Burned out drives

FYI,

For all those reading about or experiencing burned out drives, the problems
as related, reveals several issues.

1.) Just because a drive is rated to 80 volts does not mean that you should
run it there. The rating usually comes from the max rating of the
transistors being used. As an electronics designer I will never push a
device past 1/2 of the max rating just to give some reasonable margin to
the operation. Anything beyond the 80 volts is beyond the SOA (safe area of
operation, read the data sheets).

2.) Everyone running 48 volts is doing the right thing. With chopper drives
you can achieve the current required through the stepper windings without
resorting to max voltage.

3.) By running something like 48 volts then one can incorporate an active
power dump on the power supply, by using a comparitor and setting it to say
60 volts, the fet being controlled by the comparator can be turned on to
dump extra power into a power resistor anytime the power supply voltage
goes above 60 volts. Thus feed back power and spikes will not be a problem.

If someone needs an active power dump device, send me an e-mail message off
the list.

Sincerely,
Ron
ronaldsa@...

www.bsio.us