1340gt and 30mv wiring

[joeblow65]

Hey guys, I ordered a 30MV and 1340GT a month or so ago and they wont be here until Nov and Feb respectively. I had initially planned on using a single 30A breaker to power them both but I forgot to factor in motor starting amps and stepper amps. I'm converting the mill to CNC so it is conceivable that both machines will be running at the same time and I'm coming to realize it would be better to run them on separate breakers but I wanted to verify my math and thinking is correct with people much more experienced than I. I'm running a 100A subpanel for the whole garage.

The mill calls for 15A min in the manual, I'm running Nema34 steppers 7A max draw so by my math I need 36A. I understand the machine and steppers wont pull max amps all the time but if I size it so it can hold that I wont get any nasty surprise shutdowns.

The lathe calls for 9A for 3ph but I'm adding a VFD and I have no idea what that will do for the amp draw. PM said they used to recommend the hitachi WJ200-0015SF but no longer officially sell or recommend what VFDs to use.

So I think I settled on a 40A breaker for the mill and 15A breaker for the lathe and I'm looking for recommendations for a VFD for the lathe. Does all that sound appropriate or overbuilt?

 

[mksj]

Recommended breaker size for the WJ200-015SF is 30A, but it will also run on a 20A @240VCA. The 30MV they recommend a 20A @240VAC, the Nema drive 7A is DC volts probably at 40-50V, so maybe 300-400W peak, not at 240VAC. A 30A breaker at 240VAC ~7.2kW is more than sufficient to power everything. If using both at the same time, I would use a separate breaker for each machine.

 

[joeblow65]

Recommended breaker size for the WJ200-015SF is 30A, but it will also run on a 20A @240VCA. The 30MV they recommend a 20A @240VAC, the Nema drive 7A is DC volts probably at 40-50V, so maybe 300-400W peak, not at 240VAC. A 30A breaker at 240VAC ~7.2kW is more than sufficient to power everything. If using both at the same time, I would use a separate breaker for each machine.

I was just browsing through the forum and stumbled onto your amazing VFD and electrical knowledge. Are you still making VFD kits or just plans? Thank you for the info, I'm using CL86Y drivers and E series 9nm steppers which I see now is 6A rms and I don't know the voltage the stepper uses. I can find a rated current of 6A but no input voltage. This knowledge is exactly why I came, Thank you for such a quick response. 30A for mill and ill oversize to a 30A for the lathe for the recommended VFD. Its all new wiring so its easy to change right now.

 

[Ischgl99]

You’re going to want to run your idea of using one breaker for both machines by your building inspector. To stay within code, each machine needs its own circuit unless your 30 amp breaker is feeding a panel with breakers/fuses sized for each lathe and mill VFD.

The inrush current with a VFD is lower than direct on line when motors start, so you can size the feeder breaker for the VFD input current times 125%, there is no need to oversize it more than that. For example, if the VFD input current is 23 amps, you would need wiring and breakers sized for at least 28.75 amps.

 

[B2]

The concepts of Mark's comments about the current required for the stepper is on target. These Amps are not at the line voltage so do not add directly to determine the breaker requirements. What you want to look up is how much "power" the drivers require from their supply not the current. But what you really want to know is how much power the driver power supplies require from the line. Line power to a the driver power supply, which is converted to DC at a different voltage for going to the drivers or steppers. Each (power supply, drivers, motors) wastes some power at the conversions as they are not 100% efficient. Power = Voltage * Current.

My PM940M-CNC mill has a 1.5KW motor (2HP, 3 phase) and similar steppers and I wired it all up on one 220Vac 30Amp breaker. It meets code, the machine specs. It came with a Delta VFD.

My PM1440GT lathe has a 3HP 3 phase motor. It is wired at 30Amp 220Vac as well, but it is not CNC.

So I use a subpanel to hold these breakers. I put in a 125Amp 220Vac breaker in my main box, and ran this to a subpanel which was rated at as much as 200Amp 220. In this I installed multiple breakers two of which were for my lathe and Mill. The rest of the space is used for other circuits in the shop as well as for future projects.... TBD.

Also, I used the Hitachi WJ200-022SF VFD for the conversion on my PM1440GT 3phase 3HP machine and it is nice. Lots of features. Lots of documentation which is needed. You can check, but I think the 0015SF is in the same family with similar features. www.wolfautomation.com says they have them in stock, but I would call before I sent them money. There has been a supply problem. There are apparently some similar model numbers that are not quite the same device. (Mark pointed out that some of these do not even have a heat sink built attached)

Here is the post for my lathe VFD build. Somewhat different approach from others described on HM and some different features. Because of my approach its over all size is smaller and I could get it into my lathe stand rather than having a separate box from the lathe.

VFD conversion via solid state electronic components. PM1440GT, VFD, 3-phase

VFD conversion using solid state electronic components. I finally finished documenting my PM1440GT lathe VFD conversion and want share it. It took me longer to write this up than it did to actually build the new electronics! (Are these sorts of things every really finished?) I apologize...

www.hobby-machinist.com

Dave