University of Jordan Electrical Engineering Department Electric Drive

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University of Jordan Electrical Engineering
DepartmentElectric Drive

• Electrical Elevators
• Done By Mohammad Abed Ashour
• 0086628

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The Electrical Elevator

• a permanent lifting equipment
• serving two or more landing
• levels, including a car for
• transportation of passengers,
• goods, running al least partially
• between rigid guide rails.

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Basic Components

• Elevator Car.
• Hoistway.
• Machine/drive system.
• Safety system.
• Control system.

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1. Elevator Car

• Elevator Car is the vehicle that travels between
  the different elevator stops carrying passengers.
• It is usually a heavy steel frame surrounding
  a cage of metal and wood panels. 

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1.1 Standard car size

• To prevent overloading of the car by persons, the
  available area of the car shall be limited and
  related to the rated load of the elevator. The
  following table shows the standard car sizes
  related to the elevator rated loads.

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•   of passengers rated load /75 
• Where
• 75 represents the average weight
• of a person in Kg. 
• The value obtained for the
• number of passengers shall be
• rounded to the nearest whole
• number. 

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• Car Width (CW) The horizontal dimensions between
  the inner surfaces of the car walls measured
  parallel to the front entrance and at 1m above
  the car floor. Car Height (CH) The inside
  vertical distance between the entrance threshold
  and the constructional roof of the car. Light
  fittings and false ceilings are accommodated
  within this dimension. Car Depth (CD) The
  horizontal dimensions between the inner surfaces
  of the car walls measured at right angles to the
  car width and at 1m above the car floor. 

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1.2 Elevator Car Components

• Car Sling, a metal framework connected to the
  means of suspension.
• The elevator cabin.
• Mechanical accessories which are 
• Car door and door operator. 
• Guide shoes. 
• Door Protective Device. 

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2. Hoistway

• Hoistway is the space enclosed by fireproof walls
  and elevator doors for the travel of one or more
  elevators, dumbwaiters or material lifts. It
  includes the pit and terminates at the underside
  of the overhead machinery space floor or grating
  or at the underside of the roof where the
  hoistway does not penetrate the roof. (Hoistway
  is sometimes called "hatchway" or "hatch".) 

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• A simple definition for
• the hoistway is the shaft
• that encompasses the
• elevator car. 

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• Note Generally the Hoistway serving all floors
  of the building but in high-rise buildings
  hoistways may be banked with specific hoistways
  serving only the lower floors and others serving
  only middle or upper floors while traveling in a
  blind hoistway until reaching the floors that it
  serves. A blind hoistway has no doors on the
  floors that it does not serve. 

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2.1 Hoistway components

• Guide rails for both the car counterweight.
• Counterweight.
• Suspension (Hoisting) Ropes (Cables).
• Landing (Hoistway) doors.
• Buffers in the pit.

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2.1.1 Guide Rails
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2.1.2 Counterweight

• Counterweight is a
• tracked weight that is
• suspended from cables
• and moves within its
• own set of guide rails
• along the hoistway
• walls.

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• The elevator car is balanced by a heavy
  counterweight that weighs roughly the same amount
  as the car when it's loaded half-full.
• When the elevator goes up, the counterweight goes
  down and vice-versa .

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Benefits of counterweight

• Balancing the mass of the complete car and a
  portion of rated load, and it will be equal to
  the dead weight of the car plus about 40 of the
  rated load. 
• Reducing the necessary consumed power for moving
  the elevator. 

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• By using counterweight, the motor needs to use
  much less force to move the car either up or
  down. Assuming the car and its contents weigh
  more than the counterweight, all the motor has to
  lift is the difference in weight between the two
  and supply a bit of extra force to overcome
  friction in the pulleys and so on.

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• Since less force is involved, there's less strain
  on the cables which makes the elevator a little
  bit safer.
• If the motor is using less force to move the car
  the same distance, it's doing less work against
  the force of gravity so the counterweight reduces
  the amount of energy the motor needs to use.

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• The counterweight reduces the amount of braking
  the elevator needs to use so it makes it much
  easier to control the elevator car.
• Imagine if there were no counterweight
  a heavily loaded elevator car would be
  really hard to pull upwards but, on the return
  journey, would tend to race to the ground all by
  itself if there weren't some sort of sturdy brake
  to stop it.

