3 Phase for CNC

[River Runner]

Good day,

I’m looking to put a deposit on a CNC stone saw. I am in a rural area and do not have practical access to 3 phase power.

The machine in question has requirements for 480v 3 phase 60hz and 35.7 amps at full load.

The machine comes with a step up transformer to take 208v to 480v. From what I can tell I will need an 80 horse rotary phase converter with a single phase 175 amp circuit to power the RPC.

I only have a 200 amp service to the shop, but I could potentially have a new 400 amp service brought in. I’d obviously need more than the 200 amp service to power the other necessities of the building at the same time.

But, instead of paying for another service I’ve thought about using that money for a 3phase commercial generator. I’ve talked to a few electricians here about this but I mostly get some head scratching as they don’t do much complex or commercial work.

Thoughts from any experienced electricians?

 

[nadogail]

Are you on an agricultural property? If you are you may be able to get your utility to provide 3 phase power for a future well pump.

 

[River Runner]

Are you on an agricultural property? If you are you may be able to get your utility to provide 3 phase power for a future well pump.

Technically 3.5 acres is considered agricultural for tax purposes and the county. But, 3 phase is about 1/2 mile away. They would do it but the cost would be enormous.

 

[wyliesdiesels]

Good day,

I’m looking to put a deposit on a CNC stone saw. I am in a rural area and do not have practical access to 3 phase power.

The machine in question has requirements for 480v 3 phase 60hz and 35.7 amps at full load.

what is the HP rating on the motor? 30hp? Amps is not the factor to look at....

The machine comes with a step up transformer to take 208v to 480v.

the 208v X 480v transformer isnt gonna work since your service is 120/240v...

Can you post a pic of the motor nameplate? it may be able to be rewired to 240v so you dont have to use a transformer.

or what is the make and model of the saw?

From what I can tell I will need an 80 horse rotary phase converter with a single phase 175 amp circuit to power the RPC.

I only have a 200 amp service to the shop, but I could potentially have a new 400 amp service brought in. I’d obviously need more than the 200 amp service to power the other necessities of the building at the same time.

But, instead of paying for another service I’ve thought about using that money for a 3phase commercial generator. I’ve talked to a few electricians here about this but I mostly get some head scratching as they don’t do much complex or commercial work.

Thoughts from any experienced electricians?

How did you determine that?

According to this chart (using 30HP as the sizing) you would need a 60hp rotary not an 80hp...

How to size my Rotary Phase Converter? | Wolf Automation

Need a rotary phase converter for your shop? Don't know which one will do the trick? We've got you covered with our simple guide to sizing the right RPC!

www.wolfautomation.com

 

[River Runner]

I don’t have a pic of the nameplate for the motor, just the requirements from the manufacturer, but I’m sure I can get it.

My understanding is that it’s a 26hp motor on the saw. It’s a 2016 saber saw by park industries. A 60 horse converter would probably be more accurate, which I believe requires a 150 amp minimum circuit.

 

[River Runner]

Bummer that I’d need to buy a different transformer. A friend of mine who used to do electrical said that it might be better to just leave the 200 amp service and get a high quality 208v 3phase generator to power the machine.

 

[Steve from Socal]

If you plan on using the machine in production where efficiency of the electrical service is a consideration a phase perfect with a high conversion efficiency is more cost effective in the long run.

Phase Perfect Performance | Single to Three Phase Power Converter | Variable Frequency Drives and Digital Phase Converters | Phase Technologies

Phase Perfect digital phase converters power the most demanding mission critical applications.

www.phaseperfect.com

 

[Norcal]

It is not a simple matter to step up from 240V to 480V, when only single phase power is available, plus a transformer will only step up the voltage, single phase input is not going to create 3 phase. before jumping in better have everything settled power wise.

 

[River Runner]

I understand it’s more than stepping up just the voltage. If I get a dedicated 400 amp single phase service for the shop, it’s my understanding that I can use a RPC to get my 120/240 service up to 208V 3 phase, it just takes a lot more amperage to create the additional wave, basically doubling what is necessary, hence a bigger 400 amp service.

