Characteristics of aircraft power supply system

National military standards, U.S. military standards, international standards and other relevant standards have made relevant regulations on the characteristics of aircraft power supply systems.

  1. Characteristics of DC power supply system
    The characteristics of the DC power supply system are mainly measured by three indicators: steady-state voltage limit, voltage pulsation and voltage transient.

The steady-state DC voltage refers to the average value of the instantaneous DC voltage within a time interval of no more than 1s. The steady-state voltage limit refers to the maximum change range of the terminal voltage of the electrical equipment in the steady state, which is determined by the voltage regulation accuracy of the power supply and the size of the feeder voltage drop. The voltage regulation accuracy of the power supply is closely related to the performance of its voltage regulator.

Voltage pulsation refers to the periodical or random changes in the voltage around the steady-state DC voltage during the steady-state operation of the DC power supply system. Voltage pulsation is usually caused by factors such as transmission speed pulsation, commutation and voltage regulation of brushed generators, and load changes of electrical equipment. The ripple amplitude refers to the absolute value of the maximum difference between the steady-state DC voltage and the transient DC voltage, and the voltage ripple amplitude must also be limited within the allowable range.

DC voltage transient refers to the state where the voltage exceeds the steady-state limit and returns to the steady-state limit within a certain period of time. Some transients are caused by transient power interruptions or abnormal disturbances discharged by faults. It is commonly used to indicate the maximum change in voltage and the recovery time. There are two types of voltage transients, one is voltage surge and the other is voltage spike. Voltage surge is a voltage change caused by external interference in the power supply system and suppressed by internal regulation. Its duration is longer, generally from several milliseconds to tens of milliseconds. Voltage spikes are transients with a duration of less than 50us, usually caused by circuit switching. The voltage spike can be represented by parameters such as voltage and its duration, rise time and energy in its time domain, or can be equivalently represented by Fourier components.

  1. Characteristics of AC power supply system
    The characteristics of AC power supply system include voltage and frequency.

Voltage quality indicators have five aspects: steady-state voltage limit, voltage waveform, three-phase voltage symmetry, voltage modulation and voltage transient.

The steady-state AC voltage refers to the time average value of the effective value of the AC voltage in a time interval not exceeding 1s.

The AC voltage waveform should be a sine wave, but it is actually deviated. Commonly used crest factor (the ratio of the peak value of the phase voltage waveform to the effective value), the total harmonic content (the root mean square value of the AC voltage is shaped except the fundamental wave), single The sub-harmonic content or deviation coefficient (the deviation of the voltage waveform from the corresponding point of the fundamental waveform) is measured. Voltage modulation is the periodic or random change or both of the alternating voltage near the average value of its peak value during steady-state operation of the AC power supply system. It is commonly measured by modulation amplitude and modulation frequency. Factors that cause voltage modulation include AC power supply voltage regulation, changes in generator speed, and changes in loads in electrical equipment. Distortion spectrum refers to the quantified representation of AC or DC distortion through the amplitude of each frequency component. Distortion frequency includes components produced by voltage modulation and frequency modulation, and harmonic and non-harmonic content in the waveform.

The frequency index has four aspects: steady-state frequency limit, frequency drift, frequency modulation and frequency transient. Some definitions of frequency quality indicators are similar to voltage indicators.

The steady-state frequency refers to the time average of the frequency in a time interval not exceeding 1s. Frequency modulation refers to the change of the power supply frequency during steady-state operation of the AC power supply system, and frequency modulation is a measure of the stability of AC power frequency regulation.