Spindle requires higher current than rated :( - overheating...

Hello

I am currently building a cnc router table. Everything is working fine so far... steppers, mechanics, ball-screws etc.
the only thing that makes me lots of trouble is my spindle.
It is not one of the cheap ones you can buy from china. It is from a little bit higher price segment (500 USD). It has 1.5kW total power with water cooling and 3x cermaic bearings. From the manufactorer it is rated to be able to mill metal (the ceaper ones are clearly stated for wood craving only)

The spidle turns really great, makes smooth nice operation sound. I have it running with an mitsubishi VFD that I grabbed from eBay some time ago (FR-E520S-2.2K-EC) The VFD has lots of nice features.
The spinlde can spin easiliy from 0-400Hz, but the problem is, that it requires more current than the spindle is rated. I have set 5.5A current rating in the VFD parameters. The motor protection kicks in when its is load 150% for a longer time (a minute or so). Anyways the spinlde requires 7.2A (at 220V) when its full speed (400hz). I havent set the total motor power anywere. It is 1.5kW - and that is to total spindle power at 220V (220V * 7,2A)
I am too afraid to damage the motor, if I set the current limit any higher. Than the rated 5.5A. Unfortunately I dont have any information or data about the motor. I read that 5.5A just from the chinese engraving on the motor itself :(

In my mind the motor should require less current when it is with no load. So in idle full speed, I would have expected 1-2A at 220V.
So for now the spinlde gets up to 45°C when running for longer time (the temperature saturates then - I pump it into a 20l bucket with about 15l/h flow)
Hopefully you guys can give me a hint. I am searching for the proper parameter for over three entire days now - with still no success.

What currents I get at different speeds:

100Hz 3,97A 66V
150Hz 4,00A 92V
160Hz 3,80A 98V
184Hz 4,10A 111V
--> 185Hz 7,00A 111V (jup thats a problem... but why??)
200Hz 7,20A 120V
250HZ 7,10A 145V
300Hz 7,01A 170V
350Hz 7,10A 196V
400Hz 7,20A 225V


Here I post you the important configurations I made so far:

Base frequency: 400Hz
current for motor protection circuitry: 5.5A
Maximum output frequency: 120Hz
Minimum output frequency: 0Hz
current limit: 150%
current limit at higher speeds: 150% (I guess it is meant above 120Hz)
energising current: (set to "self cooled motor" - but can be also set from 0-500A)

I honestly still dont know the diefference between the base frequency and the output frequncy... (does anyone know?)

Thanks for you help anyways, even if it doesnt work then.

regards Max

Attachment 198676
Here is a picture of the motor engraving:

Max TheModder

Base frequency: 400Hz---------------This is correct
current for motor protection circuitry: 5.5A
Maximum output frequency: 120Hz--------------------This needs to be set to 400Hz
Minimum output frequency: 0Hz-------------not correct

The Maximum output frequency: should be set at 400Hz (120Hz will not be good)

The Minimum output frequency: 0Hz can't be zero because you spindle can not run at zero frequency you need to set this at what ever the lowest RPM the spindle motor can run, you can work that out from what your max RPM =400Hz lowest RPM=Hz setting

ok I set the minimum frequency to 80Hz. The Maximum output frequency has 120Hz limit int the properties, so I cant set this one to 400Hz. But this value was already overwritten by another property called "High-frequency limit" - is set this also already to 400Hz

So still no success. I think the solution is somewhere that could explain, why the spindle current rises suddenly to limit of the spindle at 184Hz. I have not set this value anywhere.

