Re: DC Motor

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

Thanks. This is a cheap (~$500) winch, so I suspect
the motor is, and the PSU was, as cheap as possible. I
wired it up to my rectifier and wired up the
forward/reverse switch. (I got a box of loose parts
with everything disassembled and the PSU missing.) I
had forgotten that I had an old version of Electronic
WorkBench. I drew up several circuits in Electronic
WorkBench and it looked like a cap in the range of 200
to 500 would eliminate most ripple. So I went to my
shop and wired up several caps and measured DC and AC,
with no load. After playing a bit, I decided to just
try the motor, to be sure I had the polarity right on
the forward/reverse switch. After running the motor
forward and reverse several cycles, it tripped my 30
amp breaker. I fried my 400 volt 10 amp rectifier.
Upon closer inspection, the motor can't be used
without the winch, as the winch gearbox is one of the
motor's endcaps. I think there may be a bad gear in
the gearbox, which may have been what blew the
original PSU.

I'm abandoning this project.
Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: FIFTYGUY@xxxxxxx
>
> In a message dated 4/15/06 5:12:29 PM Eastern
> Daylight Time,
> tesla@xxxxxxxxxx writes:
>
>  >What is the max current the motor will draw is the
>  >question. Tip, there is a lot of high power three
> phase stuff out there that
>  >should work fine with single phase. Maybe someone
> wants to do the ripple
>  >math and come up with a capacitance
> recommendation?
>
>      Industrial DC motors are rated for the "form
> factor" of the
> ripple of the DC they are run off. For a larger
> fractional horsepower
> motor, there's usually a rating on the nameplate.
> NEMA codes
> representing the number of "pulses" from a rectified
> power supply are
> used instead of the true "form factor".
>
>      A battery, DC generator, or 12 pulse/six phase
> power supply has
> a NEMA code "A".
>      A 3-phase, six SCR full converter power supply
> with a
> mathematical form factor of 1.01 is code "C".
>      A 3-phase, three SCR/three diode half converter
> power supply
> with form factor of 1.05 is code "D".
>      A 3-phase, 3-pulse, 1/2 wave power supply with
> form factor of
> 1.20 is code "E".
>      A single-phase two SCR/two diode half converter
> power supply
> with form factor 1.35 is code "K".
>
>      How important is this? Compared to a code "A"
> power supply, a
> code "C" creates 2% extra heating, code "D" 10%,
> code "E" 44%, and
> crummy code "K" 82%.
>
>      NEMA designates powers supplies by a long
> designation, of the type:
>
>      Total pulses per cycle "/" Total controlled
> pulses per cycle,
> Freewheeling (if a freewheeling diode is used) "-"
> Nominal AC voltage
> into rectifier (line-to-line) "-" Line frequency "-"
> External
> inductance to be added in series to armature (in
> milliHenries).
>
>      So in some instances an external "Load reactor"
> is part of the
> design, essentially the "filter choke" to smooth
> ripple.
>
>      Just some things to consider. It pretty much
> boils down to the
> better filtered the DC is gong into your motor, the
> happier it will be.
>
> -Phil LaBudde
>
>
>