In Reply to: AC motor + inverter for positioning application ? posted by G Gomez on 06/30/03 at 6:57 PM:
If you are located in Australia, I am able to advise where you can source a system that will acheive this function at an economical price.
If not, there are a number of vsd suppliers who have "positioning systems" on board. They work well with an ac motor/incremental encoder/forced cooling fan combination operating in "flux vector" control. Dynamic response is very good, typically 1500rpm to 0rpm in under 1sec, repeatability of 2increments using a 4096ppr encoder (2/4096 x 360deg).
If operating at full rated torque for long periods of time less than 20Hz, a forced cooling fan will be required to keep the motor cool. The inertia of the load should be no greater than 20:1 to the inertia of the motor rotor for good control. 1:1 inertia match would be ideal. Gear units are good to reduce the load inertia as the reflected inertia is the inverse ratio squared of the load inertia.
A braking resistor will be required if you wish to decelerate the load quicker than it would take to stop under power-off conditions. Claculations can be performed to determine the size of the resistor based on the duty cycle of the application.
I trust that the above helps.