How to stabilize AC voltage to CNC machine

[unimatrix93]

Hello there everybody, I'm not sure if it's the right topic to ask this but I hope so.


I have a CNC machine wired to 3-phase 230V AC.

It's a smaller CNC machine with a 3500W motor, do it does not uses much power.

The problem is, when the residents come home and put load on the network, the voltage can drop to around 207V which is fine for most household items but by CNC machine stops working from this.

I contacted the electricity company but they refuse to help me solve this problem.

So I started to look around for some DIY voltage stabilizer on the internet but those are for single phase as far I can see.

Can anybody point me to the right direction to solve this problem?

[sam_sam_sam]

What about a step up transformer but the issue is going to be when the power grid is lightly loaded the voltage will be higher and when the power grid high power demand the voltage would be correct which could be done manually weather or not it could be automated I am not sure if it could be done and be repeatable and be accurate enough to keep CNC from being destroyed by inaccurate voltage and phase changes or loss of a phase


What is the highest voltage that your CNC machine can safely handle without having any issues

I do not know if there is an auto transformer that is adjustable for 3 phase I personally have not seen one so I can not comment on this

[unimatrix93]

What about a step up transformer but the issue is going to be when the power grid is lightly loaded the voltage will be higher and when the power grid high power demand the voltage would be correct which could be done manually weather or not it could be automated I sure if it could be and be repeatable and be accurate enough to keep CNC from being destroyed by inaccurate voltage and phase changes or loss of a phase

I do not know if there is an auto transformer that is adjustable for 3 phase I personally have not seen one so I can not comment on this

Yes, I found many DIY solutions on the internet to stabilize 230V but they are all for single phase.

Looking around in aliexpress I found these units, I wonder if they actually do anything.

https://www.aliexpress.com/item/3246...Cquery_from%3A

[sam_sam_sam]

This might work but I would test it out on something you do not care about it getting damaged if the device fails while testing this inverter
Inverter in general if not designed properly have a high failure rate if the quality is not there so torcher test this inverter if you go this route first before relying on it for a complete solution to your issue

[unimatrix93]

This might work but I would test it out on something you do not care about it getting damaged if the device fails while testing this inverter
Inverter in general if not designed properly have a high failure rate if the quality is not there so torcher test this inverter if you go this route first before relying on it for a complete solution to your issue

Absolutely right, also to answer your previous question, I will look up my CNC's datasheet to the max rated voltage on it.

[unimatrix93]

This might work but I would test it out on something you do not care about it getting damaged if the device fails while testing this inverter
Inverter in general if not designed properly have a high failure rate if the quality is not there so torcher test this inverter if you go this route first before relying on it for a complete solution to your issue

Here is the power table of the CNC machine:

[sam_sam_sam]

The simplest solution would be to get a step up transformer for 220 to 380 volts 3 phase at 20 amps and be done with it and no electronics involved

[unimatrix93]

The simplest solution would be to get a step up transformer for 220 to 380 volts 3 phase at 20 amps and be done with it and no electronics involved

I did some measurements last night, so the three phases has these voltages during sleeping hours, when there is no load on it on the network:
1. 216V
2. 218V
3. 219V
So in even in the best scenario I have around 220V at max per phase.
And the machine works until 210V. We can go up to 240V safely I guess.

And when the machine stops working, I measure around 208V on every three phase.
This is the utility box where the power comes in to the machines:

[CapLeaker]

I did some measurements last night, so the three phases has these voltages during sleeping hours, when there is no load on it on the network:
1. 216V
2. 218V
3. 219V
So in even in the best scenario I have around 220V at max per phase.
And the machine works until 210V. We can go up to 240V safely I guess.

And when the machine stops working, I measure around 208V on every three phase.
This is the utility box where the power comes in to the machines:

Ahh, that's a bit better now and making more sense. Because if your 3 phase 380v goes down to 207V you got some major power problems. I think having 208V single phase is acceptable to the power company, as 99% of things keep working on that voltage. There are 3 phase voltage buck and boosters out there.I saw 10kva for about a Grand. I guess that's what you need to have. The idea is same as when a UPS does a buck or boost to compensate the voltage output without going to battery.

