In article , "Ralph Mowery" wrote:

"GregS" wrote in message
...
In article , "Ralph
Mowery" wrote:

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.



Isolation transformers such as the ones Tripplite sells, do filter well.
They also eliminate the ground to line spike issue. One leg of the
secondaries
is tied to ground, eliminating any differential noise.

greg


While there are transformers designed to keep out spikes and filter the
line, you have to look at the question.
The transformer was mentioned was with test equipment. Usually it is to
isolate the hot chassies, not to eliminate spikes and noise.

I was responding to someone who said it did not provide filtering. Regardless,
an isolation transformer should have an electrostatic shield between
the line and output, cutting down electrostatic conduction. Any standard isolation transformer
sold in the US must have the secondary tied to ground by NEC code.
In all cases, you are isolating the mains from the equipment. Even if one leg of the output
is grounded, its still isolated from the mains. The problem is if you put your body within the
chassis somewhere.

greg