1.5kw or 2.2kw spindle for aluminium, question

[tjbaudio]

The math is more complex for 3 phase, that's for sure you are right about. Read your VFD specification once again, that is if you have one... Anyway, it is pretty obvious that the 1.5kW Rexroth VFD (1K50 model) I am waiting for is specified to be able to provide an output current of 6.1A at 240V and if you run that VFD on single phase 240V it will require 13.5A. Now, since the efficiency of the VFD (this specific VFD) 95% the 6.1A simply must be per phase, it can NOT be total output because where is the rest of the current gone in that case? 95% 13.5A is 12.825A, so about 0.6A is heat and loss, but what about the other missing 6.725A between input and output?

Attachment 318900

It is pretty obvious that either Bosch is totally wrong and not know enough about their own VFD or you are missing something, because Bosch clearly claims that the input current for my VFD is 13.5A at 240V. Of course, before you correct me, I know, my mains is 230V, so that input current need will be increased to about 14.1A

You might have an education and experience in this, but if that is true than you should educate us and explain why am I wrong and why Bosch is wrong in their specification, not just emphasize what I don't keep a secret, that I am still waiting for my VFD to arrive, which is why my discussion is still purely theoretical. That comment, which you emphasized with all those stars, are meant to be read as "I am still waiting for my VFD, so I can't measure anything, and since I have never had a VFD before, I don't have any experience with one." That's all. It does not mean I don't have an education in this, even if my electrical education took place more than 40 years ago, I hardly think Ohms law have changed...

I don't understand why you mention Y connection at all. The VFDs we are discussing, and the motors we use as CNC spindle motors are all delta connected. The fourth wire is protective earth, NOT neutral. So please, don't increase the confusion here, because if you really have education in this than you should know this.

Also keep in mind that efficiency of a motor is not interesting because REGARDLESS of that, the MAXIMUM current of the VFD is already specified by the manufacturer of the VFD. We are not trying to find a VFD for a given motor with a given, fixed power here, in which case you must look at that motor efficiency, but we discuss a VFD with an already specified parameter.

I'd appreciate if you'd use your education and explained why am I wrong, not just claim that you are right. Ripping apart my answer and empasize/twist words is pretty rude in my opinion. I have no problems in being proven wrong, but claiming that "I do have education and experience in this." is a pretty lame proof. Sorry.

In short, if I am wrong please tell me why. Not that you know better, because that's not very educative.

First, please tone down the piss and vinegar. If you want to learn then read, read a second and third source, ask questions, repeat. If you want to rant then I don't care enough to help you. However I will answer the main technical question.

The input voltage and current are what is required to keep the internal DC reservoir charged under full load. The output is the available current PER LEG at the supplied voltage. There are 3 legs but not all will be full on at any given time. So the "missing" 6.725A is available to the other two legs.

Also from the specs you see two related bits of info: Output Power and Capacity. Both numbers are kVolts X Amps but "Power" also takes into account the phase angle caused by the power factor of the motor. With a really bad power factor a device could have REALLY HIGH current draw at a high voltage but the power transferred would be almost zero because the voltage and current don't happen at the same time. However there would still be heat generated from the current flow.

Typically motors will draw a specified current at a specific voltage while under load. Voltage, AKA electromotive force, is the push to move electrons. The movement of electrons is measured in Amps. The current draw is determined by the load. If you load the motor more it draws more current. Draw too much and a some form of current limit kicks in. Usually a breaker or fuse opens and shuts down the system. The Bosch appears to have some protections build in and can reduce the output drive levels to reduce current. This does not mean you can put too big of motor on it and drive too hard of load as normal operation. Just that it can offer some protection. The VFD and motor must be specified as a pair for proper operation and longevity.

Spend some quality time with Google and Wikipedia.

[A_Camera]

First, please tone down the piss and vinegar. If you want to learn then read, read a second and third source, ask questions, repeat. If you want to rant then I don't care enough to help you. However I will answer the main technical question.

The input voltage and current are what is required to keep the internal DC reservoir charged under full load. The output is the available current PER LEG at the supplied voltage. There are 3 legs but not all will be full on at any given time. So the "missing" 6.725A is available to the other two legs.

Also from the specs you see two related bits of info: Output Power and Capacity. Both numbers are kVolts X Amps but "Power" also takes into account the phase angle caused by the power factor of the motor. With a really bad power factor a device could have REALLY HIGH current draw at a high voltage but the power transferred would be almost zero because the voltage and current don't happen at the same time. However there would still be heat generated from the current flow.

