120 or 240 Power

[DLAM]

Should there be a dedicate 120 volts circuit brought into the cabinet or is alright to tap off a leg of 240 Volt line once downstream the disconnect? I have a lathe that is going to have 5 hp 3 phase spindle motor ran by a GS4-2015 VFD (15hp), DMM DYN4 drives with AC servos on the 240 side. The computer, Monitor, ACORN, fans and power supply for Misc items on the 120 Volt side.
I am thinking the 240 volt items (especially the spindle motor) could cause transients or am I being too paranoid.
I tried looking up the topic but couldn't find anything.
Thank You

DLAM

[Dave_C]

Should there be a dedicate 120 volts circuit brought into the cabinet or is alright to tap off a leg of 240 Volt line once downstream the disconnect? I have a lathe that is going to have 5 hp 3 phase spindle motor ran by a GS4-2015 VFD (15hp), DMM DYN4 drives with AC servos on the 240 side. The computer, Monitor, ACORN, fans and power supply for Misc items on the 120 Volt side.
I am thinking the 240 volt items (especially the spindle motor) could cause transients or am I being too paranoid.
I tried looking up the topic but couldn't find anything.

The way I solved this was to use 220/240 volt power to the 24 volt power supply that feeds the acorn board, bought 240 volt fans instead of 24 volt or 120 volt, and a toroid PS that could run off of 240 as well.

I then run the computer off of a wall outlet but my computer and monitor are on a wheeled stand that rolls around.

So no need for 120 volts power in the control cabinet if you do all that.

Noise? The VFD drive can cause a lot of issues! It is important to use the proper cabling that is designated for drive use, not just any old 3 or 4 wire from one of the home supply places. Automation Direct sells a good drive cable, they will cut it to length and it is not expensive!

Older drives seem to cause more issues with EMI than some of the newer ones but it all depends on how they are set up and tuned, proximity to other items and so on.

Dave C.

[deanq]

At least two ways to handle this.
1. Bring in a neutral with the two power and ground lines.
or
2. Use a 240/120 transformer in the cabinet.

Bringing in a neutral line has always seemed easier/cleaner to me. YMMV JMHO

[slodat]

Most modern computer power supplies are dual voltage and will work just fine with 240v.

[tblough]

The problem with bringing in neutral with the 240V hots and ground is you need to maintain balance on the two hot legs. I wouldn't go more than a couple of amps higher on one leg than the other as it can cause problems with the double pole breaker in the breaker box. I needed 240 for my spindle and 120 for my drives so I ended up with a 2KVA 240/120 transformer which left enough to run all my other ancillary 120V items.

If your spindle and drives are 240V, the best solution so far is to run your accessories from a 24VDC switch mode supply, and run your computer at 240VAC. As previously mentioned just about all switch mode power supplies in computers these days are 90-240VAC. If you pay attention to grounding, you should not have any noise problems.

[deanq]

The problem with bringing in neutral with the 240V hots and ground is you need to maintain balance on the two hot legs. I wouldn't go more than a couple of amps higher on one leg than the other as it can cause problems with the double pole breaker in the breaker box.

Balance on a 240VAC feed is relative. It would take a very large load (many amps) to make a difference.You just don't want to overload one side to the max. As for the 2 pole breaker, unless your using a GFI (and you SHOULD NOT) there won't be any issues.
Your talking about a computer and some fans right? Regardless, it won't make a difference.