Elevator traction drive principle and characteristics?

The elevator traction machine usually consists of an electric motor, brake, reduction box and base. If the power of the dragging device, without the intermediate reduction box and directly to the traction wheel traction machine is called gearless traction machine. The motor armature of a gearless tractor is directly connected to the brake wheel and the traction sheave coaxially. The traction machine in which the power of the drag unit is transmitted to the traction sheave through an intermediate reduction gearbox is called a geared traction machine.　　1. AC motor for elevator a. Characteristic requirements of motor for elevator To have large starting torque Starting current should be small The motor should have flat torque characteristics In order to ensure the stability of the elevator, under the rated voltage, the motor's turnover rate should not be more than 12% at high speed, and should not be more than 20% at low speed Requirements for low noise, pulsating torque is small b. Commonly used in elevators on the type of AC motor Single-speed motor Twin-speed motor Three-speed motor c. Motor type of motor Motor three-speed motor c. motor capacity estimation (see textbook)

2. worm gear transmission At present, the speed is not more than 2.5 m / s with gear traction machine gearbox most of the use of worm gear, and its main advantages are: smooth transmission, low operating noise, compact structure, small dimensions, less transmission parts, with a better resistance to shock load characteristics a. Worm wheel shaft bearing mode The worm is located on the top of the worm wheel is known as the upper part of the worm wheel, and the worm wheel is located on the top of the worm wheel. The worm gear of the worm gear pair is called the upper mounted type and the one below the worm gear is called the lower mounted type. The advantage of the top mounted type is that the case is easier to seal and easier to inspect, but the disadvantage is that the worm gear is poorly lubricated. b. Commonly Used Worm Gear Tooth Shape There are two kinds of worm gear tooth shape: cylindrical and arc rotary surface. c. Selection of worm and worm gear materials When selecting materials, the characteristics of worm gear transmission should be taken into full consideration, the worm should be selected with high hardness and good rigidity, and the worm gear should be selected with good wear-resistant and wear-reducing properties. d. Requirement of meshing characteristics of worm gear e. Calculation of efficiency of worm gear transmission f. Calculation of force on worm gear g. Thermal balance problem Since the power lost by friction in worm gear transmission is large, most of the power lost is converted into heat, which increases the oil temperature. Excessive oil temperature will greatly reduce the viscosity of the lubricant, destroying the oil film between the tooth surfaces, resulting in direct contact between the working surfaces producing tooth gluing. In order to avoid the phenomenon of lubricant overheating, the design of the worm gear box should meet, from the worm gear box heat is greater than, or at least equal to, the heat of power loss.

3. Helical Gear Transmission The following should be considered when designing helical gears for elevators: Strain forces Impact bending stresses Pitting and wear Vibration and noise

4. Brakes a. Brake type The elevator braking system shall have an electromechanical brake which shall be actuated in the event of a power failure in the main circuit or a power failure in the control circuit. Cutting off brake current shall be accomplished by at least two separate electrical devices. The braking action of the brake shall be accomplished by guided compression springs or weights. The braking torque shall be sufficient to stop a car running at rated speed and carrying 125% of the rated load. The most commonly used elevator brakes are electromagnetic brakes. b. Calculation of braking torque Braking torque consists of two parts: static torque and dynamic torque. Calculation of static and dynamic moments (see textbook) c. Heat generation of brake During the stopping process, the kinetic energy of the moving parts of the elevator is converted into heat on the brake wheel due to friction braking. If the surface temperature of the brake tile is too high, it will reduce the friction coefficient between the brake wheel and the brake tile, so as to reduce the braking torque. For most elevators, it is not necessary to calculate the thermal performance of the brake. Especially in recent years, for all passenger elevators with dense traffic flow, zero-speed holding brake technology has been used in the drag control system to reduce the mechanical friction braking process to the limit. For passenger and freight elevators with low traffic flow, the number of starts per hour is lower and, therefore, the amount of kinetic energy absorbed per hour is also lower. However, for the elevator with high level speed or large inertia of moving parts, its thermal performance should be analyzed and calculated.