ac motor control

[hngopal]

does anybody know if a single phase 115 vac motor, running at around 1700 rpm come to a dead stop if the power is switched off? by the way, the motor is driving a conveyor and the speed of the conveyor is being reduced first by a 30:1 gear box.

The idea is to start/stop the conveyor using a programmable relay.

Thanks.

 

[gcaudill]

With a 30:1 gearbox the reflected inertia from the gearbox output shaft to the motor shaft will be very low. The load will most likely "wind down" very quickly if there is and amount of mechanical damping in the system on the load side. The motor stops producing torque as soon as the power is removed from the terminals. The design of the gearbox will have a large impact on how easy or difficult it is to drive the output shaft.

 

[jraef]

"... running at around 1700 rpm come to a dead stop ..."

You left out an operative in between "rpm" and "come". Should? would? could? will? must? might? can? wants to? better not or I'll tell your father when he gets home?

In general though, the coast-to-stop time is dependant upon the load, not the motor. High inertia combined with low friction would mean a long coast time, low inertia with high friction would mean a very short coast time. Any combination variables of those two load components will result in an infinately variable outcome. In other words, no way to tell with the information you provided.

That said, conveyors are typically low inertia high friction, and combined with a 30:1 gear reduction, it is likely that it will stop quickly. But is the conveyor load going down hill? Is there a flywheel or dancer on it that has enough mass to keep it going? Is the gear reduction going the other way (I can't imagine a conveyor pulley running at 51,000rpm, but hey, who knows)?

"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla

 

[Skogsgurra]

"comes" perhaps?

English is not so easy for us foreigners...

Gunnar Englund

http://www.gke.org

 

[jraef]

Oops, duh. English is difficult even for some of the rest of us who have been speaking it all out lives! :~/