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  1. #341
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    I've edited my post to reflect that modern PWM circuits handle inrush much better than older circuits, and I just looked it up, it can be 100 - 150% of full motor current. I think your approach of comparing power rather than amps is the right one. A 13 amp UK outlet can easily supply 2.2Kw, and many people run 2.2Kw spindles perfectly well from that supply. It works well, as proven by many happy users. Your choice though.

    ABB say "It is also important to note that current is limited on the application of input power by the design of the drive's pre-charge circuit. The dc bus capacitors are soft charged based on an RC time constant such that the current at power up will be well below the motor's FLA"
    Likewise in australia, a standard 10A outlet can supply 2400W. Can you clarify the 100-150% of full motor current statement? Do you mean the start current for a motor connected to a VFD is 100-150% of the full motor current? I read that is one of the benefits of using a VFD because the start current is so much lower than the 500-600% start current of a regular AC motor. When I mentioned the start up current earlier, I was referring to the VFD when it is switched on and the initial inrush current to charge the capacitors. It makes sense that a modern device would have some sort of limiting circuitry to “soft charge” the capacitors at power up, which you did also mention.

    Your other post with the quote about Japanese drives is interesting. I had no idea there were so many different power systems in a single country. That must drive manufacturers mad trying to design a product that works on all the systems.

  2. #342
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    You are confused. BTW I am a qualified electrician and ran my electronics repair company for 15 years, mostly repairing switched-mode power supplies, but don't take my word for it - just look and see what other people are doing.
    Then you should loose your license for posting such Bs, No confusion Here, I have a degree in Electrical Engineering and I repair and Build VFD Drives.

    Switch-mode Power supplies are nothing like a VFD Drive.
    Mactec54

  3. #343
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    It's a good guess. Inrush current can be very high on older designs. Quality circuits incorporate limiting devices such as NTC ( resistors that start at a high value which rapidly drops when they get warm ), resistors that charge the caps slowly then a circuit or relay shorts those resistors when the caps are charged, or zero-point circuits that connect the caps when the mains voltage is at the 0v crossover point to avoid massive inrush. Sometimes you can hear a ping when the caps are charged and a relay clicks in. Modern PWM designs handle it much better.
    That is a load of rubbish, VFD Drive use a softstart, even the cheap one's, there is no chance of any inrush current. that will affect the starting of a motor. or have excess current.
    Mactec54

  4. #344
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by JayneV View Post
    Likewise in australia, a standard 10A outlet can supply 2400W. Can you clarify the 100-150% of full motor current statement? Do you mean the start current for a motor connected to a VFD is 100-150% of the full motor current? I read that is one of the benefits of using a VFD because the start current is so much lower than the 500-600% start current of a regular AC motor. When I mentioned the start up current earlier, I was referring to the VFD when it is switched on and the initial inrush current to charge the capacitors. It makes sense that a modern device would have some sort of limiting circuitry to “soft charge” the capacitors at power up, which you did also mention.

    Your other post with the quote about Japanese drives is interesting. I had no idea there were so many different power systems in a single country. That must drive manufacturers mad trying to design a product that works on all the systems.
    That may be correct for your circuit, that is not what this is about, you need a lot more than that on the input of your VFD Drive to have an output of 2400watts motor load, again your motor is 3 Phase your supply is Single Phase there is no magic here, where you can put 2400W into the VFD Drive and get 2400W out that is not possible. this does not happen.

    So to supply a VFD Drive output to have 2400W the input would have to be, 1.73 times more. this is what I have said from the beginning. Which would be without any safety factor required by code.

    The input to the VFD Drive will need 4128Watts to have an output of 2400Watts. this is very basic Single Phase to 3 Phase requirement.

    I would suggest you talk to your Electrician and confirm these numbers, if he has had experience with VFD Drive installations he will give you these same numbers.
    Mactec54

  5. #345
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by mactec54 View Post
    That may be correct for your circuit, that is not what this is about, you need a lot more than that on the input of your VFD Drive to have an output of 2400watts motor load, again your motor is 3 Phase your supply is Single Phase there is no magic here, where you can put 2400W into the VFD Drive and get 2400W out that is not possible. this does not happen.

    So to supply a VFD Drive output to have 2400W the input would have to be, 1.73 times more. this is what I have said from the beginning. Which would be without any safety factor required by code.

    The input to the VFD Drive will need 4128Watts to have an output of 2400Watts. this is very basic Single Phase to 3 Phase requirement.

    I would suggest you talk to your Electrician and confirm these numbers, if he has had experience with VFD Drive installations he will give you these same numbers.
    I’m not disputing the numbers, I’m just trying to understand how the numbers are calculated. From what you are saying a Watt means something different between single phase and 3 phase?