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• In a different design, known as a duplex
  counterweight-less elevator, two cars are
  connected to opposite ends of the same cable and
  effectively balance each other, doing away with
  the need for a counterweight.

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Counterweight components
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2.1.3 Suspension (Hoisting) Ropes (Cables) 
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• Suspension Ropes are Suspension means for car and
  counterweight, which are represented by steel
  wire ropes. 
• They are used on traction type elevators, usually
  attached to the crosshead and extending up into
  the machine room looping over the sheave on the
  motor and then down to the counter weights. 

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• The term Roping system can be defined as the
  arrangement of cables supporting the elevator and
  which has many types or arrangements as follows 
• Single wrap rope passes over sheave once and
  connected to counterweight.
• Double wrap rope wound over sheave twice in high
  speed elevators for additional traction.

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• 11 roping when rope connected to counterweight
  where cable travels as far as car in opposite
  direction.
• 21 roping rope wraps sheave on counterweight
  and connects to top of the shaft, rope moves
  twice as far as cab.

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2.1.4 Landing (Hoistway) Doors

• The door that is seen from each floor of a
  building is referred to as the outer or hoistway
  door.
• This hoistway door is a part of the building
  (each landing).
• It is important to realize that the car door does
  all the work the hoistway door is a dependent.
  These doors can be opened or closed by electric
  motors, or manually for emergency incidents. 

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• Safety devices are located at each landing to
  prevent inadvertent hoistway door openings and to
  prevent an elevator car from moving unless a door
  is in a locked position.
•  
• The difference between the car doors and the
  hoistway doors is that the elevator car door
  travels through the hoistway with the car but the
  hoistway doors are fixed doors in each landing
  floor. 

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2.1.5  Buffers in the pit 

• A Buffer is a device designed to stop a
  descending car or counterweight beyond its normal
  limit and to soften the force with which the
  elevator runs into the pit during an emergency.
  They may be of polyurethane or oil type in
  respect of the rated speed. 

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• There are two principal types of buffers in
  existence 
• Energy accumulation accumulate the kinetic
  energy of the car or counterweight.
• Energy dissipation dissipate the kinetic energy
  of the car or counterweight. 

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The main types of elevator buffers  
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• A Spring Buffer is one type of buffer most
  commonly found on hydraulic elevators or used for
  elevators with speeds less than 200 feet per
  minute. These devices are used to cushion the
  elevator and are most always located in the
  elevator pit. 

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• An Oil Buffer is another type of buffer more
  commonly found on traction elevators with speeds
  higher than 200 feet per minute.
• This type of buffer uses a combination of oil and
  springs to cushion a descending car or
  counterweight and are most commonly located in
  the elevator pit, because of their location in
  the pit buffers have a tendency to be exposed to
  water and flooding.
•  

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• They require routine cleaning and painting to
  assure they maintain their proper performance
  specifications. Oil buffers also need there oil
  checked and changed if exposed to flooding

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3. Elevator Machine and Drive System

• Driving machine is the power unit of the
  elevator, and usually located at the elevator
  machine room. 
• The Driving machine used to refer to the
  collection of components that raise or lower the
  elevator.
• These include the drive motor, brake, speed
  reduction unit, sheaves and encoders. 

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3.1 Types of Driving Machines

• 1- Gearless Machine
• 2- Geared Machine
• 3- Drum Machine 
• Look at the figures

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• Gearless Machine

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• Geared Machine

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• Drum Machine

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3.1.1 Gearless Machine

• It used in high rise applications whereby the
  drive motor and drive sheave are connected in
  line on a common shaft, without any mechanical
  speed reduction unit located between the drive
  motor and drive sheave. 
• Their sizes and shapes vary with load, speed and
  manufacture but the underlying principles and
  components are the same. 

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• Generally, Gearless machines are used for high
  speed lifts between (2.5 m/s) to (10 m/s) and
  they can be also used for lower speeds for
  special applications. 

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Gearless Machines Components 

• Electrical Motor.
• Traction Sheave or drum.
• Direct current armature in case of DC motor.
• Rotor in case of AC motor.
• Brake.
• Machine Bedplate.
• Supporting bearings.
• Deflector or double warp sheave.

