On 2010-09-29, Karl Townsend wrote:
Turns out I have a power supply for my Matsurra bedmill. After
stripping everything not needed away I ended up with this:
http://www.metalworking.com/dropbox/supply1.jpg
http://www.metalworking.com/dropbox/supply2.jpg

A few questions. Each of the twelve diodes has a pair of wires, 24
connections on the terminal strip. I don't know the function here and
if anything needs to be connected.

I *think* those are SCRs (Silicon Controlled Rectifiers), and
one of each pair is the gate, while the other is likely the cathode
(which the gate signal is applied relative to. Try a resistance
measurement between the black and the white to the high-current lead
from the top of the rectifier -- and to the end bolted to the heat sink.
Whichever one reads zero should be a low-current duplicate connection to
the cathode, and the other needs to go positive relative to the other
lead to turn on the SCR. It may be that you should have kept the board
which was connected to those leads to regulate the output voltage by
turning those on at the right time.

To double check -- look for part numbers stamped on the sides of
the rectifiers.

Is the part labeled 1 an isolation transformer? If so, should DC- be
grounded?

What is certain is that it is a high current three-phase
transformer..

It is likely to be an isolation transformer. Check with an
ohmmeter between the terminals on the heast sink side and the terminals
connecting to the contactor. If it isolation, you should get an
"infinity" reading for resistance -- except with certain rare meters
which can measure very tiny leakages.

And yes -- DC- should be grounded.

Can the part labeled 2 be used to read current? There are four leads,
how would they be connected. The part says "Nana Electronics NNC-05AF"

It *looks* like a current transformer -- though why there are
four leads remains to be seen. Normally, you hook a known (fairly low)
resistance across the *two* terminals, and measure the voltage
developed. This, with the turns ratio of the current transformer
(you've got two turns on the primary -- and the number or a ratio should
be somewhere on the label of the CT.) will let you turn the voltage to a
current reading.

Or -- you use a current meter on the secondary, which provides
its own low resistance.

Look for something like 250:1 (or some other ratio) on the
label. I wonder whether it includes some kind of alarm sensor to
account for the extra terminals.

Good Luck,
DoN.

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