unbalanced current and Zero sequance component
unbalanced current and Zero sequance component
(OP)
if there are 3 line (3 phase power system)passing through a ring transformer (core balanced CT) and feeding unbalanced delta load. Does the core balanced CT get an output (secondary winding) related to this imbalanced current?.
or it will only get an output in the case of earth leakage?.
or it will only get an output in the case of earth leakage?.





RE: unbalanced current and Zero sequance component
Provided that the supply to the load is a three wire system (no neutral) there will be no output from the CT. All the current going to the load passes through the CT and all the current returning also passed through the CT so the filed cancel out. If there was a neutral connected to the load, the answer would be different.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: unbalanced current and Zero sequance component
marke: even if there is a neutral, it should pass through the CT window and CT secondary will not read any current. ..(and of course the earthing wire should be out side of the CT to detect the earth leakage)
RE: unbalanced current and Zero sequance component
Yes I agree, provided that the neutral does pass through the CT as well, there will be no reading.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: unbalanced current and Zero sequance component
i have one more question ...
for the unbalanced line currents ... the magnetude of the current will be different also their summation is zero ..
** so the phase shift angle between the line currents will not be the same (120), isn't it? **
RE: unbalanced current and Zero sequance component
Yes that is correct. With a three wire system, as the current magnitudes change, their apparent phase shift also changes.
Take the exteme and connect across two phases only, the two currents are 180 degrees out of phase.
Best regards,
Mark Empson
http://www.lmphotonics.com