New day new problem

the hypertherm seems to have contacts that are rated at 120v AC / 1A.....

there is no need for 240mA of current flow to provide a wetting current.
if the relay is rated at 1A, then the wetting current will be LESS than 1mA

it's just to break the oxide layer, and is only applicable to open relays..... if they are sealed (such as a reed relay) then no wetting current is applicable given no oxide layer will form as their is no humidity for it to form.

I'll pull the cover off my pmx 45 later as I am curious what relay they have used as I'd expect it to be a quality relay..


using too much current will shorten the life span in my opinion than using just enough (above the minimum)

I tend to use Fujitsu relays personally as the data sheets are comprehensive.... TE / omron seem to kindly miss the minimum current rating .... Fujitsu clearly publish iteh 2A relay.... minimum current 0.01mA (ie  200 000 times less than the rated current)
www.google.com/url?sa=t&source=web&rct=j...zjjsvHT914D46NTBXYNC

some have a minimum current of 5000 times less than the rating 5A .... minimum 1mA

I am not saying it is a non issue.. just less of an issue than what is being portrayed..... 

I always try to design for a 10mA at 24v signal current especially when their is potential for inductance about from other sources (plasma start signals ).... I also try to use quality relays (Fujitsu or coto [reed relays])

I "think" the HT relay quoted 100mA @ 5V so roughly 21mA @ 24V

It is somewhere on the forum...

I am only aware of the bit in the operator manuals 120v AC / 1A

The relay part number is in this post:

forum.linuxcnc.org/plasmac/39929-random-...lost?start=70#180876 

this is from my hypertherm powermax 45 (non XP).... surprised they did not use a better relay.... (faster + sealed)

TE T77S1D10-24
 


www.google.com/url?sa=t&source=web&rct=j...R2FFH8C10rLl-7avOTn1
www.google.com/url?sa=t&source=web&rct=j...QwAYWjZUUS8oF8MhKnd5
min recommended = 100mA @ 5V (0.5W)

so, at 24v => 0.5 / 24 = ~ 21mA

again... surprised they did not choose a better relay.... (360 operations per hour (for an arc transfer relay on a plasma cutter) 10msec operate and 4msec release time)

Min. recommended contact load ---- 100mA at 5VDC
Frequency of operation ---- 360 ops./h
Operate/release time max. 10ms/4ms
 

I did ask Tom (the OP) to see if he can provide some logs maybe showing:
the arc OK / transfer input pin
the torch fire output pina motion pinthe plasma cutter voltage inputthe z axis machine DRO (not sure how that will read with out of bounds motion).... but if the thc is responding too fast / course or too slow and fine...  it may be loosing the arc in height
is there a way that you could setup a long term logging file as the issue seems intermittent

Ok here is the word from the shop. I changed the voltage divider in the hypertherm to 20:1 and the Arc Voltage Scale in the QTPlasmaC.prefs file and bumped up the debounce to 7 (was 5). Ran test cuts fine only arc lost was cutting over an open space in the metal.DUH. I could not get a good image of the relay on the PM65, (middle image).  Cut the wrench but dimensions are off need to redo the steps per.  
thanks again
Tom