LWI Load Weighing for Isolated Platform provides signals for various load dispatching operations and pre-torquing for IMC family controllers.
By identifying whether the load in the car is light, heavy or an overload, the system can activate loaded car hall call bypass, anti-nuisance car call cancellation, and lobby up peak mode.
The load weigher=s pre-torquing signal is used to adjust the amount of torque produced by the motor B as the brake lifts B to provide smooth starts. Every time the car leaves a floor, a new value is computed, based on how the car is loaded, insuring that every start is the smoothest possible start.
Without pre-torquing, some slight initial armature rotation occurs as the brake is lifting in order to gain complete control of the motor. As a result, the start may not be as smooth as it could be. With LWI, an initial torque value is determined to exactly counteract any tendency for the motor to move in the direction of the load as the brake is lifted, thereby insuring ideal starts under all load conditions.
How it Works
The LWI system uses a proximity sensor and amplifier, which are both mounted under the cab floor. The proximity sensor bracket is typically attached to one of the car sling channels underneath the car. A target bracket is attached to the floor itself. The clearance between the sensor and target varies with car loading, generating a signal value from 0 to eight VDC.
The LWI system is for isolated platform elevators (70-80% of all elevators with contract speed of 500 fpm or more have isolated platform cab construction). The condition and composition of rubber isolation pads (4-6 per cab typical) is critical to successful, reliable operation. Pads should be replaced every five years, or whenever any cracking or damage is detected.