The transformers are not connected on dc and never connected to a dc source. There will be no self emf in the primary when the transformer are connected to a dc supply. If a rated dc voltage is applied to the primary of a transformer, the flux produced in the transformer core will not vary but remain constant in magnitude and therefore no emf will be induced in the secondary winding except at the moment of switching on. Since the resistance of the primary winding is low, therefore a heavy current will flow through the Primary winding which may result in the burning out of the primary winding. This is reason that dc is never applied to a transformer. Subscribe, share and leave your comments in the comment box below. Thank you :)
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