transformer humm

[sceepe]

Was told by an old electrician who I respect a lot that he has had problems with dry types humming badly when a dry type (SDS) has equip grounding conductors (EGC's) from both the primary side panel and the secondary side panel tied to the ground buss in the dry type. Assume that Xo is bonded to the ground buss which is properly earthed to electrodes. Also, assume ground buss is bonded to the transformer case.

Looks like this (sorry to plagiarize the diagram)

He has proposed to terminate the EGC from the primary side panel to the xfmr case. Then insulate the ground buss from the xfmr case. Basically only bonding the transformer case to the primary side EGC

Has anyone else run into this?

 

[ron]

Re: transformer humm

If he terminates the EGC from the primary side panel to the xfmr case, then insulates the ground buss from the xfmr case, the case is then no longer bonded to the equip grounding conductor on the primary.

I have not seen any problem with bonding as shown on that diagram, and having everything together is required. Humming is generally due to low quality transformer windings and electrical load.

http://www.federalpacific.com/university/transnoise/transnoise.html

[ July 15, 2005, 09:41 AM: Message edited by: ron ]

 

[don_resqcapt19]

Re: transformer humm

J,
How does that change anything electrically, other than creating a very long fault clearing path in the event of a secondary winding to case fault? Have you seen this work to reduce the hum? I don't see how it would have any effect on the hum.
Don

 

[charlie]

Re: transformer humm

Transformers have to Hummmmmmm since they don't know the words.