While I do like the idea of a generator, especially in a rural area, I figured it would cost more to generate the energy.

35kw generator uses roughly 5 gallons of propane per hour. So that’s about $15 hr when buying $3 gallon propane, plus maintenance.

local utility sells tier 3 electricity for $.13 a KWh. 25 horse motor will probably be using 40kwh i determined, so that’s a little over $5 hr, if I did any of that correct.

 

[Steve from Socal]

A 25 HP motor would use 19~20 KW at full power. Is the "saw" a combo water-jet and saw? The 240/480 step up is going to be a pretty big inrush when you saturate the transformer. Your PoCo may have limitations on the current inrush? A generator is the least cost effective way to power the machine where utility power is available. That and you would need a pretty good size generator to keep the power from sagging on a CNC machine. Probably more like a 50KVA gen set.

Start with getting some answers from your power company. Buying/ordering anything until you know what is possible could be a costly mistake.

 

[wyliesdiesels]

I don’t have a pic of the nameplate for the motor, just the requirements from the manufacturer, but I’m sure I can get it.

My understanding is that it’s a 26hp motor on the saw. It’s a 2016 saber saw by park industries. A 60 horse converter would probably be more accurate, which I believe requires a 150 amp minimum circuit.

this newer model is 27hp

SABERjet™ XL CNC Sawjet | Stone Fabrication Saw + Waterjet

Unleash SABERjet™ XL — the next-generation of the industry’s leading single-table sawjet, now with complete table coverage for even the largest slabs.

www.parkindustries.com

Bummer that I’d need to buy a different transformer. A friend of mine who used to do electrical said that it might be better to just leave the 200 amp service and get a high quality 208v 3phase generator to power the machine.

That doesnt make any logical sense whatsoever. Why bother with the waste, power loss and added complexity of a 208v to 480v transformer? why not just buy a 480v generator?

adding a transformer into the mix requires addl overcurrent protection, disconnects, 2 different gauges of wire, etc....

 

[wyliesdiesels]

If you plan on using the machine in production where efficiency of the electrical service is a consideration a phase perfect with a high conversion efficiency is more cost effective in the long run.

Phase Perfect Performance | Single to Three Phase Power Converter | Variable Frequency Drives and Digital Phase Converters | Phase Technologies

Phase Perfect digital phase converters power the most demanding mission critical applications.

www.phaseperfect.com

except that doesnt solve his 480v issue. he would still need a 240v to 480v 3 phase transformer which for the power he needs wouldnt be cheap...

I understand it’s more than stepping up just the voltage. If I get a dedicated 400 amp single phase service for the shop, it’s my understanding that I can use a RPC to get my 120/240 service up to 208V 3 phase, it just takes a lot more amperage to create the additional wave, basically doubling what is necessary, hence a bigger 400 amp service.

Why do you keep bringing up 208v? the RPC idler motor would need to be rated for 240v since thats the voltage you have coming in. The RPC wont convert the 240v down to 208v. only a transformer can do that. your understanding is totally incorrect.

There is no point in bringing up 208v. the transformer that came with this saw is useless with your single phase 120/240v service...

While I do like the idea of a generator, especially in a rural area, I figured it would cost more to generate the energy.

35kw generator uses roughly 5 gallons of propane per hour. So that’s about $15 hr when buying $3 gallon propane, plus maintenance.

local utility sells tier 3 electricity for $.13 a KWh. 25 horse motor will probably be using 40kwh i determined, so that’s a little over $5 hr, if I did any of that correct.

and your PoCo may have limits on motor HP as brought up by steve... you really should check with them first.

A 25 HP motor would use 19~20 KW at full power. Is the "saw" a combo water-jet and saw? The 240/480 step up is going to be a pretty big inrush when you saturate the transformer. Your PoCo may have limitations on the current inrush? A generator is the least cost effective way to power the machine where utility power is available. That and you would need a pretty good size generator to keep the power from sagging on a CNC machine. Probably more like a 50KVA gen set.

