varistor nonlinearity between two given operating currents, I 1 and I 2 , as described by I = kV a where k is a device constant, I 1 I I 2 , and a 12 = ( logI 2 / I 1 ) ( logV 2 / V 1 ) a Dynamic Impedance (Varistor). A measure of small signal impedance at a given operating point as defined by: Z X = ( dV X ) ( dI X ) Z X Resistance (Varistor). Static resistance of the varistor at a given operating point as defined by: R X = ( V X ) ( I X ) R X Capacitance (Varistor). Capacitance between the two terminals of the varistor measured at C specified frequency and bias. C AC Standby Power (Varistor). Varistor AC power dissipation measured at rated RMS voltage V M(AC) . P D Voltage Overshoot (Varistor). The excess voltage above the clamping voltage of the device for a given current that occurs when current waves of less than 8 s virtual front duration are applied. This value may be expressed as a % of the clamping voltage (V C ) for an 8/20 current wave. V OS Response Time (Varistor). The time between the point at which the wave exceeds the clamping voltage level (V C ) and the peak of the voltage overshoot. For the purpose of this definition, clamping voltage as defined with an 8/20 s current waveform of the same peak current amplitude as the waveform used for this response time. - Overshoot Duration (Varistor). The time between the point voltage level (V C ) and the point at which the voltage overshoot has decayed to 50% of its peak. For the purpose of this definition, clamping voltage is defined with an 8/20 s current waveform of the same peak current amplitude as the waveform used for this overshoot duration. - TABLE 3. VARISTOR CHARACTERISTICS (IEEE STANDARD C62.33-1982 SUBSECTION 2.3 AND 2.4) Varistor Characteristics, Terms and Consideration Factors (continued)

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