Re: [CAD_CAM_EDM_DRO] Where to buy non induction resistors

lenskeeper2000 wrote:

> Where can I buy non-induction power resistors? I'm using a simple
> L/R style drive circuit and want to step up my voltage but have found
> I have too much inductance to get my speed rate up. I'l thinking if
> I can reduce the effect of the wire wond reisitor's im using this
> will help.

I seriously doubt it. Think about it - an iron core increases the
inductance of a coil thousands of times. The resistor has no iron
core and the windings are spread out in space. The motor has an
iron core, and the windings are wound as tightly together as they
can. The motor has VASTLY more inductance than the resistor.

Secondly, if you use the common circuit with a resistor from the power
supply to the center tap of each winding, and the transistors grounding
one end of each winding, the current is always going the same way
in the power resistor, so the inductance has even less effect.

> I've seem lots of power resistors for sale (allied etc.) but none
> seem to be non inducting. Looking for 25 watt in the 20-25 hom
> range. Any suggestions?

They are available, but probably not from Allied. I have gotten some
3 W non-inductive resistors for current sensing from Newark, but
I don't think they have them in the 25 W size, either.

R/L drives are really poor performers unless you use HUGE resistors
and high voltages, then the power loss is also huge!

Jon