How do I choose a motor to operate a rotary switching device?

Question

I need to build a device that has a motor which operates a hefty rotary disconnect switch. The switch is spring loaded in the On and Off positions and I know the operating torque requirement of the switch. The switch has an Aux contact so I can read the position of the switch at any time. I also want to be able to operate the switch manually when the motor is turned off. The motor only has to turn 90 degress back and forth to turn the switch On or Off. I intend to use a Geneva Mechanism between the motor and the switch. I don't know what type of motor is most suited for this project.

Thank you for the comments. What I'm really asking is do I choose a stepper motor, a servo motor, a DC motor (brushless or not?), gearmotor? I haven't worked with motors much - I do mostly embedded PIC stuff - so I'm just trying to pick a path to go down for this design.

Answer 1

you want some sort of gear-motor that has enoiugh torque to drive your mechanism.

Note that a classic geneva drive has a large levet on drive side than on the driven side when it's in the middle of the movement.

The internal geneva is the opposite and will probably work better for your task

animated version: https://en.wikipedia.org/wiki/File:Internal_Geneva_wheel_ani.gif

also note that the internal geneva is free-wheeling when the drive pin is in the parked position.

As you only need to rotate 90 degrees your driven wheel only needs two arms.

if you go with a motor whose datasheet torque exceeds the datasheet operating torque of the switch it should work well. When new the motor will likely have more torque and the switch require less, but as they age their performance may decay towards what the datasheet promises. the geneva drive will give a slight torque multiplication which will help too.