On 2007-10-08, Pete C. wrote:
Jon Elson wrote:

Ignoramus3938 wrote:
On 2007-10-07, Pete C. wrote:

Ignoramus12852 wrote:

I am thinking about something. 480 VAC drives can be bought for next
to nothing. What they have is an inverter circuit and control
circuit.

They probably would not run on 240v because the internal transformer
that would supply voltage to the control circuit would supply only 1/2
voltage. They also might have an indervoltage sensor. I cannot think
of more things that depend on 480 volts being there.

So, if a hack could be done and a 1:2 transformer inserted between
480v inputs and the control circuit, then the drive would become a
240v drive with the same amp rating (and half HP).

What am I missing?

i

It might be an interesting experiment, but since new drives up to a
couple HP are in the $200-300 range and have a warrantee it would seem
to not be worthwhile if you put some reasonable value on your time to
make the modifications and on having a drive with a warrantee operating
within it's design parameters.


I am thinking more about 40+HP drives. But the experiment has value. I
placed a few snipes on 480v VFDs and will report my findings.
Yikes! 40 PLUS Hp? Even derating it to 20 Hp, assuming no
losses, and just steady state running, would draw 15 KW, and 62
A at 240 V. If the starting surge was only 100%, that would
take it up to 124 A. You won't need much else on in your entire
house to trip the service entry breaker.

Jon

My TIG welder (I think Iggy's as well) will happily suck down 100A at
240V, and for longer than that motors startup too. I haven't had any
problems yet.

Mine draws about 60 amps.

i