Chokes in series with servomotors

[MikeAber]

Hi Mariss,

I'm in the process of replacing Analam controls in an EX-CELL-O mill with G320's for the drivers. The original driver boards have chokes wired in series with the motor outputs. I am guessing these are there to "soften" the current load to the 1985 driver transistors. You can see the chokes at the bottom of the control cabinet in the first picture.

Do you recommend removing the chokes? These are some huge SEM motors!

Do you have any recommendations for settings when using the original Analam glass scales to provide feedback for the 320's? I don't mind if the machine runs @ 60 or so IPM. Ball screws are .200 pitch, belt drive reduction is 2:1 and the new power supply is 70VDC @ 35A. Running Mach2Mill @ 45KHZ with the Sound Logic PC-2 controller board.

[ViperTX]

Generally the chokes are used to provide nearly instantaneous current....there is always some lag when doing the same from a capacitor.....so, it's an instant resevoir...keep them.

[crazyman]

Will your gekos even handle the current rating of these hugr servos?
Or are you saying you'll just be fine with the low amp rating of the geckos?

[MikeAber]

The current isn''t an issue as I tested the servos with a variable voltage power supply and there is plenty of power to move the axes with 5 or 10 amps and the geckos can handle twice that. I was looking for Mariss to give me his recommendation to leave the chokes in series or to remove them, I wouldn't want to damage the G320's from the interaction of the chokes, if the chokes help protect the G320's it would be prudent to leave them. As he has not commented, I'll run tests with and without the chokes to see if there is any difference. I'm curious as to why the original drivers had chokes in series with the motors.

Of course if I blow one of the G320's during testing I'll send it back for warranty!

[Al_The_Man]

The original drive manufacturer had a specified minimum inductance that the motor should meet, those S.E.M. motors are very low inductance therefore to ensure the current was properley filtered, the chokes were used.
Most manufactures of PWM drives quote a minmum load inductance so motors should always be checked to see if they meet the criteria.
Al.

[MikeAber]

Good answer Al,

Thanks!