On 10/21/2013 03:00 PM, Dave Cole wrote:
> The 24 volt transformers are called commonly called Buck/Boost transformers.
>
> Oftentimes used to boost 208 to 240 volts or buck 240 down to 208..
>
> http://en.wikipedia.org/wiki/Buck%E2%80%93boost_transformer
>
> Dave
... snip

Well the proof is in the putting.
http://www.wallacecompany.com/tmp/img_1475-1a.jpg

The transformer is rated 120VAC to 12@6A or 24@3A. I wired it to buck at 
12V and got 300VDC on the Delon, which is the setup in the picture. The 
AC setting on the multimeter showed 2V, so there isn't much ripple. I 
also wired it to buck at 24V and got 280VDC. The VFD is a Mitsubishi 
U120 240VAC 400Watt unit. It is running a coolant pump at 60Hz here. The 
AC setting on the multimeter showed 2V, so there isn't much ripple. No 
drama, heat or noises on any of the bits.

For fun, I wired this setup to boost at 24V and got 420VDC, which 
powered up my 440VAC VFD.  I didn't run the motor because the VFD needed 
programming to run from the front panel.

So, if one has a 240VAC VFD and only a 120VAC source, this might be a 
valid setup.
-- 
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/

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