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3.1.2 Geared Machine 

• It used in low and mid rise applications. This
  design utilizes a mechanical speed reduction gear
  set to reduce the rpm of the drive motor (input
  speed) to suit the required speed of the drive
  sheave and elevator (output speed). 
• Their sizes and shapes vary with load, speed and
  manufacture but the underlying principles and
  components are the same. 

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• Generally, geared machines are used for speeds
  between (0.1 m/s) and (2.5 m/s) and are suitable
  for loads from (5 Kg) up to (50,000 Kg) and
  above. 

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Geared Machines Components

• Drive motor.
• Brake.
• Speed reduction unit or gearbox.
• Drive sheave.
• Bedplate.
• Deflector sheave (if mounted as integral part of
  the bedplate assembly).

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Types of geared machine drive according to
location of installation

• 1-Overhead traction The drive machine located
  directly over top its hoistway or shaft.

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• 2-Basement traction
• The drive machine
• located at a basement.

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• 3-Offset traction  
• The drive machine
• located at the side of
• the hoistway.

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• Note 
• Basement and offset applications require
  additional deflector sheaves to properly lead
  suspension ropes off the drive sheave and to the
  car top or counterweight. 

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3.1.3 Drum Machine 

• It widely used in older passenger and freight
  elevator applications, though now rarely seen
  except for dumbwaiters.
• A drum design has one end of the suspension rope
  affixed to the inside of the winding drums drive
  sheave, and then allows to rope to reel in or off
  the outer surface of its sheave, depending upon
  the car direction of travel. 

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3.2 Main Components of machine drive system

• 1- Electrical Motor
• 2- Traction (Drive) Sheave
• 3- Secondary Sheave
• 4- Deflector Sheave
• 5- Brake
• 6- Speed reduction unit or gearbox
• 7- Machine Bedplate

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3.2.1 Electrical Motor

• Electrical Motor is used to raise and lower the
  elevator cab, the direction of motor rotation and
  speed (rpm) are directed and supervised by
  devices located within the elevator controller.
• The motor component of the elevator machine can
  be either a DC motor or an AC motor . 

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A) DC Motor

• DC motors use carbon brushes to control or
  regulate the operational speed of its motor.
• It is an important maintenance task to
  regularly inspect, repair and replace these
  brushes.
• Failure to do so in a timely fashion can result
  in equipment mis-operation and lead to
  significant motor damage.

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• Advantages of using DC motors
• Has a good starting torque. 
• Ease of speed control using a DC generator with a
  variable output or static converters. 

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B) AC Motor

• Advantages of using AC motors
• More regularly used because of its ruggedness and
  simplicity. 
• More ride quality. 

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Types of Electrical Traction Drive Systems

• A- Geared traction control, which includes 
• Single speed AC motor.
• Two speed AC motor.
• Variable voltage AC motor (VVAC).
• Variable voltage, variable frequency AC motor
  (VVVFAC).
• Variable voltage DC motor(VVDC). 

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• B- Gearless traction drives, which include
• Variable voltage DC motor (VVDC). 
• Variable voltage, variable frequency AC
  motor(VVVFAC). 

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3.2.2 Traction (Drive) Sheave

• The powered pulley connected to either the
  elevator drive motors output shaft (gearless) or
  to the output side of the mechanical speed
  reduction unit (geared).
• The circumference of the sheave has a series
  of U or V shaped grooves cut into it , in
  which sit the elevator suspension or hoist ropes.
• The friction loads created as the suspension
  ropes pass over the grooved surface of the sheave
  causes motion to be transmitted from the drive
  motor to the elevator cab or counterweight. 

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3.2.3 Secondary Sheave

• Pulley that is normally used on gearless
  elevators and is located directly beneath the
  machine or drive sheave.
• It has a grooved surface over which pass the
  suspension or hoist ropes. 

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3.2.4 Deflector Sheave

• Pulley used to offset or direct the vertical drop
  or location of the steel hoist ropes running
  between the elevator car and its counterweight.
• Where the horizontal distance between the hitch
  point for the car and the counterweight is larger
  than the diameter of the drive sheave, one or
  more deflector sheaves are used to guide the
  hoist ropes. 

