Can someone please explain this.......

Roland Fresitad has quite a reputation, but I am more than a bit confused on
the power supply engineering in his current article in "Home Shop
Machinist".

1)
The transformer is .5 KVA with an input voltage at 110 VAC. This would
suggest a continuous current rating of 4.5 amps. I would think that a slow
blow fuse ( 5A or 6A) would be needed to account for cap inrush, but a
continuous rating on the fuse should not exceed the continuous rating of the
transformer. His article prescribes a 10A fuse.

2)
The output rating of the transformer is stated as 64 VAC at 8A, consistent
with 0.5 KVA. With the 1.414 factor to DC, this puts the DC supply at 90
volts. Hello? Isn't the Gecko rated to 80 volts? Any back EMF on
deceleration will take it even further. A rapid stop on this machine could
drive it over 100 V if there is much mass moving around. I realize that,
with such an undersized transformer, the voltage will sag when drives are
moving, but it still gets back up there when there is no current being
sucked up.

3)
The dropping cap is listed as 500K Ohm. Maybe I did my calculations wrong,
but that looks like it will drop the cap from 90 volts in 11 hours. I would
think 60 seconds would be a nicer number to go for.

4)
There are 3 drives in the system show, each rated to 7 A. While they will
be current limited through induction at high speed and go into current fold
back when at rest, there are actually times when all three drives will be
operating at 7 A. Even if the DC bus is at a reduced voltage due to the
limits of the transformer, we're still talking about at least 1500 watts DC
being delivered through a 0.5 KVA transformer.

These are questions, not necessarily criticisms. I know Roland has lots of
operating machines out in the field so I would think he knows how to do
this. Never the less, the details here do challenge my understanding of
power supply design. Can anyone enlighten me?

G. Jackson