On Wed, 29 Sep 2010 13:41:14 -0500, Pete C. wrote:
Tim Wescott wrote:
On 09/29/2010 09:55 AM, Karl Townsend wrote:
....
Is the part labeled 1 an isolation transformer? If so, should DC- be
grounded?

Most likely it's a three-phase step up or down transformer. It looks a
bit small compared to the diode array, but what do I know? If the
leads on the left don't show any conductance to the leads on the right
it isolates as well as any step-up or -down.

It may be a 1:1 isolation transformer which may help explain it's
relatively small size. If it were a step-up or step-down I expect there
would be a few voltage taps.
....

Item 1 seems to have 2 contacts per winding so probably is a
choke (inductor) rather than a transformer. Each left wire is
attached to the inside of a coil and each right wire to the outside,
and each winding probably is a wide, thin, copper strip.

--
jiw