When a transformer is de-energized, the core retains some level of residual magnetism, known as remanent flux. This remanent flux can significantly impact the transformer's performance upon re-energization. Here’s how it affects the process:
𝐄𝐟𝐟𝐞𝐜𝐭𝐬 𝐨𝐟 𝐑𝐞𝐦𝐚𝐧𝐞𝐧𝐭 𝐅𝐥𝐮𝐱
𝟏. 𝐈𝐧𝐫𝐮𝐬𝐡 𝐂𝐮𝐫𝐫𝐞𝐧𝐭:
When a transformer is re-energized, if the voltage waveform coincides with the polarity and level of the remanent flux, a large inrush current can occur. This inrush current can be several times higher than the transformer's rated current and can cause mechanical stress, insulation damage, and maloperation of protection devices.
𝟐. 𝐂𝐨𝐫𝐞 𝐒𝐚𝐭𝐮𝐫𝐚𝐭𝐢𝐨𝐧:
If the remanent flux is high, it can push the core into saturation quickly when re-energized. Saturation of the core reduces its inductive properties, leading to higher magnetizing currents.
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