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• These devices are grooved sheaves that lead
  elevator suspension ropes off the drive sheave
  down to the car top and counterweight.
• The number and size of deflector sheaves will be
  a function of the elevators size, machine
  placement and roping arrangement. 

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Drive Sheave without
Deflector Sheave

• Drive Sheave with
• Deflector Sheave

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3.2.5 Brake

• Traction and drum machines are provided with a
  mechanical brake, designed to stop and safely
  hold an elevator.
• A centrifugal force governor is provided on most
  elevators to guard against over speeding (when a
  car travels in excess of 20 of top speed, the
  governor will activate a safety stop device).
• Safeties are installed at the bottom of an
  elevator car and occasionally on counterweights
  to provide positive emergency stopping when
  activated by the governor. 

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• During typical operation, this
• brake is electrically lifted or
• picked against adjustable
• tensioned springs.
• In the event electrical power is
• removed from the brake, these springs ensure it
  immediately drops back against its drum or disk,
  bringing the car to a safe stop.
• While applied, the brake will securely hold in
  place the elevator and its counterweight.

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• Some older elevators have a control design
  whereby the brake is used to decelerate the car
  from full speed to a stop.
• Modern elevator controls use electrical circuitry
  to slow and stop the car under normal operation.
• Once the car has stopped, the brake is released
  to hold the car in position.

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• However, in the event an elevators safety
  circuit is actuated, the brake is immediately
  applied to stop and hold the car and its
  counterweight, regardless of the type of control. 

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Brake Components and Configurations

• The most common form of elevator brake consists
  of a machined drum onto which two curved shoes or
  pads drop onto the surface of the drum.
• The brake drum or disk is directly coupled to the
  elevator drive shaft. On some machines, the brake
  is an external element whereby the brake arms and
  their shoes are located outside and above the
  rotating drum surface as shown

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• There is one type of gearless machine that has
  its two brake arms applying force against an
  inside or interior rim on the drive sheave as
  shown

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3.2.6 Speed reduction unit or gearbox

• The most common type of speed reduction unit
  consists of a hardened steel worm shaft, mated
  with a bronze ring or crown gear (worm-gear set).
• The mating surfaces of these two elements are
  contained within an oil bath for lubrication.
• Regular access to the machine to check the level
  of oil, as well as the condition of the oil and
  the ring gear is an important aspect of ongoing
  equipment maintenance. 

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3.2.7 Machine Bedplate

• The gear box, motor and brake may be assembled on
  a common bedplate. This fabricated steel
  structure serves to keep all parts in accurate
  alignment and allows one-piece shipment. 
• Some machines have the motor and brake as an
  integral part of the gear case, removing the need
  for a separate bedplate. 

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4. Safety system

• Safety system components
• 1- Device for locking landing doors (Hoistway
  Door Interlock).
• 2- Progressive safety gear.
• 3- Overspeed governor.
• 4- Buffers.
• 5- Final Limit switches.
• 6- Other safety devices and switches.

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4.1 Device for locking landing doors (Hoistway
Door Interlock).

• Device for locking landing doors
  Hoistway Door Interlock

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• It shall not be possible in normal operation to
  open the landing door (or any of the panels in
  the case of a multi-panel door) unless the car
  has stopped, or is on the point of stopping, in
  the unlocking zone of the door. 
• The unlocking zone shall not extend more than 0.2
  meter above and below the landing level.
• The hoistway door locking mechanism provides a
  means to mechanically lock each hoistway door and
  the elevator cannot leave a landing unless the
  doors are fully closed and secured. 

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• They are also interconnected electrically to
  prevent operation of the elevator if any of the
  elevators hoistway doors are open. Should the
  doors be forced open, the interlock circuit will
  be broken, causing the elevator to immediately
  stop. 
• Each landing door shall be provided with a
  locking device satisfying the previous
  conditions. This device shall be protected
  against deliberate misuse. 
• Landing doors shall be capable of being unlocked
  from the outside with the aid of key , which fit
  the unlocking triangle (Hoistway Emergency Door
  Keys).

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• Hoistway Emergency Door Keys permit the unlocking
  of the hoistway door interlock. 

