Re: [CAD_CAM_EDM_DRO] 220 Voltage To Feed Machine Motor and CNC Drives

Hi Jon,

Unfortunately SJ100-022NFU 3HP drive doesn't use just a braking
resistor. They call it a braking resistor but it has additional stuff
in it. On Automation Direct's website, it is priced at $265.00 - rather
a lot for a 50 ohm 300W resistor! I have this same drive and tried a 50
ohm 250W power resistor I had and in seconds of powering it up, smoke
started coming out of the drive - it still works fine, however... That
was when AD's tech support told me that it won't work on just a 50 ohm
resistor - I assume the switch transistor is in the Braking Unit.

I've since swapped the SJ100 to a smaller machine and purchased a
GS2-23P0 drive (AD's in house brand) which does use just any old power
resistor of the correct resistance and power. I have also found that
even with rapid stop start cycles the braking resistor only gets warm to
the touch, maybe 15-20 degrees above ambient.

Cheers, Peter


Jon Elson wrote:

>Peter Renolds wrote:
>
>
>
>>Hi Dave,
>>
>>You'll be very happy with the SJ100 - except if you want to decelereate
>>the spindle quickly. The braking unit is expensive.
>>
>>
>>
>Braking resistors are really not that bad, unless you insist on a totally
>UL-rated setup. I use ordinary 100 W wirewound Vitreous enamel
>resistors that are available on the surplus market. I think the VFD would
>burn out before I could get these resistors hot from rapid start/stop
>cycles. Nearly all VFDs have the switch transistor for the braking resistor
>built in.
>
>
>
>