On Aug 15, 9:57 pm, "azotic" wrote:
"Carl" wrote in message

...



On Aug 15, 6:19 am, "azotic" wrote:
Just in case anyone is intrested, here are some pix of my 100 amp DIY
VFD
being
assembled. As soon as time permits i will post a video of the VFD in
opperation.
I still have to make a remote control pannel.

http://members.cox.net/azotic/inv1.j...x.net/azotic/i...

Best Regards
Tom.

Just wondering, does the little bridge rectifier on the lower right of
picture inv6 provide the power to the much larger switching elements
on the heat sink. Is the large white cylinder in the last couple of
pics the rectified DC filter cap? What do you calculate the ripple
current in the DC filter cap to be?

Carl

The output of the bridge rectifier is connected directley to the large white
filter cap ( 2700uF @ 420Vdc ). I didnt do any ripple calculations for
the HV dc buss since motors and transformers dont seem to have problem
with ripple. However there are seperate regulated power supplies for the
logic and gate drivers where ripple would be a huge problem. The large
white filter capacitor at the end of the buss just happened to have the
same center to center hole spacing as the GTRs which makes it possible
to mount it right on the buss bars and eliminate the additional wiring that
would be needed if i had to mount it elsewhere.

Best Regards
Tom.


Filter Caps do have a problem with ripple currents. You should also
consider stored energy in the motor magnetics (1/2 * I * I * L)
versus the capacitor (1/2 * V * V *C). Inductive kickback into the
supply caps in a PWM system can cause some really spectacular
capacitor failures. I highly recommend you have that cap in a stout
box before you test at more than an amp or 2. If the cap blows you
will be releasing 500+ joules explosively.

I think your rectifier bridge looks too small for the rest of the
circuit.

Best of luck
Carl