What is the differance between those drives?
There is no output performance difference. The only difference is in the communication protocol. B and C add Modbus & CAN communications
If you plan on using the drive in step/direction or 0-10v analog, then get the A version.
Keep in mind that there have been numerous reports of issues using the DYN4 in analog
position mode. Step/dir works fine (I've got 3 installations working great), but there appears to be a 5ms delay from the motor encoder back to the controller (LCNC). DMM uses a proprietary serial encoder signal from the motor to the DYN4, and then processes it and outputs a standard A-quad-B encoder signal for use by the external controller (LCNC).
This buffer/delay plays havoc with the servo loop unless you use external linear scales and program LCNC to ignore the DMM motor encoders.
I've seen no reports of serious problems with analog velocity mode, such as for a spindle motor, other than one or two unverified reports of motors not reaching top speed (can only get ~2700rpm vs 3kRPM nameplate, regardless of line voltage).
If your intention is to use the servo as a spindle because you also want homing capability (for an ATC), then there are less expensive/less complicated VFD's that can accomplish simple positioning (i.e Hitachi) using an induction motor with an encoder.
If you want a C-axis where the motor can hold a position (like a regular servo), then you might look in to the Delta drives/motors as an alternative.
If you want higher RPM and expect to have to over-drive your spindle because the DMM can only reach 3kRPM, you might consider an induction motor instead. There are plenty of quality induction motors with a max RPM of >5kRPM. Leeson, Baldor, Marathon and others all make VFD-ready motors with a CT ratio of 1000:1 or better that can hit 6kRPM no problem. They are heavier and larger than an equivalent kw permanent magnet AC servo, but the increased rotor inertia of an induction motor can actually be an advantage in a spindle application.
