The inner workings of a residential or commercial elevator may not be something most people have a deep understanding of, so today we’re going to discuss the type of motor that’s used in a lift elevator. We’ll also cover how to choose the right residential elevator to meet all of your needs.
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The most common types of elevators for residential or commercial use are traction (geared or gearless) or hydraulic (holed or holeless) elevators. Now, let’s explore how these two types of elevators work as well as what kind of motor you tend to find with them.
These are the three most common types of elevator motors:
Traction elevators are operated with a counterweight that offsets the weight of the cab and its passengers. The motor doesn’t have to move as much weight which means traction elevators are much more energy-efficient than hydraulic systems.
Geared traction elevators are controlled or “driven” by AC or DC electric motors. With the electric motor in this design, it drives a worm-and-gear-type reduction unit, which turns the hoisting sheave. In a geared elevator, the gear reduction offers the advantage of requiring a less powerful motor to turn the sheave.
For a machine roomless traction elevator, a smaller gearless traction motor is required. This means it can be placed inside the shaft to take up less space than a larger motor.
Hydraulic elevators also use electric motors, and these elevators are powered by a piston that travels inside a cylinder. The electric motor pumps hydraulic oil into the cylinder which moves the piston, then the piston smoothly lifts the elevator cab.
Recently, more homeowners are choosing to have pneumatic elevators or vacuum elevators in their homes. They don’t require a motor, or any gears or cables, which is a big reason they’re becoming so popular — they’re very low maintenance!
Rather than relying on this equipment, pneumatic elevators use air pressure to move up and down. When the vacuum is “told” the elevator is going up, it uses its powerful pumps to reduce the air pressure above the elevator car. When this happens, the pressure under the car pushes the car upwards. When it’s time for the car to descend, the pump begins to work, reducing the pressure below the car. As the pressure is reduced, the car slowly falls.
When you talk about the different types of elevator motors, a phrase you’ll often hear is “elevator drive system.”
The drive system refers to the mechanisms the elevator uses to go up and down as well as the speed controlling mechanisms. In most cases, this is referring to the motor. But it also includes other important components like the brakes, the speed reduction unit, sheaves, and encoders.
How to choose the perfect elevator for your home
Now that you know a bit more about the different types of elevators and their drive systems, let’s discuss how to pick the right elevator for your home.
For some homeowners, a vertical lift like a wheelchair lift or a stair chair lift is the perfect solution for getting from floor to floor. A stair chair lift is a seat attached to a track installed along a staircase. An electric motor moves the chair up and down the track. A wheelchair lift, on the other hand, is a platform that a wheelchair and its occupant can be placed on and lifted up and down.
Rise Above Elevator offers several different options for direct drive vertical platform lifts if you’re in need of a wheelchair lift or stair chair lift.
All of our lifts are the highest quality in the industry with the smoothest and quietest ride available! We also offer both indoor and outdoor units to handle any climate or weather conditions.
Our direct drive wheelchair lift units have a battery backup system that allows you to use it even during a power outage. Every lift is also equipped with an emergency stop switch for your safety.
Give Rise Above Elevator a call to install your new platform lift.
For many homeowners, the two vertical lifts we just discussed are the most economical option. But in some cases, a traditional elevator is the right choice.
Our hydraulic elevator options include the QRL “Quiet Ride Lift” and the MRL “machine roomless” elevator.
Our Quiet Ride Lift ‘QRL’ basic standard package travels at 40 feet per minute, but we also offer faster speeds depending on overhead and the clearance of the hoist-way. Additionally, our quiet ride lift is built to fit your hoist-way which allows for the maximum amount of square footage for your cab.
Our MRL elevator also travels at 40 feet per minute, and has a winding drum overhead motor. This elevator uses two ⅜ of an inch top grade cables to lift and lower the elevator, as well as a variable frequency drive to ensure the quietest and smoothest ride you can get.
Hydraulic elevators are a good choice for a home because they are the quickest to install and they’re less expensive to build and maintain. Usually, they can accommodate heavier weights than traction elevators, and above-ground models are available with or without machine rooms. Crane or roof access is not required for their installation. Hydraulic elevators also have lower pit and overhead requirements with standard travel than traction elevators.
If you’d like to learn more about how elevators work or find out what kind of elevator is the best choice for your home, give us a call today!
We also offer 24/7 emergency service because we know some of our customers rely on their home lift as a means to get around their home. There’s always a trained technician monitoring the phone on nights, weekends, and holidays, so just give us a call! If you don’t receive an answer right away, we’ll get back to you as soon as possible.
HOW AN ELEVATOR WORKS QUESTIONS OR COMMENTS AUTHOR: Rhonda Salzmon E-MAIL: [email protected] COURSE: 2 CLASS/YEAR: 3
MAIN FUNCTIONAL REQUIREMENT: Move people and heavy objects from one location to another higher or lower, location.
DESIGN PARAMETER: An elevator can be used to meet these requirements.
BACKGROUND SECTION:
In order to do this, the elevetor turns electrical power into mechanical (rotational) power. The brake of the elevator must be designed in order to guarantee safety during normal day use. The brake must also be able to engage in extreme cases in which the elevator cable is broken or other unforeseen circumstances arise. In addition, the elevator must pick up and drop off passengers as efficiently as possible. If a collection of elevators is used, a complex controller usually controls them.