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4.2 Progressive safety gear 

• Safety gear is a mechanical device for stopping
  the car (or counterweight) by gripping the guide
  rails in the event of car speed attaining a
  pre-determined value in a downward direction of
  travel, irrespective what the reason for the
  increase in speed may be. 
•  

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• Progressive safety gear retardation is affected
  by a breaking action on the guide rails and for
  which special provisions are made so as to limit
  the forces on the car, counterweight o balancing
  weight to a permissible value.
• Pair of safety gears is mounted in the lower part
  of car sling and operated simultaneously by a
  linkage mechanism that actuated by overspeed
  governor. 

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Safety Mechanism

• The progressive safety
• gear and the braking
• device are activated by
• means of a linkage with
• a shearing mechanism as
• shown beside. 

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Operation of Safety Mechanism

• Dependent on the direction the safety lever is
  pulled upwards or downwards the movement of the
  lever is transmitted to the shearing mechanism by
  means of a rocker.
• The grip wedges of progressive safety gear or
  braking device which are linked with the
  safety-gear levers are released from their rest
  position between rail and jaw body which is
  maintained by a spring assembly.
• The safety-gear lever assembly which is arranged
  in the form of a shearing mechanism ensures that
  the progressive safety gears and/or braking
  device are activated simultaneously and in
  pairs. 

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Reset

• The progressive safety gear and the braking
  device are reset by moving the car opposite to
  direction of safety gear operation.
• (Move car in electric recall mode, or if
  necessary, by releasing the car from the engaged
  position). 

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Safety switch

• Safety switch is mounted on the bottom transom on
  the side of the safety-gear.
• The switch is operated by the movement of the
  safety-gear lever up or down according to
  actuation direction if the car travels at over
  speed.
• The switch interrupts the safety circuit causing
  machine drive power off. 

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4.3 Over Speed Governor
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• Over speed governor function is to actuate the
  safety gear if the car speed exceeds 115 of its
  rated value. 
• Usually a cable is attached to the safeties on
  the underside of the car, called the governor
  rope. This rope runs down through a pulley at the
  bottom of the shaft and back up to the machine
  room and around the governor sheave. 
• When over-speeding is detected, the governor
  grips the cable which applies the safeties that
  wedge against the guide rails and stops the car.

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• The over speed governor works on the floating
  principle with a cam curve and roller guided
  rocker. 
• It is situated either in the machine room or in
  the head room. 
• Over speed governor is provided by a factory
  adjusted switch activated when the tripped speed
  is reached to disconnect the machine drive
  starting with governor pulley blocking. 

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4.4 Buffers 

• A Buffer is a device designed to stop a
  descending car or counterweight beyond its normal
  limit and to soften the force with which the
  elevator runs into the pit during an emergency.
• They may be of polyurethane or oil type in
  respect of the rated speed.

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• There are two principal types of buffers in
  existence A- Energy accumulation accumulate
  the kinetic energy of the car or
  counterweight. B- Energy dissipation dissipate
  the kinetic energy of the car or counterweight. 
• Polyurethane buffers which are energy
  accumulation type with non-linear characteristics
  are used for lifts that have rated speed not more
  than 1 m/sec. 

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• The main types of elevator buffers are
• look at slides (30,31,32) to get more details.

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4.5 Final Limit Switches 

• Final limit switches shall be set to function as
  close as possible to the terminal floors (the
  highest or lowest landing of lifts), without risk
  of accident. 
• Final limit switches shall operate before the car
  comes into contact with the buffers. The action
  of the final limit switches shall be maintained
  whilst the buffers are compressed. 
• After the operation of final limit switches, the
  return to service of the lift cannot occur
  automatically. 

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4.6 Other Safety Devices and Switches 

• A- Overload Device.
• B- Door Protective Device such as
  (photo-electric and infrared sensors, safety
  edges).
• C- Emergency Stop Switch.
• D- Emergency Alarm Switch.
• E- Anti-Egress Lock Device.

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5. Elevator Control System

• Elevator Control System is the system responsible
  for coordinating all aspects of elevator service
  such as travel, speed, and accelerating,
  decelerating, door opening speed and delay,
  leveling and hall lantern signals.
• It accepts inputs like (button signals) and
  produces outputs like (elevator cars moving,
  doors opening, etc.).

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5.1 Aims of the control system

• To bring the lift car to the correct floor.
•  
• To minimize travel time. 
• To maximize passenger comfort by providing a
  smooth ride. 
• To accelerate, decelerate and travel within safe
  speed limits. 

