[Boatanchors] Big, old & heavy transformer ID

Barrie Smith barrie at centric.net
Sun Jan 31 19:18:24 EST 2010


Hello:

I have a large, heavy transformer I'm trying to figure out.  It's 13" X 9" X 
9" and certainly weights over 100 lbs.

It does have a rather difficult to read label on it.  The manufacturer is 
"Ameritran". The model number is 31029. The KVA test is 7.5.  Primary is 220 
volts and secondary is 1500/3000 volts.  The rated KVA is 2.1.

While I'm pretty sure the secondary is not center-tapped, it does have three 
terminals.  One is much larger than the other two.  I'm guessing that the 
larger one is one end of the winding, the center one is 1500 volts and the 
third is 3000 volts.

The primary also has three terminals, and that's where I'm lost.

Using a 120 volt (not 220) variac earlier today, I measured (using the outer 
terminals, which I would think correspond to full primary and full 
secondary), 1100 volts, or 2200 volts if I were using 220 on the primary.

If I put the primary voltage to the leftmost terminal (which I would think 
would be number 1), and terminal number two I got, with the variac only half 
way up, 3600 volts!  Looks as if I was using only a small portion of the 
primary and the turns ratio was very high.

If I put the 120 primary voltage to terminals number 2 & 3 I got 1600 volts, 
which sounds about right for 220 in and 3000 out.

My confussion is regarding the primary terminals.  It looks as if terminal 
number three is common, and number two is the tap?  Usually, with tapped 
windings, terminal number 1 is on the left.

I've done a lot of Googling on this manufacturer and have come up short.

If anyone has any information on this transformer, or ideas on the primary, 
I'd sure appreciate it.

73, Barrie, W7ALW






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