Typically motors will draw a specified current at a specific voltage while under load. Voltage, AKA electromotive force, is the push to move electrons. The movement of electrons is measured in Amps. The current draw is determined by the load. If you load the motor more it draws more current. Draw too much and a some form of current limit kicks in. Usually a breaker or fuse opens and shuts down the system. The Bosch appears to have some protections build in and can reduce the output drive levels to reduce current. This does not mean you can put too big of motor on it and drive too hard of load as normal operation. Just that it can offer some protection. The VFD and motor must be specified as a pair for proper operation and longevity.

Spend some quality time with Google and Wikipedia.

You need to cool down and get off your high horses. I decided to edit and remove my answer, except the last part. below. Though I must admit, I found your redefinition of per phase to "PER LEG" quite a bit amusing. My teachers called it phases, not legs. My motor have no legs, at least not as far as I can see it. It has three windings connected in delta and is run by using a VFD which converts a single phase 50Hz to three phases 0-400Hz. The part which is not removed is:

Yippee... I just noticed there is an "Ignore" feature on this forum. I try it out on you, so I don't have to waste more time on you and hopefully you won't see my posts so you won't have to get upset any more. So it is hopefully a win-win..

Bye.

[toyeacnc]

Hi,dear,

About the spindle power for aluminum ,if engraving, 1.5KW is good. If you cut,surely,bigger spindle is better,so cutting aluminum,2.2KW spindle is good choice.

any help,you can contact with me by email toyeacnc@hotmail.com or jenny@toyeacnc.com .

Good luck.

Jenny

[Jon.N.CNC]

My 2.2kw is only just up to the task of aluminium. It's not great at it. 4-5kw would be better.

Using single phase 13a, you may need to consider using AC stepper drivers on a toroidal, this frees up some single phase current.

[mactec54]

Something to consider - although your 2.2kW spindle may draw a million amps at full load, chances are you're never going to bog it down to a tenth of that. They ship here with a standard power socket where, in Australia, anything over 10A per appliance needs a special 15A plug with a larger earth and, I believe, a dedicated circuit.

You could put an 8A breaker onto the unit between it and the power cord so that it tripped before it took anything else out, and just rely on the fact you're unlikely to go anywhere near full power draw.

If you set the VFD correctly it can't draw more than the max amps set in the VFD

It would be very foolish to put an 8Amp breaker on the input power supply, the input power supply has to have the required supply needed for the VFD, which is near double of the output Amps when running on single phase

[mactec54]

I think that display is only for the motor current, not the input current. Never the less, to measure the input current is very easy, there are cheap energy meters which can be plugged in into the wall, between a machine and the wall plug, showing mains voltage, used current, used power and kWh, run time, costs and some other things.

Anyway, what would be interesting to know if there is a setting to limit the current.

Whatever you set in the VFD is all the spindle can draw, so if the 2.2Kw spindle is set at 9 Amps in the VFD that is all the VFD will supply, there are other Parameter setting that can allow the Spindle/Motor to draw more but when set at 100% it will not supply more than the 9 Amps

Yes the input power supply will need to have the required supply also, for single phase operation, the input Amp draw is almost double of what the output Amp will be, so they need to have a supply that can support this

[Atomic_Sheep]

These spindles have amin RPM of 8000. Isn't that much too high for working with aluminium?

[A_Camera]

These spindles have amin RPM of 8000. Isn't that much too high for working with aluminium?

I am milling aluminium at 18-22krpm but the motors are speced for min 6000 rpm not 8000. I do use mine below 6000 also.

[mactec54]

You need to cool down and get off your high horses. I decided to edit and remove my answer, except the last part. below. Though I must admit, I found your redefinition of per phase to "PER LEG" quite a bit amusing. My teachers called it phases, not legs. My motor have no legs, at least not as far as I can see it. It has three windings connected in delta and is run by using a VFD which converts a single phase 50Hz to three phases 0-400Hz. The part which is not removed is

I see that I replied to one of your old posts as no one seemed to correct you

Snip below shows how the word Leg is used as an electrical term

That is a common term for electrical engineers to use Leg instead of Phase, so your teacher did not teach you everything, and by the posts that you both have posted there are many things posted that are incorrect, I guess wannabe's strike again

[m1n1m]

I wouldn’t worry to much about the fuse. I run this 2tonn machine with 3.6kW spindle, 3x 750W servo motors, flood coolant pump, conveyor screw motor + controls off a 16A breaker. I don’t do heavy cutting tho but still more than I think a router can do. If you have the same fuses as in Norway they have I2=1.45xIn normally and that basically means that you can pull 5.3kW over 1hour before it trips. In my case with 3 phase it’s over 9kW. I never run that hard that long

(Sorry for the rotation... posted from phone)

[mactec54]

These spindles have amin RPM of 8000. Isn't that much too high for working with aluminium?

