Transformer for power supply for G100/G320

[jamma]

Hi there:

I've got my eye on a 1.5KVA transformer at 52Vac and 12Vac. Rectified to DC, I should get 72V @ 20A on one secondary and 17V @ 4A on the other.

The larger secondary is getting close the the G320's ratings (given voltage fluctuations, etc) - anyone see a problem here?

On the smaller secondary, would this work to power the G100?

Am I in danger of tripping my 15A breaker with this power supply? The math says 1500VA/115V = 13A, but I know mains voltage can range quite a bit. Practical experience welcomed!

Bonus question: are the popular limit switches happy with 17V?

[NC Cams]

Slow blow fuses and/or small size limit infeed wiring can help tame the inrush current problem. HOWEVER, If you pull the rated 20 amps for the one winding, you'l fry 15 amp fuses regardless of the precautions you take to the contrary.

Current draw is a function of load - your high amp transformer will not 'SHOVE' current into motors - they'll draw what the motors or downstram load draws currentwise. Check the sum of locked rotor current ratings and figure accordingly.

this might help:

CNC Dictionary
http://www.cnczone.com/forums/showth...662#post186662
http://www.thewarfields.com/MTCNCDictionary.htm

Electronics books
http://www.forrestmims.com
or
http://www.amazon.com/gp/product/pro...lance&n=283155

What gage wire to use:
http://www.cnczone.com/forums/showthread.php?t=17350
http://www.cnczone.com/forums/showth...480#post136480

Wiring practices:
http://www.a-m-c.com/download/docume...gpractices.pdf

There is no "universal limit switch voltage rating". What is/are the voltage rating(s) of the "popular limit" switch(es) that you're using?

[CJL5585]

Originally Posted by jamma Hi there: I've got my eye on a 1.5KVA transformer at 52Vac and 12Vac. Rectified to DC, I should get 72V @ 20A on one secondary and 17V @ 4A on the other. The larger secondary is getting close the the G320's ratings (given voltage fluctuations, etc) - anyone see a problem here? On the smaller secondary, would this work to power the G100? Am I in danger of tripping my 15A breaker with this power supply? The math says 1500VA/115V = 13A, but I know mains voltage can range quite a bit. Practical experience welcomed! Bonus question: are the popular limit switches happy with 17V?

You did not mention the servo's that you intend to use. Many of the surplus units on e-bay max out at some voltage a lot lower than 72 VDC. One can get the magic smoke from overvoltage on servos, and I mean only by a factor of maybe 5 to 8 volts.

If you intend to power the 5 Volt pin on the G320's or G340's from the 17 Volts DC, it will have to be regulated to 5.0 Volts. The current required by the Gecko is only about 20 milliamp per drive.

Also, if you intend to use a parallel port breakout board and run the limit switches via the board, the limits will be switching only 5 VDC logic level signals.

Most industrial type limit switches are rated at 115/240 VAC at either 15 or 20 Amps AC, so the 17 volts would not be a problem with this type limit.

[jamma]

Originally Posted by CJL5585 You did not mention the servo's that you intend to use. Many of the surplus units on e-bay max out at some voltage a lot lower than 72 VDC.

I plan on using NEMA 34 850 oz-in servos factory rated at 72V.

Originally Posted by CJL5585 If you intend to power the 5 Volt pin on the G320's or G340's from the 17 Volts DC, it will have to be regulated to 5.0 Volts.

I was hoping to run the G320s off of a 5V from the G100. Is this not possible?

Originally Posted by CJL5585 Also, if you intend to use a parallel port breakout board and run the limit switches via the board, the limits will be switching only 5 VDC logic level signals.

Was hoping to power the limit switches from the G100. I will regulate the 17VDC to 12VDC with a suitable voltage regulator and use this to power the G100. The more I think of it, though, it seems I might want to branch the 17V output via a little circuit to have both a 12VDC and 5VDC regulated source.

Originally Posted by CJL5585 Most industrial type limit switches are rated at 115/240 VAC at either 15 or 20 Amps AC, so the 17 volts would not be a problem with this type limit.

Cool. This means I might be OK running them off of the G100 @ 12V.