[unimatrix93]

Ahh, that's a bit better now and making more sense. Because if your 3 phase 380v goes down to 207V you got some major power problems. I think having 208V single phase is acceptable to the power company, as 99% of things keep working on that voltage. There are 3 phase voltage buck and boosters out there.I saw 10kva for about a Grand. I guess that's what you need to have. The idea is same as when a UPS does a buck or boost to compensate the voltage output without going to battery.

I see can you point me to an european supplier?

Another question:
I guess getting 3 step up transformers (one on each phase) is not feasible? I asking because of the cost of an industrial buck and booster.

[sam_sam_sam]

What I was referring to was a 3 phase step up transformer 220 volts to probably 300 volts @ 20 amps

[sam_sam_sam]

This is what I was referring

https://store.maddox.com/products/3-...yABEgKuRPD_BwE

[CapLeaker]

This is what I was referring

https://store.maddox.com/products/3-...yABEgKuRPD_BwE

I thought about something similar like this first. But then I found that 3 phase buck boost thing. Problem is this thing is quite expensive compared to that wye 3 phase auto transformer.

Kinda odd:
The machine rated for 380V 3 phase power clunks out at 207V single phase which calculates out to about 358V 3 phase as wye supply. You wouldn't think that 22V difference will stop the machine…

Question is, will it keep running once it is already on, or she won't run (start) once the voltage is low?

[sam_sam_sam]

The problem is that the servo motor drives are very picky about having the right voltage and I am surprised that it works down to that voltage to be honest with you in fact if it were me with this machine I would not keep using with that low of voltage because you might damage the switching power supply it bad enough when you are using the right voltage and the power supply section goes bad for some reason it is even worse when you are running with very low voltage because then you take a chance of frying the IGBT modules and depending on how old this machine and where it was made it can be a challenge to find replacement parts for it plus you have the issue with higher current when running at extremely low voltage and your machine is complaining about it in the sense that it refuses to run

And if one phase happens to be even lower than that voltage when loaded this is even worse because with VFD drive if you want to run it on single phase you have double the current capability of the drive and in some cases it might be better to be 3 times higher than what you motor amps are because you will burn up the IGBT module I have first hand experience with this issue from a previous employer that use to work for

I would agree with you that an auto transformer would work as long as you do not exceed the maximum voltage of the machine we already know that it will not work at 207 volts and the operating voltage is 380 volts you might get away with 350 the reason I say this is that because when off peak power usage the voltage will be higher and if you go higher voltage than what it rated for then you have other problems with high voltage as well but these issues are different and some times very difficult to determine because of being intermittent voltage fluctuations now if you were to have a voltage monitor and when your voltage output from the auto transformer is extremely high for the machine disconnect the auto transformer as long as the voltage is much higher than 207 volts yes this will be a pain in the a** but if your power supply company is not going to do anything for you then this is your own opinion unless you buy a 3 phase generator which might be out of the question depending upon the cost of one and or how easy is it to find one

The person who I do consulting technical work for and repair his CNC machine want to use a 3 phase lathe that I made a post about and was thinking about using it at his home shop that only has single phase and wanted to use a VFD drive for it

I told him you can BUT you need to double the current capacity of the drive and probably be better if you went 3 times the current capacity and you have to find a drive that can work on a single phase because a lot of VFD drives complain about losing a phase so you can NOT just use just any drive and of course when you buy a drive this big the cost becomes a big factor when deciding weather or not to go down this road he decided to go down this road when he retires

One note I am not sure if they make single phase servo drives if they do it properly has the same issue where you have to double or triple the current output capacity and that it can handle being used in a single phase mode

If you could find one if they are available and are made that way I can tell you that they are probably very expensive and a 3 phase auto transformer would be the cheapest option I can think of the next best option would probably be a three phase step up transformer and probably be more expensive

