Re: [CAD_CAM_EDM_DRO] Re: Power Supply

--- Ron K <godsone@...> wrote:

>

There is something I read that is very important to
the point of running stepper motors at current levels
above there rating.

What I read says that every time the current level
exceeds the rated level it has the effect of
demagnitizing the motor,deterorating the torque that
the motor is capible of.

I can't say that this is true for all motors or at
all, but I read it. If there is a magnet inside the
motor it makes sence.

Larry Wright

>
> ballendo wrote:
>
> >Hello,
> >
> >Didn't see this mentioned yet...
> >
> >WHY are you running 6.1 amp motors at 7 amps???
> >
> Because on 6 amps the motors never warmed up at all
> .
> With them set at 7 they will come up to just
> slightly warm but defiantly
> not hot during a long run ( 1 or 2 hours )
> and the Geckos also run very cool .
>
> > Do yourself and the
> >motors a favor and get the resistors in the geckos
> to limit the
> >current to the rated value. Unless you feel your
> motor design skills
> >exceed those of the mfr... (Would you exceed
> redline of your
> >automobile engine "for months"???)
> >
> >The side benefits will include longer motor life,
> cooler operation,
> >and smoother motor rotation. Excess amps might help
> an ego, but not a
> >motor.
> >
> >Next, motors are BOTH motor and generator anytime
> they are turning...
> >
> >Factor in what the turning motor is adding to the
> supply for
> >the "other" motors to use and you might have
> another part of your
> >answer
> >
> >Hope this helps,
> >
> >Ballendo
> >
> >
> >
> >--- In CAD_CAM_EDM_DRO@yahoogroups.com, Ron K
> <godsone@e...> wrote:
> >
> >
> >>caudlet wrote:
> >>
> >>
> >>
> >>>SNIP
> >>>
> >>>
> >>>
> >>>>In reality the 5amp fuse was a mistake I thought
> I had put in a
> >>>>
> >>>>
> >>>>
> >>>>
> >>>10amp but the system has been running like this
> for several
> >>>
> >>>
> >months .
> >
> >
> >>>
> >>>
> >>>
> >>>
> >>>>--
> >>>>Ron Kline
> >>>>
> >>>>American Precision Ceramics
> >>>>
> >>>>
> >>>>
> >>>>
> >>>Ron what you are seeing is reality vs theory.
> There are a lot of
> >>>factors that may be at work here. The motors
> Average current
> >>>
> >>>
> >which
> >
> >
> >>>is the Gecko 7 A limit times the duty factor is
> evidently a lot
> >>>
> >>>
> >less
> >
> >
> >>>than the nameplate rating. If a motor only needs
> 20% of the pulse
> >>>width to move the load then the AVERAGE current
> over time is only
> >>>20%. Since things like transformers and fuses can
> withstand short
> >>>periods of 100% overloads the 5A fuse could
> easily handle 10A at
> >>>
> >>>
> >50%
> >
> >
> >>>duty cycle.
> >>>
> >>>The only real way to test is put a DC ammeter in
> the DC line in
> >>>series with the load and do some measurements. A
> current probe on
> >>>
> >>>
> >a
> >
> >
> >>>scope would give you the real picture from a
> dynamic perspective.
> >>>
> >>>
> >You
> >
> >
> >>>might be surprised to see how much less the
> current draw is on
> >>>average than you would calculate from the motor
> specs.
> >>>
> >>>If you run mostly two axis moves then two motors
> would probably
> >>>
> >>>
> >only
> >
> >
> >>>draw 8 to 10 amps worst case. Sounds like you
> are not running the
> >>>motors anywhere near their max limits.
> >>>
> >>>Another good indicator is that things are
> probably not running
> >>>
> >>>
> >hot:
> >
> >
> >>>motors, power supply, etc are warm but not too
> hot to leave you
> >>>
> >>>
> >hand
> >
> >
> >>>on I would guess.
> >>>
> >>>Take it as good news and don't worry about it too
> much. The only
> >>>true way to design a power supply is to have the
> actual load in
> >>>
> >>>
> >the
> >
> >
> >>>actual conditions it runs in to measure then do
> the calculations.
> >>>Taking numbers off components and adding them all
> up will only get
> >>>you in the ballpark parking lot. We all tend to
> overdesign the
> >>>
> >>>
> >power
> >
> >
> >>>supply because of the fear of putting a lot of
> time and effort
> >>>
> >>>
> >into
> >
> >
> >>>something that ends up being too small and to
> combat Murphy's Law.
> >>>
> >>>The good news is that your power supply will last
> a long time.
> >>>
> >>>
> >>>
> >>>
> >>>
> >> Now that is an explination I can understand
>

=== message truncated ===


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