Re: What Makes A Transformer Hum (continued)

David, et al, I just learned that a toroid core is wound from a single strip of metal, like a coiled clock spring, one continuous piece. But whether this one is welded, I cannot say. My guess is probably not. As for impregnation, I do not think so. The construction details I saw describe core,

Re: Mains test - India

Hi, Thanks for those that replied. Basically, I would conclude that this test it's not a must requirement. Just an additional test that the customer requires. Regards Koh Koh wrote: Hi group, We had a request from an India customer. They need to have the following test performed on our

Re: What Makes a Transformer Hum in the UK?

In message f72651ec60c2c945878cf1cf6a3e5af401bc8...@ntxboimbx13.micron.com, dated Thu, 22 Dec 2005, drcuthb...@micron.com writes Loading a transformer secondary does absolutely nothing to the magnetic core flux. The core flux is set by the magnetizing current and not the load current. Does

RE: What Makes a Transformer Hum in the UK?

To first order it is true that the magnetic flux in the core does not change with load current. It would be exactly true if the permeability of the core were infinite. For real materials with finite permeability, a load current on the secondary does force some flux out of the core into the air.

RE: What Makes a Transformer Hum in the UK?

Peter, When John Woodgate said that secondary current does not change the core flux I went back to the books to see where I went wrong. Here is what I think is going on: The primary current that is caused by the secondary load creates a magnetic flux in the core. The secondary current creates a

RE: What Makes A Transformer Hum (continued)

I should have added that the most probable cause of noise besides lamination, is the mmf between loaded windings. Are the windings tightly constrained or impregnated? Best Regards David Greig From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of David Greig Sent: 22 December 2005

RE: What Makes A Transformer Hum (continued)

Is the lamination stack welded? This could provide a outside rigid axis for the laminations to pivot against, given that any impregnation will be more compressible than the weld. Welds may also distort the stack. Best Regards David Greig __ GigaDyne Ltd Buchan

Re: Mains test - India

I don't see any contradiction here. Step 3 clearly states that if the sample passes the earlier test, then keep increasing the voltage until the sample fails. Regards, Ravinder Server PCB Development Hitachi Global Storage Technologies Email: ravinder.ajm...@hitachigst.com Robert A. Macy