Hi,
I thought it would be wise to ask for component suggestions for an AC servo drive that is most likely going to be produced industrially. I discussed about it on these threads:
http://www.cnczone.com/forums/showthread.php?t=14477
http://www.cnczone.com/forums/showthread.php?t=22028
The goal is to make the best price/performance drive ever and that's why also component selection plays an important role. Because component prices directly reflect to drive price it is favourable not to use the most expensive parts.
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Here are some components where I would like to see if there are better alternatives. I listed some features that are the most important criteria for choosing part.
MOSFET/IGBTs (current choice: IRF640N)
- 200-250 Vdc breakdown voltage
- higher than 15 amps rated current
- low total gate charge (Qg) (IRF640N, 67nC)
- fast internal diode, short reverse recovery time (Trr) (IRF640N 167-251ns, not very good)
Current sensing op-amp:
-Rail-to-rail inputs and outputs
-Operates on 5V (or even 3.3V) single supply
-Low input offset temperature drift (less than 5µV/C)
-Low input offset voltage (5 mV MAX)
-Low input noise voltage (5-15 nV/squareHz is very good)
-Bandwidth at least 1MHz, 2-10MHz is very suitable
AD8604 looks quite good. Now only if that has less noise... (has 33 nV/sqHz)
Step/dir optoisolator:
-Fast, determines how short pulses it accepts
-High current transfer ratio (CTR) or sensitivity, determines how much current requires to switch on. CTR of about 50% would allow control directly from parallel port without buffer circuit.
-Possibly logic gate output, or just transistor output
HCPL2630 is quite nice but probably needs buffering after parallel port.
Suggestions?![]()