Q for Mariss (was Re: Here's my proposed power supply setup.)

Hi Mariss,

I'm currently building my 4 axis power supply and would prefer to do
it right the first time.
I'm assuming fuses or circuit breakers are placed between the power
supply main filter capacitor and each individual motor driver as
Lloyd mentioned in his setup.
A while back there was a discussion about disconnecting motors while
powered up and the back EMF generated by the collapsing magnetic
field in the motor would damage the driver. So what happens when a
fuse blows on the driver's supply side?
Do you have any general guidelines for placement and sizing of fuses
or CB's in our stepper power supplies? What if the main capacitor
breaks down and shorts? Should the primary or secondary sides of the
transformer have fuse or CB protection that would kick in before my
garage's 20A CB does?

X,Y,Z steppers are 3.5 V 5A 650oz/in. No 4th axis yet.
Transformer is 700VA Plitron toroid 50VAC @14A output. Should be
around 70VDC after bridge.
Bridge rectifier is 25A 600PIV.
Surplus capacitor is rated 56,000uF 80VDC. Kinda big I guess after
seeing your calc but the higher voltage ones are harder to find and
the price was right.
Drivers are APC CMD260's (Sorry, got 'em cheap)

Thanks,
Ralph Wenzl