Start with getting some answers from your power company. Buying/ordering anything until you know what is possible could be a costly mistake.

Bingo! many PoCos limit motor loads on single phase service to 10hp.... and if he's on the end of the HV primary line, he may have issues with voltage drop when starting such a big load....

 

[loganb]

Don't forgot the demand charge for the power company based on hoe much power you turn on in a given period(usually 15 min). With that big of potential power draw you need to confirm with them the capacity exists on the single phase service and that they won't have to upgrade the service to support you and if so what your fee would be.

 

[wyliesdiesels]

Don't forgot the demand charge for the power company based on hoe much power you turn on in a given period(usually 15 min). With that big of potential power draw you need to confirm with them the capacity exists on the single phase service and that they won't have to upgrade the service to support you and if so what your fee would be.

most PoCos dont charge demand fees for single phase residential services (non-commercial)

 

[loganb]

most PoCos dont charge demand fees for single phase residential services (non-commercial)

I'm maybe falsely assuming that as it sounds like a slightly more rural area he could be on a REA in which case the ones I've been served by may charge demand charge on large single phase loads based on how much of strain it puts on the grid

 

[Steve from Socal]

The areas where TOU meters are installed demand or what ever you want to call it can be applied. That is NOT the same as 'demand" for industrial power. I have demand on my industrial service, if I light off my 60 HP motor for half an hour I pay that demand for the next quarter.

 

[River Runner]

Thanks for all the input. I kept brining up the 208V because that was the transformer that comes with the machine. It being useless for my 120/240V service was the answer I was looking for, so thank you.

I hope to get some more answers from the power company tomorrow but my previous two conversations with them have been pretty uninformative. There is one designer for our entire county and the next available appointment is end of May and the customer service people can only refer me to a designer. Per my conversation with him last year he said that the transformer at the property line would support an additional 400 amp service.

This saw is not the saw jet. Its the older version of the Voyager, which has a 26hp motor and is a saw and router combo. Supposedly per the rep this saw has a smaller motor than the voyager but I haven't been able to get a solid number on that yet.

I've never head of any demand charges before, I'll look into that.

I do know, per the sales rep, that the newer larger Voyager saw is being run off a phase converter by another shop that is being serviced by the same power company, but in the city and not a rural area like I would.

 

[wyliesdiesels]

The areas where TOU meters are installed demand or what ever you want to call it can be applied. That is NOT the same as 'demand" for industrial power. I have demand on my industrial service, if I light off my 60 HP motor for half an hour I pay that demand for the next quarter.

TOU and demand are not the same thing

TOU is merely calculated by the metering hub back at the PoCo's office based on usage for the time of day.

The basic single phase smart meter on my residence is capable of calculating demand usage (my bill shows what my demand is) but since its a residence, demand nor TOU is charged. we just get billed @ a flat rate even if i had motors running here.

The PoCo has floated the idea of TOU rates in the future but never made a decision on it. The other PoCo (Profit Gouge & Execute/PG&E) that services the next town over, has adopted TOU rates for residences. Its currently optional for residential and people who've signed up for it are already regretting it...

My shop on the other hand, which has 3Ø 208Y service, provided by a different PoCo than the previous mentioned ones, gets billed for demand usage but not TOU usage.... go figure...

 

[wyliesdiesels]

Thanks for all the input. I kept brining up the 208V because that was the transformer that comes with the machine. It being useless for my 120/240V service was the answer I was looking for, so thank you.

I hope to get some more answers from the power company tomorrow but my previous two conversations with them have been pretty uninformative. There is one designer for our entire county and the next available appointment is end of May and the customer service people can only refer me to a designer. Per my conversation with him last year he said that the transformer at the property line would support an additional 400 amp service.

This saw is not the saw jet. Its the older version of the Voyager, which has a 26hp motor and is a saw and router combo. Supposedly per the rep this saw has a smaller motor than the voyager but I haven't been able to get a solid number on that yet.

