I'm seeking some guidance for the design of a PWM amplifier noise filter
for a 180v 1/2 hp DC motor that drives a ring rotator. My googling
turns up a lot of information for 3 phase VFD filters but little for DC
motor applications, so I'm hoping there is some experience/expertise
among towertalkians.
The PWM amp is a commercial Minarik 16Khz switch and drives the motor
via twisted pair. The amp is in a RFI gasketed Hoffman steel enclosure
and I have a Corcom 20a/240v line filter on the AC source. However, I
have hash everywhere and S9 noise on a separate tower 20m antenna. The
overwhelming source is the PWM amp, not motor brush hash. The box is
grounded to the tower master ground plate.
I think a DC filter design is similar that of AC line filters, a equal
current forcing/common mode balun followed by capacitors followed by an
L-C filter in each leg. My major question is about the practical
parameters of a balun in this application. A high perm toroid seems a
likely choice for a parallel L1-L2 balanced winding. I have some
FT-193-JA cores, u=5000 and the question is what assumptions/parameters
govern the balun winding design? For the L in the L-C section, high
current toroid inductors are widely available (e.g 50uH @ 10amps).
Any links to references would be appreciated.
Grant KZ1W
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|