MaxThModder

Is you VFD rated for 400Hz??? if not then this is were your problem is, the VFD has to be able to have those settings, There are very few settings that you have to do for these spindles, so you may have changed settings that you don't need to, Reset the VFD to the default settings, & start again

The most important settings are

Base frequency: 400Hz
current for motor protection circuitry: 5.5A
Maximum output frequency: 400Hz
Minimum output frequency: 120Hz
Voltage 220
Amps 5.5
Number of poles

You don't need much more than this to get it running, if you can't set the Max frequency to 400Hz then you have a problem with the VFD being not suited for your spindle

hello

thanks for you help so far! Resetting the VFD and setting these parameters again did not change anything - still the same at 184Hz (current jumps to 7A from 4A)
I have no Idea what I could do, and I have no idea, what could be the cause. The VFD is clearly rated for up to 400Hz output in the datasheet.
Now I have attached the manuel of the VFD to this post. It would be very kind If you could take a look.

regards, Max

EDIT: I have now tried to lower the V/F Base_frequency from 400 to 320Hz to see what happens. The jump occurs exacly at the same frequency of 184Hz, but with a jump from 7 to 10A. So thats a mess.
Now I have either an expensive broken VFD or an expensive broken Spinlde, according to Schrödinger they are both at the same time... till I figure out.

MaxTheModdler

You must have the Base frequency at 400Hz You can not use different numbers this is what your spindle is 400Hz,I will take a look at the manual to see why you can't set to the
Max frequency also

MaxTheModdler

Your VFD may not be good enough for your spindle it has a parameter that may not allow, your spindle to run at 400Hz, it has a strange setup for the parameters

I found one you can set, Parameter 18
High Speed Max frequency to 400Hz

But there is another one that may be a problem Parameter 84
Motor Rated Frequency has a max setting of 120Hz You need it set at 400Hz for your spindle, so this is a problem

You need to set the number of Poles I think your spindle may be 4 Pole

Do you have the spindle wired correctly U V W needs to match spindle & VFD

I don't think you have a problem with the spindle, most likely the VFD is no good for your spindle, but try parameter 18 this will help

Hey Thanks for taking a look into the manual! Yes some paramters are quite confusing. But it is stated that paramter 18 overrwrites the value from the maxiumum output frequency. This parameter is only used for high frequency. The VFD has something like a current-vector mode, which is useful, when you need a motor to have high tourque at very low rpm. This setting with the motor frequency you found (with the 120Hz limit) is only for that mode, which seems to not allow any higher speeds.
Yes I have set back everything to the 400Hz settings.
Hmm - I havnt any information about the phase connection on the motor. I just found 4 Pins, which three of them where the coils and one was connected to nothing. So I just connected the phases without big attention - just swapped two to change the direction. Or is that a problem that I hav not connected U, V, and W 1:1 ?

MaxTheModder

The pins may be labeled 1 2 3

The fourth pin is ground make sure the ground pin in the spindle does make ground, some are not connected

1=U

2=V

3=W

If it is rotation is not correct, you can change that in the VFD

Max;
It looks like you have a VFD that must be electronically matched to the motor it is connected to. This is a common requirement for a VFD theses days. I took a look and found another manual for your VFD that provides much more setup info. See the attached manual starting at page 126. A 400Hz motor is anything but standard. The auto tuning function determines the proper settings and makes them for you. I suspect this is why you are pushing the current too high. (Or could be related to the problem). With an inverter that was not an auto tuning type you would simply set the base frequency to 400Hz and your max freq to 400Hz and you would be done. Regardless of what you do with any other settings the base freq must be set to 400Hz or you will get into trouble.
Good luck, VFDs can be tricky to setup sometimes.

Jim

jknee2

He still has to do the basic settings, before he can use the auto tune I think setting 84 will be a problem, this is the Spindle/motor frequency setting, the VFD drive has a max of 120Hz, & he needs to be able to set this to 400Hz

I noticed the 120 hz max on the max speed parameter. It was stated above that the motor was already running above 120 hz so that max must change when you set 400 hz as your base. Yes you are certainly correct. The base settings have to be made. Never meant to imply otherwise. What I am saying is that the auto tune will yield good results and could fix the over current situation.
Cheers


Jim Knee

Yup, that parameter 84 might be a problem if it can't go past 120 hz.
These VFDs are designed for standard 50/60 hz motors.
You would think that the VFD should handle a 400 hz motor if the base freq can be set up to 400. Sounds like a call to the manufacturer is in order. The only time you would want to set the base freq to 400 is if you had a 400 hz motor. The base freq sets the volt/freq relationship and is normally what keeps the load current in its normal range.


Jim Knee