Re: [CAD_CAM_EDM_DRO] Re: Power Supply

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
>>
>>Thanks
>>
>>--
>>Ron Kline
>>
>>American Precision Ceramics
>>
>>
>>
>>[Non-text portions of this message have been removed]
>>
>>
>
>
>
>
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--
Ron Kline

American Precision Ceramics



[Non-text portions of this message have been removed]