Air circuit breakers (ACBs) and vacuum circuit breakers (VCBs) are both types of circuit breakers that differ in their voltage applications, working principles, and other characteristics: Voltage applications ACBs are used in applications with voltages less than 690 volts, while VCBs are ideal for medium voltage levels with voltages less than 33 kV. Working principle ACBs use a combination of air pressure and conductive elements to guide the arc away from the circuit, while VCBs use a vacuum to quench arcs. Medium pressure VCBs must maintain a vacuum pressure ranging from 10-2 to 10-6 torr, while ACBs do not require manual refilling. Advantages ACBs are reliable for industrial plants and electrical machines, and have high resistance power. Disadvantages ACBs are inefficient in low current, have weak electromagnetic fields, and are more complex and expensive than VCBs.