Re: [CAD_CAM_EDM_DRO] Re: Power Supply

I'm noty sure of the specifics but I think the demanitization problem is
the result of heat. Of course current is directly related to that.
I know a very long time ago one manufacture had us checking heat on a
problem installation.

It would seem to me that current and the magnetic field it generates
would have a tendency to do the opposite. That is magnitize the
PM's. On the other hand a quickly changing magnetic field is often
used to demagnitize things so this might be a issue as well.

DAve

Larry Wright wrote:

>--- 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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