Today we study about Switching current in Transformers.
Switching current in Transformers:- In particularly unfavorable condition transformer under no load, large residual flux and zero voltage tripping with a initial half-wave flux on the same polarity as the residual flux and the magnetic core become very saturated, with the winding taking in up to three times its rated flux.
Due to this saturation, the apparent inductance of the coil significantly drops, approaching of an air coil increasing the leakage flux. the resulting current in the winding may reach very high peak values up to a dozen times the peak rated current with an extremely distorted current waveform due to saturation phenomena.
This switching phenomena damp down with a time constant that is dependent on the transformer related to its magnetic characteristics and leakage flux the time constant is of the order of a few hundreds of milliseconds for distribution transformer.
The switching current is necessary to determine to choice or the setting or short circuit protection devices located on the transformer's primary.
This switching current required to monitoring device to integrate the ideas of time delay in order not to generate spurious actions.
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