What Is a Zero-Phase Reactor?
A zero-phase reactor is a type of reactor used as a peripheral device of an inverter.
The reactor has a structure of coiled electric wire and is installed on the input or output side of the inverter to block high-frequency currents and reduce noise.
While a general reactor consists of a single wire wound like a choke coil, a zero-phase reactor consists of three phases of wire wound with equal polarity and number of turns. The zero-phase reactor reduces the noise generated when the inverter is operated.
Uses of Zero-Phase Reactors
Zero-phase reactors are installed on the input and output sides of inverters to reduce the impact of noise generated by the inverter on peripheral equipment.
Inverters are used in a wide variety of fields, including household air conditioners, refrigerators, rice cookers, industrial motors and pumps, elevators, and medical electronic equipment. Zero-phase reactors, which are peripheral devices of inverters, are also widely used.
Zero-phase reactors are effective in suppressing noise in the frequency range of up to several MHz and are used to reduce radio interference to radios and televisions and to prevent malfunctions of measuring instruments and sensors.
Principle of Zero-Phase Reactors
The zero-phase reactors have a structure of three-phase wires wound with equal polarity and number of turns. The zero-phase reactors have a ring shape, and the wires on the input or output side of the inverter are either wound around the ring or penetrated through the ring.
When the inverter is operated, an alternating current flows through the wire, generating a circumferential magnetic flux in the ring of the zero-phase reactors. As the AC current changes, the magnetic flux also changes, generating a back EMF on the wire in a direction that prevents the current from changing. The effect of this back EMF reduces the zero-phase current, which is the cause of radiated noise.
Zero-phase reactors can be installed on either the input or output side of the inverter. There are single-phase and three-phase input/output types of inverters. When installing a zero-phase reactor in a three-phase inverter, each phase must be penetrated altogether or wound in the same direction. The more times the wires are wound, the more effective noise reduction will be.
When wires are penetrated into the ring, multiple zero-phase reactors should be penetrated side by side. In this case, if the number of zero-phase reactors and the number of windings when wrapping the wire around the ring are the same, the noise reduction effect will be equal.