No that is not to high for mill aluminum, if your machine is up to it you can cut aluminum at 60,000 RPM

The Minimum speed is 6000 RPM, for most of these spindles, I'm playing with one now that is more powerful than the normal 2.2Kw that are everywhere, this one is a 2.2Kw 10A rated for a Minimum of 3000RPM and has full torque at that speed it has a much longer rotor and stator that the normal spindle

The regular 2.2Kw does not have any useful torque for cutting below 7000RPM

[A_Camera]

I see that I replied to one of your old posts as no one seemed to correct you

Snip below shows how the word Leg is used as an electrical term

That is a common term for electrical engineers to use Leg instead of Phase, so your teacher did not teach you everything, and by the posts that you both have posted there are many things posted that are incorrect, I guess wannabe's strike again

It took you two years to find that EXAMPLE... Nice work.

Did you actually read and UNDERSTOOD what it says and why?

Let me help you... It starts with "If you're NOT electrically minded...." and then it uses the word "leg" instead of phase, putting "phase" in parenthesis for a reason, so that people who are "electrically minded" would not get upset. I don't know where you found that picture, but it certainly is NOT from a book for electrical engineers.

You are though probably right, my teachers did not teach me everything, but whatever I learned gave me a good career life and during the five years I worked as electrical engineer in South Africa between 1975 and 1980, I have NEVER heard the term "leg" being used by any trained engineer or electrician. Perhaps in the USA the normal term is "leg", but it can't be that common if this was the best example you could find... and even if it is common, who cares really, other than you?

[mactec54]

It took you two years to find that EXAMPLE... Nice work.

Did you actually read and UNDERSTOOD what it says and why?

Let me help you... It starts with "If you're NOT electrically minded...." and then it uses the word "leg" instead of phase, putting "phase" in parenthesis for a reason, so that people who are "electrically minded" would not get upset. I don't know where you found that picture, but it certainly is NOT from a book for electrical engineers.

You are though probably right, my teachers did not teach me everything, but whatever I learned gave me a good career life and during the five years I worked as electrical engineer in South Africa between 1975 and 1980, I have NEVER heard the term "leg" being used by any trained engineer or electrician. Perhaps in the USA the normal term is "leg", but it can't be that common if this was the best example you could find... and even if it is common, who cares really, other than you?

Ignorance at its best

It is a common term widely used, and not just in the USA, no it did not take me 2 years to find the example, I stated that it was an old post, I was reply too, as nobody else had corrected you

We have seen how much you know about wiring with your failed Spindle Cable install, not only did you use the incorrect size cable for the spindle plug, you showed an electrical code violation, I have the photo you posted, of what you had done, that I use as an example, for training exercises, of how not to wire a plug like this

https://en.wikipedia.org/wiki/High-leg_delta

[automationtechinc]

2.2KW Spindle (4 Bearing ) for aluminium
https://www.automationtechnologiesin...uter-ethernet/

Or thi sone is ok too
https://www.automationtechnologiesin...r/3-axis-6040/

[A_Camera]

Mactec54,

I have no time to waste on you and not interested in your flame war. You have said what you felt you needed to say, now you can go on with your life and find something more meaningful to do.

[Littlemango]

The problem here is that in your previous explanations it sometimes seems as if you mean to say the all the phases will draw 6.1 amps at the same time, which is obviously not the case as you cant input 13.5 and get 18.3 out. Stating that it outputs 6.1A per phase is misleading , though I think you understood it correctly it was simply stated it in a way that was not communicated well to others.

The specs on your bosch are maximums and do not correlate to a scenario where you will draw 13.5A total and output 6.1A on every phase, or even 6.1 on two of the phases.
It will distribute some of that power to each phase at a given time. Thus the whole square root of 3 formula.
6.1x1.73.....theres your missing current. or 13.5 /1.73 These apply to "real" motors and the 6.1 A is what one phase at a time might hit at peak during revolution.
Your VFD maximums do not carry over to the way the chinese motors are rated.
your VFD will laugh at a chinese 1.5kw and never come near drawing 13.5A
these chinese motors are rated at absolute maximums (stall current) so yes you can indeed look at a 2.2's 10 amp rating and say well 11 or 12 will most definitely run it, until its smoking. I've only seen my 1.5 spike to 1420w total draw and that was a full stall.