Study on the Vibration Frequency Characteristics of Dry-type Air-core Reactors Loaded Harmonic Currents

Dry-type air-core reactors are electrical equipment that form passive filters. During operation, harmonic current will be filtered and made to flow through the reactors, causing mechanical vibration on the windings. Experiments has shown that the vibration spectrum of the dry-type air-core reactor contains components with the same frequency as the loaded harmonic current. The underlying physical process of this equal-frequency part has not been determined. The sources of each component in the vibration of dry-type air-core reactors were studied in this paper. It was verified through experiments that the vibration of dry-type air-core reactors was proportional to square of the loading current amplitude at different frequencies. It was determined that the 2 times frequency part in the vibration spectrum originated to the excitation of the winding magnetic field force. Through vibration comparison tests in three scenarios, it was determined that the leakage magnetic field of the dry-type air-core reactor would enter the test system through the internal conditioning circuit, output terminal and signal trans-mission line of the instrument to generate a magnetic field coupling signal. This process would generate the frequency components, which is identical with loaded current frequencies, of the vibration spectrum.