Transformer Name Plate

[necr]

Hi there,

Can anyone aid on how to establish the rating of the transformer with a missing name plate. we are intending to add couple of loads on the transformer, and to our sup rise we discovered that someone removed the nameplate.

 

[jbartos]

Suggestion:
Try to obtain typical transformer parameters for your transformer that may have estimated/guessed size and voltage levels by an experienced transformer specialist.
1. Measure insulation resistance
2. Measure input and output winding impedances and find out transformer winding connections
3. Measure turns ratio by a relatively low voltage
4. Gradually increase the primary voltage and monitor transformer temperature on no load conditions, while monitoring the output voltage waveform for its sinusoidal waveform
5. Gradually load the transformer while monitoring the transformer temperature and output current waveform for its sinusoidal form
6. Leave some temperature margins, e.g. 55degC might suffice as maximum
Alternately, have it shipped to testing labs to establish the transformer parameters

 

[peebee]

How much do you know about the tx?

Do you know the vendor? Can you ask him?

Is it a general purpose tx? Relatively new? By a big-name manufacturer? Maybe you can compare the dimensions to the catalog information?

Are you sure the installation was properly designed to NEC? Can you determine the tx size from the installed primary and/or secondary overcurrent device trip settings/ratings or cable sizes?

Can you check if there's any markings or labels on the coils inside?

I suppose destructive testing is inappropriate. Too bad, could be fun.