The elevator must fit within the given space requirements of the building. It must be made large enough to deal with the normal daily traffic and to move the necessary objects within the building. It cannot be made too large and, therefore, affect the structure of the building itself. Possible restrictions on the weight carried within the elevator may be determined from the size of the motor and the other components within the elevator system. This weight limit must be large enough to handle daily usage.
GEOMETRY/STRUCTURE AND EXPLANATION OF HOW IT WORKS/ IS USED:
Traction Drive/Roping System
A roping system is used to attach the motor/gear reducer, the elevator car and the counter weight. There are many different kinds of arrangements that can be used. In one possible arrangement, such as shown in Figure 2, both ends of the elevator rope are anchored to the overhead beam. Both the elevator car and the counter weight are attached to free moving pulleys. The traction drive is attached to a stationary pulley.
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The traction drive is the method of converting the input mechanical power (in this case the turning of a shaft) into useable mechanical power in the system (the vertical movement of the elevator). The friction between the ropes and the sheave grooves, which are cut on the pulley, initiates the traction force between the traction drive and the rope.
When the traction drive is rotated power is transferred from the traction drive to the elevator car and counter weight. Power is only needed to move the unbalanced load between the elevator and the counterweight.
Gears
An elevator's function is to convert the initial electrical power, which runs the motor, into mechanical power, which can be used by the system. The elevator is composed of a motor and, most commonly, a worm gear reducer system. A worm gear system is made up of a worm gear, typically called the worm, and a larger round gear, typically called the worm gear. These two gears which have rotational axes perpendicular to each other, not only decrease the rotational speed of the traction pulley (1), but also change the plane of rotation. By decreasing the rotation speed, with the use of a gear reducer, we are also increasing the output torque, therefore, having the ability to lift larger objects for a given pulley diameter. A worm gear is chosen over other types of gearing possibilities because of its compactness and its ability to withstand higher shock loads. It is also easily attached to the motor shaft, sometimes through use of a coupling. The gear reduction ratios typically vary between 12:1 and 30:1.
The motor component of the elevator machine can be either a DC motor or an AC motor. A DC motor had a good starting torque and ease of speed control. An AC motor is more regularly used because of its ruggedness and simplicity. A motor is chosen depending on design intent for the elevator. Power required to start the car in motion is equal to the power to overcome static, or stationary friction, and to accelerate the mass from rest to full speed. Considerations that must be included in the choice of an acceptable motor are good speed regulation and good starting torque. In addition, heating of various electrical components in continuous service should not be excessive.
Brakes
The most common elevator brake is made up of a compressive spring assembly, brake shoes with linings, and a solenoid assembly. When the solenoid is not energized, the spring forces the brake shoes to grip the brake drum and induce a braking torque. The magnet can exert a horizontal force for the break release. This can be done directly on one of the operating arms or through a linkage system. In either case, the result is the same. The break is pulled away from the shaft and the velocity of the elevator is resumed.
In order to improve the stopping ability, a material with a high coefficient of friction is used within the breaks, such as zinc bonded asbestos. A material with too high a coefficient of friction can result in a jerky motion of the car. This material must be chosen carefully.
Typically the efficiency of the geared machine is 60 percent for the motor and gear box assembly. This efficiency was estimated for a load of 2500lb, which matches a regularly sized residential elevator, being driven at 1.75 m/s.
DOMINANT PHYSICS:
There is a transfer of power throughout the elevator system. Electrical power put into the motor is equal to:
(for an AC motor)
Where V is the voltage and I/Ö 2 is the AC current source. This power is then transferred through the output of the motor shaft,
.
Where T is the torque and w is the rotational speed. Once the power is transferred through the gear reducer the output speed will be reduced and the torque will be greater. The overall power will be slightly lower as the system is not 100% efficient. Tension on the rope from the elevator pulley is equal to the weight of the elevator, We. The tension on the rope from the counter weight is Wc.
Figure 1. Free body diagram of the pulley systemThe following analysis has been done for steady state (no acceleration )operation. The
force on the driving pulley is equal to the difference of the two exerted tensions on each
side. On one side, this force is equal to We and on the other side, it is Wc.
Therefore, the net force exerted on pulley 1 (the drive
pulley) is:
In order to find the power required for elevator movement, either the rotational speed
of the drive shaft (attached to pulley 1) or the velocity of the elevator must be known.
The output power is (assumming 100% efficiency),
where r is the radius of the pulley (pulley 1).
Figure 2. Power flow through a typical elevatorLIMITING PHYSICS:
As explained above, the brake is held closed by a spring and released using a magnet. The free body diagram below shows how these forces are distributed. The force exerted by the spring is much closer to the pin joint and, therefore, is easily overridden by the force of the magnetic pull because of its longer moment arm (great distance from the point of rotation).
Figure 3. Diagram of the break systemFigure 4. Free body diagram of the break system
PLOTS/GRAPHS/TABLES:
None Submimtted
WHERE TO FIND ELEVATORS:
Elevators can be found in many residential and business buildings. They are used not only to transport people but also heavy object which would in other cases be difficult to transport.
REFERENCES/MORE INFORMATION:
Lubomir Janovský. Elevator Mechanical Design: principles and concepts.
England: Ellis Horwood Limited, 1987.
George R. Srakosch. The Vertical Transportation Handbook
Third Edition. John Wiley & Sons, Inc., 1998.
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