Thyristor Semiconductor Products Page 75 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1008 The dissipation for non-sinusoidal waveshapes can be determined in several ways. Graphically plotting instantaneous dissipation as a function of time is one method. The total maximum allowable power dissipation (P D ) may be determined using the following equation for temperature rise: T J(MAX) -T C P D = R JC where T J (max) is the maximum rated junction temperature (at zero rated current), T C is the actual operating case temperature, and R JC is the published junction-to-case thermal resistance. Transient thermal resistance curves are required for short interval pulses. Triac The limiting factor for RMS current is determined by multiplying power dissipation by thermal resistance. The resulting current value will ensure an operating junction temperature within maximum value. For convenience, dissipation is converted to RMS current at a 360 conduction angle. The same RMS current can be used at non-sinusoidal waveshapes and a discussion of dissipation, refer to the preceding description of SCR current rating. I TSM : Peak Surge (Non-repetitive) On-state Current -- SCR and Triac The peak surge current is the maximum peak current that may be applied to the device for one full cycle of conduction without device degradation. The maximum peak current is usually specified as sinusoidal at 50 Hz or 60 Hz. This rating applies when the device is conducting rated current before the surge and, thus, with the junction temperature at rated values before the surge. The junction temperature will surpass the rated operating temperature during the surge, and the blocking capacity may be decreased until the device reverts to thermal equilibrium. The surge-current curve in Figure AN1008.3 illustrates the peak current that may be applied as a function of surge duration. This surge curve is not intended to depict an exponential current decay as a function of applied overload. Instead, the peak current shown for a given number of cycles is the maximum peak surge permitted for that time period. The current must be derated so that the peak junction temperature during the surge overload does not exceed maximum rated junction temperature if blocking is to be retained after a surge. 1 10 100 1000 10 20 30 40 50 60 80 100 120 150 250 300 400 1000 Surge Current Duration - Full Cycles Peak Surge (Non-repetitive) On-state Current (I TSM ) - Amps 40 A TO-218 25 A T0-220 15 A TO-220 1) Gate control may be lost during and immediately following surge current interval. 2) Overload may not be repeated until junction temperature has returned to steady-state rated value. SUPPLY FREQUENCY: 60 Hz Sinusoidal LOAD: Resistive RMS ON-STATE CURRENT [ I T(RMS)]: Maximum Rated Value at Specified Case Temperature Notes: Figure AN1008.3 Peak Surge Current versus Surge Current Duration I TM : Peak Repetitive On-state Current - SCR and Triac The I TM rating specifies the maximum peak current that may be applied to the device during brief pulses. When the device operates under these circumstances, blocking capability is maintained. The minimum pulse duration and shape are defined and control the applied di/dt. The operating voltage, the duty factor, the case temperature, and the gate waveform are also defined. This rating must be followed when high repetitive peak currents are employed, such as in pulse modulators, capacitive- discharge circuits, and other applications where snubbers are required. di/dt: Rate-of-change of On-state Current - SCR and Triac The di/dt rating specifies the maximum rate-of-rise of current through a Thyristor device during turn-on. The value of principal voltage prior to turn-on and the magnitude and rise time of the gate trigger waveform during turn-on are among the conditions under which the rating applies. If the rate-of-change of current (di/dt) exceeds this maximum value, or if turn-on with high di/dt during minimum gate drive occurs (such as dv/dt or overvoltage events), then localized heating may cause device degradation. During the first few microseconds of initial turn-on, the effect of di/dt is more pronounced. The di/dt capability of the Thyristor is greatly increased as soon as the total area of the pellet is in full conduction. The di/dt effects that can occur as a result of voltage or transient turn-on (non-gated) is not related to this rating. The di/dt rating is specified for maximum junction temperature. As shown in Figure AN1008.4, the di/dt of a surge current can be calculated by means of the following equation. di I TM ---- = ----- dt 2 t 1 Explanation of Maximum Ratings and Characteristics for Thyristors (continued)

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