    Are both of these equations correct statements (keeping the numbers very simple)?
    1 phase: 1W = 1V x 1A
    3 phase: 1W = 1V x 0.577A x 1.732

    In other words, is 1 Watt of energy the same amount of energy independent of how many volts, amps or phases are used to create that 1 Watt?

  6. #346
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by JayneV View Post
    At the risk of opening Pandora’s Box I’m going to present some calculations for (respectful!!!) comments because I am confused as hell! The example I will present will use the figures from the attachment. I will assume a 220V single phase supply and will also assume 100% efficiency in the VFD and a power factor if 1 to keep things simple.

    Rated Output: 2.2kW
    Input: 220V single phase
    Output: 220V 3 phase
    Rated Input Current: 23A
    Rated Output Current: 10A
    Power Factor(PF): 1

    At the input:
    Input Watts: W = V x I = 220 x 23 = 5060W = 5.06kW

    Output Watts: W = V x I x PF x 1.732
    2200 = 220 x I x 1 x 1.732
    Solving for I: I = 2200 / (220 x 1 x 1.732) = 5.77A (per phase??)
    5.77 x 1.732 = 10A (3 phase current)

    Output using a PF of 0.85:
    2200 = 220 x I x 0.85 x 1.732
    I = 2200 / (220 x 0.85 x 1.732) = 6.79A

    The numbers are not adding up.

    Looking at it differently, a Watt is a measure of energy. 1W= 1 joule per second. It shouldn’t matter if the energy is created by single phase or 3 phase electricity or even a GE CF6 jet engine burning jet fuel, energy is energy. So for a VFD that has an efficiency greater than 90%, it should not take more than 5kW to output 2.2kW.
    At 90% efficiency, 2.45kW x 90% = 2.2kW. So for a 220V supply, 2450W/220V = 11.14A. So why does the VFD require a 13A supply?



    I keep trying and can’t make the numbers add up, there has to be a reason why all the manufacturers list the input current so high. It’s not being consumed by the spindle and it’s not being dissipated as heat so where is it being used?

    I hope someone can explain this to me in simple terms because it’s driving me crazy.

    My brain has now exploded and I need to take a nap.
    Your answer, So why does the VFD need a higher input, This is what I have said from the start, SINGLE PHASE to THREE PHASE
    You are wanting a 3 Phase output but only have a Single Phase supply. does not get any simpler than this.

    I missed what you did here your Power supply voltage you said was 240v, when you do your calculations you need to use your supply voltage. the Power factor will never be ( 1 ) this is ok to put some basic numbers together though.

    This is the important part Single Phase to Three Phase and the only part you need to focus on, and what ever your Code requirements are, for Circuit size.

    Single phase to 3 phase power calculation input requirement = The square root of 3 (1.732) x 10 amps = 1.732 x 10 amps = 17.32 Amps. Single phase power input in this instance is 17.32 Amps. The total load draw should not be any higher than the rated motor load.

    You might like this if you are interested in Power Factor.

    https://www.fluke.com/en-us/learn/bl...factor-formula
    Mactec54

  7. #347
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by mactec54 View Post
    That is a load of rubbish, VFD Drive use a softstart, even the cheap one's, there is no chance of any inrush current. that will affect the starting of a motor. or have excess current.
    I'm sure ABB will appreciate your help designing their next VFD.

    LVD-EOTN151U-EN_VFDs_And_Maximum-Inrush-Current.pdf (abb.com)

  8. #348
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by mactec54 View Post
    Your answer, So why does the VFD need a higher input, This is what I have said from the start, SINGLE PHASE to THREE PHASE
    You are wanting a 3 Phase output but only have a Single Phase supply. does not get any simpler than this.

    I missed what you did here your Power supply voltage you said was 240v, when you do your calculations you need to use your supply voltage. the Power factor will never be ( 1 ) this is ok to put some basic numbers together though.

    This is the important part Single Phase to Three Phase and the only part you need to focus on, and what ever your Code requirements are, for Circuit size.

    Single phase to 3 phase power calculation input requirement = The square root of 3 (1.732) x 10 amps = 1.732 x 10 amps = 17.32 Amps. Single phase power input in this instance is 17.32 Amps. The total load draw should not be any higher than the rated motor load.

    You might like this if you are interested in Power Factor.

    https://www.fluke.com/en-us/learn/bl...factor-formula
    I used 220V in those equations because that is the vintage that was listed in the attachment. Also, I understand the power factor would never be 1. It was a hypothetical example, keeping the numbers as simple as possible to try and understand the conversion. There was also an example using a power factor of 0.85, again just a hypothetical number for the sake of discussion.