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5.2 Types of elevator control systems

• 1- Single Automatic operation
• First automated system w/o single call button on
  each floor and single button for each floor
  inside car.
• Called if no one is using it.
• Passenger has exclusive use of the car until rip
  is complete.

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• 2- Selective collective operation
• Most common, remembers and answers calls in one
  direction then reverses. When trip complete,
  programmed to return to a home landing.
• 3- Group automatic operation 
• For large buildings with many elevators which are
  controlled with programmable microprocessors to
  respond. 

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5.3 Elevator control system components

• 1. Inputs (sensors, buttons, system controls).
• 2. Outputs (actuators, bells, displays).
• 3. Controllers such as
• a. (Relay based controller electromechanical
  switching)
• b. (Solid-state logic technology,
• c. PLC controller computer based technology).

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5.3.1.A Sensors

• A.1 Magnetic and/or photo electric 
• These pick up signals regarding the location of
  the car. This sensor is usually placed on the car
  itself and reads the position by counting the
  number of holes in the guide rail as they pass by
  in the photo-electric sensor or in the case of
  the magnetic sensor, the number of magnetic
  pulses. 

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• A.2 Infrared
• This is used to detect
• people entering or
• leaving the elevator.

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• A.3 Weight sensor (Over Load Device)
• This is placed on the car to warn the control
  system if the design load is exceeded. 
• A.4 PVT (primary velocity transducer) 
• Velocity of the drive sheave is sensed with this
  encoder

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5.3.1.B Buttons
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5.3.1.C System Controls

• They are used to turn the elevator system on and
  off.
• They are only accessible from an elevator control
  room.
• They would typically be used quite infrequently.

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5.3.2.A Actuators

• 5.3.2.A.1 Door Opening Device
• It opens the inner door of the elevator cab and
  the outer door of the elevator shaft
  simultaneously at each floor.
• 5.3.2.A.2 Electric Motor
• The controller interacts with the elevator engine
  by sending it a signal that specifies at which
  speed and in what direction the engine should be
  going in.
• A stop signal is constructed by setting the speed
  parameter of the signal to zero.

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• 5.3.2.A.3 Brake
• Brakes in elevator system are electromagnetic and
  mechanical.
• The electromagnetic brakes activate automatically
  if there is sudden loss of power or when the car
  is stationary.
• The mechanical brakes at the sheave itself also
  stop the car from moving when the car is inactive.

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5.3.2.B Bells

• 5.3.2.B.1 Emergency Bell
• It is used to alert people outside of the
  elevator system when someone is trapped inside
  the elevator cab.
• 5.3.2.B.2 Load Bell
• It is used to alert the passengers inside the cab
  that there is too much weight in it.
• The controller interacts with the emergency bell
  and the load bell by sending each one of them a
  signal to ring.

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5.3.2.C Displays
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5.3.3 Controller

• It is a device which manages the visual
  monitoring, interactive command control and
  traffic analysis system to ensure the elevators
  are functioning efficiently.

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What is the function of the elevator controller?

• It controls the speed of elevator engines.
• Processes elevator summons and floor requests
  from passengers.
• Controls the operation of the elevator doors of a
  cab through communication with door opening
  devices.

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5.3.3.1 Relay Based Controller (Electromechanical
Switching)

• A simple elevator with few
• stops and manual door
• operation can be served
• well by a relay controller.

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5.3.3.2 Solid State Logic Technology

• It includes both discreet
• transistors circuits and
• integrated circuit boards.
• It gives improved reliability,
• lower power consumption
• and easy fault diagnosis than
• electromagnetic relay technology.

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5.3.3.3 PLC Controller (Computer Based Technology)

• Elevator concepts utilizes a
• special type of industrial
• computer called a (PLC) or a
• Programmable Logic Controller
• to control the logic of more
• complex jobs.
• They are very dependable, compact and simple
• to troubleshoot.

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5.4 Elevator Control System Sequence Diagrams

• The elevator control system may be viewed either
  from
• The point of view of an individual user.
• or as
• A system being acted on by many users.

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5.4.1 The Point of View of an Individual User
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5.4.2 A System Being Acted On By Many Users
118

• Thank you