RE: The tape-O-matic...

Ah, I see. Oops. Let's hope he waited for the second opinion or that the
SCR's are beefy and the fuses fast. Anyway, all he needs is a little phase
order indicator. They must be in the Grainger catalog, somewhere.

Jeff

-----Original Message-----

From: Jon Elson <jmelson@...>

Jeff Barlow wrote:

> From: "Jeff Barlow" <barlow@...>
>
> Hi Brad,
>
> I'm an EE and an electrical contractor, among other things, so maybe I can
> help a little. It sounds like the transformer is 240v delta to 480v wye.
> 480v wye is 480v phase to phase and 277v phase to neutral. How many
> terminals are there on the primaries and secondary of the transformer(s)

and

> how are they all labeled? I'm more concerned about voltage than phase

right

> now.
>
> You don't need a scope to get phase order right. About the only bad thing
> that will happen with the phase order reversed is the motor will turn
> backwards. Tell me more about the motors on this thing.

Not necessarily so. That vintage would likely have an SCR cycloconverter
for a variable speed spindle drive. The control logic of the cycloconverter
needs to know the order in which the input phases are coming in to select
which SCRs to trigger at what time. If the input phase sequence is wrong
it would be firing SCRs when the phase angle is all wrong, and causing
conduction when high currents would flow. It shouldn't cause damage
other than some blown fuses, but it depends on the safety factor built
into the design.

Jon