escalataor,more load, slower? or still in the same speed...?greenspun.com : LUSENET : Elevator Problem Discussion : One Thread
i have a project at school, and i have escalator as my topic. I just want to ask, if more people are on the escalator, is the escalator getting slower or still in the constant speed? is there any relationship between the load and the speed of the escalator. please help me... i need the reply as soon as possible
-- Margaret A (firstname.lastname@example.org), February 06, 2005
Escalators are essentially a single speed device. There would probably be a very slight reduction in speed with more load, but not enough to matter for any practical purpose.
-- John Brannon (email@example.com), February 06, 2005.
Come on John,
Get out your abacus, protractor and slide rule out and give us some sort of a formula that has no use to us whatsoever so this girl can get an A on her paper...
-- Will (firstname.lastname@example.org), February 06, 2005.
the motors used for Escalators are normally the standard induction motors of the squirrel cage type these motors are used by all manufacturers. by using these motors you can achive constant speed where the speed not vary under load conditions, whether in the driving or electrical braking mode
-- (email@example.com), February 07, 2005.
As most escalators use induction motors, the change in speed against load is very small. For most induction motors the difference in speed between light load and full load is around 3% to 5% (so-called slip).
-- Lutfi Al-Sharif (firstname.lastname@example.org), February 07, 2005.
The escalator is driven by an A.C. motor which automatically attempts to run at a constant speed (the A.C. supply frequency divided by the number of pairs of poles in the motor). It does this by consuming more electricity automatically as the torque (load trying to stop it turning) on its shaft increases, thus making more power from the more electricity to hold its speed fairly constant. Hence, it's the electricity that increases rather than the speed that decreases (this all fails if the motor is overloaded but of course they are sized big enough to handle a full escalator). The mechanism is beyond a posting explanation but basically the A.C. motor makes a magnetic field that opposes and controls the electricity and this magnetic field reduces as the load increases, causing more electricity to flow. Sort of.
-- Barry Finch (email@example.com), February 08, 2005.
The escalator will essentially travel the same speed fully loaded or empty. Newer escalators use frequency drives and can inject more than 60 Hertz into the motor to keep the speed perfectly consistent whether loaded or unloaded. Hope this helps.
Davies Elevator Corporation Toronto, Canada
-- Warren Davies (firstname.lastname@example.org), February 08, 2005.