8i20 with 7i77/7i74 combo

Just to be on the safe side, after reading through the 8i20 manual i could not find any reference to 7i74, only 7i44, but as far as i know they are the same thing with the different host connector ( 7i74 25 pin, 7i44 50 pin ), or did i miss something?
The situation is that i need to change 1 drive ( or maybe 2 ) on a hurco BMC 20 with Yaskawa drives, but i do not like paying over 2000 euro a piece for 30 years old equipment for a lot of reasons. The motors on it are 0.85 KW AC on all axis, so using 3 x 8i20 would cost less even with the time and modifications required to make that work.
While i am at it, would a 7i80 work with two 7i29 and a 8i20 for a 4 axis and spindle system? I am fairly certain that it will, just need a confirmation.
A lot more questions but for now i will stop.
I am poised at using anything Mesa as much as i possibly can.
Thanx

I am anxious to see how this turns out.

The only issue i see is the 8i20 is torque mode only. I did see a on of 8c20? for board that you can use velocity mode. Not sure but I am sure i read it. maybe 3C20.

I never used servo's in torque mode so I dont know how that would pan out.

"The 8I20 is a low cost 2200W 400V three phase torque mode/voltage mode
amplifier for synchronous permanent magnet servo motors (Brushless AC servo) up to
approximately 3HP. The 8I20 will supply peak currents of 30A."
That is a quote from 8i20 manual, meaning torque or voltage mode, as far as i could understand.
I read on this forum that torque mode is best set up with 2 PID loops for each axis, but i never did try that.

This is from the mesa site: Mesa site link for 8i20

For applications that require a smart amplifier, the 8C20 daughter card can be added. The 8I20/8C20 combination adds the features of analog input velocity and torque modes, step and direction mode, quadrature input mode, smart position control mode, and four isolated inputs and outputs.


I cant seem to find the 8C20 card anywhere.

Just checked mesanet.com, mesaus.com, eusurplus.com, none of them have 8i20 on stock !!! I wonder when would they be available ??? PCW? JT? Filipe?
Andy, you have used 8i20, any tips?
Thank you,
Tom

tommylight wrote: Andy, you have used 8i20, any tips?

I haven't seen any need to use cascaded PID, but I do agree that it ought to work better.

You have Yaskawa motors. What type of feedback do they have?

5000 PPR incremental encoders with diferential outputs including index, 5V power supply so they are perfect for 7i77. There are no tachos.
As far as i understood from the manual, they can be used as is with the 8i20, but not certain. Could not find any more info on them aside form your youtube videos.
I would like to use another 7i?? That is a dual H bridge ( bigest one ) for a plasma cutter as i already have a 5i25/7i77 combo on it.

Double PID was mentioned on this forum, if i remember correctly.

Any commutation feedback from the motors?

No HAL sensors, nothing. Just 3 phase and encoder.

The encoder probably does something clever at startup to give absolute position for commutation.