I've never head of any demand charges before, I'll look into that.

I do know, per the sales rep, that the newer larger Voyager saw is being run off a phase converter by another shop that is being serviced by the same power company, but in the city and not a rural area like I would.

the shop it came from probably had 208Y 3Ø service so all they needed was a transformer.... I wouldve left the transformer out of the sale to save some money...

As to the PoCo engineer, I would ask him if they have a limit on motor HP for your service....

 

[River Runner]

Perhaps I can sell the transformer and make a few bucks....

I found this unit and was curious what the thought is on it. Its a 240v single phase to 480v 3phase VFD, rated for 25hp. I will hopefully confirm with the manufacturer tomorrow about the exact horsepower on the machine but I have a feeling its a little under 25hp. My understanding is that VFD's reduce inrush? I will hopefully also get some information from the power company too. Thanks!

1LH Series – Configured Panel | Variable Frequency Drives and Digital Phase Converters | Phase Technologies

www.phasetechnologies.com

 

[Steve from Socal]

I think you can buy the Phase Perfect I listed AND a 240/480 transformer for less than the VFD above. Are you sure the machine can not be changed to 240 service?

Steve

 

[River Runner]

I think you can buy the Phase Perfect I listed AND a 240/480 transformer for less than the VFD above. Are you sure the machine can not be changed to 240 service?

Steve

I will look into that, thanks

 

[wyliesdiesels]

I think you can buy the Phase Perfect I listed AND a 240/480 transformer for less than the VFD above. Are you sure the machine can not be changed to 240 service?

Steve

looks like thats a static converter which starts the motor on 3 phase and then single phases it while its running. the cnc machine may not like that...

 

[Steve from Socal]

looks like thats a static converter which starts the motor on 3 phase and then single phases it while its running. the cnc machine may not like that...

Phase perfect are NOT static phase converters, they are quasi inverter/power supplies. They are very highly electrically efficient and they are rated for CNC machines with regen braking. They are the closest thing to utility 3 phase you can find.

Steve

 

[mike93lx]

Demand charges can be hugely expensive. In the manufacturing plants I work in, demand can make up more than half of our electric bills and it just takes one short period of time in the month to create that charge.

If you are in a residential area, I would bet there is no way your poco will let you run that size motor. The transformers won't be sized to support it.

Thinking you can sell the transformer will very likely end up with either a transformer sitting around your shop or you having to unload it for scrap value. I'd try hard to avoid taking it if you can.

 

[River Runner]

I got some more specs on the machine after the manufacturer ran the serial number. The machine itself has one power source input requesting 480V 3 phase 24.7 full load amps. The actual motor/spindle is a 15HP motor with 18.2 full load amps that is not wired independently but within the wiring of the machine.

It sounds like the phase perfect digital phase converter is the way to go. Phase Technologies says it keeps voltage within 2% and has the capability to also double the voltage without the need for an additional transformer. Cost on the complete unit is $6400. They also claim that because the way it soft starts there won't be any inrush and that it won't effect the grid.

 

[River Runner]

PTE220RQT is the model number for the Phase Perfect digital converter that Phase Technologies recommended based on the machine specs I gave them.

 

[mike93lx]

They also claim that because the way it soft starts there won't be any inrush and that it won't effect the grid.

That's a lot to hang on an assurance. I think I'd want data as it would **** to get all that installed and have it brown out your neighborhood

 

[PoorUB]

One big question? Is the incoming control power separate from the incoming power for the motor? If not, can it be separated?

If the incoming power runs to both the controls and the motor you have more issues. A soft start for the motor won't work if the controls need 480v/3PH all the time.

I would assume the controls can be powered separately, but it might be worth checking into.

 

[wyliesdiesels]

One big question? Is the incoming control power separate from the incoming power for the motor? If not, can it be separated?

If the incoming power runs to both the controls and the motor you have more issues. A soft start for the motor won't work if the controls need 480v/3PH all the time.

