PID, brushed vs brushless

[unterhaus]

Originally Posted by Al_The_Man You are not refering to an AC servo are you? That sounds like a typical AC induction motor description. Al

I have heard that some servomotors are induction motors, but I don't know which companies, if any, make them this way

[Swede]

For what it's worth, every brushless motor that I have exhibits distinct stiffness when shorted, as Einar suggests. So once again, I am back into the brushless DC camp. The system shipped with 3 brushless motors, unlabeled, which also do this.

My next step is to compare every spec I have on my problematic Parker motors with a motor that I know works fine. There is a slight chance that the one specimen I unwrapped, of the 5 NIB, may be faulted internally, but I think that's a long shot.

I still need to trim the shafts of the brushless MCG's that do run fine so that I can mount them and actually run more comprehensive brushed vs. brushless tests.

This is an informative thread; thanks everybody who contributed.

[ESjaavik]

@Swede: Also check your driver specs. Usually there is a minimum required motor inductance. If your motor have too little inductance for the drive, it may not be able to handle the current rise. I don't know what will happen then, but blowing a fuse does sound like one possible outcome. My drives are directly connected to the line voltage and goes into fault mode in such a case. It took me a while to figure that one out.

[CNCAddict]

[QUOTE=Swede]For what it's worth, every brushless motor that I have exhibits distinct stiffness when shorted, as Einar suggests. So once again, I am back into the brushless DC camp.

I'm not sure what you mean by this? Any motor with permanent magnets will resist motion if the leads are shorted. This includes stepper motors and AC servos. Can you elaborate?

David Bloomfield