The other option would probably be an inverter but the concern I have with this option is what is the quality of the inverter because I have read about a lot of failures with these devices if I were to choose this option and I had a motor that could handle 30 running amps I would torcher test the hell out of and would try to make it fail meaning that when your voltage is low or lower than 207 volts is when I be doing these test and when your voltage is very high or higher than 220 volts how well does the inverter work and how hot does it get when starting and stopping it repeatedly and under a very heavily loaded what you would be looking for is how well dose it control the voltage and is the current stable under all test conditions

Yes I am trying to make it fail if can pass these test you might not have anything to worry about under these conditions and circumstances and yes these would not be normal operating conditions but you have to plan for the unexpected conditions sense you can not expect your power supply company to help you with any of it

[unimatrix93]

I thought about something similar like this first. But then I found that 3 phase buck boost thing. Problem is this thing is quite expensive compared to that wye 3 phase auto transformer.

Kinda odd:
The machine rated for 380V 3 phase power clunks out at 207V single phase which calculates out to about 358V 3 phase as wye supply. You wouldn't think that 22V difference will stop the machine…

Question is, will it keep running once it is already on, or she won't run (start) once the voltage is low?

The machine itself does turn on but it halts when I try to start the motor.

[sam_sam_sam]

The machine itself does turn on but it halts when I try to start the motor.

This is because the voltage monitoring / 3 phase monitoring system locking
Question I have for you do you get a error message when you have this low voltage situation if so what is the exact message that you are getting because I want to know if the servo motor drive is locking it out or the CNC controller locking it out or is it both locking it out because it is protecting it self from destruction

[unimatrix93]

This is because the voltage monitoring / 3 phase monitoring system locking
Question I have for you do you get a error message when you have this low voltage situation if so what is the exact message that you are getting because I want to know if the servo motor drive is locking it out or the CNC controller locking it out or is it both locking it out because it is protecting it self from destruction

The machine outputs a incomprehensible errors.
A technician checked it before and he is sure that it's caused by the voltage fluctuation.

[CapLeaker]

Found out that a CNC machine on 3 phase does have a +10% / -6% voltage tolerance rating. And the math is there when this machine cuts out. 380v -6%=357.8V. I calculated out 358v using the 207V single phase measurement taken from the op. On the other hand 380v + 10%= 418v. Calculate that down with wye calc and that ends up at 241V per phase. Bang on then.

Problem is going to be on how to fix it. Best solution is getting a heavier power entrance with thicker cables. Cheapest solution is to ignore it and live with it I guess. The buck / boost transformer is an idea but no matter how I spin it, it ends up costing an arm and 2 legs.

[unimatrix93]

Found out that a CNC machine on 3 phase does have a +10% / -6% voltage tolerance rating. And the math is there when this machine cuts out. 380v -6%=357.8V. I calculated out 358v using the 207V single phase measurement taken from the op. On the other hand 380v + 10%= 418v. Calculate that down with wye calc and that ends up at 241V per phase. Bang on then.

Problem is going to be on how to fix it. Best solution is getting a heavier power entrance with thicker cables. Cheapest solution is to ignore it and live with it I guess. The buck / boost transformer is an idea but no matter how I spin it, it ends up costing an arm and 2 legs.

I see now!
Problem is that the power utility company ignores my problem, since every other household appliances does tolerate these fluctuations.

So I have to find some kind of solution.
Do you think this unit or a similar kind could solve this issue? The 9kVA model could be enough for my machine, no?

[CapLeaker]

Or moving. Lol
Nah, 9kva is not cutting it. You need something more closer to 15kva! You need to transform 208V to 240V per phase. Problem with that is while it works when the power is low, you got way too much Volatage when the power returns normal. If you put in 208V and get 240V out, what do you get when you put in 220V per phase? 253V! That is 438V 3 phase and above your 10% upper tolerance rating. So, you be darned if you do and still darned if you don't.