    Btw, I like the beer mug analogy in the attached Fluke document, it made me laugh. But it was an effective way to explain their point. Lol

    I do understand all of your numbers converting between single phase and 3 phase amps. What I don’t understand is the way power (watts) are defined between single and three phase. That is what I was trying to ask in my last post by rephrasing the question.

  9. #349
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by JayneV View Post

    In other words, is 1 Watt of energy the same amount of energy independent of how many volts, amps or phases are used to create that 1 Watt?
    Yes, 1 Watt is 1 Watt
    Jim Dawson
    Sandy, Oregon, USA

  10. #350
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Jim Dawson View Post
    Yes, 1 Watt is 1 Watt
    Indeed. Just because an inverter spec sheet quotes worst case scenario input current ( example: lowest input voltage, 200% motor overload condition ) doesn't mean the motor won't run perfectly well from a household power supply ( especially in the UK at 240v ), as many users will agree.

    Here's another explanation of it all: Larger VFD/Motors | Model Engineer (model-engineer.co.uk)

    "Another reason for the input current of 23.2A specified for the Eaton DE1 2.2kW drive linked to by Carl **LINK** is the overload rating and input voltage range. It says 2.2kW output so about 95% efficiency gives 2.31kW. Minimum input voltage is 200V 2.31 /200 = 11.55A. The overload rating is 200% for 1.875s 2 x 11.55 = 23.1A no missing power or incorrect data If running at nominal 230 V this becomes 10.05A full load and 20.1 at 200% overload. Thus a "13A" outlet would be adequate."

    Which is a long-winded way of saying what loads of users know - it runs fine from a 13A socket.

  11. #351
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    Indeed. Just because an inverter spec sheet quotes worst case scenario input current ( example: lowest input voltage, 200% motor overload condition ) doesn't mean the motor won't run perfectly well from a household power supply ( especially in the UK at 240v ), as many users will agree.

    Here's another explanation of it all: Larger VFD/Motors | Model Engineer (model-engineer.co.uk)

    "Another reason for the input current of 23.2A specified for the Eaton DE1 2.2kW drive linked to by Carl **LINK** is the overload rating and input voltage range. It says 2.2kW output so about 95% efficiency gives 2.31kW. Minimum input voltage is 200V 2.31 /200 = 11.55A. The overload rating is 200% for 1.875s 2 x 11.55 = 23.1A no missing power or incorrect data If running at nominal 230 V this becomes 10.05A full load and 20.1 at 200% overload. Thus a "13A" outlet would be adequate."

    Which is a long-winded way of saying what loads of users know - it runs fine from a 13A socket.
    That accounts for every single number in the specs. Thanks for that.
    I realise my build thread has gone off track a little but I couldn’t just accept the mismatched numbers without a reasonable explanation to balance the equations. My OCD wouldn’t let it go.

  12. #352
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    Indeed. Just because an inverter spec sheet quotes worst case scenario input current ( example: lowest input voltage, 200% motor overload condition ) doesn't mean the motor won't run perfectly well from a household power supply ( especially in the UK at 240v ), as many users will agree.

    Here's another explanation of it all: Larger VFD/Motors | Model Engineer (model-engineer.co.uk)

    "Another reason for the input current of 23.2A specified for the Eaton DE1 2.2kW drive linked to by Carl **LINK** is the overload rating and input voltage range. It says 2.2kW output so about 95% efficiency gives 2.31kW. Minimum input voltage is 200V 2.31 /200 = 11.55A. The overload rating is 200% for 1.875s 2 x 11.55 = 23.1A no missing power or incorrect data If running at nominal 230 V this becomes 10.05A full load and 20.1 at 200% overload. Thus a "13A" outlet would be adequate."

    Which is a long-winded way of saying what loads of users know - it runs fine from a 13A socket.
    Hi Zorbit,

    *** I tried to edit my last post but the time limit for editing expired hence this second reply to your same post ***

    I just finished reading through the whole thread you linked to at model-engineer.co.uk. Near the end of the thread, on page 5, there is a post where the writer (Dave) connected an oscilloscope at the VFD input and took some readings at VFD power on with motor OFF and a couple readings with the motor running no load and under some load. The screen shots are interesting and graphically show how messy the AC waveform gets as the load on the VFD increases. It also shows the spikes increasing in amplitude but decreasing in duration as the load increases. Dave then goes on to talk about different types of fuses and current ratings which I won't replicate here because we are starting to go round in circles here and I don't want to turn this build thread into an endless discussion about VFD parameters, but if anyone is interested in some interesting discussion, that thread is not a bad read to pass some time.

