On Wednesday 13 February 2013 13:49:02 Jon Elson did opine: > >> On Tuesday 12 February 2013 22:36:22 Przemek Klosowski did opine: > >>> I thought this is a no-no---opening of the circuit causes the servo > >>> driver stage to abruptly change from high-current to zero current > >>> flow, bound to cause transients in every inductance in the system. > > (I think I got the attribution right, above.) > > Another way to do this is to open the DC supply to the servo drive and > cut in > a braking resistor. If it is a control loop fault, the usual > freewheel/protection > diodes in the servo amp's bridges will conduct energy from the motor to > the braking resistor, resulting in a well-controlled stop. If > transistors have failed to short in the servo amp, then the braking may > be more abrupt. But, in all cases, the motors should stop, and this > method of braking should not cause any further damage to drives, > motors, etc. than might have been caused by the original fault. > > Also, you can use one set of relays for all your servo amps. > > (I actually make a solid state device that does this, it has the main > pass transistor and a transistor to switch the braking resistor on.) > > Jon
And this of course would be ideal since the transistors don't normally have a contact bounce. I wasn't aware you were making that Jon, thanks. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> There is no comfort without pain; thus we define salvation through suffering. -- Cato I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
