Haas CNC machine sizing Help

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PowerdT

Senior Member
Location
San Diego
Occupation
Electrical Engineer
Hi everyone,

In advance, I would Like to thank everyone in this forum for all the supports and educations it provides.

I have two CNC machines that I am trying to size and I would like a help on confirming if I size correctly.

CNC machine 1 name plate:
Voltage: 220Vac
Phase: 3
Full load: 70A
Largest load: 65A

Spec says I can use voltage between 195-260V
So I will use 208V since I have a 120/208V panel in the shop.

220V*1.73*70*1.25 = 33341 VA, then 33341/1.73*208 = 92.5A Per 240.6 the ocp will be 100A And the conductor size (1) #3AWG+(1)#8AWG cu at 75 degree C

CNC machine 2 Name plate
Voltage: 208/240V
Phase: 3/1
Full load: 25/40A
Largest load: 25A

Again, I will be using 120/208V panel so
208V*1.73*25*1.25 = 11245 VA, then,
11245/208*1.73 = 31.2A per 240.6 the ocp will be 40A and the conductor size (1)#10AWG+#(1)#10AWG cu at 75 degree C

Thank you again.
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
My opinion is that you go off the name plate current. It's probably already sized for the lowest acceptable voltage. Otherwise you would have to calculate the total VA at the nameplate voltage and then calculate what the actual current is at the actual voltage from that number. That would kind of make the name plate superfluous.
 
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PowerdT

Senior Member
Location
San Diego
Occupation
Electrical Engineer
petersonra said:
My opinion is that you go off the name plate current. It's probably already sized for the lowest acceptable voltage. Otherwise you would have to calculate the total VA at the nameplate voltage and then calculate what the actual current is at the actual voltage from that number. That would kind of make the name plate superfluous.
Click to expand...
Are you referring for the CNC machine 1?
 
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gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
201001-2017 EDT

Etanuye:

Read the HAAS manual and do what they recommend.

More important than anything else is that you properly adjust the HAAS taps for the voltage you actually operate at. At my son's place we have 6 HAAS machines. all rated at 20 HP, and a few others with fair size motors. These run from a 240 V wild leg open delta with a 200 A main panel. More than 200 ft of 000 copper from the two pole transformers.

For most CNC machines average power used is way below peak rating.

Most important is DC bus voltage. Low voltage will trip out when low. High voltage will trip on high. These machines use dynamic breaking, and most do not have regrenerative transfer of energy to the mains. This means DC bus voltage rises on braking, and above a level dumps to resistors. Too much power to the resistors, and you get trip out. Lathes have a lot of inertia, and this is a bigger problem for them. Type of machine cycle, shape of part being made, has a major effect.

.

.
 
R

retirede

Senior Member
Location
Illinois
Gar covered it nicely.

I’ll add that since the nameplate gives you amps, you don’t need to recalculate using your voltage. Just use what is given.
 
P

PowerdT

Senior Member
Location
San Diego
Occupation
Electrical Engineer
gar said:
201001-2017 EDT

Etanuye:

Read the HAAS manual and do what they recommend.

More important than anything else is that you properly adjust the HAAS taps for the voltage you actually operate at. At my son's place we have 6 HAAS machines. all rated at 20 HP, and a few others with fair size motors. These run from a 240 V wild leg open delta with a 200 A main panel. More than 200 ft of 000 copper from the two pole transformers.

For most CNC machines average power used is way below peak rating.

Most important is DC bus voltage. Low voltage will trip out when low. High voltage will trip on high. These machines use dynamic breaking, and most do not have regrenerative transfer of energy to the mains. This means DC bus voltage rises on braking, and above a level dumps to resistors. Too much power to the resistors, and you get trip out. Lathes have a lot of inertia, and this is a bigger problem for them. Type of machine cycle, shape of part being made, has a major effect.

.

.
Click to expand...
Thank you.
 
P

PowerdT

Senior Member
Location
San Diego
Occupation
Electrical Engineer
retirede said:
Gar covered it nicely.

I’ll add that since the nameplate gives you amps, you don’t need to recalculate using your voltage. Just use what is given.
Click to expand...
When you say use what is given. Should I get step up transformer since I only have 208V?
 
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