    **** Back to the CNC machine ****

    Unfortunately, there hasn't been a whole lot of progress on Carlos. I returned to my full time day job on Monday after being unable to work for almost 7 months so I've been busy getting up to speed with training and loads of emails. The only work on Carlos has been minor stuff like adding bolt holes to various parts and adding a cable chain to the Y axis to get a rough idea how to mount it.

  13. #353
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    Indeed. Just because an inverter spec sheet quotes worst case scenario input current ( example: lowest input voltage, 200% motor overload condition ) doesn't mean the motor won't run perfectly well from a household power supply ( especially in the UK at 240v ), as many users will agree.

    Here's another explanation of it all: Larger VFD/Motors | Model Engineer (model-engineer.co.uk)

    "Another reason for the input current of 23.2A specified for the Eaton DE1 2.2kW drive linked to by Carl **LINK** is the overload rating and input voltage range. It says 2.2kW output so about 95% efficiency gives 2.31kW. Minimum input voltage is 200V 2.31 /200 = 11.55A. The overload rating is 200% for 1.875s 2 x 11.55 = 23.1A no missing power or incorrect data If running at nominal 230 V this becomes 10.05A full load and 20.1 at 200% overload. Thus a "13A" outlet would be adequate."

    Which is a long-winded way of saying what loads of users know - it runs fine from a 13A socket.
    Long winded and still incorrect information for circuit / cable size, simple Math which you don't seem to have any knowledge of. you are quoting from manufacturers Spec's which anyone can see and use.

    Full13A Single Phase supply will only give you 7.5A 3 Phase output, so the Spindle can never reach full power. if it could then it would over load the 13A circuit.

    Lets see you run one of these spindles and have a 200% over load, and see what happens, being an electrician you should know how to calculate the circuit /cable size for, Code requirements, she has a whole machine to run not just the VFD Drive
    Mactec54

  14. #354
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by mactec54 View Post
    Full13A Single Phase supply will only give you 7.5A 3 Phase output, so the Spindle can never reach full power. if it could then it would over load the 13A circuit.
    How much current do you think a 2200w motor needs ? That will be input power.

    2200 / (1.732 * 220 * 0.85 ) = 6.8 ?

  15. #355
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    Re: My CNC Router Build Adventure

    That is a good example in the link, he is only running a regular Ac 50Hz low speed motor not a ( 24,000 RPM 400Hz motor ) and he still had trouble to get them running until he increased his power requirement's, up to a 25A circuit.

    https://www.model-engineer.co.uk/for...?th=128681&p=3
    Mactec54

  16. #356
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    How much current do you think a 2200w motor needs ? That will be input power.

    2200 / (1.732 * 220 * 0.85 ) = 6.8 ?
    Again you post more incorrect information.

    Check the Spindle motor spec's it's 10A
    Attached Thumbnails Attached Thumbnails G-Penny.PNG  
    Mactec54

  17. #357
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by mactec54 View Post
    Again you post more incorrect information.

    Check the Spindle motor spec's it's 10A
    Then it's not a 2200w motor.

  18. #358
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    Re: My CNC Router Build Adventure

    If we're going to rely on imaginary figures then here's a 2200w spindle motor claiming to run at 6A

    2.2kw Air-cooled square spindle motor kit 2200w spindle 2.2kw 220V inverter ER20 collet air spindle motor engraving milling - Moret Motors - cnc spindle motor

    Nevertheless, actual "simple maths" say we can run one on less than the 7.5A you admit is available, unless we are once again considering that the motor is running low voltage and overload condition.

  19. #359
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    How much current do you think a 2200w motor needs ? That will be input power.

    2200 / (1.732 * 220 * 0.85 ) = 6.8 ?
    Here are the Amp spec's for regular AC motors, single phase and 3 Phase motors, you should know that this calculation is incorrect.
    Attached Files Attached Files
    Mactec54

  20. #360
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    Re: My CNC Router Build Adventure

    Quote Originally Posted by Zorbit View Post
    If we're going to rely on imaginary figures then here's a 2200w spindle motor claiming to run at 6A

    2.2kw Air-cooled square spindle motor kit 2200w spindle 2.2kw 220V inverter ER20 collet air spindle motor engraving milling - Moret Motors - cnc spindle motor

    Nevertheless, actual "simple maths" say we can run one on less than the 7.5A you admit is available, unless we are once again considering that the motor is running low voltage and overload condition.
    These spindles are loaded when cutting, unless you just take light cuts which get's old fast.

    Yes there are many listing like this, and you will find that to be incorrect, and is for 380v Amp rating.

    Running and get full power of the spindle motor is too different things, 13A circuit will not do it, if you want your spindle to have a normal performance.

    You posted the link, did you not read it. where he now has a 25A circuit, which would be the correct size for what he is doing.
    Mactec54

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