300V DC Power Supply? [RE-wrenches]

[Kent Sheldon]

Sorry guys, I've been out of the office for a few days and missed most
of this thread.

It depends on what you want to do with the supply. If you are just
trying to apply control power to the inverter for communication purposes
(configuring a Windy Boy or testing RS485 communication) I suggest
building a very simple DC supply. All you need is 120:240 (isolated) 50
mVA transformer and a full-wave bridge rectifier. You should add a fuse
and perhaps some capacitance, which is not required because the inverter
has enough bridge capacitance to smooth out the ripple to almost
nothing. Total cost is around $30.

You must be careful to keep inverter from trying to start, I doubt it
would hurt anything, but you will certainly overpower the small
transformer, and may clear the fuse, if it is sized properly.

If you want to run any real power through the inverter you will need a
real supply (or build a much bigger xfmr/rectifier supply). We recommend
the HP/Agilent supplies, but they are quite spendy and you need to
series two to get to 600V. I'm reluctant to admit this, and expect this
will cause a stir, but I'll say it anyway. We (SMA) bought a Xantrex XFR
600-4 600Vdc supply, because it was in stock when we needed it, and used
240Vac (it looked good on paper). After the first run we immediately
tried to return it (you know where that got us). There seems to be a
problem with this supply sourcing another switching power supply. The
supply howls/screeches somewhere around 5kHz, to the point it gives you
headaches. The output is also totally trashed with ripple. Xantrex tech
support suggested adding a roomful (literally) of inductors and
capacitors to the DC output. They could never give me any values, and
quit returning my phone calls.

Anyway, hope this helps.

____________________________________________
Kent Sheldon
Projects Manager, Industrial Power Systems
SMA America
ksheldon at sma-america.com
530 271 1821 Office

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