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KA2803B Datasheet(PDF) 2 Page - Fairchild Semiconductor |
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KA2803B Datasheet(HTML) 2 Page - Fairchild Semiconductor |
2 / 11 page © 2000 Fairchild Semiconductor Corporation www.fairchildsemi.com KA2803B • Rev. 1.0.7 2 Block Diagram Figure 1. Block Diagram Application Circuit Figure 2. Full-Wave Application Circuit Figure 3. Half-Wave Application Circuit Application Information (Refer to full-wave application circuit in Figure 2) Figure 2 shows the KA2803B connected in a typical leakage current detector system. The power is applied to the VCC terminal (Pin 8) directly from the power line. The resistor RS and capacitor CS are chosen so that Pin 8 voltage is at least 12V. The value of CS is recommended above 1µF. If the leakage current is at the load, it is detected by the zero current transformer (ZCT). The output voltage signal of ZCT is amplified by the differential amplifier of the KA2803B internal circuit and appears as a half-cycle sine wave signal referred to input signal at the output of the amplifier. The amplifier closed-loop gain is fixed about 1000 times with internal feedback resistor to compensate for zero current transformer (ZCT) variations. The resistor RL should be selected so that the breaker satisfies the required sensing current. The protection resistor RP is not usually used when high current is injected at the breaker; this resistor should be used to protect the earth leakage detector IC (KA2803B). The range of RP is from several hundred to several k. Capacitor C1 is for the noise canceller and a standard value of C1 is 0.047µF. Capacitor C2 is also a noise canceller capacitance, but it is not usually used. When high noise is present, a 0.047µF capacitor may be connected between Pins 6 and 7. The amplified signal finally appears at the Pin 7 with pulse signal through the internal latch circuit of the KA2803B. This signal drives the gate of the external SCR, which energizes the trip coil, which opens the circuit breaker. The trip time of the breaker is determined by capacitor C3 and the mechanism breaker. This capacitor should be selected under 1µF to satisfy the required trip time. The full-wave bridge supplies power to the KA2803B during both the positive and negative half cycles of the line voltage. This allows the hot and neutral lines to be interchanged. |
Similar Part No. - KA2803B_11 |
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Similar Description - KA2803B_11 |
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