Cincinnati Milacron Arrow 750 Retrofit

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22 Apr 2020 12:26 #165091 by stegrg
I quickly reviewed the 8i20 manual and it states that motor supply voltage can be between 35 and 400VDC. Does that mean the 8i20 can accept any voltage within that range and still produce up to 400V 2200W 3 phase power depending on available DC current?

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22 Apr 2020 12:48 #165095 by tommylight
Might want to wait for PCW to reply to this, but i do not think so. It will produce up to nearly the input voltage on the motor outputs.
I.E. powering it with 100V will give 90 to 95V on the outputs depending on the output stage ( if MosFets are used in the output stage it will be very near the max, IGBT's and Bipollar transistors will have a bit more loses, so lower output voltage ).
The thing with servo motors is that they are made to work with less voltage than the drive voltage, so the drive has to be set up properly to keep from pushing them to far. That has to do with the inductance and the speed the coils in the motor can be charged, the current running through them, load, etc. Most of the time the motors do not have a rated voltage on them, just the KV value, or how many rotations it will do for every volt put through them, and the torque produced depending on the current, and the max RPM.

To put it simply, you can drive a 100V motor with a 200V drive if it is set up properly. You can also drive a 200V motor with a 100V drive, but it will not be able to reach the torque and speed it was designed for.
Did i complicate it to much ?

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22 Apr 2020 13:43 - 22 Apr 2020 13:44 #165102 by stegrg
I'm lucky enough to have the complete manuals for the servos on this machine. The motor I have is the 1FT6064-6AF71 on the Z axis. What you are describing is shown on the a, b, and c curves in the attached diagram below with regards to speed/torque and voltages.

If I'm understanding this information correctly, if the 8i20 is capable of supplying 400Vrms in 3 phase, then I should be able to produce a maximum speed-torque curve between curves b and c on the chart. I suppose if I'm using the maximum output of the 8i20 card, I will likely need to provide it with a full 400VDC voltage supply, if input and output voltages are closely related.
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Last edit: 22 Apr 2020 13:44 by stegrg.
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22 Apr 2020 14:00 #165103 by tommylight
Yes and yes, although i would not go that high, i would try to keep it between 200 and 300V as that should have still enough torque and speed for a Z axis.
You can have a look at ebay for VFD power supplies, i've seen a lot of them a while back at reasonable prices. It looks like a VFD but it only has rectifying and protections inside.
www.ebay.com/sch/i.html?_from=R40&_trksi...dkw=VFD+power+supply

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22 Apr 2020 17:49 #165141 by stegrg
My plan is to retrofit the x, y and z axis servos with the 8i20 card. I think the x and y axis servos are the same as the z axis but I'm not entirely sure until I remove them from the machine.

Thanks for the feedback. I'll keep an eye out for the VFD power supplies you mentioned.
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22 Apr 2020 20:07 #165153 by tommylight

stegrg wrote: Thanks for the feedback. I'll keep an eye out for the VFD power supplies you mentioned.

Building a 6KW power supply is not easy or cheap, so finding used ones is a much better option. Some guy here had several of them, mostly 3X380V inputs, but i could not buy them as he was insisting they are the actual drives and wanted 750 Euro a piece for used ones.
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27 May 2020 12:46 #169128 by stegrg
Does the power supply need to be able to provide +400VDC relative to ground or does it need to able to provide +/-400VDC relative to ground for an 8i20 card?

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