Varistor Metal Oxide Varistor Products Page 172 Varistor Metal-Oxide Varistor Products

2017 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 09/14/17 Metal-Oxide Varistors (MOVs) Industrial High Energy Terminal Varistors > BA/BB Series TYPICAL TEMPERATURE COEFFICIENT OF POWER DISSIPATION = 2.2%/ o C MAX AT T A = 85 o C MAX AT T A = 25 o C TYP AT T A = 25 o C 1.0 0.8 0.6 0.4 0.2 0.1 0.08 0.06 0.04 80 90 100 110 PERCENTAGE OF MAXIMUM RATED V RMS (%) POWER DISSIPATION (W) PER kV OF RATED V RMS Stand by Power Dissipation vs Applied V Rms at Varied Temperatures Typical Stability of Standby Power Dissipation at Rated V RMS vs Time 1,000 HOURS, T A = 85 o C 0.5 0.4 0.3 0.2 0.1 0 10 100 1,000 POWER DISSIPATION (W) PER kV OF RATED V RMS TIME AT RATED V RMS (HOURS) Should transients occur in rapid succession, the average power dissipation required is simply the energy (watt-seconds) per pulse times the number of pulses per second. The power so developed must be within the specifications shown on the Device Ratings and Characteristics Table for the specific device. Furthermore, the operating values need to be derated at high temperatures as shown in the above diagram. Because varistors can only dissipate a relatively small amount of average power they are, therefore, not suitable for repetitive applications that involve substantial amounts of average power dissipation. Power Dissipation Ratings 100 90 80 70 60 50 40 30 20 10 0 -55 50 60 70 80 90 100 110 120 130 140 150 AMBIENT TEMPERATURE ( o C) PERCENT OF RATED VALUE 100 90 50 10 O 1 T 1 T 2 TIME PERCENT OF PEAK VALUE Peak Pulse Current Test Waveform 0 1 = Virtual Origin of Wave T = Time from 10% to 90% of Peak T 1 = Rise Time = 1.25 x T T 2 = Decay Time Example - For an 8/20 s Current Waveform: 8 s = T 1 = Rise Time 20 s = T 2 = Decay Time Figure 1 Figure 2 Figure 3 Figure 4

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