> > Even though it's unlikely it could fail. Commercial drives use to have a > > safe > > torque off input. I expect it work for AC motors but if a DC motor is > > overloaded semiconductors usually fail with short so it could run at full > > speed > > in one direction even if control signals are turned off. > > > The HP_UHU DC Servo drives track the encoder verses input pulses. So if the > motor goes off and exceeds the tracking error a fault is generated. The > board has a coupled FAULT_OUT/IN circuit so that when one motor faults it > pulls down the fault line (Open Collector). Since the other drives are also > connected to this same signal a fault from one drive takes the whole works > down.
Maybe except for a failed sensor. Semiconductors usually fail short circuited so properly designed it could probably be made safe with high integrety. To be really sure position sensor must "continuously" which in practice might be periodically often enough read a known sensor value, it is important failure of sensor does not produce known sensor value, not necessarily with accuray good enough for normal use, accuracy good enough to keep it from move far enough away to get unsafe should be good enough. If this is not fulfilled I would not consider machine really safe from uninteded movement unless E-stop is pressed. Even if risc of failure is small it add up if you work within reach of machine year after year. I have seen fork lifts with automatic leveling, if this is not properly done so that it move to the end in case a sensor fail I would not be suprised if it would happen to a few after some years if many enough is manufactured. Logical errors are common so I might have made some misstake above. _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
