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Jamie

wrote:

On Tue, 03 Apr 2012 12:47:48 -0500, amdx
wrote:

On 4/3/2012 11:43 AM, wrote:

I have a CNC lathe, a Miyano, that I just bought. The machine was made
in the early 90s. I ran it in a different shop for the last year and
it worked fine. The shop had only single phase power available, like
my shop. But in the old location the machine ran on solid state phase
converter and in my shop it runs on a rotary converter. The line
voltage at the old location was 235 volts. In my shop it is 245 volts.
The machine is made to run on 230 volts. My phase converter is well
balanced and the manufactured leg measures 245 volts. The problem is
one three phase fractional hp motor that powers a chip conveyor. The
power supply wires for this motor are wound through some sort of
current sensing transformer. Thes are regular 14 gauge stranded
insulated wires that appear to be hand wound through the current
sensing transformer. So I'm thinking that with the higher voltage
running through the wires the voltage output from the transformer is a
little high and it causes the machine to alarm out on the chip
conveyor. I disconnected the output from the current xmfr and the
machine now does not throw an alarm, but this also removes the
protection. I'm thinking that if I take a couple turns out of the xmfr
then the voltage output would be lower and I can then still use the
xmfr to protect the motor. Will that work?
Thanks,
Eric

I'm over my head, it seems your saying all three phases run through
the current sensing transformer. Didn't know that worked.
I think we need to know how many turns of the 14 Gauge stranded wire
are wound through the current sensing transformer? Per phase?
From that someone can decide how many turns to remove.
Mikek

I was able to push the wires aside enough and using a mirror and
flashlight I was able to read on the device that it is an Omron SET-3A
current converter. Looking at the data sheet at omron.com I see that
the SET-3A device connects to another device and the two together
operate as a unit. The sheet also says that the setup won't work with
waveform distortion. I'm thinking now that maybe my rotary phase
converter must have too much waveform distortion and that's the real
reason for the problem. Anybody have any thoughts about a device that
I can use to replace the current converter? Maybe just a circuit
breaker? Afterall, the motor just runs the chip conveyor, which just
pulls all the metal shavings (chips, AKA swarf) out of the machine.
And the motor is exposed so I can feel it to see if it's too hot. I
can see if the magic smoke is coming out too, but I don't want to wait
that long.
Thanks,
Eric.
Get a 1:1 3 phase transformer for it. pass the power through that and
then supply the electronics with that. The transformer will correct that
issue, if that is really the problem.

Jamie