The complete elevator control system regulates the movements of each car in the system and organizes the total movement of the entire group of cars, with the goal of maximizing customer satisfaction. In a large hotel; the system keeps track of all up calls and down calls and when the call was made.
The system knows the location of all cars and their travel direction: in addition, the system knows when cars are full of passengers. As a result of micro computer chips and printed circuits, many of the older control systems are now obsolete, and are being replaced to improve the overall efficiency of the elevator system.
A good control system can eliminate the requirement of additional cars, or a system can be modernized with a new control and cars can be permanently taken out of service. The obsolete control systems are the single automatic push-button and collective-control systems are still being used and installed in small hotels.
This system has a push-button on each guest room floor, up and down calls are not registered, hence a passenger wanting to go up waits for a car and only when the car doors open does the passenger know which way the car is going.
The passenger must push the call button again to call another car. The chances are greatly improved that the next car will be going in the desired direction.
The minimum standard-control system is the selective collective control system. The system registers all up and down calls and sends the closest car travelling in the correct direction to the appropriate level. When all calls have been satisfied, the car stops and shuts off the MG. set if it is a variable voltage drive system.
One or more cars can be removed from the basic control system and be used as service elevators; these are placed on manual control. A potential problem with this system is that cars have a tendency to bunch at various floor levels in a hotel.
The car-bunching problem can be reduced with a selective collective-control multiple-zoning system. The basic control system operates a specified number of cars in predetermined building zones. When cars are assigned to a specific zone, the car always returns to that zone and awaits further instructions.
Zones can be time programmed. During busy up-load periods, several cars will return to the hotel lobby to pick up more passengers. During the down-load time, cars return to predetermined upper-level zones rather than stay at the lobby level. The multiple-zoning control refinement is a good minimum-control system for a conventional hotel.
An improved control system is the programmed traffic pattern control. Degrees of up loads and down loads are specified, time periods are specified, zoning is accomplished, and off-hour operations are specified.
Some of you may recall the elevator floor starter system, in which a person directed traffic to zoned cars at the lobby elevator foyer during busy periods. The starter manually starts the car after it was loaded or within a specified time period. A computer program has replaced the starter.
The current optimal elevator control system is the computerized control. It does everything the previous system does plus analyse the system status every two or three seconds and revises its built-in programs to satisfy changing demand characteristics.
It also keeps a time log record of lobby calls and optimizes service quality at the lobby level. These modern control systems use solid-state printed circuits, which can be changed or reprogrammed by simply removing one printed circuit and replacing it with another.
Modern elevator control systems also have a lobby panel that can be visually checked at any time to observe the location of all cars. Cars can be added or removed from service at this panel. Manual overrides are also possible for selected cars at any time from the lobby control panel. In these cases, the computerized control system would then recomputed its car movement plans with the remaining cars left in the systems.
Computerized and semi computerized control systems with printed circuits are relatively easy to maintain. Have a backup printed circuit in case one ceases to function, or manually override portions of the system while repairs are being made. Printed circuits are generally very dependable.
Malfunctioning printed circuit panels are generally sent back to the manufacturer for reprogramming or repair. Naturally, all electrical connections must be checked to make sure they are secure. Supply voltage must be monitored and controlled; low voltage can have serious effects on the microchip memory characteristics.
High voltage can burn out the panels and must be corrected prior to installing a new printed circuit panel. The motor requires a higher degree of maintenance than a variable voltage control system.
Such a system is frequently used for hotel freight elevators or to satisfy an elevator requirement for a building of a limited number of guest-room floors (3 to 8 levels).
There are two elevator m/c control system Variable Voltage & Rheostatic.
The variable voltage elevator machine control is superior in all aspects, except for initial cost, when compared to the rheostatic. The rheostatic elevator machine control is used for low-speed cars generally in low-rise buildings. An alternating- current motor drives the sheave.
Voltage is controlled to the motor with a variable resistor. The system may result in jerky car movements when accelerating and decelerating. It is a low-cost system with a high maintenance requirement. Resistor components may have to be replaced by elevator machine control.
The sheave driving motor is a direct-current motor and DC energy must be provided to the motor. Controlling the voltage on the DC motor controls its speed and resulting car speed.
Motor response to changing voltage is almost instant, even to micro voltage changes. The result is a very smooth car ride, high-speed cars, and use in high-rise buildings. Variable voltage can be supplied by an MG set or a solid- state control panel.
Most modern elevator systems incorporate the solid-state variable voltage. System maintenance is greatly reduced when compared to the MG set and its series of controls. A major factor regarding the use of solid-state controls is improved electrical energy characteristics for the building.
Generally, the building power factor can be maintained at a high level, and overall elevator energy consumption is reduced because MG sets are not operating in the ideal state.
The elevator room ventilation requirements are much lower, there is less noise and fewer vibrations in the room and the emergency stand-by building generator requirements may be less with solid state controls. This system should be seriously considered if a present MG. set control system elevator machine is to be modernized in the near future.