How can a low frequency transformer with a wider frequency range increase the output power?

author: MagTop
Input a voltage of 220V to an existing power frequency transformer (the size of the iron core is unchanged, and the input and output currents have a margin), and the frequency is steplessly adjusted from 50 Hz to 400 Hz, then what is the maximum output power of the low frequency transformer? change?

We know that according to the law of electromagnetic induction, the inductive electromotive force is proportional to the frequency and the maximum value of the main magnetic flux. When the frequency increases (the data of the transformer are unchanged at this time) the main magnetic flux becomes smaller, and the excitation current also becomes smaller. After superimposing the eddy current loss of the iron core and the increase of the copper loss as the frequency increases, the no-load loss gradually decreases in the low frequency range.

However, because the transformer data remains unchanged, the primary inductance leakage inductance and primary impedance of the power transformer are fixed values. When the frequency increases, according to the calculation formula of the inductive reactance, the inductive reactance of the transformer is proportional to the frequency, and the short-circuit impedance and the voltage regulation rate are proportional to the frequency. As the rise continues to increase, the voltage drop at load will increase with the increase of frequency, resulting in a decrease in the output capacity of the transformer.