Hello All,

My query is about analog ampere meters that I recently installed to measure load of induction motors (90KW). When I installed it about 15 meters away the ampere meters showed variations i.e if the load of the motor was 70 Amperes it is showing around 100 A even after calibration it does not work properly. When I installed it on the panel near CT it works properly so I am planning to use a shielded cable for it or can that be a CT (current Transformer) problem which is highly unlikely.

 

Mawais... sounds like CT-Burden is too high!

Regards,
Phil Corso

 

You would have to define analog meter and calibration to really say your meter isn't reading correctly.

My first guess would be that there are harmonics on the wire or that the waveform wasn't sinusoidal, which really mean the same thing. Unless calibrated with that same waveshape, it may read differently. With a really distorted waveform, such as from a VFD (either end) you may well get different reading at different places along the cable. Also magnetic meters are sensitive to magnetic fields, around transformers and motors, for example. Even orientation of some meters will cause a shift. Most analog panel meters should be considered indicators and used for relative readings.

Regards
cww who was around when all meters were analog.