SLYY234 December 2024 AMC0106M05 , AMC0106M25 , AMC0136 , AMC0311D , AMC0311S , AMC0386 , AMC0386-Q1 , AMC1100 , AMC1106M05 , AMC1200 , AMC1200-Q1 , AMC1202 , AMC1203 , AMC1204 , AMC1211-Q1 , AMC1300 , AMC1300B-Q1 , AMC1301 , AMC1301-Q1 , AMC1302-Q1 , AMC1303M2510 , AMC1304L25 , AMC1304M25 , AMC1305M25 , AMC1305M25-Q1 , AMC1306M05 , AMC1306M25 , AMC1311 , AMC1311-Q1 , AMC131M03 , AMC1336 , AMC1336-Q1 , AMC1350 , AMC1350-Q1 , AMC23C12 , AMC3301 , AMC3330 , AMC3330-Q1
Figure 108 shows how AMC23C12 can be used for bidirectional in-phase overcurrent detection.
Figure 108 Bidirectional in-phase
overcurrent detection.In a fully operational three-phase AC motor-drive system, the sum of three-phase current to the AC motor should be zero, regardless of braking or running conditions (that is, IA + IB + IC = 0).
Calculating the third-phase current in low- to mid-end motor drives from measured current on two phases can help reduce costs. I recommend monitoring the current on the third phase to detect any electrical fault events. While you could place a current sensor on the third phase with an isolated amplifier or isolated modulator, you could also use a reinforced isolated window comparator AMC23C12 for simplicity, cost-effectiveness and solution size. The AMC23C12offers bidirectional overcurrent detection with an integrated window comparator.
As shown in location 1 of Figure 108, a shunt resistor produces a voltage drop that the AMC23C12 reinforced window comparator senses. The AMC23C12 has an open-drain output, OUT, which actively pulls low when the input voltage exceeds the pre-defined threshold values of the voltage on the reference pin for the purposes of overcurrent detection. Figure 109 shows an overcurrent event output waveform.
For both overcurrent and short-circuit detection, you can use the AMC23C14 dual window comparator.