Need Help!- calculating rc snubber

[xinzc28]

I'm building stepper driver using L297+L6203.
since the snubber circuit on L6203 datasheet seem not operate very well, I need to redesign it. I found an application note with snubber formula.

my stepper motor current rate is 3 amp.
my power supply is 24volt.
my chopper rate is 25880 Hz (~26 Khz)

1st equation: (done)
Rmax = Vs min / I peak = 22.5 / 3 = 7.5 ohm

2nd equation:
C = I peak * dt/dv --> how to determine my dt & dv ???

3rd equation:
Pd = (I1 * I1 * R * DC) + (I2 * I2 * R * DC)
I1 = current at turn on
I2 = current at turn off
R = snubber resistor (7.5 ohm)
DC = duty cycle of current flow
how can i determine I1, I2 and DC ???

[MJLFR]

Hi,

Snubber bible is here :
http://www.cde.com/tech/design.pdf
http://www.cde.com/catalogs/igbtAPPguide.pdf

The most important is to use MICA or POLYPROPYLENE capacitors forget ceramic or tantalum.

Have fun,
MJLFR

[xinzc28]

great link!

is Metallized polypropylene film capacitor (MKP) also count?

[chepot]

on L6203's datasheet C= Ip / (dV/dt)