Re: [CAD_CAM_EDM_DRO] Cap at the Gecko, motor heating, fuse protection??

Hi Ron,

Switching drives act like a sort of transformer. If the motor is
stalled the drive will supply full current at a low voltage. It will
only draw a small amount of current from the supply to do this.

Say the motor is stalled and the Gecko is supplying 20A at 10V. This
equates to 200W. Ignoring other losses it will draw roughly
(200/60)=3.3A from a 60V supply. At high speed and high acceleration the
Gecko could be supplying something like 50V at 15A, equating to 750W. It
would then draw (750/60)= 12.5A from the supply.

Les


R Rogers wrote:

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>Hi All,
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>Just recently I got around to installing the 100volt 1000 uf caps at the Geckos. Today I was drilling .860" holes 3" deep with a pre-drilled pilot in steel and normally the Z motor will heat considerably but not excessively. Since I installed the caps at the drives the Z motor seems to run alot cooler. Is this possible? Usually in an hour of two of drilling with heavy loads the Z motor is up to temp, today it was like 4 or 5 hours continual drilling before it got that warm. The Z gecko seems to stay cooler too.
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>Also, I've asked this before about the fuse in between the power supply and the gecko. And the concensus was that If an axis stalled the fuse would not blow as the current would be isolated between the drive and the servo, if I understood correctly. Wouldn't this only be possible if the encoder was dead stopped and on only one count where the stall occured? Seems that if it stalled on one count and than made it to the next that the current would then be imposed on the circuitry coming to the drive and hence blow the protective fuse. If they dont blow why do some people say we need them? I read that Les had one fail today but it was only a 2amp that he forgot to replace after testing.
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>I've got 1280 .860" holes 3"deep to drill then ream to .875 and it would be nice to know what is going to fry if the bit stalls and I dont catch it in time. :-)
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>Ron
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