Ward Leonard Machines Vs. VVVF (Gearless)greenspun.com : LUSENET : Elevator Problem Discussion : One Thread
We have four elevators with Ward Leonard machines (about 28 years old), one of our modernization contractors plans to replace them with VVVF machines, the other modernization contractor plans to maintain the CC machines, where I can found something like a comparative table of the main characteristics of each type of technology.
-- Armando José Gallo Guillén (email@example.com), January 03, 2002
look in your yellow pages for elevator consultants, they're always around (like flies). they typically can "expound eloquently" about a vast array of subjects, including elevators.
-- cliff (firstname.lastname@example.org), January 04, 2002.
There is a good article written by Adrian Schiner, Kone Lifts, Ltd. in Elevator World (USA), January 1997.
SCR DC drives may be used to replace the motor-gen set and use the existing DC lift machine. Magnetek supplys many DC drives for the elevator industry in USA & UK markets via elevator service OEMs.
Replacement of the DC motor to convert to VVVF/VFAC is relativy easy with a geared machine, but usually requires the lift machine itself to be replaced for low rpm gearless lifts (as the motor and sheave are often inseparable). Low speed gearless requires very special motors, AC or DC. Magnetek also supplies AC drives for this purpose, for geared or gearless, through elevator/lift OEMs.
-- Don Vollrath (email@example.com), January 04, 2002.
Dear Sir, Having some 10 years experience with this matter, you have the following options: 1) determine the cost for replacement of the motors (and often the machines themselfs) in combination with the VVVF drives towards and AC system. 2) determine if your solution doesn't require a change on the controller side (complete or partial replacement of the controller cabinet and/or shaft equippement) 3) try to find out if you could reach an affordable solution with an AC inverter (e.g. Control Techniques Mentor Drive if the mechanics ar OK) Please let me know if you still further questions. Kind Regards, Manu Verhelst
-- emmanuel verhelst (firstname.lastname@example.org), September 30, 2003.
how the break of gearless machine work?
-- salim samir ghreizy (email@example.com), June 19, 2004.
The break on a gearless machine works exactly in the same way as the classical brake does. In Europe it consists of a dual coil that opens the brake when powered. Sometimes there is a feedback towards the controller to confirm the actual status of the breake: opened or closed.
-- (firstname.lastname@example.org), July 07, 2004.