Answer / satendra

On increasing the voltage the current will also be increase (as the res. is constant)in turn flux will also be increase.
But after the saturation point on increasing the voltage the current will go infinite momently. This point is called KNEE-POINT. After the knee point there are a more chances to get the coil as a permanent magnet. So we never perform the test upto knee-point.

satendra.svnit@gmail.com

Answer / chetan sharma

10 % increase in voltage gives you 50 % increase in
excitation current is called knee point voltage.
To measure this first demagnetise the CT and apply
voltage gradually from secondary keeping primary
winding open circuited. while doing this above
phenomeneo will be obsesrved.

I have a question, I visit 01 site and face a problem, there is 2.5 ton Air Con working, when air con compressor is running at that time rectifier voltages are increasing upto 290-295 v and rectifier is giving main high alarm (rectifier is APC single phase, before starting compressor rectifier voltages was 230v. when air con is going off rectifier voltages are decreasing smoothly at its actual voltages 230v. Load on Genset phases is this: Red-13.5 amp AC (Air Con load), Yellow-1.7 amp AC (BTS lights etc.) and Blew-4 amp AC (telecom system load), Genset phase to phase and neutral to phase voltages are also ok. These are 10 sites having same system and same rectifier APC brand at every site 02 genset are working but the problem is same at all these 10 sites. What will be the reason behind???

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