Re: How many kva for a control transformer...?

Hey,
Yes I know, but this machine will actually be in an industrial
environment. My goal is to have only the 220 3ph coming into the
machine as power. Therefore, all lower voltages will be derived from
the 220 3ph input power.


I've got 2x 1 kva transformers with 120 secondaries, and then I've
got a single 2 kva with 120 secondary.

I've got 2 separate NEMA 3R enclosures. My plan is to mount all
the 3ph in one and 1ph in the other. These will be physically
separated on the machine, about a 5 ft separation.

1)... Being that the VFD is the big noise maker, should I mount the
control transformer(s) in the 3ph box with the VFD and run the 120
1ph across to the 1ph enclosure?. Or should I run the 3ph across to
the 1ph enclosure and mount the control transformer(s) in the 1ph box?


Also note, there will be 120 back to the 3ph box for the contactor
coils.

2)... Then there is the Digispeed, PWM to analog converter, which is
used to control the VFD. Somehow these low voltage control wires
will have to cross the ~5ft span to the 3ph box. Which would be more
noise tolerant, the PWM side or the analog output side? (IE should
the Digispeed be mounted in the 1ph box with the breakout boards or
in the 3ph box with the VFD it will control?)


Thanks for any info.

> 36 V 10 A is only 360 VA. You can get 1700 VA out of a 15 A 120 V
> outlet.
>
> > Wouldn't it be beneficial, electrical isolation-wise, to have
> >separate transformers supplying the servo drives and for the PC

and

> >control components? Or, should I just go with one big transformer

to

> >power all the 120VAC components?
> >
> >
> >
> Possibly, but most computers, etc. are pretty tolerant of noisy

power.

> Actually, the VFD is the real culprit, the servo drives are going

to be

> much more benign.
>
> Jon