6 pulse rectifier - transformer overheating

[tonyflair]

I'm considering a 6 pulse recitifer which is used to control a dc motor. A delta-wye transformer is located before this rectifer and is being subjected to excessive heating. I am interesting in seeing the Irms^2*R (heat) that is being produced, due to the harmonics of this rectifier. I'd like to determine the relationship between heat and the firing angle of the scr's.

I've determined the frequency domain representation of the a.c current in on phase (using Fourier Analysis)....but this is not a function of the firing angle.

Any suggestions ?

Thanks

 

[jghrist]

The relationship between firing angle and harmonic content can be found in IEEE Std 519, IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems. The relationship between transformer losses and harmonic content can be found in ANSI/IEEE C57.110, IEEE Recommended Practice for Establishing Transformer Capability When Supplying Nonsinusoidal Load Currents.