Re: [CAD_CAM_EDM_DRO] Blown Gecko 320..Strange noises from control???

R Rogers wrote:

>
>
>
>Anyway, on the noise, does it sound like the sound the drive box makes
>when you turn it on?
>I'm thinking if you can hear it when the machine is cutting, it must be
>pretty loud.
>
>Jon
>
>Yes it was loud, However, the control does not make this noise when powering up. All I can hear is the cooling fan start. Today, before beginning work I went over it thoroughly looking for anything suspect and even blew the enclosure out with compressed air. It never made any noises at all. I think you are right that it was probably voltage spikes. It sounded like a big current surge, Like when powering up a welder.
>

OK, that's what I had in mind. That sound is the sound of a transformer
in core saturation. Why this happens
is the magnetic circuit in the transformer is designed to tolerate the
Volts*Time of the standard line service.
When a positive half cycle of the line begins, the transformer iron
already has integrated the V*T of the
preceding negative half cycle, and so the magnetic flux actually reaches
zero at the time of the voltage
peak. But, when the transformer is turned on "cold", the magnetic flux
is near zero. If you turn on at
either voltage peak, then the transformer just starts right into the
normal pattern. But, if you turn on at
the voltage zero crossing, then you integrate a complete half cycle of
flux wit the transformer starting
at zero. About when the voltage peak occurs the iron reaches
saturation, the inductance of the transformer
disappears, and only the resistance of the winding limits current. A
huge buzz develops, lights flicker,
and large pulses of current are drawn on alternate half cycles. These
large currents eventually bring
the transformer flux into eqilibrium.

If you hear these humming noises when the supply is just running, there
are two causes. One is
that another, larger, transformer somewhere is doing the same thing, and
the large currents have
unbalanced the + to - voltage peaks of the line. Somebody else's big
welder being started up
somewhere, especially on the same pole transformer, is a possible cause.

A surge supressor will be practically useless to deal with this type of
line anomaly. The only thing
it will do is get rid of the high voltage spikes that these saturation
events can cause.

Another possible cause is a defective rectifier circuit that is only
drawing current on one half
cycle. This can unbalance the flux in the transformer, and the only way
to return to balance
is to draw large currents from the line.

> It seems strange that what has worked for a year and a half now needs to be changed. Obviously something changed and was a first event when the drive went. I wasnt doing anything unusual, so i'm thinking voltage spikes on the line for some odd reason.
>
>

Yeah, getting back to that, did you have fuses on each Gecko drive? If
not, what happened when the
cap and then Gecko blew? Did it shut down the whole system?

Jon