Answer / iamdon

The CT secondary should not be left opened secondary due to
following reasons:

1)Zero current in secondary leads zero back emf.So primary
current becomes very high.Large heat generated may burn the
winding and core.If the transformer sustain this heat, even
then its operation becomes improper as explained below.

2)CT is bascially a step up transformer.So high voltage
induced in secondary may saturate the core (core becomes
permanently damaged).So the operating point advances in non
linear region,which makes the transformer operation improper
(secomdary current will not replicate the primary according
to the turn ratio).

3)High voltage induced in secondary side may endanger the
life of personnel working on the side.

Author:arbelectbit@yahoo.com

Answer / bhautik patel

due to the absence of the counter ampere-turns of the secondary, the unopposed primary mmf will set up high flux in the core which will produce excessive core loss with subsequent heating & high voltage across the secondary terminals.

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