I would assume the controls can be powered separately, but it might be worth checking into.

Thats a good point

He did say the machine only has 1 input.

If the control power input cant be separated out then the phase perfect wont work like he wants it to.

 

[River Runner]

I think I may have mis stated by saying "soft start". My understanding is that it still provides adequate power but the grid doesn't see a hard start. Here is a link to material and data

https://www.phasetechnologies.com/support/pt

 

[River Runner]

I know that a manufacturers claim may not always be 100% perfectly accurate but here is some verbiage.

Versatility


The Phase Perfect® can safely power virtually any three-phase application within its rated capacity. It can power resistive and capacitive loads as well as motor or inductive loads. Its power quality makes it ideal for powering demanding loads such as CNC machine equipment, submersible pumps and other voltage sensitive applications. The Phase Perfect PT Series can operate with 60 Hz input

 

[mike93lx]

That doesn't address the inrush restrictions in residential services.

I've read here of people being limited to 5hp, others say 7.5, others 10. All I am suggesting is to get data and confirm it will work, before dropping all that coin.

 

[River Runner]

The recommended breaker size for my application would be 150 Amp. I think getting more accurate information about the machines requirements is showing that the load isn't as great as originally thought. I just got off the phone with a friend of mine in the area who is running a 30 Hp rotary converter for his wood shop and says he has no problems at all.

 

[PoorUB]

I think I may have mis stated by saying "soft start". My understanding is that it still provides adequate power but the grid doesn't see a hard start. Here is a link to material and data

https://www.phasetechnologies.com/support/pt

I am aware of how they work. The point is they ramp up the power to the motor relatively slowly. (just a few seconds) If it was simply powering a motor, no issues, but you can not power controls through it. It will run 480V output all the time, but the frequency will ramp up slowly to keep the inrush low. You controls will not like that!

Call the company and ask if you can soft start a motor and run CNC controls on the same output. I seriously don't see how.

 

[River Runner]

Power Company says no demand fees. But they recommend anything over 10Hp single phase be viewed by their engineer. This systems claims the grid will only see a 7.5hp start.

 

[River Runner]

I am aware of how they work. The point is they ramp up the power to the motor relatively slowly. (just a few seconds) If it was simply powering a motor, no issues, but you can not power controls through it. It will run 480V output all the time, but the frequency will ramp up slowly to keep the inrush low. You controls will not like that!

Call the company and ask if you can soft start a motor and run CNC controls on the same output. I seriously don't see how.

I will do that

 

[mike93lx]

Power Company says no demand fees. But they recommend anything over 10Hp single phase be viewed by their engineer. This systems claims the grid will only see a 7.5hp start.

Nice, so if it will run the controls, it looks like a solution

 

[River Runner]

Manufacturer says that the machine needs a consistent 480V + or - 10%. I also just spoke to Phase Technologies and they state that there won't be a lag that would effect controls. They are stating that this new unit is being used on CNC's and that he could provide a metal fabricator who is using the same system on a 3phase plasma CNC.

I'm not sure what more I can do other than take the words of both manufacturers. I think that the 18.2 FLA of the spindle motor shows that when it starts up the draw will be even less than the capability that I would be providing.

After talking to my cabinet making friend who is running a 30 hp RPC in an even more remote area with an old transformer I feel more confident. Good news is the power company told me my transfer is only 5 years old and one of the bigger ones in the area.

Yes, having 3 phase power would be way more ideal, but its not going to happen at my current location. I'm trying to start this new business and it seems that I'm not having to reinvent the wheel here as I know for certain from the Park Industries that they have bigger machines (27HP) running off phase converters that are under the same power company.

 

[PoorUB]

They are stating that this new unit is being used on CNC's and that he could provide a metal fabricator who is using the same system on a 3phase plasma CNC.

I would contact him, and perhaps even stiop in at this shop if he is in the area.

It would blow my mind if they can soft start a motor and run CNC controls from one output.